- Email: [email protected]
Paradigm shifts and current challenges in wastewater management
Journal Pre-proof Assessment of current challenges and paradigm shifts in wastewater management Mar´ıa C. Villar´ınData Curation) (Writing original draft) (Writing - review and editing) (Visualization) (Project administration), Sylvain Merel (Conceptualization)Data Curation) (Writing original draft) (Writing - review and editing) (Supervision)
PII:
S0304-3894(20)30127-8
DOI:
https://doi.org/10.1016/j.jhazmat.2020.122139
Reference:
HAZMAT 122139
To appear in:
Journal of Hazardous Materials
Received Date:
19 September 2019
Revised Date:
10 January 2020
Accepted Date:
18 January 2020
Please cite this article as: Villar´ın MC, Merel S, Assessment of current challenges and paradigm shifts in wastewater management, Journal of Hazardous Materials (2020), doi: https://doi.org/10.1016/j.jhazmat.2020.122139
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2020 Published by Elsevier.
Assessment of current challenges and paradigm shifts in wastewater management María C. Villarín1*, Sylvain Merel2,3*
1
Department of Human Geography, University of Seville, c/ Doña María de Padilla s/n, 41004, Sevilla, Spain
Institute of Marine Research (IMR), PO Box 1870 Nordnes, N-5817 Bergen, Norway
ro of
2
3
National Research Institute for Agriculture Food and Environment (INRAE), 5 rue de la Doua, CS 20244, 69625 Villeurbanne Cedex, France
Sylvain Merel
E-mail: [email protected]
María C. Villarín
E-mail: [email protected]
Jo
ur
na
lP
re
Graphical abstract
-p
* Corresponding authors:
1
Highlights The number of publication on wastewater is growing exponentially Paradigm shifts are water reuse, wastewater-based epidemiology, cradle to cradle Public acceptance, legislation and access to basic sanitation are social challenges Chemical and toxicological characterization of wastewater are technical challenges Contaminants of concern and treatments evolve with science and society
Jo
ur
na
lP
re
-p
ro of
2
Abstract Wastewater is a significant environmental and public health concern which management is a constant challenge since antiquity. Wastewater research has increased exponentially over the last decades. This paper provides a global overview of the exponentially increasing wastewater research in order to identify current challenges and paradigm shifts. Besides households, hospitals and typical industries, other sources of wastewater appear due to emerging activities like hydraulic fracturing. While the composition of wastewater needs
ro of
constant reassessment to identify contaminants of interest, the comprehensive chemical and toxicological analysis remains one of the main challenges in wastewater research. Moreover, recent changes in the public perception of wastewater has led to several paradigm shifts: i)
-p
water reuse considering wastewater as a water resource rather than a hazardous waste, ii) wastewater-based epidemiology considering wastewater as a source of information regarding
re
the overall health of a population through the analysis of specific biomarkers, iii) implementation of treatment processes aiming at harvesting valuable components such as
lP
precious metals or producing valuable goods such as biofuel. However, wastewater research should also address social challenges such as the public acceptance of water reuse or the access
na
to basic sanitation that is not available for nearly a third of the world’s population.
ur
Keywords: wastewater-based epidemiology, contaminants and transformation products,
Jo
microplastics, basic sanitation, water conflict and legislation, yuck factor
3
1. Introduction The amount and the composition of wastewater produced by households, hospitals and industries represent a major concern for human and environmental health. Therefore, an efficient management of wastewater, which involves collection, treatment and discharge with
ro of
the smallest possible environmental impact, is necessary. In fact, sanitation systems and wastewater management strategies were already developed by different ancient cultures (Lofrano and Brown, 2010). For instance, around the 6th century BC, in the Ancient Rome, the Cloaca Maxima was built as a large sanitation network and drainage system in case of flooding
-p
in the city (Hopkins, 2012). This characterizes a management strategy that was still largely
re
applied a few decades ago, and even remains in use in some countries, which consists in preserving public health by simply sending wastewater away from the population.
lP
Nowadays, wastewater management is still an issue and strategies evolve in order to protect public health while limiting the ecological impact on receiving waters. For instance,
na
ongoing research constantly adapts to new emerging contaminants generated by modern societies and aims at improving their attenuation through the development of new treatment
ur
processes. Moreover, this quick and recent evolution also results from the fact that wastewater management is no longer considered as a local issue faced by each municipality individually
Jo
but as a priority increasingly tackled globally. For example, communication on phenomena such as the “feminization” of fish population downstream of wastewater treatment plant due to endocrine disruptors discharged with wastewater effluents (Sumpter and Johnson, 2005) has created greater social and political awareness. As a consequence, the treatment of wastewater and the discharge of effluents are increasingly regulated at the country level and even at international level like in the European Union (EU) where a first common wastewater 4
regulation was established in the 1990s (EEC, 1991). However, some member states do not observe with the EU legislation (Voulvoulis et al., 2017) which must be enforced and updated periodically in order to ensure compliance and environmental protection while avoiding social conflicts. The current needs of modern societies also change the perception of wastewater and create paradigm shifts that drive wastewater research. For instance, the increase of population in urban agglomerations generates a growing water demand which worsens the water footprint
ro of
of major cities. This encourages the paradigm shift consisting in converting wastewater from an unwanted substance to a valuable resource (Grant et al., 2012; Pradel et al., 2016; Salgot and Folch, 2018).
-p
The simultaneous evolution of wastewater management, wastewater perception and new requirements of modern societies results in growing research. However, the large amount of
re
publications from different fields (analytical science, engineering, social sciences…) makes it
lP
more complex for the readers to have and keep a broad overview of recent evolution in a given topic. In this context, this paper aims to provide the expert as well as non-expert readers with a global and comprehensive view of wastewater research and its evolution. In particular, the
na
paper will present a bibliometric analysis leading to considerations on the sources of wastewater, the description of paradigm shifts, and the characterization of technical and social
Jo
ur
challenges (Fig. 1).
2. Bibliographic search and data collection The publications reflecting wastewater research were retrieved using the Web Of
Science (WOS) from Clarivate Analytics. As described in a previous bibliometric study (Merel et al., 2013a), an initial search by “topic” across all databases was performed in May 2018 using the word “wastewater”. The items retrieved were filtered according to the document type,
5
language and publication year in order to restrict the bibliometric study to articles and reviews published in English up to 2017. Among the remaining items, the “highly cited papers” were particularly considered as they represent recent research (published over the last ten years) which received enough citations to be placed in the top 1% of a relevant academic field. These highly cited papers were used as a basis to determine the most significant emerging challenges in wastewater research. The bibliometric overview of wastewater research worldwide was obtained from the
ro of
raw amount of publications retrieved as described previously. When an article was published by co-authors from different countries, the paper was counted only once to assess the overall amount of literature available but it was affected to the publication record of each contributing
-p
country. This allowed the accurate assessment of both the total amount of publication and the relative contribution of each country worldwide. In addition, for each country, the research
re
output was considered along with other parameters such as the population, the inequality-
lP
adjusted human development index (IHDI) and the percentage of the population with access to basic sanitation. Data related to population and basic sanitation were retrieved form the World Bank Group (WBG, 2018a, b) while the IHDI was obtained from the United Nations
na
Development Programme (UNDP, 2016).
ur
3. Bibliometric assessment of wastewater research
Jo
3.1. Overall bibliometric evolution of wastewater research The number of studies related to wastewater has strongly increased over the last decades
(Fig. 2). The total number of articles and reviews retrieved through WOS until December 2017 reached 126,765 items. Among them, 120,553 items (95%) were published in English and were considered in this study. The first four articles retrieved about wastewater were published in 1959. Since then, the number of yearly publications kept increasing with an exponential growth
6
from the 70s until today (Fig. 2). In fact, over 100 papers were published in the year 1975 while 13,612 papers were published in the year 2017. Similarly, the amount of publications on water reuse (today a significant field of wastewater research) have been increasing gradually (Fig. 2) since the first publication retrieved from 1959. The number of yearly publications remained below 12 until 1985 but progressively increased to 100 articles in the year 2000. Since then, the number of yearly publications kept growing exponentially to reach 1051 items in the year 2017. Overall, WOS sorted the publications into six general categories, allowing each
ro of
publication to be assigned several categories. The main categories were “Science Technology” with 99% of the publications, “Life Science Biomedicine” with 85% of the publications, “physical Sciences” with 77% of the publications and “Technology” with 71% of the
-p
publications. On the contrary, the categories “Social Sciences” with 20% of the publications and “Arts Humanities” with less than 1% of the publications were largely underrepresented.
re
This distribution tends to indicate that a major part of wastewater research focuses on improving
lP
treatment technology or assessing the toxicity of effluents while much less is done on areas such as the legal and economical aspect of wastewater treatment or the public perception of wastewater management. This observation is further sustained when refining the distribution of
na
the publications. For instance, WOS also sorted the publications into 150 research areas. Overall, “Environmental Sciences Ecology”, “Public Environmental Occupational Health”,
ur
“Water Resources” and “Engineering” were the main research areas with 56% to 84% of the
Jo
publications. Another height research areas including “Chemistry” or “Toxicology” also gathered 20% to 30% of the publications. However, research areas belonging to social sciences were much less significant. In fact, while the research area “Business Economics” still gathered 18% of the publications, the remaining research areas including “Public Administration”, “Geography” and “Government Law” gathered less than 1% of the publications.
7
3.2. Geography of wastewater research Besides the chronological trend described previously, the bibliometric assessment of wastewater research also reveals a heterogeneous spatial distribution. During the twentieth century, several countries changed their borders as a result of two World Wars, the dismantling of the USSR and Yugoslavia or the creation of new countries in Africa. Therefore, the overall
ro of
political stability that limited the alteration of borders worldwide only allowed the geography of wastewater research to be assessed over the last 25 years, which still reflects 94% of all publications.
-p
Overall, over the period 1993-2017, wastewater research was mostly dominated by China and the USA (Table 1), each of them accounting for more than 10% of the publications
re
(Fig.3). Next in the ranking are India and Spain representing between 5 and 10% of the
lP
publications. Finally, the ranking of countries with the highest amount of publication also included Canada, Germany, UK, Turkey, South Korea and Japan, each of them accounting for 3-5% of wastewater research. However, the geography of wastewater research is not rigid and
na
the progressive evolution across the period 1993-2017 is reflected by the relative distribution of yearly publications by continent (Fig.2). Indeed, while Africa and Oceania kept a steady
ur
relative scientific production around 4%, the relative contribution of Asia increased from 23%
Jo
in 1993 to 51% in 2017. In return this was compensated by the decreasing relative contribution of Europe and North America. This trend appears even more clearly when considering specifically the relative contribution of China, the EU and the USA (Fig.2). Additionally, as suggested in a previous bibliometric study (Merel et al., 2013a) and in order to account for the intrinsic possibilities of each country, wastewater research was also assessed after adjusting the number of publications to the population size. Such normalization
8
to the population size for the year 2015 changes considerably the geography of water research (Fig. 3) since China, India and USA no longer appear in the top ten ranking even though they were the countries with the largest raw number of publications (Table 1). On the contrary, the most productive countries based on their population size are Singapore, Finland, Australia, Cyprus, Portugal, Denmark, Greece, Brunei, Switzerland and Spain. Finally, in order to account for additional country-specific parameters such as the level of education and income, the scientific production adjusted to population size was also plotted
ro of
as a function of the inequality-adjusted human development index (IHDI). This revealed that the amount of publication/million inhabitant increased exponentially with the growing IHDI (Fig. 2), which was expected since a higher IHDI implies conditions that favor research
-p
(education, infrastructure and funding availability).
re
3.3. Major research institutions and funding bodies
lP
The main research institutions in the field of wastewater were rather representative of the country ranking over the period 1993-2017 (Table 1). The Chinese Academy of Sciences was the institution with the highest number of publications (3163 items) before the Indian
na
Institute of Technology (1548 items) and the Council of Scientific Industrial Research of India (1417 items). The French National Centre for Scientific Research (CNRS) was ranked as the
ur
fourth research institution with 1380 publications even though France was only the 12 th most
Jo
publishing country. Overall, the ranking of institutions mostly highlights a consortium of universities (for instance the University system of California) or large research entities with researchers extensively distributed nationwide and internationally (for instance, the Academy of Sciences in China, the CNRS in France or the CSIC in Spain). Similarly, the main funding bodies also reflected the most publishing countries over the period 1993-2017 (Table 1). The National Natural Science Foundation of China (10,758
9
articles) appeared as the main source of funding before the European Union (1521 articles) and the Chinese Fundamental Research Funds for the Central Universities (1492 articles). Spanish ministries represent the fourth source of funding (897 articles) before the US national Science Foundation (828 articles), which sustains the previously described and constantly good ranking of Spain according to wastewater research publications (Table 1). Moreover, wastewater research in Spain is also funded at the local level with autonomous regions (Andalusia, Catalonia, Galicia and Valencia) all together ranked as the tenth major funding source with 437
ro of
articles. However, it should be noticed that such ranking according to WOS is based on the assumption that each funding body was truthfully acknowledged in each article. While such assumption is likely to be accurate for publications released over the last few years because
-p
journals put a strong emphasis on mentioning all funding sources, it might be less accurate for the earliest publications. Moreover, it is also essential to recognize that the ranking of funding
re
bodies is only based on the number of publications that mentioned them, but the ranking does
usually not readily available.
na
4. Sources of wastewater
lP
not take into account at all the actual amount of funding provided since such information is
ur
Modern societies enclose a perpetually growing number of activities which generate waste and wastewater. Therefore, the accurate understanding of the multiple sources of
Jo
wastewater is a precondition for an optimal management at the local and global scale by determining the need for collection (where, when and how much?) and the most relevant treatment options (which treatment for which contaminant?). However, while some sources of wastewater are well identified and characterized, other sources are either emerging or remain largely overlooked.
10
4.1. Common sources of wastewater Statistics regarding the origin of wastewater and the volume discharged at the country level are scarce and incomplete (Eurostat, 2018). For instance, a yearly discharge of 1010 m3 of wastewater equivalent to 125 m3/inhabitant can be considered for Germany (Statista, 2013), a Western European country with high IHDI.
ro of
Households are well known contributors to the global amount of wastewater discharged each year worldwide. Indeed, human individuals use at least several liters of water per day in order to satisfy basic requirements such as drinking water for survival, hygiene, sanitation and
-p
food preparation (Gleick, 1996). While understanding the domestic water demand remains challenging (Villarín and Rodriguez-Galiano, 2019), several European capitals present an
re
average water consumption ranging from 136 to 289 L/day/inhabitant (Villarín, 2019). A large part of this domestic consumption will become wastewater carrying a large set of chemicals
lP
such as pharmaceuticals and their metabolites excreted after consumption or improperly disposed via the toilets (Mompelat et al., 2009), fungicides and flame retardants leaching from
na
cloths being washed (Merel et al., 2018), insect repellents and other personal care products removed from the skin when showering (Merel and Snyder, 2016), and compounds like
ur
denatonium used as additives to multiple consumer products (Lege et al., 2017).
Jo
Hospitals are other contributors to the amount of wastewater produced and treated each year (Mompelat et al., 2009). With a concentration of patients using water for personal hygiene, and additional water needs in order to keep the facilities clean, the actual volume of wastewater generated by hospitals is not well characterized. Such wastewater contains a wide range of pharmaceuticals which partially differ from those released by households since patients treated internally receive heavier treatments, for instance antineoplastics against cancer. Nevertheless, with the constant progress in medicine, a trend consists in increasing prescription to outpatients, 11
therefore progressively reducing the dissimilarity between pharmaceuticals in wastewater from households and hospitals (Mompelat et al., 2009). Rainfalls and subsequent runoff form another source of wastewater, particularly in urban areas largely impermeable and often equipped with a collection system. For instance, in Germany, the collection of water from rainfalls represent 26% of the overall wastewater discharged (Statista, 2013). Water collected after rainfalls may contain contaminants leaching from roofs and the facades of buildings, including pesticides such as diuron, terbutryn and
ro of
carbendazim (Burkhardt et al., 2011; Jungnickel et al., 2008; Merel et al., 2018; Schoknecht et al., 2009).
Industries are also well-known sources of wastewater due to their respective activities.
-p
However, since industrial wastewater effluents are usually treated internally before being discharged, assessing the actual volume of wastewater generated remains a challenge. The
re
composition of wastewater and related concerns will not be discussed in this paper as there are
lP
large differences between different industries. For instance, paper industries that produce a large amount of wastewater will mostly focus on removal of relevant contaminants (Ashrafi et al., 2015; Toczyłowska-Mamińska, 2017) while power production sites that generate large amount
na
of wastewater from their cooling operations will particularly care about the temperature of the
ur
effluent before discharge (Lee et al., 2018).
Jo
4.2. Examples of overlooked and emerging sources of wastewater 4.2.1. Hydraulic fracturing Nowadays, hydraulic fracturing, also referred to as fracking, is mostly associated with
unconventional gas production such as shale gas extraction. While combining vertical and horizontal drilling enhances access to gas-containing shale matrices, injecting under high pressure a large volume of water mixed with sand and various chemicals into the borehole
12
allows fracturing the shale. Once the fracturing fluid is removed, shale gas can flow through the cracks to the well and be collected. However, there is a growing concern regarding the production and fate of wastewater related to such process. In fact, 209 publications associated with the topics “wastewater” AND “hydraulic fracturing” could be retrieved in WOS, over twenty of them being “highly cited”. While the first publication was from the year 2000, the amount of yearly publications strongly increased since 2012 and reached 66 for the year 2017. Shale gas extraction through hydraulic fracturing generates three types of wastewater: Wastewater from drilling operations. Because drilling wastewater conveys
ro of
drilling waste, it contains high levels of suspended and dissolved solids in addition to a range of chemicals used to lubricate the drilling equipment (Lutz et
-p
al., 2013).
Wastewater from the hydraulic fracturing operation itself. After fracturing the
re
shale, the mixture of water, sand and chemicals injected under high pressure is
lP
removed from the borehole and referred to as flowback water (Lutz et al., 2013). A recent study performed on a well located in Colorado in the USA revealed that flowback water contained 22,500 mg/L total dissolved solids and a high amount
na
(590 mg/L) of dissolved organic carbon (Lester et al., 2015). The elemental analysis also revealed the occurrence of metals such as sodium, calcium and
ur
magnesium while heavy metals were detected at levels similar to those usually
Jo
observed in municipal wastewater or not detected. In addition, high resolution mass spectrometry showed the occurrence of numerous trace organic contaminants including the surfactant cocamidopropyl dimethylamine and multiple linear alkyl ethoxylates also used to improve surfactant properties of the fracturing fluids (Lester et al., 2015; Thurman et al., 2014). Finally, another study reported high concentration of ammonium (reaching 420 mg/L) chloride
13
(reaching over 100 g/L), bromide (reaching over 1 g/L) and iodide (reaching over 50 g/L) in flowback water (Harkness et al., 2015).
Wastewater from the operation of the well which are referred to as brine. Along with gas production, wells usually produce brine water coming from the shale matrices which might contain residuals of the fracturing fluid, metals, trace organic contaminants and halides (Harkness et al., 2015; Lutz et al., 2013).
Overall, the volume of wastewater generated by shale gas extraction through hydraulic
ro of
fracturing remains imprecise, particularly since drilling fluids are often neglected while flowback water is not clearly distinguished from the brine. For instance, some estimations report that wastewater represent 10% to 70% of the volume of fracking fluid injected per well,
-p
which itself varies between 11,000 to 19,000 m3 (Lutz et al., 2013). Another study indicates that 1,788,000 m3 of wastewater were generated for the year 2013 in the state of Pennsylvania
re
(USA), out of which 5% were drilling fluids, 23% were flowback water and 72% were brine
lP
(Harkness et al., 2015). However, with the growing number of operating wells and future drillings, the volume of wastewater associated with shale gas production is likely to increase therefore causing significant challenges as well as environmental and health concerns.
na
The major concern associated with wastewater from shale gas extraction is the potential contamination of local groundwater and surface water. In theory, this can occur through
ur
different circumstances including leaks through fractured rock (no evidence found so far) or
Jo
well casing, discharge at the drilling site, spills during transportation, and wastewater disposal (Rozell and Reaven, 2012; Vengosh et al., 2014). On the first hand, direct groundwater contamination have scarcely been reported (Llewellyn et al., 2015; Vidic et al., 2013) and the constant progress in drilling techniques and well casing will further help preventing such environmental issue. On the other hand, concerns related to the contamination of surface water is growing as the discharge of treated wastewater from shale gas production would increase the
14
concentration of halides (I-, Br-) and of the non-ionized form of nitrogen (NH3) in the receiving waters (Harkness et al., 2015; Warner et al., 2013). Such increase in halide concentration could impact the drinking water treatment located further downstream by enhancing the formation of toxic iodinated and brominated disinfection by-products while (NH3) could also have deleterious effects on aquatic species (Harkness et al., 2015). In order to avoid the discharge of wastewater into the environment, some areas rely on deep-well injection to place the liquid into geologic formations that prevent potential migration towards aquifers. However, deep-well
ro of
injection is also subject to discussion since several studies have linked this practice with an increase in seismicity (Keranen et al., 2014; Weingarten et al., 2015; Yeck et al., 2017). Therefore, in this context of quickly growing shale gas extraction by hydraulic fracturing, the
-p
management of related wastewater requires further research aiming at achieving a full characterization of chemical composition, evaluating the efficacy as well as the affordability of
lP
re
potential treatments, and assessing the toxicity of the effluents for the environment and human.
4.2.2. Fire extinguishing operations
The extinguishment of wildfires, urban fires and industrial fires often relies on applying
na
large amount of water. This water is usually not retained nor treated after the fire has been extinguished and becomes wastewater that reaches the nearby river or the local treatment plant
ur
if a precipitation runoff collection system exists. Because such source of wastewater shows a
Jo
random spatial distribution with a short time span, no estimation of volume could be found. However, a brief calculation indicates that the fire extinguishing process would generate several cubic meters of wastewater for operations lasting only a few minutes to thousands of cubic meters or more for operations lasting hours and even days. Indeed, fire trucks used in France are commonly equipped with fire hoses delivering a flow of water ranging from 0.1 to 1 m3/min with sometimes several of them operated for hours in parallel.
15
The composition of wastewater from fire extinguishing operations depends on the material burning. For instance, wildfires or fire in compost production sites would result in wastewater with a high content of natural organic matter. Moreover, wastewater might also contain fire suppressants (Plucinski et al., 2017) often used in aerial firefighting. On the other hand, urban fire would result in wastewater containing substances like fungicides leaching from construction materials (Burkhardt et al., 2011; Merel et al., 2018). Finally, other extinguishing operations specific to means of transport (aircraft, car, trucks…) and industrial sites like oil
ro of
refineries rely on the application of foam. Therefore, related wastewater would contain high amount of proteins or surfactants such as perfluorinated compounds (PFCs) frequently used in
-p
the composition of firefighting foam (Moody and Field, 2000; Moody et al., 2003).
4.2.3. Other examples
re
Overlooked sources of wastewater also include landfills. Lixiviation of materials buried
lP
in landfills through the infiltration of water from rainfall leads to the production of leachate containing high concentrations of a wide range of chemicals including pharmaceuticals, personal care products, brominated flame retardants, pesticides, endocrine disruptors, and
na
perfluorinated compounds (Clarke et al., 2015). Ships transporting passengers and those transporting cargo also generate wastewater in the form of bilge water usually containing oil,
ur
polycyclic aromatic hydrocarbons (PAHs), surfactants and heavy metals (Magnusson et al.,
Jo
2018). Finally, other overlooked sources of wastewater might also include municipalities through the cleaning of streets and market places with water later collected by the sewer system; ski resorts through the production of artificial snow which reaches nearby streams when melting; public services through the prevention of icing on the streets by the application of salty water which later reach the sewer system or a nearby watercourse; desalination plants which
16
produce drinking water from sea water but generate concentrated brines; local business such as laundry services and car wash stations…
5. Current technical challenges 5.1. Contaminants to remove Wastewater carries a wide range of contaminants that reflect the society and which need to be removed. The peer-reviewed literature offers multiple reviews on the occurrence and fate
ro of
of specific contaminants. Consequently, this article will provide an overview of wastewater contaminants associated with highly cited papers and therefore of particular interest but without
-p
entering in the details of their attenuation.
5.1.1. Chemical contaminants
re
Nutrients represent the first and potentially the oldest class of wastewater contaminant.
lP
Indeed, nutrients such has ammonium and phosphate are constituents of urine, which therefore already occurred when wastewater was first collected in 3500-2500 BC in the Mesopotamian
na
Empire (Lofrano and Brown, 2010). When released in the receiving water, nutrients increase the eutrophication process and favor the formation of potentially toxic blooms of algae or
ur
cyanobacteria (Merel et al., 2013b; Paerl et al., 2016; Watson et al., 2016). Therefore, processes to improve the removal of nutrients are still a major research focus (Cao et al., 2017; Desmidt
Jo
et al., 2015; Garcia et al., 2017; Guaya et al., 2015; Kelly and He, 2014). Pharmaceuticals and personal care products represent a second but major class of
wastewater contaminant (Petrie et al., 2015). As new molecules are regularly authorized while other are progressively withdrawn, the suite of pharmaceuticals detectable in wastewater varies over the years and from a country to another. Therefore, compound libraries used with high resolution mass spectrometry should be regularly updated to include new chemicals of interest 17
and assess their occurrence and fate in wastewater. Overall, the attenuation of pharmaceuticals is an important research focus since their biological activity is a major environmental health concern with residuals of antibiotics favoring the development of resistant bacteria (Novo et al., 2013; Rizzo et al., 2013; Sousa et al., 2017) and hormones causing endocrine disruption (Huerta et al., 2016; Liu et al., 2009; Samaras et al., 2013). Poly- and perfluoroalkyl substances (PFASs) that were developed for their stability are commonly used in multiple consumer products since the 1950s (Richardson and Kimura, 2017)
ro of
and represent a third class of major wastewater contaminant (Ahrens, 2011; Zareitalabad et al., 2013). In the literature, perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) are the most commonly reported PFAS in wastewater. However, wastewater is likely to contain
-p
many other PFASs that might remain unnoticed due to the lack of specific monitoring. For instance, with the growing application of high resolution mass spectrometry, 455 new PFASs
re
have been characterized in a wide range of matrices over the period 2009-2017 (Xiao, 2017).
lP
As preliminary evidence suggests significant health effects associated with exposure to emerging PFASs (Sunderland et al., 2019), the occurrence of such chemicals in wastewater is of particular interest, particularly when implementing water reuse strategies.
na
Biocides are often associated with agriculture and multiple molecules are currently authorized as plant protection products by the European Union. However, pesticides are also a
ur
significant class of wastewater contaminants. For instance, wastewater effluent from food
Jo
processing industry has been shown to contain 20 pesticides along with 14 of their transformation products (Campos-Mañas et al., 2019). In addition, some biocides like carbendazim that might be used to protect cloths as well as the facades of buildings against fungi growth also occur in municipal wastewater after progressive leaching (Merel et al., 2018). Some pesticides also occur in wastewater effluent without satisfactory explanation, therefore revealing an unknown input source. For instance, in France, atrazine could still be detected in
18
wastewater effluent collected by dry weather several years after prohibiting the commercialization and use of this pesticide for agricultural purpose (Becouze-Lareure et al., 2016). Due to their biological properties, the occurrence of biocides in wastewater effluent represents a significant environmental health concern. Heavy metals enclose a wide range of chemicals among which cadmium, chromium, copper, iron, lead, mercury, selenium or zinc. Since several heavy metals have been associated with human health issues, their occurrence and fate in wastewater is greatly studied. However,
ro of
while the concentration of heavy metal in the treated effluent is a concern for the implementation of water reuse strategies, a major concerns relates to their concentration in wastewater sludge which have to be disposed or reused. Nowadays, beyond attenuating the
-p
concentration of heavy metals in wastewater, a growing trend consist in harvesting them as a valuable good from wastewater (Westerhoff et al., 2015), as described in the following sections.
re
Dyes gather chemicals that also represent a major focus in wastewater treatment. Over
lP
the last decade, the removal of dyes from wastewater related to the textile industry was the topic multiples papers including several reviews (Bilal et al., 2017; Raman and Kanmani, 2016; Singh et al., 2015). However, it should also be considered that dyes might leach from cloths over
na
subsequent wash, therefore becoming also compounds of concern in domestic wastewater generated by households. These chemicals such as azo dyes and their cleaved products could
ur
be carcinogenic (Chung, 2016) and therefore represent a public health concern, particularly in
Jo
the context of water reuse.
Another group of chemicals of concern in wastewater are radionuclides. These are
radioactive isotopes of elements including strontium, selenium or uranium. They might occur in laundry wastewater from nuclear power plants (Park et al., 2010) but they might also occur in regular wastewater treatment plants (Montaña et al., 2013), and hospital wastewater due to the application of specific treatments for certain diseases (Verlicchi et al., 2010). Measures such
19
as the separated collection and treatment of discharges from toilets of patients receiving nuclear medicine therapy prevents elevated level of radionuclides in public sewer. However, radionuclides should remain carefully monitored. In additions to the main groups of chemicals mentioned previously, transformation products (TPs) should also be considered very carefully, particularly after disinfection processes (Le Roux et al., 2017). Indeed, while some TPs formed during wastewater treatment have a chemical structure closely related to that of their parent compound, they might remain
ro of
biologically active. In addition, most of the TPs remain unknown. Therefore, the chemical and toxicological characterization of TPs in wastewater is a major environmental and public health
-p
concern.
5.1.2. Non-chemical contaminants
re
Among non-chemical contaminants, microplastics have been reported in wastewater by
lP
multiple studies (Carr et al., 2016; Dris et al., 2015; Mintenig et al., 2017) therefore gaining increasing attention over the last decade. Microplastics, defined as polymer particles smaller than 5 mm, can be intentionally produced with a size of 60-800 μm to enter the composition of
na
personal care products (Chang, 2015). Therefore, microplastics are collected by the sewer system and sent to local wastewater treatment plants which are usually not designed to ensure
ur
their retention. Thus the discharge of treated wastewater is often considered as a major source
Jo
of microplastics in the aqueous environment. Nanoparticles, which are often described as particles with a diameter in the range 1-100
nm (Richardson and Kimura, 2017), have also become a significant concern for wastewater treatment. Engineered nanomaterials include for instance silver (Ag), titanium dioxide (TiO2), zinc oxide (ZnO), silicon dioxide (SiO2) or carbon nanotubes. Nanoparticles are used in the composition of personal care products, paints, food packaging and therefore reach the local
20
wastewater treatment plant (Zhang et al., 2015) which might not be designed to ensure their removal. However, nanomaterials also have a role in wastewater treatment where they can be employed in order to enhance the removal of other contaminants of concern (Santhosh et al., 2016). Consequently, a major challenge consists in designing treatment plants able to retain nanoparticles from wastewater while using the properties of immobilized nanomaterials to achieve an enhanced attenuation of trace organic contaminants. Finally, pathogens represent another class of contaminants of concern that wastewater
ro of
treatment should aim to remove. While providing an exhaustive overview of pathogens in wastewater is a complex task that is not the aim of the current study, it should be noticed that common wastewater pathogens can be distributed into several categories. A first category of
-p
pathogens gathers viruses, including the human adenovirus, JC polyomavirus, norovirus and rotaviruses (Eftim et al., 2017; Prado et al., 2019) as well as enterovirus, hepatitis A and E viruses
re
(Hellmér et al., 2014). A second category of pathogens gathers parasites, including helminths
lP
which eggs have been reported in wastewater effluent (Ajonina et al., 2015) and protozoa such as Cryptosporidium and Giardia (Adeyemo et al., 2019; Moutinho et al., 2019) which are well known to cause diarrhea when reaching and contaminating drinking water (Daniels et al., 2018).
na
Finally, a third category of wastewater pathogens gathers bacteria such as Legionella, Clostridium perfringens and the well-known diarrhea causing agent Escherichia coli (Ajonina
ur
et al., 2015; Caicedo et al., 2019; Paulshus et al., 2019). In addition, Vibrio cholera is another
Jo
wastewater bacteria responsible for cholera epidemic occurrence like in Yemen where the contamination of water wells by wastewater and the use of untreated wastewater for irrigation caused 500,000 individuals to be infected resulting in 2,000 deaths (Al-Gheethi et al., 2018). Overall, when considering the population of bacteria in wastewater, a study based on gene fingerprinting revealed that 0.06% and up to 3.20% were pathogenic (Cai and Zhang, 2013). Therefore, due the related consequences for human health, the attenuation of wastewater
21
pathogens during wastewater treatment is of high importance, more particularly when considering water reuse strategies. In practice and according to local legislation, treated wastewater discharged in the environment is not necessarily disinfected, which leaves to any entity (usually a drinking water treatment plant) using river water further downstream the responsibility of ensuring its own disinfection. However, when implementing potable or nonpotable water reuse, treated effluent must be carefully disinfected in order to ensure the removal of pathogens below guidelines set by local authorities. In fact, treatment plants aiming at water
ro of
reuse usually rely on the successive application of several disinfection processes. For instance, a facility in North Carolina provides a dual disinfection with a UV irradiation step followed by chlorination (Bailey et al., 2018) and consistently achieves log 10 removals up to 6 for bacteria,
-p
4 for virus and 4 for protozoan parasite surrogates. However, while chlorination is often selected as the last treatment step in order to ensure a residual of free chlorine that prevents the regrowth
re
of pathogens in the distribution network (Whitton et al., 2018), it is also well known that
lP
chemical oxidants including chlorine form a large amount of unknown disinfection by-products which should also be investigated (Postigo and Richardson, 2014; Richardson et al., 2007).
na
5.2. Treatment of wastewater
Wastewater management strategies were already implemented by ancient civilizations
ur
(Lofrano and Brown, 2010). Throughout the centuries and mostly over the last decades,
Jo
wastewater treatment technology has dramatically improved and current research keeps developing new processes. Since the recent literature offers reviews for most treatment technologies (Roccaro, 2018), providing a detailed examination of each process is not in the scope of this study. However this paper will rely on bibliometry to provide a brief overview of current wastewater treatment strategies and research.
22
Nowadays, conventional wastewater treatment consists in a combination of physical, chemical and biological processes that allow removing solids, organic matter and sometimes nutrients. Currently, the literature survey on wastewater reveals a significant amount of research on membrane bioreactor (MBR) to improve treatment efficacy (Krzeminski et al., 2017; Neoh et al., 2016; Skouteris et al., 2012). However, with MBR and other treatment processes, a major issue is the production of sludge which require specific management. Therefore, current wastewater research also aims at reducing sludge production and improving their handling
ro of
(Cieslik et al., 2015; Kelessidis and Stasinakis, 2012; Wang et al., 2017). In addition, the publication of several recent papers (Cao et al., 2017; Du et al., 2017; Garcia et al., 2017) also indicates that the removal of nutrients from wastewater remains a major research interest since
-p
the discharge of nitrogen and phosphorus aggravates the eutrophication of receiving waters (Paerl et al., 2016; Watson et al., 2016) and related issues such as the occurrence of harmful
re
blooms (Merel et al., 2013b).
lP
Improvement of wastewater treatment is also achieved through the application of processes based on the retention of contaminants. In recent years, several publications (Fane et al., 2015; Lee et al., 2016; Mohammad et al., 2015; Park et al., 2017a) show significant
na
investigation in the field of membranes in order to maximize the attenuation of contaminants. Filtration processes include ultrafiltration, nanofiltration but also osmosis (Chekli et al., 2016;
ur
Luo et al., 2017). While improving the retention of contaminants, research also focuses on the
Jo
mitigation of fouling (Perreault et al., 2016; Tijing et al., 2015), an issue inherent to membrane processes. Beyond membrane technology, the retention of contaminants in wastewater treatment also relies on processes based on sorption (Hai Nguyen et al., 2017; Khan et al., 2013). Over the last years, sorption research intensified with a focus on the application of biochar (Tan et al., 2016; Thines et al., 2017), an adsorbent produced by pyrolysis of agricultural waste such as coconut shell, empty fruit bunch and rice husk.
23
Finally, the attenuation of trace organic contaminants during wastewater treatment is also improved through the application of advanced oxidation processes (Asghar et al., 2015; Boczkaj and Fernandes, 2017; Roccaro, 2018) referred to as AOPs. The high reactivity of oxidants like ozone or radical species allows transforming contaminants not removed by conventional treatments, therefore reducing the impact of the discharge in receiving waters. Currently, the amount of literature indicates that a strong research effort is made on AOPs, which enclose multiple approaches (Oturan and Aaron, 2014) such as TiO2-based processes
ro of
(Wei et al., 2017), Fenton-related processes (Amor et al., 2015; Bokare and Choi, 2014), and ozone-based processes (Gomes et al., 2017) which have shown promising results for the attenuation of pharmaceuticals for many years (Snyder et al., 2006; Zwiener and Frimmel,
-p
2000). However, as implementing AOPs infer an additional cost, short term upgrading of conventional wastewater treatment plants with ozonation for instance might be limited to
re
countries like Switzerland that impose newer and stricter water protection acts (Bourgin et al.,
lP
2018). Nonetheless, even though AOPs significantly reduce the amount of known contaminants discharged in the environment, a major drawback is the production of new and unknown transformation products (Merel et al., 2017; Richardson and Kimura, 2016; Sgroi et al., 2018c;
na
Wert et al., 2007). Indeed, water contaminants are not removed by AOPs but rather transformed
ur
into multiple by-products the chemistry and toxicity of which remain largely unknown.
Jo
5.3. Analysis of wastewater samples Wastewater samples of different kinds (influent, primary, secondary or tertiary effluent)
are commonly analyzed for multiple purposes. These can include the detection of known compounds in order to assess treatment efficiency, the analysis of unknown components in order to identify transformation products, or the toxicity assessment through multiple endpoints.
24
However, the results do not only depend on the analytical technique used but also on how the sample was collected, preserved and prepared (Fig. 4).
5.3.1. Sample collection, preservation and preparation Overall, samples can be collected according to the three different approaches of which the most relevant is determined by the question to be addressed. The first approach, which consists in collecting a single sample at a specific time and location (grab sample), would
ro of
provide a punctual assessment of wastewater composition and properties. The second approach, which consists in collecting multiple samples across a given period of time (often 12 or 24 hours) and combining them before analysis (composite sample), would provide a representative
-p
average sample accounting for the temporal variation in the concentration of chemicals. The third approach, which consists in the continuous collection of chemicals by sorption on a
re
sorbent (passive sampling), would provide a time-integrated average over long periods (days or weeks) particularly useful to assess long term exposure.
lP
Sample preservation is critical in order to avoid any alteration of the composition (oxidation microbial degradation…) between collection and the analysis. Typical procedures
na
usually rely on storage at 4 °C, acidification (Trenholm et al., 2006) or addition of azide to limit biological activity (Anumol et al., 2013; Anumol and Snyder, 2015). However, in the absence
ur
of a detailed study on the most suitable preservation method for wastewater samples, two other
Jo
studies related to surface water but focusing on relevant contaminants could be considered (Mompelat et al., 2013; Vanderford et al., 2011). Overall, surface water samples collected in amber bottle to prevent photodegradation, quenched with ascorbic acid and spiked with sodium azide could be stored at 4 °C for up to 28 days with less than 15% loss for the pharmaceuticals and personal care products tested (Vanderford et al., 2011). Nonetheless, these results should
25
be considered with caution since they concern a limited set of test compounds and wastewater matrix is more complex than surface water. Sample preparation before analysis also largely evolved over the last decades. Initially, enrichment of the analytes was a pre-requisite often achieved by liquid-liquid extraction (LLE) but progressively replaced by solid phase extraction (SPE) more easily automated and allowing to extract a larger amount of contaminants (Merel and Snyder, 2016). With technological improvement, the sample volume required to performed SPE also decreased from several liters
ro of
(Snyder et al., 2001) to only a few milliliters with the development of online-SPE (Anumol and Snyder, 2015). In the recent years, wastewater analysis could even be performed without previous extraction, through the direct injection of 80-100 μL while achieving limit of
-p
quantification in the ng/L range (Anumol et al., 2015b). However, despite these major improvements, sample preparation remains challenging. For instance, the potential loss of
re
analytes inherent to sample preparation can be assessed and corrected by the addition of internal
lP
standards (isotope dilution) for known compounds of interest (Vanderford and Snyder, 2006) but it is still a major concern when assessing the fate of unknown contaminants. Moreover, sample preparation also remains a complex task for toxicity assessment which often requires a
na
higher enrichment factor than chemical analysis with a much lower fraction of organic solvent
ur
that could disrupt the normal activity of the organism/tissue/cell tested.
Jo
5.3.2. Analysis of known and unknown components Overall, high specificity and high sensitivity made mass spectrometry rather essential
for the detection of contaminants in wastewater through two different approaches. The first approach, referred to as “targeted analysis”, consists in selecting chemicals of interest in order to detect them and only them in a sample. The second approach, referred to as “untargeted
26
analysis”, consists in detecting all chemicals that can be ionized in the mass spectrometer while their tentative identification is carried out afterwards. Targeted analysis relies on chromatographic separation coupled to tandem mass spectrometry. Each compound is identified according to its retention time and its specific fragments with respect to an analytical standard which also allows an accurate quantification. When using isotope dilution, quantification can also include a correction factor accounting for any loss of analyte during sample preparation and ion suppression in the mass spectrometer
ro of
(Vanderford and Snyder, 2006). Nowadays, routine methods can often quantify several dozens of compounds for a measurement time below 30 minutes (Anumol et al., 2013; Anumol and Snyder, 2015). While data processing offers limited difficulty (Merel et al., 2015a), the results
-p
of target analysis still lead to some interrogations and new findings regarding the origin of contaminants in wastewater. For instance, the detection of the insect repellent DEET in
re
wastewater is commonly attributed to the dermal application of the molecule which is
lP
subsequently washed from the skin when showering and collected by the sewer system. However, the common detection of DEET in wastewater during the winter period, in dry areas that are not associated with the abundance of mosquitoes, together with the detection of the
na
insect repellent in blank samples (Anumol et al., 2013; Kolpin et al., 2013; Wode et al., 2015) has led to suspect the occurrence of potential analytical interferences or an uncharacterized
ur
source of DEET (Merel et al., 2015b; Merel and Snyder, 2016). Similarly, recent studies using
Jo
targeted analysis to monitor biocides identified households and paper production industries as previously unknown sources of the fungicide carbendazim in wastewater and the environment (Bollmann et al., 2014; Merel et al., 2018; Singer et al., 2010). On the contrary, compounds not considered in the targeted analysis cannot be detected with the consequence that some wastewater contaminants might remain unnoticed despite their potential ubiquity. For instance, a recent study suggested the potential ubiquity of denatonium (Lege et al., 2017), a bitter
27
substance added to certain products like detergents in order to prevent their ingestion. Yet the overall absence of targeted analysis for this compound excludes it and probably many other relevant chemicals from further research on occurrence, fate and environmental health risk assessment. The untargeted analysis relies on chromatographic separation coupled to high resolution mass spectrometry (HRMS), which allows detecting all chemicals within a given range of mass to charge ratio and without preliminary consideration as long as they can be ionized. This
ro of
approach has gained significance in the last decade, particularly due to the necessity to fully characterize wastewater samples and treatment efficacy when trying to reduce environmental impact and promoting water reuse. However, with untargeted analysis, each compound detected
-p
is initially an unknown chemical characterized by a retention time, an accurate mass, and potential fragment ions. Therefore, the first challenge associated with untargeted analysis
re
consists in identifying the compounds detected. This is often achieved by performing a “suspect
lP
screening” that matches the acquired data with a compound library. Thus, developing compound libraries and efficient algorithms are crucial needs to improve the identification rate (Zedda and Zwiener, 2012). In addition, new mass spectrometers that include ion mobility
na
separation allow a better compound characterization by providing their collision cross section (CCS) value which can be used to improve data processing (Bijlsma et al., 2019) and lower the
ur
rate of false positive (Regueiro et al., 2016). The second challenge with untargeted analysis
Jo
consists in identifying new compounds such as transformation products formed during wastewater treatment. For instance, while some studies rely on external software that predict potential transformation products for a given compound (Bijlsma et al., 2019), other studies identify transformation products according to the specific fragments (Hernández et al., 2015; Negreira et al., 2017) or the Kendrick mass defect (Merel et al., 2017) they share with the native compound. Nonetheless, the identification of a compound based on accurate mass, fragments
28
and retention time remains tentative until a standard can be procured. Therefore, the third challenge with untargeted analysis consists in communicating the confidence for each compound tentatively identified. Currently, a scale containing five confidence levels based on specific HRMS criteria has been proposed (Schymanski et al., 2014) and becomes commonly used even though periodic revisions might be required in order to incorporate constant progress in analytical science.
ro of
5.3.3. Development of alternative to mass spectrometry The development of alternative to mass spectrometry for the analysis of wastewater contamination can be observed in recent publications (Korshin et al., 2018; Park et al., 2017b;
-p
Sgroi et al., 2018a; Ziska et al., 2016). The aim is to enable on-site measurement in order to obtain simpler, near real-time and more affordable results. Instead of detecting specific
re
compounds, the approach consists in measuring bulk parameters of water contamination such
lP
as UV absorbance and fluorescence in order to estimate the occurrence of some pollutants. For instance, it is now well established that an excitation-emission matrix obtained from fluorescence measurement can be divided into several areas that characterize the presence of
na
compounds like proteins, fulvic acid, humic acid and soluble microbial by-products (Chen et al., 2003; Merel et al., 2015a). In particular, the measurement of bulk parameters is particularly
ur
useful when monitoring the efficacy of wastewater treatment. Indeed, several studies were able
Jo
to use fluorescence and UV absorbance to characterize the breakthrough of contaminants from activated carbon filters (Anumol et al., 2015a; Sgroi et al., 2018a; Ziska et al., 2016). In addition, using the attenuation of fluorescence during full scale wastewater treatment was also shown to be a successful surrogate to assess the removal of emerging contaminants (Huang et al., 2019; Park et al., 2017b; Sgroi et al., 2017a). Consequently, developing the continuous measurement of fluorescence and UV absorbance directly at the wastewater treatment plant for
29
real-time monitoring of water composition would allow designing “smart treatment plants” able to detect any potential failure or decreased efficiency without delay, triggering the automatic adjustment of the treatment (increase of reagent dose) and alerting the operator in charge. Such application of fluorescence and UV absorbance measurement would require further research but shows particular significance in the context of water reuse (Yu et al., 2015) and could be extended to assess potential contamination of surface water (Sgroi et al., 2017b).
ro of
5.3.4. Toxicity assessment The potential toxicity of wastewater effluent has always been and remains a major public concern, particularly when trying to reduce the environmental impact of wastewater
-p
discharge or implementing water reuse strategies. With the changes in society and the constant progress in science, the approach to toxicity assessment permanently evolves in order to face
re
new challenges. A first evolution in toxicity assessment is the shift from in-vivo methods to in-
lP
vitro methods that are not only more specific and more sensitive but also more acceptable from the current ethical perspective. However, while in-vivo methods could assess the overall toxicity of a sample for a complex organism, specific in-vitro methods assess the toxicity of wastewater
na
effluent with respect to specific biological endpoints. In order to cover several relevant endpoints, a single sample requires evaluation using numerous in-vitro assays (Escher et al.,
ur
2014), therefore increasing the need for techniques allowing high throughput.
Jo
A second evolution in toxicity assessment is the growing synergy with the chemical characterization of wastewater samples. Initially, bioassays were often used to complement mass spectrometry results by characterizing individually the biological relevance of new contaminants or transformation products. In recent years, the opposite approach has also been applied with bioassays used to monitor the overall biological activity of complex mixtures like wastewater samples and mass spectrometry used as a supporting tool in order to identify the
30
compounds responsible for a positive biological response (Jia et al., 2016; König et al., 2017; Leusch et al., 2014; Neale et al., 2017). For instance, this approach allowed proving that the glucocorticoid activity in treated wastewater was entirely due to the remaining occurrence of several known synthetic glucocorticoid compounds (Jia et al., 2016). Similarly, another study showed that endocrine disruption due to wastewater discharge was in agreement with concentrations of detected hormones (König et al., 2017). However, when monitoring other parameters such as the xenobiotic metabolism and the adaptive stress response, the chemicals
ro of
detected could explain only a limited fraction of the observed effects (König et al., 2017; Neale et al., 2017), corroborating the importance of the dual chemical and toxicological characterization of wastewater.
-p
Finally, besides considering the toxicity of mixtures instead of individual compounds, another challenge in toxicity assessment is to consider the effect of chronic exposure in addition
re
to acute toxicity. This is particularly relevant in order to assess potential effects on aquatic
lP
organisms exposed continuously to the chemicals discharged by wastewater treatment plants as well as on humans who might be exposed for years when implementing water reuse strategies. However, nowadays data remain scarce when it comes to the chronic effect of chemicals and
na
mixture of chemicals and future research should aim at filling this gap.
ur
6. Paradigm shifts
Jo
After several decades of constant technological and population growth resulting in the ever increasing demand in energy and in all kinds of natural resources (water, nutrients…), there is now a global awareness that these natural resources are limited since the negative consequences of their past/current overexploitation are becoming more and more palpable. Therefore, in an attempt to limit the human footprint on the Earth, a circular economy is being developed worldwide. Overall, the circular economy aims at avoiding as much as possible the
31
constant extraction of natural resources leading to waste production and disposal (also known as the chain: take, make, use, dispose and pollute) by favoring the full valorization of any residual (also known as the cycle: make, use, reuse, remake and recycle). This concept of circular economy together with social awareness and environmental issues have led to several paradigm shifts in wastewater management.
6.1. Water reuse
ro of
The world´s population has been rapidly increasing, particularly in urban areas. For instance, only around 1 billion people (30% of the population) lived in urban areas in 1950 but it steadily increased until reaching over 4 billion people (55% of the population) in 2018. In
-p
fact, 68% of the world´s population is projected to be urban in 2050 (United Nations, 2018). In addition, the increase of extreme droughts due to climate change will worsen existing troubles
re
to satisfy water demand in growing urban areas (Pedrero et al., 2010). The lack of water has
lP
been avoided with traditional models based on increasing the resources available through dams or artificial canals like in Arizona (Chowdhury et al., 2013). However, these alternatives tend to be insufficient, costly and environmentally unsustainable. Conversely, reusing adequately
na
treated wastewater (water reuse) could ensure the supply and regular distribution of water to the population (Fig. 5). The quality of treated wastewater will determine if it can be classified
ur
as non-potable or potable and therefore the potential application of reclaimed water. According
Jo
to the literature (Bixio et al., 2008; Michael-Kordatou et al., 2015), non-potable water reuse can be grouped into four categories based on its application: i) agricultural irrigation; ii) industrial activities such as cooling; iii) urban and environmental uses (including recreational use and aquifer recharge), and iv) the combination of all activities mentioned previously. Using reclaimed water for agricultural irrigation is a common practice worldwide. Such water reuse requires more specific treatment to attenuate the contaminants described previously and limit
32
the exposure for the population and the environment. In particular, there is a need to accurately characterize the water composition in heavy metals, pharmaceuticals, pesticides and transformation products (Le Roux et al., 2017; Qadir et al., 2010; Singh et al., 2010) to assess how those components can be taken up by plants and if they can be transferred to fruits and vegetables. Potable water reuse can be classified into “direct” and “indirect” (Fig. 5) respectively if water is consumed by the population directly after treatment (known as pipe to pipe), or after
ro of
using an environmental buffer like in the case of aquifer recharge (Gerrity et al., 2013; US EPA, 2012). Direct potable reuse (DPR) is defined as purified water which is directly discharged into a municipal water supply system (Leverenz et al., 2011). The first DPR scheme was established
-p
in Windhoek (Namibia) and dates back to 1968 but only an handful of plants have been built since then, including those in Cloudcroft (New Mexico, USA) operating since 2007, Western
re
Cape (South Africa) operating since 2010, and Big Spring (Texas, USA) operating since 2014
lP
(Warsinger et al., 2018). Despite the implementation of advanced wastewater treatment and monitoring to ensure that water quality requirements are fulfilled, direct potable reuse implies direct human exposure and therefore a high level of public concerns. One concern is the
na
exposure to some well-known wastewater contaminants such as pharmaceuticals, personal care products or artificial sweetener (acesulfame and sucralose among others) which were not fully
ur
removed during wastewater treatment (Bottoni et al., 2010; Dias and Petit, 2015; Malchi et al.,
Jo
2014; Richardson and Ternes, 2018). Indeed, little is known regarding how human health may be affected due to the chronic exposure to low doses and to a mixture of components (potential antagonism, addition or synergistic effect). Another concern is the fraction of water composition that is not known (unknown molecules or biological agents) and how advanced treatments can protect consumer’s health from that perspective. Finally, a major concern is the very short time available to detect any potential treatment failure and prevent water
33
consumption. Due to this, most country require indirect potable water reuse with an environmental buffer. This might be implemented as aquifer recharge or discharge in rivers with increased residence time through damns (Michael-Kordatou et al., 2015). The aim is to delay human exposure in order to take corrective measure and avoid health issue in case of treatment failure. Nowadays, in order to develop potable water reuse, many studies are carried out to improve treatment technology but also public acceptance as described in subsequent
ro of
sections.
6.2. Wastewater-based epidemiology
Traditionally, many organic compounds are contained in municipal wastewater
-p
including pharmaceuticals, personal care products (PPCPs) and illicit drugs (Carballa et al., 2004; Ort et al., 2010). However, the occurrence of these substances and their metabolites
re
reflects human habits and lifestyle, providing information about both the exposure to specific
lP
chemicals and the prevalence of certain diseases (Castiglioni et al., 2015; Kasprzyk-Hordern et al., 2014; Thomas and Reid, 2011). The advanced analysis of wastewater in order to assess the exposure and health status of a population (Fig. 5) is referred to as wastewater-based
na
epidemiology (WBE). Over the last decades, this approach has increasingly focused on the detection of illicit drugs in order to estimate their consumption at the population level
ur
(Daughton, 2001; Daughton, 2011; McCall et al., 2016). In addition, the geographic and
Jo
temporal analysis of drug residuals matched with the related population according to age, economic level or spatial distribution can help understanding and discriminating the different use of drugs. For instance, some studies revealed an increase in the use of cocaine and 3,4methylenedioxymethamphetamine (MDMA) for recreational purposes during the weekends while for methadone and 3,4-methylenedioxypyrovalerone (MDPV) there were no variations patterns depending on the day of the week (Kankaanpää et al., 2014; Ort et al., 2014).
34
Similarly, WBE also includes the detection of biomarkers which can quantify the health status of the population (Thomas and Reid, 2011). The biomarkers can be grouped into two categories: i) biomarkers of exposure; ii) biomarkers of effect. On the first hand, biomarkers of exposure are chemicals excreted by human and resulting from the detoxification process after exposure to xenobiotics such as pesticides or illicit drugs mentioned previously. Knowing their excretion rate and their concentration in wastewater, these biomarkers allow to back calculate the exposure of the population. On the other hand, biomarkers of effect are molecules secreted
ro of
by the body when developing a disease. For instance, isoprostanes would reflect the level of oxidative stress in the population while other biomarkers of effect could reflect the incidence of diabetes or cancer. However, compounds of interest are usually at low level in very complex
-p
matrices and extensive sample preparation is necessary before their accurate quantification. In addition, in order to obtain meaningful data, the stability of biomarkers in wastewater should
re
be determined thoroughly in order to avoid any underestimation.
lP
Overall, WBE allows obtaining information about the health status of a complete population instead of analyzing urine samples of specific individuals. However, WBE can be conducted with more or less resolution according to the sampling area. For instance, collecting
na
samples at the entrance of the wastewater treatment plant will average the entire city but collecting samples at different places in the sewer network would allow isolating specific
ur
districts or neighborhoods in order to carry out a geographical and socio-demographic
Jo
comparison. The results obtained can be compared with population surveys or even used to create estimates where such data does not exist, for instance regarding the consumption of illicit drugs (Castiglioni et al., 2015; Ort et al., 2014; Senta et al., 2015; Zuccato et al., 2008). WBE carried out on well characterized substances (known excretion rate, stability…) in accurately defined sewer systems (knowledge of total population concerned, fraction of households vs offices…) and with robust analytical methods (suitable sample preparation, accurate
35
quantification with internal standards…) might provide better estimates than anonymous surveys in which candidates might not always disclose the complete information. Moreover, WBE is also a non-invasive approach in comparison to collection of blood or urine samples from individuals, and there is no need to obtain personal consent. Only the consent of the entity in charge of wastewater collection and treatment is necessary but this is also problematic since municipalities could be prone to refuse wastewater sampling in order to avoid bad press. Despite this latter limitation, WBE could help to better design prevention campaigns by
ro of
focusing on the most relevant geographic areas and population groups. This could be an important tool in addition to conventional socio-epidemiological studies (Castiglioni et al.,
-p
2015; Thomas and Reid, 2011; van Nuijs et al., 2011).
6.3. Recovery of valuable components
re
Traditionally, wastewater treatment has been focusing on improving water quality by
lP
removing components like pathogens or micro-pollutants that can be a threat for the environment and human health. However, with the concept of circular economy, a major paradigm shift consists in turning wastewater components such as nutrients which were
na
historically considered as pollutants to be removed into valuable components to recover. For instance, nitrogen, ammonium, phosphorus and potassium occurring in wastewater might be
ur
valuable since they can be used as fertilizers for agriculture (Randall and Naidoo, 2018; Simha
Jo
and Ganesapillai, 2017). On its own, this sole paradigm shift provides a new resource of nutrients while avoiding the release of chemicals responsible for eutrophication of natural waters, the energy consumption and the emission of greenhouse gases traditionally associated with the biological nutrient removal. Similarly, rare-earth elements and metals such as Y, La, Ce, Pr can have industrial applications (Peccia and Westerhoff, 2015).
36
Therefore, recent research has been focusing on developing cost-efficient and implementable technologies to concentrate, recover and recycle (Fig. 5) those valuable components from wastewater (Ganesapillai et al., 2016). For instance, several recovery processes can be used for P and N, including adsorption, electrodialysis or struvite precipitation, although only few can produce a fertilizer with minimal post-processing (Perera et al., 2019). Likewise, as progress in science and technology rapidly increments the use of rare-earth elements and precious metals in several electronics and communication applications (He and
ro of
Kappler, 2017), their amount in wastewater becomes increasingly valuable. Therefore, harvesting metals (Ag, Au, Ni, Cu, Zn, Pb or Cd), rare-earth elements and other less-studied elements, such as Nb, Ta, Ga, Ge, In, Tl, and Te (Vriens et al., 2017) prevents the negative
-p
impacts for human and the environment but also provides a new source to obtain these materials at lower cost. For instance, while wastewater production in the U.S. is decreasing due to water
re
conservation measures, metal concentration in related biosolids remains stable and may
lP
increase in the future, which would convert biosolids into a more economical and sustainable source of valuable metals (Westerhoff et al., 2015). Overall, wastewater treatment should not only focus on achieving water reuse but also
na
on harvesting components to be recycled as raw material for different purposes (Puyol et al., 2017). This concept is known as cradle-to-cradle cycle (McDonough and Braungart, 2002), and
ur
encourages the manufacture of products that have a better environmental quality or value
Jo
(upcycling or creative reuse).
6.4. Lowering the carbon footprint Although it is often neglected in the non-expert community, the activity of wastewater treatment plant can be examined in term of carbon footprint since every treatment step requires energy (Mannina et al., 2019). For instance, the traditional biological removal of nutrients
37
requires energy for aeration, and so does the treatment of sludge which relies on drying before exportation by trucks. Therefore, another paradigm shift in wastewater treatment is to lower the carbon footprint through the reduction of energy consumption. In order to reduce the consumption of energy, several strategies can be employed. For instance, wastewater treatment plant and incineration plants can be integrated (Montorsi et al., 2018; Nakatsuka et al., 2020) in order to achieve the self-production of up to 25% of the electric energy required for the operation of the facilities while decreasing the dramatically the final amount of residues sent to
ro of
landfill. Another approach consists in installing treatment processes that can achieve similar removal capacity with lower energy demand, for instance using the Anammox process instead of the conventional biological removal of nutrients (Larsen, 2015). However, in the case of
-p
nutrient removal, the benefit from lower energy consumption should not be overcome by an increase in the inherent generation of greenhouse gases (Fenu et al., 2019). Indeed, the emission
re
of nitrous oxide (N2O) during nutrient removal contributes significantly to the total carbon
lP
footprint of wastewater treatment plants (Zaborowska et al., 2019). Therefore, in addition to developing more energy-efficient treatment and processes limiting the emission of greenhouse gases, numerous studies are also carried out to monitor, model and assess the carbon footprint
na
of wastewater treatment plants (Gruber et al., 2020; Mannina et al., 2016).
ur
6.5. Production of valuable goods
Jo
Wastewater treatment is rapidly evolving from simply ensuring public sanitation and environmental protection to allowing water reuse while harvesting valuable components. However, in order to optimize the benefit of wastewater, another approach consists in developing treatment technologies that will not only attenuate contaminants but also produce valuable goods (Fig. 5). For instance, wastewater can contribute to the production of biofuels which have the potential to replace a part of fossil fuels (Lin et al., 2012). Anaerobic digestion
38
is the typical process to achieve the biological production of energy and biofuel like methane from organic products (Batstone and Virdis, 2014). However, several technologies are currently under development to convert organic matter to bioenergy (Puyol et al., 2017). Thereby, an upgrade of conventional wastewater treatment could achieve an additional attenuation of contaminants while producing valuable material. For instance, wastewater could be used to grow certain types of algae which will extract and fix some metals and nutrients like phosphorous and nitrogen (Chen et al., 2015; de-Bashan and Bashan, 2010). The algal biomass
6.6. Segregation at source and decentralized treatment
ro of
produced might then be used for biofuel production.
-p
The implementation of collective wastewater treatment in urban and semi urban areas is undoubtedly recognized as a major step in wastewater management and environmental
re
protection (Roccaro et al., 2014). Indeed, when the aim is to attenuate specific contaminants,
lP
small facilities designed to treat wastewater at the households scale tend to achieve lower removal rate and it is more efficient to collect and convey all types of wastewater together to large centralized facilities with treatment processes specifically designed to achieve legal
na
requirements before discharge. However, with the concept of circular economy, a potentially upcoming paradigm shift consists in promoting decentralized treatment that tend to be more
ur
sustainable than centralized systems (Diaz-Elsayed et al., 2019; Sgroi et al., 2018b) while
Jo
offering a lower cost (Jung et al., 2018). This approach often adopted in developing countries can also be implemented in industrialized countries through a major change in the modus vivendi (Tchnobanoglous and Leverenz, 2013). In addition, with the circular economy the aim of wastewater treatment is no longer solely to remove contaminants but to recover valuable components as mentioned previously. In this context, segregation at source followed by immediate decentralized treatment would likely be more beneficial. For instance, when
39
considering nutrients cycle, those nutrients which must not be discharged into the environment but recovered from wastewater largely originate from urine excretion. Therefore, collecting urine together with water resulting from shower, washing machine and rain water to a centralized treatment plant result in a severe dilution of nutrients which will difficult their recovery. On the contrary, segregation of urine at the household scale would prevent issues related to dilution and allow developing efficient decentralized nutrient recovery units (Almeida et al., 2019). For instance, a complete nutrient recovery from source-separated urine could be
ro of
achieved by nitrification and distillation (Udert and Wächter, 2012). In fact, a study showed that a wide range of technical options are available for the on-site collection and treatment of urine but none of them was yet able to fulfill all purposes of hygienisation, volume reduction,
-p
stabilization recovery of nutrients and attenuation of trace organic contaminants (Maurer et al., 2006). Consequently, even though it is currently not well developed (Sgroi et al., 2018b),
re
segregation of organic waste, feces, urine, graywater and rainwater at source for decentralized
lP
valorization treatment might be an upcoming trend.
na
7. Current social challenges 7.1. Access to basic sanitation
ur
In the last census of 2018 the world population was estimated to 7.7 billion people.
Jo
However, only approximately 5.4 billion people have access to basic sanitation defined as facilities such as pit latrine, composting toilets and amenities connected to piped sewer or septic tanks that are not shared with other households. The general assembly of the United Nations, through the resolution 64/292 of 2010 (United Nations, 2010), recognized sanitation as a human right that is essential to prevent mortal diseases but 2.3 billion people still live without access to a basic sanitation service (UNICEF and WHO, 2017).
40
Despite the high number of people without access to basic sanitation, the worldwide status has steadily improved over the last decades. In fact, the world population with access to basic sanitation increased from 58% in the year 2000 to 68% in the year 2015 (Fig. 6). Although, the trend might differ according to the country, for instance with France showing a status quo and limited room for improvement, Laos showing dramatic improvement and the Gambia showing a constant worsening (Fig. 6). For the year 2015, up to 148 countries could provide basic sanitation to more than 80% of their population, whereas only 16 countries ensured basic
ro of
sanitation to less than 20% of their population (Fig. 7). In particular, some countries such as Ethiopia, Madagascar and South Sudan provided basic sanitation to less than 10% of their population. Overall, access to basic sanitation improves with the human development index and
-p
countries of highest concern are mainly located in Africa and Asia (Fig. 6 and Fig. 7).
In the next decades, projections indicate a population growth worldwide, so improving
re
and maintaining the requirement of sanitation services will imply a large investment for the
lP
countries. Nowadays, in the countries where the access to basic sanitation is mainly limited by the high cost of sanitation facilities, low-cost solutions based on ecological sanitation that are safe for health and the environment should be engineered. This involves for instance the
na
conservation of water (dry sanitation), the treatment of human excreta to prevent environmental contamination and disease transmission while recycling nutrients for agriculture or home
Jo
ur
gardens among others (Moe and Rheingans, 2006).
7.2. Legal aspects Water resources are often shared between riparian countries. Therefore, many
hydropolitical tensions and conflicts around the world might arise from water scarcity and water quality. Indeed, with climate change, arid and semi-arid regions of the world already face difficulties to meet the rapidly increasing water demand for more than a decade (Swain, 2001).
41
A recent study (De Stefano et al., 2017) reveals that very high risk of potential hydropolitical tension exists for instance between China and Vietnam (Bei Jiang/Hsi basin), Lesotho and South Africa (Thukela basin), Colombia and Ecuador (Mira basin) and even between countries within the European Union. In order to lower the risk of hydropolitical tension and since wastewater can spread diseases all along the river basins from upstream towns to the mouth (Salgot and Folch, 2018), the disposal of wastewater in the environment and water reuse should be regulated through
ro of
national and international legislation in the case of watershed shared by different countries. In United States, The Federal Water Pollution Control Act (known as Clean Water Act) of 1948 revised in 1972 (US Congress, 1972) was the first enacted law to address water pollution and
-p
included funding to improve wastewater treatment. In 1978, the United States and Canada agreed to reduce certain toxic pollutants in the Great Lakes. In 1980, the U.S. Environmental
re
Protection Agency released guidelines to assist municipalities in planning for the
lP
implementation of programs on the non-potable reuse of municipal wastewater (US EPA, 1980). Similarly, in 1991, the European Union adopted the Directive 91/271/EEC (under revision since 2017) which specifies the requirements concerning the collection, treatment and
na
discharge of urban wastewater and certain industrial sectors (EEC, 1991). This Directive also considers the eventuality that wastewater discharge from a member State would adversely
ur
contaminate waters from another member State. However, in 2014, while 18 countries fully
Jo
complied with the requirements related to wastewater collection (article 3), 7 countries complied with the obligation of secondary treatment (article 5) and only 4 countries complied with the necessity of more stringent treatment for discharge in sensitive areas (article 5). Overall, only Austria, Germany and the Netherlands fully complied with all requirements (European Commission, 2017). Failure to comply might result in financial consequences as in the case of Spain condemned by the European Court of Justice to pay 12 M€ to the European
42
Commission for 17 urban agglomerations of more than 15.000 inhabitants without adequate wastewater collection and treatment systems (European Court of Justice, 2018). In parallel, the European Union also strengthened the engagement to preserve water quality through the Water Framework Directive adopted in the year 2000 (European Parliament, 2000) and now completed by guidelines on Integrating Water Reuse into Water Planning and Management, taking into account underlying environmental and socio-economic benefits. Finally, since 2017, a proposal for a Regulation on minimum requirements for water reuse within the European
ro of
Union has been drafted (Council of the European Union, 2019). This proposal covers the obligations regarding reclaimed water permit, risk management, compliance check, information to the public, cooperation between states and reclaimed water quality requirements which
-p
include maximum values for E. coli number, biological oxygen demand and turbidity. However, a critical evaluation of the regulation proposal highlighted that it did not sufficiently address
re
some key points of interest such as the contaminants of emerging concern as well as the
lP
antibiotic resistance spread via the treated effluent of wastewater treatment plants (Rizzo et al., 2018). Moreover, it should be noticed that the scope of such regulation refers to agricultural irrigation without considering potential potable water reuse.
na
Despite the increasing efforts to implement global regulations aiming at preserving water quality by imposing standards for wastewater treatment, new paradigm shifts presented
ur
previously might bring new legal challenges and concerns. For instance, in countries where
Jo
water is not considered as public domain, cities implementing extensive water reuse would dramatically decrease their discharge of wastewater effluent with the potential to impair the water resources and therefore the economy of downstream cities. Similarly, as wastewater becomes a resource from which to extract valuable content (nutrients, metals, energy, and information related to public health), future regulation might need to address more specifically the right to access and use wastewater.
43
7.3. Social acceptance The concept of water reuse presented previously is overall well understood in the context of increasing awareness with respect to water poverty and growing water demand. However, the implementation of water reuse as a drinking water source is less likely to be accepted by society in comparison to non-potable purposes such as irrigation of parks (Rodriguez et al., 2009). Negative emotional reactions gathered under the term “yuck factor”
ro of
are important obstacles to social acceptance which reflect the visceral disgust and fear associated with recycled wastewater (Smith et al., 2018). Overall, the variables explaining the yuck factor include trust, subjective social norms, perceived control and emotional aversion
-p
(Wester et al., 2015). However, reducing the yuck factor in order to increase the acceptance of water reuse is possible, for instance using suitable vocabulary (Rock et al., 2012). Indeed, an
re
experiment showed a significant improvement in public perception when the term “recycled water” was used instead of “treated wastewater” (Menegaki et al., 2009) or when “purified
lP
water” was used instead of “effluent” (Furlong et al., 2019). Similarly, the case of Singapore which strongly avoids using the term “wastewater” and called recycled water “NEWater” is
na
usually given as an example of water reuse with a large (74%) social acceptance (Lee and Tan, 2016; Timm and Deal, 2018). In addition, communication and public dialogue in order to build
ur
and maintain trust (Rodriguez et al., 2009) while educating the population around treatment
Jo
technologies and safety (Stenekes et al., 2006) will further strengthen social acceptance of water reuse to augment drinking water resources. Therefore, water reuse shows important advantages for the environment and to satisfy human requirements but future research should not only focus on improving treatment technologies but also include more social sciences and outreach in order to convince the public. More particularly, public institutions should involve stakeholders and
44
include public participation in decision-making while promoting active communication programs on water reuse. Similarly to water reuse, it should be noticed that public acceptance is a key factor for most of the previously mentioned paradigm shifts. Indeed, after decades of communication aiming at promoting centralized wastewater treatment reinforcing the idea of the necessity to send away wastewater effluents, the implementation of urine separation at source for better recovery of nutrient meets social resistance. As for water reuse, reluctance is mostly due to
ro of
concerns regarding hygiene and safety, as well as the necessity to adapt housing buildings.
8. Conclusion
-p
The bibliometric assessment of wastewater research indicates that the amount of publication has been growing exponentially over the last decades. The examination of the
Identifying the sources of wastewater. While households, hospitals and
lP
re
literature reveals multiple technical challenges:
industries are the main producers of wastewater, new activities like hydraulic
na
fracturing are now emerging or growing and generate large volumes of wastewater which need to be accurately characterized and treated. In addition,
ur
unpredictable activities such as that of fire departments are also often overlooked even though they can generate a large amount of wastewater with specific
Jo
contaminants.
Assessing the composition of wastewater. Despite the tremendous progress in analytical science, wastewater analysis often consists in quantifying known chemicals. However, with the growing application of high resolution mass spectrometry over the last decade, the identification of new contaminants and their transformation products has become a major research focus. 45
Removing trace contaminants. Modern societies often generate wastewater containing new contaminants that conventional treatment were not designed to remove. While recent research focuses on the development of advanced oxidation processes or retention processes to remove such contaminants, another trend consists in developing treatments also able to harvest or generate valuable goods from wastewater.
The examination of the literature also evidenced several paradigm shifts related to
ro of
wastewater: Water reuse. With the growing water demand and the growing hydric stress worldwide, wastewater effluents progressively cease to be a substance that needs
-p
to be disposed to become a valuable water resource that can be used for multiple purposes including irrigation or even the production of drinking water. Wastewater based epidemiology. Collecting both environmental contaminants
re
lP
and urinary metabolites, wastewater is a mirror of the population from which many information can be extracted in order to assess the exposure to certain
na
chemicals or even the prevalence of some diseases. Recovery and production of valuable goods. More than removing contaminants from wastewater, new treatment options tend to harvest valuable components
ur
such as rare-earth elements and precious metals in order reuse them. In addition,
Jo
new treatment options also intend to produce valuable goods from wastewater, for instance by growing certain algae species that will remove nutrients and which could be used subsequently for the production of biofuel.
The multiple challenges and paradigm shifts revealed by the peer-reviewed literature also imply some social impacts which are yet poorly investigated. For instances, while technological progress allows converting wastewater to high quality water suitable for human
46
consumption, heavy efforts in social research and outreach are required to ensure public acceptance. Moreover, even though paradigm shifts such as water reuse and wastewater based epidemiology are increasingly promoted and gain in popularity due to their undoubtable contribution to a more sustainable development of communities, it must be noticed that the peer-reviewed literature has not considered their potential drawbacks on a global level. Indeed, with the large application of water reuse the discharge of wastewater might strongly decrease, which could affect the ecosystem of receiving waters but also the economy of downstream
ro of
cities. For instance, a scenario where several cities upstream reduce their discharge should be simulated in order to assess the subsequent restriction in water resources for downstream cities which might progressively struggle to meet the water demand and therefore have their growth
-p
(population and industries) impaired. In addition, this scenario should also evaluate the ecological impact of a widespread water reuse considering that the fraction of wastewater still
re
discharged (from cities not implementing water reuse, or from households not connected to the
lP
sewer network) might have a lower dilution factor that could induce an increased concentration of contaminants in the receiving water. Finally, considering wastewater as something valuable will imply competition and potential conflict to access it. Therefore, legislation should be
na
drafted at the local and international level and further research is required in order to assess and anticipate the social outcome of progress in wastewater management.
ur
Credit Author Statement
Jo
María C. Villarín: Data Curation, Writing - Original Draft, Writing - Review & Editing, Visualization, Project administration Sylvain Merel: Conceptualization, Data Curation, Writing - Original Draft, Writing - Review & Editing, Supervision
Conflict of interest
47
The authors declare no conflict of interest. The authors declare that they have no known competing financial interests or personal relationships that could have influenced the work reported in this paper.
Acknowledgements María C. Villarín is grateful to Åse Åtland from the Norwegian Institute of Water Research
ro of
(NIVA) for allowing her to join the group located in Bergen as visiting scientist.
References
Jo
ur
na
lP
re
-p
Adeyemo, F.E., Singh, G., Reddy, P., Bux, F., Stenstrom, T.A., 2019. Efficiency of chlorine and UV in the inactivation of Cryptosporidium and Giardia in wastewater. Plos One 14. Ahrens, L., 2011. Polyfluoroalkyl compounds in the aquatic environment: a review of their occurrence and fate. Journal of Environmental Monitoring 13, 20-31. Ajonina, C., Buzie, C., Rubiandini, R.H., Otterpohl, R., 2015. Microbial pathogens in Wastewater Treatment Plants (WWTP) in Hamburg. Journal of Toxicology and Environmental Health - Part A: Current Issues 78, 381-387. Al-Gheethi, A., Noman, E., David, B.J., Mohamed, R., Abdullah, A.H., Nagapan, S., Mohd, A.H., 2018. A review of potential factors contributing to epidemic cholera in Yemen. Journal of Water and Health 16, 667-680. Almeida, J.A.S., Azevedo, A.L., Brett, M., Tadeu, A., Silva-Afonso, A., Costa, A., Rufo, E., Além, S., 2019. Urine recovery at the building level. Building and Environment 156, 110-116. Amor, C., De Torres-Socias, E., Peres, J.A., Maldonado, M.I., Oller, I., Malato, S., Lucas, M.S., 2015. Mature landfill leachate treatment by coagulation/flocculation combined with Fenton and solar photoFenton processes. Journal of Hazardous Materials 286, 261-268. Anumol, T., Merel, S., Clarke, B.O., Snyder, S.A., 2013. Ultra high performance liquid chromatography tandem mass spectrometry for rapid analysis of trace organic contaminants in water. Chemistry Central Journal 7, 104. Anumol, T., Sgroi, M., Park, M., Roccaro, P., Snyder, S.A., 2015a. Predicting trace organic compound breakthrough in granular activated carbon using fluorescence and UV absorbance as surrogates. Water Research 76, 76-87. Anumol, T., Snyder, S.A., 2015. Rapid analysis of trace organic compounds in water by automated online solid-phase extraction coupled to liquid chromatography–tandem mass spectrometry. Talanta 132, 77-86. Anumol, T., Wu, S., Marques dos Santos, M., Daniels, K.D., Snyder, S.A., 2015b. Rapid direct injection LC-MS/MS method for analysis of prioritized indicator compounds in wastewater effluent. Environmental Science: Water Research & Technology 1, 632-643. Asghar, A., Raman, A.A.A., Daud, W.M.A.W., 2015. Advanced oxidation processes for in-situ production of hydrogen peroxide/hydroxyl radical for textile wastewater treatment: a review. Journal of Cleaner Production 87, 826-838.
48
Jo
ur
na
lP
re
-p
ro of
Ashrafi, O., Yerushalmi, L., Haghighat, F., 2015. Wastewater treatment in the pulp-and-paper industry: A review of treatment processes and the associated greenhouse gas emission. Journal of Environmental Management 158, 146-157. Bailey, E.S., Casanova, L.M., Simmons, O.D., Sobsey, M.D., 2018. Tertiary treatment and dual disinfection to improve microbial quality of reclaimed water for potable and non-potable reuse: A case study of facilities in North Carolina. Science of The Total Environment 630, 379-388. Batstone, D.J., Virdis, B., 2014. The role of anaerobic digestion in the emerging energy economy. Current Opinion in Biotechnology 27, 142-149. Becouze-Lareure, C., Dembélé, A., Coquery, M., Cren-Olivé, C., Barillon, B., Bertrand-Krajewski, J.L., 2016. Source characterisation and loads of metals and pesticides in urban wet weather discharges. Urban Water Journal 13, 600-617. Bijlsma, L., Berntssen, M.H.G., Merel, S., 2019. A Refined Nontarget Workflow for the Investigation of Metabolites through the Prioritization by in Silico Prediction Tools. Analytical Chemistry 91, 6321-6328. Bilal, M., Asgher, M., Parra-Saldivar, R., Hu, H., Wang, W., Zhang, X., Iqbal, H.M.N., 2017. Immobilized ligninolytic enzymes: An innovative and environmental responsive technology to tackle dye-based industrial pollutants - A review. Science of The Total Environment 576, 646-659. Bixio, D., Thoeye, C., Wintgens, T., Ravazzini, A., Miska, V., Muston, M., Chikurel, H., Aharoni, A., Joksimovic, D., Melin, T., 2008. Water reclamation and reuse: implementation and management issues. Desalination 218, 13-23. Boczkaj, G., Fernandes, A., 2017. Wastewater treatment by means of advanced oxidation processes at basic pH conditions: A review. Chemical Engineering Journal 320, 608-633. Bokare, A.D., Choi, W., 2014. Review of iron-free Fenton-like systems for activating H2O2 in advanced oxidation processes. Journal of Hazardous Materials 275, 121-135. Bollmann, U.E., Tang, C., Eriksson, E., Jönsson, K., Vollertsen, J., Bester, K., 2014. Biocides in urban wastewater treatment plant influent at dry and wet weather: Concentrations, mass flows and possible sources. Water Research 60, 64-74. Bottoni, P., Caroli, S., Caracciolo, A.B., 2010. Pharmaceuticals as priority water contaminants. Toxicological and Environmental Chemistry 92, 549-565. Bourgin, M., Beck, B., Boehler, M., Borowska, E., Fleiner, J., Salhi, E., Teichler, R., von Gunten, U., Siegrist, H., McArdell, C.S., 2018. Evaluation of a full-scale wastewater treatment plant upgraded with ozonation and biological post-treatments: Abatement of micropollutants, formation of transformation products and oxidation by-products. Water Research 129, 486-498. Burkhardt, M., Zuleeg, S., Vonbank, R., Schmid, P., Hean, S., Lamani, X., Bester, K., Boller, M., 2011. Leaching of additives from construction materials to urban storm water runoff. Water Science and Technology 63, 1974-1982. Cai, L., Zhang, T., 2013. Detecting Human Bacterial Pathogens in Wastewater Treatment Plants by a High-Throughput Shotgun Sequencing Technique. Environmental Science & Technology 47, 54335441. Caicedo, C., Rosenwinkel, K.H., Exner, M., Verstraete, W., Suchenwirth, R., Hartemann, P., Nogueira, R., 2019. Legionella occurrence in municipal and industrial wastewater treatment plants and risks of reclaimed wastewater reuse: Review. Water Research 149, 21-34. Campos-Mañas, M.C., Plaza-Bolaños, P., Martínez-Piernas, A.B., Sánchez-Pérez, J.A., Agüera, A., 2019. Determination of pesticide levels in wastewater from an agro-food industry: Target, suspect and transformation product analysis. Chemosphere 232, 152-163. Cao, Y., van Loosdrecht, M.C.M., Daigger, G.T., 2017. Mainstream partial nitritation-anammox in municipal wastewater treatment: status, bottlenecks, and further studies. Applied Microbiology and Biotechnology 101, 1365-1383. Carballa, M., Omil, F., Lema, J.M., Llompart, M., García-Jares, C., Rodríguez, I., Gómez, M., Ternes, T., 2004. Behavior of pharmaceuticals, cosmetics and hormones in a sewage treatment plant. Water Research 38, 2918-2926. Carr, S.A., Liu, J., Tesoro, A.G., 2016. Transport and fate of microplastic particles in wastewater treatment plants. Water Research 91, 174-182. 49
Jo
ur
na
lP
re
-p
ro of
Castiglioni, S., Senta, I., Borsotti, A., Davoli, E., Zuccato, E., 2015. A novel approach for monitoring tobacco use in local communities by wastewater analysis. Tobacco Control 24, 38-42. Chang, M., 2015. Reducing microplastics from facial exfoliating cleansers in wastewater through treatment versus consumer product decisions. Marine Pollution Bulletin 101, 330-333. Chekli, L., Phuntsho, S., Kim, J.E., Kim, J., Choi, J.Y., Choi, J.-S., Kim, S., Kim, J.H., Hong, S., Sohn, J., Shon, H.K., 2016. A comprehensive review of hybrid forward osmosis systems: Performance, applications and future prospects. Journal of Membrane Science 497, 430-449. Chen, G., Zhao, L., Qi, Y., 2015. Enhancing the productivity of microalgae cultivated in wastewater toward biofuel production: A critical review. Applied Energy 137, 282-291. Chen, W., Westerhoff, P., Leenheer, J.A., Booksh, K., 2003. Fluorescence Excitation−Emission Matrix Regional Integration to Quantify Spectra for Dissolved Organic Matter. Environmental Science & Technology 37, 5701-5710. Chowdhury, F., Lant, C., Dziegielewski, B., 2013. A century of water supply expansion for ten U.S. cities. Applied Geography 45, 58-76. Chung, K.T., 2016. Azo dyes and human health: A review. Journal of Environmental Science and Health Part C-Environmental Carcinogenesis & Ecotoxicology Reviews 34, 233-261. Cieslik, B.M., Namiesnik, J., Konieczka, P., 2015. Review of sewage sludge management: standards, regulations and analytical methods. Journal of Cleaner Production 90, 1-15. Clarke, B.O., Anumol, T., Barlaz, M., Snyder, S.A., 2015. Investigating landfill leachate as a source of trace organic pollutants. Chemosphere 127, 269-275. Council of the European Union, 2019. Interinstitutional File: 2018/0169(COD). Daniels, M.E., Smith, W.A., Jenkins, M.W., 2018. Estimating Cryptosporidium and Giardia disease burdens for children drinking untreated groundwater in a rural population in India. PLOS Neglected Tropical Diseases 12, e0006231. Daughton, C.G., 2001. Illicit Drugs in Municipal Sewage, Pharmaceuticals and Care Products in the Environment. American Chemical Society, pp. 348-364. Daughton, C.G., 2011. Illicit drugs: Contaminants in the environment and utility in forensic epidemiology, Reviews of Environmental Contamination and Toxicology, pp. 59-110. de-Bashan, L.E., Bashan, Y., 2010. Immobilized microalgae for removing pollutants: Review of practical aspects. Bioresource Technology 101, 1611-1627. De Stefano, L., Petersen-Perlman, J.D., Sproles, E.A., Eynard, J., Wolf, A.T., 2017. Assessment of transboundary river basins for potential hydro-political tensions. Global Environmental Change 45, 3546. Desmidt, E., Ghyselbrecht, K., Zhang, Y., Pinoy, L., Van der Bruggen, B., Verstraete, W., Rabaey, K., Meesschaert, B., 2015. Global Phosphorus Scarcity and Full-Scale P-Recovery Techniques: A Review. Critical Reviews in Environmental Science and Technology 45, 336-384. Dias, E.M., Petit, C., 2015. Towards the use of metal-organic frameworks for water reuse: A review of the recent advances in the field of organic pollutants removal and degradation and the next steps in the field. Journal of Materials Chemistry A 3, 22484-22506. Diaz-Elsayed, N., Rezaei, N., Guo, T., Mohebbi, S., Zhang, Q., 2019. Wastewater-based resource recovery technologies across scale: A review. Resources, Conservation and Recycling 145, 94-112. Dris, R., Gasperi, J., Rocher, V., Saad, M., Renault, N., Tassin, B., 2015. Microplastic contamination in an urban area: a case study in Greater Paris. Environmental Chemistry 12, 592-599. Du, R., Cao, S., Li, B., Niu, M., Wang, S., Peng, Y., 2017. Performance and microbial community analysis of a novel DEAMOX based on partial-denitrification and anammox treating ammonia and nitrate wastewaters. Water Research 108, 46-56. EEC, 1991. Council Directive 91 /271 /EEC concerning urban waste water treatment, p. 13. Eftim, S.E., Hong, T., Soller, J., Boehm, A., Warren, I., Ichida, A., Nappier, S.P., 2017. Occurrence of norovirus in raw sewage - A systematic literature review and meta-analysis. Water Research 111, 366374. Escher, B.I., Allinson, M., Altenburger, R., Bain, P.A., Balaguer, P., Busch, W., Crago, J., Denslow, N.D., Dopp, E., Hilscherova, K., Humpage, A.R., Kumar, A., Grimaldi, M., Jayasinghe, B.S., Jarosova, B., Jia, A., 50
Jo
ur
na
lP
re
-p
ro of
Makarov, S., Maruya, K.A., Medvedev, A., Mehinto, A.C., Mendez, J.E., Poulsen, A., Prochazka, E., Richard, J., Schifferli, A., Schlenk, D., Scholz, S., Shiraishi, F., Snyder, S., Su, G., Tang, J.Y.M., Burg, B.v.d., Linden, S.C.v.d., Werner, I., Westerheide, S.D., Wong, C.K.C., Yang, M., Yeung, B.H.Y., Zhang, X., Leusch, F.D.L., 2014. Benchmarking Organic Micropollutants in Wastewater, Recycled Water and Drinking Water with In Vitro Bioassays. Environmental Science & Technology 48, 1940-1956. European Commission, 2017. Ninth Report on the implementation status and the programmes for implementation (as required by article 17) of Council Directive 91/271/EEC concerning urban waste water treatment. European Court of Justice, 2018. European Commission v Kingdom of Spain, Case C-205/17. European Parliament, 2000. Directive 2000/60/EC of the European Parliament and of the Council of 23 October 2000 establishing a framework for Community action in the field of water policy. Eurostat, 2018. Generation and discharge of wastewater in volume. Fane, A.G., Wang, R., Hu, M.X., 2015. Synthetic Membranes for Water Purification: Status and Future. Angewandte Chemie-International Edition 54, 3368-3386. Fenu, A., Smolders, S., De Gussem, K., Weemaes, M., 2019. Conflicting carbon footprint and energy saving in a side-stream Anammox Process. Biochemical Engineering Journal 151, 107336. Furlong, C., Jegatheesan, J., Currell, M., Iyer-Raniga, U., Khan, T., Ball, A.S., 2019. Is the global public willing to drink recycled water? A review for researchers and practitioners. Utilities Policy 56, 53-61. Ganesapillai, M., Simha, P., Gupta, K., Jayan, M., 2016. Nutrient Recovery and Recycling from Human Urine: A Circular Perspective on Sanitation and Food Security, pp. 346-353. Garcia, D., Alcantara, C., Blanco, S., Perez, R., Bolado, S., Munoz, R., 2017. Enhanced carbon, nitrogen and phosphorus removal from domestic wastewater in a novel anoxic-aerobic photobioreactor coupled with biogas upgrading. Chemical Engineering Journal 313, 424-434. Gerrity, D., Pecson, B., Shane Trussell, R., Rhodes Trussell, R., 2013. Potable reuse treatment trains throughout the world. Journal of Water Supply: Research and Technology - AQUA 62, 321-338. Gleick, P.H., 1996. Basic Water Requirements for Human Activities: Meeting Basic Needs. Water International 21, 83-92. Gomes, J., Costa, R., Quinta-Ferreira, R.M., Martins, R.C., 2017. Application of ozonation for pharmaceuticals and personal care products removal from water. Science of The Total Environment 586, 265-283. Grant, S.B., Saphores, J.-D., Feldman, D.L., Hamilton, A.J., Fletcher, T.D., Cook, P.L.M., Stewardson, M., Sanders, B.F., Levin, L.A., Ambrose, R.F., Deletic, A., Brown, R., Jiang, S.C., Rosso, D., Cooper, W.J., Marusic, I., 2012. Taking the “Waste” Out of “Wastewater” for Human Water Security and Ecosystem Sustainability. Science 337, 681-686. Gruber, W., Villez, K., Kipf, M., Wunderlin, P., Siegrist, H., Vogt, L., Joss, A., 2020. N2O emission in fullscale wastewater treatment: Proposing a refined monitoring strategy. Science of The Total Environment 699, 134157. Guaya, D., Valderrama, C., Farran, A., Armijos, C., Luis Cortina, J., 2015. Simultaneous phosphate and ammonium removal from aqueous solution by a hydrated aluminum oxide modified natural zeolite. Chemical Engineering Journal 271, 204-213. Hai Nguyen, T., You, S.-J., Hosseini-Bandegharaei, A., Chao, H.-P., 2017. Mistakes and inconsistencies regarding adsorption of contaminants from aqueous solutions: A critical review. Water Research 120, 88-116. Harkness, J.S., Dwyer, G.S., Warner, N.R., Parker, K.M., Mitch, W.A., Vengosh, A., 2015. Iodide, Bromide, and Ammonium in Hydraulic Fracturing and Oil and Gas Wastewaters: Environmental Implications. Environmental Science & Technology 49, 1955-1963. He, J., Kappler, A., 2017. Recovery of precious metals from waste streams. Microbial Biotechnology 10, 1194-1198. Hellmér, M., Paxéus, N., Magnius, L., Enache, L., Arnholm, B., Johansson, A., Bergström, T., Norder, H., 2014. Detection of Pathogenic Viruses in Sewage Provided Early Warnings of Hepatitis A Virus and Norovirus Outbreaks. Applied and Environmental Microbiology 80, 6771. 51
Jo
ur
na
lP
re
-p
ro of
Hernández, F., Ibáñez, M., Botero-Coy, A.-M., Bade, R., Bustos-López, M.C., Rincón, J., Moncayo, A., Bijlsma, L., 2015. LC-QTOF MS screening of more than 1,000 licit and illicit drugs and their metabolites in wastewater and surface waters from the area of Bogotá, Colombia. Analytical and Bioanalytical Chemistry 407, 6405-6416. Hopkins, J., 2012. The ‘sacred sewer’: Tradition and religion in the Cloaca Maxima, Rome, Pollution and Propriety: Dirt, Disease and Hygiene in the Eternal City from Antiquity to Modernity, pp. 81-102. Huang, Y., Cheng, S., Wu, Y.-P., Wu, J., Li, Y., Huo, Z.-L., Wu, J.-C., Xie, X.-C., Korshin, G.V., Li, A.-M., Li, W.-T., 2019. Developing surrogate indicators for predicting suppression of halophenols formation potential and abatement of estrogenic activity during ozonation of water and wastewater. Water Research 161, 152-160. Huerta, B., Rodriguez-Mozaz, S., Nannou, C., Nakis, L., Ruhi, A., Acuna, V., Sabater, S., Barcelo, D., 2016. Determination of a broad spectrum of pharmaceuticals and endocrine disruptors in biofilm from a waste water treatment plant-impacted river. Science of The Total Environment 540, 241-249. Jia, A., Wu, S., Daniels, K.D., Snyder, S.A., 2016. Balancing the Budget: Accounting for Glucocorticoid Bioactivity and Fate during Water Treatment. Environmental Science & Technology 50, 2870-2880. Jung, Y.T., Narayanan, N.C., Cheng, Y.L., 2018. Cost comparison of centralized and decentralized wastewater management systems using optimization model. Journal of Environmental Management 213, 90-97. Jungnickel, C., Stock, F., Brandsch, T., Ranke, J., 2008. Risk assessment of biocides in roof paint. Environmental Science and Pollution Research 15, 258. Kankaanpää, A., Ariniemi, K., Heinonen, M., Kuoppasalmi, K., Gunnar, T., 2014. Use of illicit stimulant drugs in Finland: A wastewater study in ten major cities. Science of The Total Environment 487, 696702. Kasprzyk-Hordern, B., Bijlsma, L., Castiglioni, S., Covaci, A., de Voogt, P., Emke, E., Hernández, F., Ort, C., Reid, M., van Nuijs, A.L.N., Thomas, K.V., 2014. Wastewater-based epidemiology for public health monitoring. Water & Sewerage Journal 4, 25-26. Kelessidis, A., Stasinakis, A.S., 2012. Comparative study of the methods used for treatment and final disposal of sewage sludge in European countries. Waste Management 32, 1186-1195. Kelly, P.T., He, Z., 2014. Nutrients removal and recovery in bioelectrochemical systems: A review. Bioresource Technology 153, 351-360. Keranen, K.M., Weingarten, M., Abers, G.A., Bekins, B.A., Ge, S., 2014. Sharp increase in central Oklahoma seismicity since 2008 induced by massive wastewater injection. Science 345, 448-451. Khan, N.A., Hasan, Z., Jhung, S.H., 2013. Adsorptive removal of hazardous materials using metalorganic frameworks (MOFs): A review. Journal of Hazardous Materials 244, 444-456. Kolpin, D.W., Blazer, V.S., Gray, J.L., Focazio, M.J., Young, J.A., Alvarez, D.A., Iwanowicz, L.R., Foreman, W.T., Furlong, E.T., Speiran, G.K., Zaugg, S.D., Hubbard, L.E., Meyer, M.T., Sandstrom, M.W., Barber, L.B., 2013. Chemical contaminants in water and sediment near fish nesting sites in the Potomac River basin: Determining potential exposures to smallmouth bass (Micropterus dolomieu). Science of The Total Environment 443, 700-716. König, M., Escher, B.I., Neale, P.A., Krauss, M., Hilscherová, K., Novák, J., Teodorović, I., Schulze, T., Seidensticker, S., Kamal Hashmi, M.A., Ahlheim, J., Brack, W., 2017. Impact of untreated wastewater on a major European river evaluated with a combination of in vitro bioassays and chemical analysis. Environmental Pollution 220, 1220-1230. Korshin, G.V., Sgroi, M., Ratnaweera, H., 2018. Spectroscopic surrogates for real time monitoring of water quality in wastewater treatment and water reuse. Current Opinion in Environmental Science & Health 2, 12-19. Krzeminski, P., Leverette, L., Malamis, S., Katsou, E., 2017. Membrane bioreactors - A review on recent developments in energy reduction, fouling control, novel configurations, LCA and market prospects. Journal of Membrane Science 527, 207-227. Larsen, T.A., 2015. CO2-neutral wastewater treatment plants or robust, climate-friendly wastewater management? A systems perspective. Water Research 87, 513-521. 52
Jo
ur
na
lP
re
-p
ro of
Le Roux, J., Plewa, M.J., Wagner, E.D., Nihemaiti, M., Dad, A., Croué, J.-P., 2017. Chloramination of wastewater effluent: Toxicity and formation of disinfection byproducts. Journal of Environmental Sciences 58, 135-145. Lee, A., Elam, J.W., Darling, S.B., 2016. Membrane materials for water purification: design, development, and application. Environmental Science-Water Research & Technology 2, 17-42. Lee, H., Tan, T.P., 2016. Singapore’s experience with reclaimed water: NEWater. International Journal of Water Resources Development 32, 611-621. Lee, P.-W., Tseng, L.-C., Hwang, J.-S., 2018. Comparison of mesozooplankton mortality impacted by the cooling systems of two nuclear power plants at the northern Taiwan coast, southern East China Sea. Marine Pollution Bulletin 136, 114-124. Lege, S., Guillet, G., Merel, S., Yanez Heras, J.E., Zwiener, C., 2017. Denatonium – A so far unrecognized but ubiquitous water contaminant? Water Research 112, 254-260. Lester, Y., Ferrer, I., Thurman, E.M., Sitterley, K.A., Korak, J.A., Aiken, G., Linden, K.G., 2015. Characterization of hydraulic fracturing flowback water in Colorado: Implications for water treatment. Science of The Total Environment 512, 637-644. Leusch, F.D.L., Khan, S.J., Gagnon, M.M., Quayle, P., Trinh, T., Coleman, H., Rawson, C., Chapman, H.F., Blair, P., Nice, H., Reitsema, T., 2014. Assessment of wastewater and recycled water quality: A comparison of lines of evidence from in vitro, in vivo and chemical analyses. Water Research 50, 420431. Leverenz, H.L., Tchobanoglous, G., Asano, T., 2011. Direct potable reuse: A future imperative. Journal of Water Reuse and Desalination 1, 2-10. Lin, C.Y., Lay, C.H., Sen, B., Chu, C.Y., Kumar, G., Chen, C.C., Chang, J.S., 2012. Fermentative hydrogen production from wastewaters: A review and prognosis. International Journal of Hydrogen Energy 37, 15632-15642. Liu, Z.-h., Kanjo, Y., Mizutani, S., 2009. Removal mechanisms for endocrine disrupting compounds (EDCs) in wastewater treatment - physical means, biodegradation, and chemical advanced oxidation: A review. Science of The Total Environment 407, 731-748. Llewellyn, G.T., Dorman, F., Westland, J.L., Yoxtheimer, D., Grieve, P., Sowers, T., Humston-Fulmer, E., Brantley, S.L., 2015. Evaluating a groundwater supply contamination incident attributed to Marcellus Shale gas development. Proceedings of the National Academy of Sciences of the United States of America 112, 6325-6330. Lofrano, G., Brown, J., 2010. Wastewater management through the ages: A history of mankind. Science of The Total Environment 408, 5254-5264. Luo, W., Phan, H.V., Xie, M., Hai, F.I., Price, W.E., Elimelech, M., Nghiem, L.D., 2017. Osmotic versus conventional membrane bioreactors integrated with reverse osmosis for water reuse: Biological stability, membrane fouling, and contaminant removal. Water Research 109, 122-134. Lutz, B.D., Lewis, A.N., Doyle, M.W., 2013. Generation, transport, and disposal of wastewater associated with Marcellus Shale gas development. Water Resources Research 49, 647-656. Magnusson, K., Jalkanen, J.-P., Johansson, L., Smailys, V., Telemo, P., Winnes, H., 2018. Risk assessment of bilge water discharges in two Baltic shipping lanes. Marine Pollution Bulletin 126, 575-584. Malchi, T., Maor, Y., Tadmor, G., Shenker, M., Chefetz, B., 2014. Irrigation of root vegetables with treated wastewater: Evaluating uptake of pharmaceuticals and the associated human health risks. Environmental Science and Technology 48, 9325-9333. Mannina, G., Ekama, G., Caniani, D., Cosenza, A., Esposito, G., Gori, R., Garrido-Baserba, M., Rosso, D., Olsson, G., 2016. Greenhouse gases from wastewater treatment — A review of modelling tools. Science of The Total Environment 551-552, 254-270. Mannina, G., Rebouças, T.F., Cosenza, A., Chandran, K., 2019. A plant-wide wastewater treatment plant model for carbon and energy footprint: Model application and scenario analysis. Journal of Cleaner Production 217, 244-256. Maurer, M., Pronk, W., Larsen, T.A., 2006. Treatment processes for source-separated urine. Water Research 40, 3151-3166. 53
Jo
ur
na
lP
re
-p
ro of
McCall, A.K., Bade, R., Kinyua, J., Lai, F.Y., Thai, P.K., Covaci, A., Bijlsma, L., van Nuijs, A.L.N., Ort, C., 2016. Critical review on the stability of illicit drugs in sewers and wastewater samples. Water Research 88, 933-947. McDonough, W., Braungart, M., 2002. Cradle to Cradle: Remaking the Way We Make Things. North Point Press. Menegaki, A.N., Mellon, R.C., Vrentzou, A., Koumakis, G., Tsagarakis, K.P., 2009. What’s in a name: Framing treated wastewater as recycled water increases willingness to use and willingness to pay. Journal of Economic Psychology 30, 285-292. Merel, S., Anumol, T., Park, M., Snyder, S.A., 2015a. Application of surrogates, indicators, and highresolution mass spectrometry to evaluate the efficacy of UV processes for attenuation of emerging contaminants in water. Journal of Hazardous Materials 282, 75-85. Merel, S., Benzing, S., Gleiser, C., Di Napoli-Davis, G., Zwiener, C., 2018. Occurrence and overlooked sources of the biocide carbendazim in wastewater and surface water. Environmental Pollution 239, 512-521. Merel, S., Lege, S., Yanez Heras, J.E., Zwiener, C., 2017. Assessment of N-Oxide Formation during Wastewater Ozonation. Environmental Science & Technology 51, 410-417. Merel, S., Nikiforov, A.I., Snyder, S.A., 2015b. Potential analytical interferences and seasonal variability in diethyltoluamide environmental monitoring programs. Chemosphere 127, 238-245. Merel, S., Snyder, S.A., 2016. Critical assessment of the ubiquitous occurrence and fate of the insect repellent N,N-diethyl-m-toluamide in water. Environment International 96, 98-117. Merel, S., Villarín, M.C., Chung, K., Snyder, S., 2013a. Spatial and thematic distribution of research on cyanotoxins. Toxicon 76, 118-131. Merel, S., Walker, D., Chicana, R., Snyder, S., Baurès, E., Thomas, O., 2013b. State of knowledge and concerns on cyanobacterial blooms and cyanotoxins. Environment International 59, 303-327. Michael-Kordatou, I., Michael, C., Duan, X., He, X., Dionysiou, D.D., Mills, M.A., Fatta-Kassinos, D., 2015. Dissolved effluent organic matter: Characteristics and potential implications in wastewater treatment and reuse applications. Water Research 77, 213-248. Mintenig, S.M., Int-Veen, I., Loeder, M.G.J., Primpke, S., Gerdts, G., 2017. Identification of microplastic in effluents of waste water treatment plants using focal plane array-based micro-Fourier-transform infrared imaging. Water Research 108, 365-372. Moe, C.L., Rheingans, R.D., 2006. Global challenges in water, sanitation and health. J Water Health 4 Suppl 1, 41-57. Mohammad, A.W., Teow, Y.H., Ang, W.L., Chung, Y.T., Oatley-Radcliffe, D.L., Hilal, N., 2015. Nanofiltration membranes review: Recent advances and future prospects. Desalination 356, 226-254. Mompelat, S., Jaffrezic, A., Jardé, E., Le Bot, B., 2013. Storage of natural water samples and preservation techniques for pharmaceutical quantification. Talanta 109, 31-45. Mompelat, S., Le Bot, B., Thomas, O., 2009. Occurrence and fate of pharmaceutical products and byproducts, from resource to drinking water. Environment International 35, 803-814. Montaña, M., Camacho, A., Devesa, R., Vallés, I., Céspedes, R., Serrano, I., Blàzquez, S., Barjola, V., 2013. The presence of radionuclides in wastewater treatment plants in Spain and their effect on human health. Journal of Cleaner Production 60, 77-82. Montorsi, L., Milani, M., Venturelli, M., 2018. Economic assessment of an integrated waste to energy system for an urban sewage treatment plant: A numerical approach. Energy 158, 105-110. Moody, C.A., Field, J.A., 2000. Perfluorinated surfactants and the environmental implications of their use in fire-fighting foams. Environmental Science & Technology 34, 3864-3870. Moody, C.A., Hebert, G.N., Strauss, S.H., Field, J.A., 2003. Occurrence and persistence of perfluorooctanesulfonate and other perfluorinated surfactants in groundwater at a fire-training area at Wurtsmith Air Force Base, Michigan, USA. Journal of Environmental Monitoring 5, 341-345. Moutinho, G.M., dos Santos, I., Matos, M., Auxtero, M.D., 2019. Research and identification of Cryptosporidium and Giardia lamblia in wastewater treatment plants. Annals of Medicine 51, S73-S73.
54
Jo
ur
na
lP
re
-p
ro of
Nakatsuka, N., Kishita, Y., Kurafuchi, T., Akamatsu, F., 2020. Integrating wastewater treatment and incineration plants for energy-efficient urban biomass utilization: A life cycle analysis. Journal of Cleaner Production 243, 118448. Neale, P.A., Munz, N.A., Aїt-Aїssa, S., Altenburger, R., Brion, F., Busch, W., Escher, B.I., Hilscherová, K., Kienle, C., Novák, J., Seiler, T.-B., Shao, Y., Stamm, C., Hollender, J., 2017. Integrating chemical analysis and bioanalysis to evaluate the contribution of wastewater effluent on the micropollutant burden in small streams. Science of The Total Environment 576, 785-795. Negreira, N., Regueiro, J., Valdersnes, S., Berntssen, M.H.G., Ørnsrud, R., 2017. Comprehensive characterization of ethoxyquin transformation products in fish feed by traveling-wave ion mobility spectrometry coupled to quadrupole time-of-flight mass spectrometry. Analytica Chimica Acta 965, 72-82. Neoh, C.H., Noor, Z.Z., Mutamim, N.S.A., Lim, C.K., 2016. Green technology in wastewater treatment technologies: Integration of membrane bioreactor with various wastewater treatment systems. Chemical Engineering Journal 283, 582-594. Novo, A., Andre, S., Viana, P., Nunes, O.C., Manaia, C.M., 2013. Antibiotic resistance, antimicrobial residues and bacterial community composition in urban wastewater. Water Research 47, 1875-1887. Ort, C., Lawrence, M.G., Rieckermann, J., Joss, A., 2010. Sampling for pharmaceuticals and personal care products (PPCPs) and illicit drugs in wastewater systems: Are your conclusions valid? A critical review. Environmental Science and Technology 44, 6024-6035. Ort, C., van Nuijs, A.L.N., Berset, J.D., Bijlsma, L., Castiglioni, S., Covaci, A., de Voogt, P., Emke, E., FattaKassinos, D., Griffiths, P., Hernández, F., González-Mariño, I., Grabic, R., Kasprzyk-Hordern, B., Mastroianni, N., Meierjohann, A., Nefau, T., Östman, M., Pico, Y., Racamonde, I., Reid, M., Slobodnik, J., Terzic, S., Thomaidis, N., Thomas, K.V., 2014. Spatial differences and temporal changes in illicit drug use in Europe quantified by wastewater analysis. Addiction 109, 1338-1352. Oturan, M.A., Aaron, J.-J., 2014. Advanced Oxidation Processes in Water/Wastewater Treatment: Principles and Applications. A Review. Critical Reviews in Environmental Science and Technology 44, 2577-2641. Paerl, H.W., Scott, J.T., McCarthy, M.J., Newell, S.E., Gardner, W.S., Havens, K.E., Hoffman, D.K., Wilhelm, S.W., Wurtsbaugh, W.A., 2016. It Takes Two to Tango: When and Where Dual Nutrient (N & P) Reductions Are Needed to Protect Lakes and Downstream Ecosystems. Environmental Science & Technology 50, 10805-10813. Park, H.B., Kamcev, J., Robeson, L.M., Elimelech, M., Freeman, B.D., 2017a. Maximizing the right stuff: The trade-off between membrane permeability and selectivity. Science 356. Park, M., Anumol, T., Daniels, K.D., Wu, S., Ziska, A.D., Snyder, S.A., 2017b. Predicting trace organic compound attenuation by ozone oxidation: Development of indicator and surrogate models. Water Research 119, 21-32. Park, Y., Lee, Y.-C., Shin, W.S., Choi, S.-J., 2010. Removal of cobalt, strontium and cesium from radioactive laundry wastewater by ammonium molybdophosphate-polyacrylonitrile (AMP-PAN). Chemical Engineering Journal 162, 685-695. Paulshus, E., Kühn, I., Möllby, R., Colque, P., O'Sullivan, K., Midtvedt, T., Lingaas, E., Holmstad, R., Sørum, H., 2019. Diversity and antibiotic resistance among Escherichia coli populations in hospital and community wastewater compared to wastewater at the receiving urban treatment plant. Water Research 161, 232-241. Peccia, J., Westerhoff, P., 2015. We Should Expect More out of Our Sewage Sludge. Environmental Science and Technology 49, 8271-8276. Pedrero, F., Kalavrouziotis, I., Alarcón, J.J., Koukoulakis, P., Asano, T., 2010. Use of treated municipal wastewater in irrigated agriculture-Review of some practices in Spain and Greece. Agricultural Water Management 97, 1233-1241. Perera, M.K., Englehardt, J.D., Dvorak, A.C., 2019. Technologies for Recovering Nutrients from Wastewater: A Critical Review. Environmental Engineering Science 36, 511-529.
55
Jo
ur
na
lP
re
-p
ro of
Perreault, F., Jaramillo, H., Xie, M., Ude, M., Nghiem, L.D., Elimelech, M., 2016. Biofouling Mitigation in Forward Osmosis Using Graphene Oxide Functionalized Thin-Film Composite Membranes. Environmental Science & Technology 50, 5840-5848. Petrie, B., Barden, R., Kasprzyk-Hordern, B., 2015. A review on emerging contaminants in wastewaters and the environment: Current knowledge, understudied areas and recommendations for future monitoring. Water Research 72, 3-27. Plucinski, M.P., Sullivan, A.L., Hurley, R.J., 2017. A methodology for comparing the relative effectiveness of suppressant enhancers designed for the direct attack of wildfires. Fire Safety Journal 87, 71-79. Postigo, C., Richardson, S.D., 2014. Transformation of pharmaceuticals during oxidation/disinfection processes in drinking water treatment. Journal of Hazardous Materials 279, 461-475. Pradel, M., Aissani, L., Villot, J., Baudez, J.-C., Laforest, V., 2016. From waste to added value product: towards a paradigm shift in life cycle assessment applied to wastewater sludge – a review. Journal of Cleaner Production 131, 60-75. Prado, T., de Castro Bruni, A., Barbosa, M.R.F., Garcia, S.C., de Jesus Melo, A.M., Sato, M.I.Z., 2019. Performance of wastewater reclamation systems in enteric virus removal. Science of The Total Environment 678, 33-42. Puyol, D., Batstone, D.J., Hülsen, T., Astals, S., Peces, M., Krömer, J.O., 2017. Resource recovery from wastewater by biological technologies: Opportunities, challenges, and prospects. Frontiers in Microbiology 7. Qadir, M., Wichelns, D., Raschid-Sally, L., McCornick, P.G., Drechsel, P., Bahri, A., Minhas, P.S., 2010. The challenges of wastewater irrigation in developing countries. Agricultural Water Management 97, 561-568. Raman, C.D., Kanmani, S., 2016. Textile dye degradation using nano zero valent iron: A review. Journal of Environmental Management 177, 341-355. Randall, D.G., Naidoo, V., 2018. Urine: The liquid gold of wastewater. Journal of Environmental Chemical Engineering 6, 2627-2635. Regueiro, J., Negreira, N., Berntssen, M.H.G., 2016. Ion-Mobility-Derived Collision Cross Section as an Additional Identification Point for Multiresidue Screening of Pesticides in Fish Feed. Analytical Chemistry 88, 11169-11177. Richardson, S.D., Kimura, S.Y., 2016. Water Analysis: Emerging Contaminants and Current Issues. Analytical Chemistry 88, 546-582. Richardson, S.D., Kimura, S.Y., 2017. Emerging environmental contaminants: Challenges facing our next generation and potential engineering solutions. Environmental Technology & Innovation 8, 4056. Richardson, S.D., Plewa, M.J., Wagner, E.D., Schoeny, R., DeMarini, D.M., 2007. Occurrence, genotoxicity, and carcinogenicity of regulated and emerging disinfection by-products in drinking water: A review and roadmap for research. Mutation Research - Reviews in Mutation Research 636, 178-242. Richardson, S.D., Ternes, T.A., 2018. Water Analysis: Emerging Contaminants and Current Issues. Analytical Chemistry 90, 398-428. Rizzo, L., Krätke, R., Linders, J., Scott, M., Vighi, M., de Voogt, P., 2018. Proposed EU minimum quality requirements for water reuse in agricultural irrigation and aquifer recharge: SCHEER scientific advice. Current Opinion in Environmental Science & Health 2, 7-11. Rizzo, L., Manaia, C., Merlin, C., Schwartz, T., Dagot, C., Ploy, M.C., Michael, I., Fatta-Kassinos, D., 2013. Urban wastewater treatment plants as hotspots for antibiotic resistant bacteria and genes spread into the environment: A review. Science of The Total Environment 447, 345-360. Roccaro, P., 2018. Treatment processes for municipal wastewater reclamation: The challenges of emerging contaminants and direct potable reuse. Current Opinion in Environmental Science & Health 2, 46-54. Roccaro, P., Santamaria, A.E., Vagliasindi, F.G.A., 2014. Historical development of sanitation from the 19th century to nowadays: centralized vs decentralized wastewater management systems, in: 56
Jo
ur
na
lP
re
-p
ro of
Angelakis, A., Rose, J. (Eds.), Evolution of sanitation and wastewater technologies through the centuries. IWA Publishing, pp. 437-456. Rock, C., Solop, F.I., Gerrity, D., 2012. Survey of statewide public perceptions regarding water reuse in Arizona. Journal of Water Supply: Research and Technology-Aqua 61, 506-517. Rodriguez, C., Van Buynder, P., Lugg, R., Blair, P., Devine, B., Cook, A., Weinstein, P., 2009. Indirect potable reuse: a sustainable water supply alternative. International journal of environmental research and public health 6, 1174-1209. Rozell, D.J., Reaven, S.J., 2012. Water Pollution Risk Associated with Natural Gas Extraction from the Marcellus Shale. Risk Analysis 32, 1382-1393. Salgot, M., Folch, M., 2018. Wastewater treatment and water reuse. Current Opinion in Environmental Science & Health 2, 64-74. Samaras, V.G., Stasinakis, A.S., Mamais, D., Thomaidis, N.S., Lekkas, T.D., 2013. Fate of selected pharmaceuticals and synthetic endocrine disrupting compounds during wastewater treatment and sludge anaerobic digestion. Journal of Hazardous Materials 244, 259-267. Santhosh, C., Velmurugan, V., Jacob, G., Jeong, S.K., Grace, A.N., Bhatnagar, A., 2016. Role of nanomaterials in water treatment applications: A review. Chemical Engineering Journal 306, 11161137. Schoknecht, U., Gruycheva, J., Mathies, H., Bergmann, H., Burkhardt, M., 2009. Leaching of biocides used in façade coatings under laboratory test conditions. Environmental Science & Technology 43, 9321-9328. Schymanski, E.L., Jeon, J., Gulde, R., Fenner, K., Ruff, M., Singer, H.P., Hollender, J., 2014. Identifying Small Molecules via High Resolution Mass Spectrometry: Communicating Confidence. Environmental Science & Technology 48, 2097-2098. Senta, I., Gracia-Lor, E., Borsotti, A., Zuccato, E., Castiglioni, S., 2015. Wastewater analysis to monitor use of caffeine and nicotine and evaluation of their metabolites as biomarkers for population size assessment. Water Research 74, 23-33. Sgroi, M., Anumol, T., Roccaro, P., Vagliasindi, F.G.A., Snyder, S.A., 2018a. Modeling emerging contaminants breakthrough in packed bed adsorption columns by UV absorbance and fluorescing components of dissolved organic matter. Water Research 145, 667-677. Sgroi, M., Roccaro, P., Korshin, G.V., Greco, V., Sciuto, S., Anumol, T., Snyder, S.A., Vagliasindi, F.G.A., 2017a. Use of fluorescence EEM to monitor the removal of emerging contaminants in full scale wastewater treatment plants. Journal of Hazardous Materials 323, 367-376. Sgroi, M., Roccaro, P., Korshin, G.V., Vagliasindi, F.G.A., 2017b. Monitoring the Behavior of Emerging Contaminants in Wastewater-Impacted Rivers Based on the Use of Fluorescence Excitation Emission Matrixes (EEM). Environmental Science & Technology 51, 4306-4316. Sgroi, M., Vagliasindi, F.G.A., Roccaro, P., 2018b. Feasibility, sustainability and circular economy concepts in water reuse. Current Opinion in Environmental Science & Health 2, 20-25. Sgroi, M., Vagliasindi, F.G.A., Snyder, S.A., Roccaro, P., 2018c. N-Nitrosodimethylamine (NDMA) and its precursors in water and wastewater: A review on formation and removal. Chemosphere 191, 685-703. Simha, P., Ganesapillai, M., 2017. Ecological Sanitation and nutrient recovery from human urine: How far have we come? A review. Sustainable Environment Research 27, 107-116. Singer, H., Jaus, S., Hanke, I., Lück, A., Hollender, J., Alder, A.C., 2010. Determination of biocides and pesticides by on-line solid phase extraction coupled with mass spectrometry and their behaviour in wastewater and surface water. Environmental Pollution 158, 3054-3064. Singh, A., Sharma, R.K., Agrawal, M., Marshall, F.M., 2010. Health risk assessment of heavy metals via dietary intake of foodstuffs from the wastewater irrigated site of a dry tropical area of India. Food and Chemical Toxicology 48, 611-619. Singh, R.L., Singh, P.K., Singh, R.P., 2015. Enzymatic decolorization and degradation of azo dyes - A review. International Biodeterioration & Biodegradation 104, 21-31. Skouteris, G., Hermosilla, D., Lopez, P., Negro, C., Blanco, A., 2012. Anaerobic membrane bioreactors for wastewater treatment: A review. Chemical Engineering Journal 198, 138-148. 57
Jo
ur
na
lP
re
-p
ro of
Smith, H.M., Brouwer, S., Jeffrey, P., Frijns, J., 2018. Public responses to water reuse – Understanding the evidence. Journal of Environmental Management 207, 43-50. Snyder, S.A., Villeneuve, D.L., Snyder, E.M., Giesy, J.P., 2001. Identification and Quantification of Estrogen Receptor Agonists in Wastewater Effluents. Environmental Science & Technology 35, 36203625. Snyder, S.A., Wert, E.C., Rexing, D.J., Zegers, R.E., Drury, D.D., 2006. Ozone Oxidation of Endocrine Disruptors and Pharmaceuticals in Surface Water and Wastewater. Ozone: Science & Engineering 28, 445-460. Sousa, J.M., Macedo, G., Pedrosa, M., Becerra-Castro, C., Silva, S.C., Pereira, M.F.R., Silva, A.M.T., Nunes, O.C., Manaia, C.M., 2017. Ozonation and UV254 nm radiation for the removal of microorganisms and antibiotic resistance genes from urban wastewater. Journal of Hazardous Materials 323, 434-441. Statista, 2013. Discharge of wastewater in 2013 in Germany. Stenekes, N., Colebatch, H.K., Waite, T.D., Ashbolt, N.J., 2006. Risk and Governance in Water Recycling:Public Acceptance Revisited. Science, Technology, & Human Values 31, 107-134. Sumpter, J.P., Johnson, A.C., 2005. Lessons from Endocrine Disruption and Their Application to Other Issues Concerning Trace Organics in the Aquatic Environment. Environmental Science & Technology 39, 4321-4332. Sunderland, E.M., Hu, X.C., Dassuncao, C., Tokranov, A.K., Wagner, C.C., Allen, J.G., 2019. A review of the pathways of human exposure to poly- and perfluoroalkyl substances (PFASs) and present understanding of health effects. Journal of Exposure Science & Environmental Epidemiology 29, 131147. Swain, A., 2001. Water wars: fact or fiction? Futures 33, 769-781. Tan, X.-f., Liu, Y.-g., Gu, Y.-l., Xu, Y., Zeng, G.-m., Hu, X.-j., Liu, S.-b., Wang, X., Liu, S.-m., Li, J., 2016. Biochar-based nano-composites for the decontamination of wastewater: A review. Bioresource Technology 212, 318-333. Tchnobanoglous, G., Leverenz, H., 2013. The rationale for decentralization of wastewater infrastructure, in: Larsen, T., Udert, K., Lienert, J. (Eds.), Source separation and decentralization for wastewater management. IWA Publishing, pp. 101-115. Thines, K.R., Abdullah, E.C., Mubarak, N.M., Ruthiraan, M., 2017. Synthesis of magnetic biochar from agricultural waste biomass to enhancing route for waste water and polymer application: A review. Renewable & Sustainable Energy Reviews 67, 257-276. Thomas, K.V., Reid, M.J., 2011. What else can the analysis of sewage for urinary biomarkers reveal about communities? Environmental Science and Technology 45, 7611-7612. Thurman, E.M., Ferrer, I., Blotevogel, J., Borch, T., 2014. Analysis of Hydraulic Fracturing Flowback and Produced Waters Using Accurate Mass: Identification of Ethoxylated Surfactants. Analytical Chemistry 86, 9653-9661. Tijing, L.D., Woo, Y.C., Choi, J.-S., Lee, S., Kim, S.-H., Shon, H.K., 2015. Fouling and its control in membrane distillation-A review. Journal of Membrane Science 475, 215-244. Timm, S.N., Deal, B.M., 2018. Understanding the behavioral influences behind Singapore's water management strategies. Journal of Environmental Planning and Management 61, 1654-1673. Toczyłowska-Mamińska, R., 2017. Limits and perspectives of pulp and paper industry wastewater treatment – A review. Renewable and Sustainable Energy Reviews 78, 764-772. Trenholm, R.A., Vanderford, B.J., Holady, J.C., Rexing, D.J., Snyder, S.A., 2006. Broad range analysis of endocrine disruptors and pharmaceuticals using gas chromatography and liquid chromatography tandem mass spectrometry. Chemosphere 65, 1990-1998. Udert, K.M., Wächter, M., 2012. Complete nutrient recovery from source-separated urine by nitrification and distillation. Water Research 46, 453-464. UNDP, 2016. Human Development Report, New York, USA. UNICEF, WHO, 2017. Progress on Drinking Water, Sanitation and Hygiene: 2017 Update and SDG Baselines, Geneva. 58
Jo
ur
na
lP
re
-p
ro of
United Nations, 2010. The human right to water and sanitation. Resolution 64/292 adopted by the General Assembly on 28 July 2010. . United Nations, 2018. The World's Cities in 2018 - Data Booklet US Congress, 1972. Public Law 92-500 to amend the Federal Water Pollution Control Act. US EPA, 1980. Guidelines for water reuse. EPA-600/8-80-036. US EPA, 2012. Guidelines for water reuse. EPA/600/R-12/618. van Nuijs, A.L.N., Castiglioni, S., Tarcomnicu, I., Postigo, C., de Alda, M.L., Neels, H., Zuccato, E., Barcelo, D., Covaci, A., 2011. Illicit drug consumption estimations derived from wastewater analysis: A critical review. Science of The Total Environment 409, 3564-3577. Vanderford, B.J., Mawhinney, D.B., Trenholm, R.A., Zeigler-Holady, J.C., Snyder, S.A., 2011. Assessment of sample preservation techniques for pharmaceuticals, personal care products, and steroids in surface and drinking water. Analytical and Bioanalytical Chemistry 399, 2227-2234. Vanderford, B.J., Snyder, S.A., 2006. Analysis of Pharmaceuticals in Water by Isotope Dilution Liquid Chromatography/Tandem Mass Spectrometry. Environmental Science & Technology 40, 7312-7320. Vengosh, A., Jackson, R.B., Warner, N., Darrah, T.H., Kondash, A., 2014. A Critical Review of the Risks to Water Resources from Unconventional Shale Gas Development and Hydraulic Fracturing in the United States. Environmental Science & Technology 48, 8334-8348. Verlicchi, P., Galletti, A., Petrovic, M., Barceló, D., 2010. Hospital effluents as a source of emerging pollutants: An overview of micropollutants and sustainable treatment options. Journal of Hydrology 389, 416-428. Vidic, R.D., Brantley, S.L., Vandenbossche, J.M., Yoxtheimer, D., Abad, J.D., 2013. Impact of Shale Gas Development on Regional Water Quality. Science 340. Villarín, M.C., 2019. Methodology based on fine spatial scale and preliminary clustering to improve multivariate linear regression analysis of domestic water consumption. Applied Geography 103, 22-39. Villarín, M.C., Rodriguez-Galiano, V.F., 2019. Machine learning for modelling water demand in Seville city (Spain). Journal of Water Resources Planning and Management (Article in press). Voulvoulis, N., Arpon, K.D., Giakoumis, T., 2017. The EU Water Framework Directive: From great expectations to problems with implementation. Science of The Total Environment 575, 358-366. Vriens, B., Voegelin, A., Hug, S.J., Kaegi, R., Winkel, L.H.E., Buser, A.M., Berg, M., 2017. Quantification of Element Fluxes in Wastewaters: A Nationwide Survey in Switzerland. Environmental Science and Technology 51, 10943-10953. Wang, Q., Wei, W., Gong, Y., Yu, Q., Li, Q., Sun, J., Yuan, Z., 2017. Technologies for reducing sludge production in wastewater treatment plants: State of the art. Science of The Total Environment 587, 510-521. Warner, N.R., Christie, C.A., Jackson, R.B., Vengosh, A., 2013. Impacts of Shale Gas Wastewater Disposal on Water Quality in Western Pennsylvania. Environmental Science & Technology 47, 1184911857. Warsinger, D.M., Chakraborty, S., Tow, E.W., Plumlee, M.H., Bellona, C., Loutatidou, S., Karimi, L., Mikelonis, A.M., Achilli, A., Ghassemi, A., Padhye, L.P., Snyder, S.A., Curcio, S., Vecitis, C.D., Arafat, H.A., Lienhard, J.H., 2018. A review of polymeric membranes and processes for potable water reuse. Progress in Polymer Science 81, 209-237. Watson, S.B., Miller, C., Arhonditsis, G., Boyer, G.L., Carmichael, W., Charlton, M.N., Confesor, R., Depew, D.C., Hook, T.O., Ludsin, S.A., Matisoff, G., McElmurry, S.P., Murray, M.W., Richards, R.P., Rao, Y.R., Steffen, M.M., Wilhelm, S.W., 2016. The re-eutrophication of Lake Erie: Harmful algal blooms and hypoxia. Harmful Algae 56, 44-66. WBG, 2018a. People using at least basic sanitation services. World Bank Group. WBG, 2018b. Total population. World Bank Group. Wei, Z., Liang, F., Liu, Y., Luo, W., Wang, J., Yao, W., Zhu, Y., 2017. Photoelectrocatalytic degradation of phenol-containing wastewater by TiO2/g-C3N4 hybrid heterostructure thin film. Applied Catalysis BEnvironmental 201, 600-606. Weingarten, M., Ge, S., Godt, J.W., Bekins, B.A., Rubinstein, J.L., 2015. High-rate injection is associated with the increase in US mid-continent seismicity. Science 348, 1336-1340. 59
Jo
ur
na
lP
re
-p
ro of
Wert, E.C., Rosario-Ortiz, F.L., Drury, D.D., Snyder, S.A., 2007. Formation of oxidation byproducts from ozonation of wastewater. Water Research 41, 1481-1490. Wester, J., Timpano, K.R., Çek, D., Lieberman, D., Fieldstone, S.C., Broad, K., 2015. Psychological and social factors associated with wastewater reuse emotional discomfort. Journal of Environmental Psychology 42, 16-23. Westerhoff, P., Lee, S., Yang, Y., Gordon, G.W., Hristovski, K., Halden, R.U., Herckes, P., 2015. Characterization, Recovery Opportunities, and Valuation of Metals in Municipal Sludges from US Wastewater Treatment Plants Nationwide. Environmental Science & Technology 49, 9479-9488. Whitton, R., Fane, S., Jarvis, P., Tupper, M., Raffin, M., Coulon, F., Nocker, A., 2018. Flow cytometrybased evaluation of the bacterial removal efficiency of a blackwater reuse treatment plant and the microbiological changes in the associated non-potable distribution network. Science of The Total Environment 645, 1620-1629. Wode, F., van Baar, P., Dünnbier, U., Hecht, F., Taute, T., Jekel, M., Reemtsma, T., 2015. Search for over 2000 current and legacy micropollutants on a wastewater infiltration site with a UPLC-high resolution MS target screening method. Water Research 69, 274-283. Xiao, F., 2017. Emerging poly- and perfluoroalkyl substances in the aquatic environment: A review of current literature. Water Research 124, 482-495. Yeck, W.L., Hayes, G.P., McNamara, D.E., Rubinstein, J.L., Barnhart, W.D., Earle, P.S., Benz, H.M., 2017. Oklahoma experiences largest earthquake during ongoing regional wastewater injection hazard mitigation efforts. Geophysical Research Letters 44, 711-717. Yu, H.-W., Anumol, T., Park, M., Pepper, I., Scheideler, J., Snyder, S.A., 2015. On-line sensor monitoring for chemical contaminant attenuation during UV/H2O2 advanced oxidation process. Water Research 81, 250-260. Zaborowska, E., Lu, X., Makinia, J., 2019. Strategies for mitigating nitrous oxide production and decreasing the carbon footprint of a full-scale combined nitrogen and phosphorus removal activated sludge system. Water Research 162, 53-63. Zareitalabad, P., Siemens, J., Hamer, M., Amelung, W., 2013. Perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) in surface waters, sediments, soils and wastewater - A review on concentrations and distribution coefficients. Chemosphere 91, 725-732. Zedda, M., Zwiener, C., 2012. Is nontarget screening of emerging contaminants by LC-HRMS successful? A plea for compound libraries and computer tools. Analytical and Bioanalytical Chemistry 403, 2493-2502. Zhang, Y., Leu, Y.-R., Aitken, R.J., Riediker, M., 2015. Inventory of Engineered Nanoparticle-Containing Consumer Products Available in the Singapore Retail Market and Likelihood of Release into the Aquatic Environment. International journal of environmental research and public health 12, 8717-8743. Ziska, A.D., Park, M., Anumol, T., Snyder, S.A., 2016. Predicting trace organic compound attenuation with spectroscopic parameters in powdered activated carbon processes. Chemosphere 156, 163-171. Zuccato, E., Chiabrando, C., Castiglioni, S., Bagnati, R., Fanelli, R., 2008. Estimating community drug abuse by wastewater analysis. Environmental Health Perspectives 116, 1027-1032. Zwiener, C., Frimmel, F.H., 2000. Oxidative treatment of pharmaceuticals in water. Water Research 34, 1881-1885.
60
Figure Caption
-p
ro of
Fig. 1: Overview of the study on wastewater research.
Jo
ur
na
lP
re
Fig. 2: Bibliometric overview of wastewater research.
Fig. 3: Worldwide distribution of scientific publications related to wastewater.
61
ro of -p
Jo
ur
na
lP
re
Fig. 4: Steps of wastewater analysis and related challenges.
Fig. 5: Paradigm shift in wastewater management.
62
ro of -p re lP
Jo
ur
na
Fig. 6: Percentage of population with access to basic sanitation.
63
ro of -p
Jo
ur
na
lP
re
Fig. 7: Worldwide access to basic sanitation for the year 2015.
64
65
ro of
-p
re
lP
na
ur
Jo
Table 1: Ranking of countries, research institutions and funding bodies with respect to publications in the field of wastewater research Country
Institutions
Funding bodies Publications (1993-2017)
Ra nk
Publicati ons (19932017)
Public ations (2015)
Publications/I nhabitant (2015)
Publications (1993-2017)
1
China (22903)
China (3149)
Singapore (22.04)
Chinese Academy of Sciences (3163)
2
USA (15357)
USA (1315)
Finland (18.25)
3
India (7327)
India (917)
Australia (18.03)
4
Spain (6559)
Spain (596)
Cyprus (17.23)
5
Canada (4400)
Portugal (15.54)
6
Germany (4091)
Iran (495) Austral ia (430)
Indian Institute of Technology (1548) CSIR - Council of Scientific Industrial Research of India (1417) CNRS - Centre National de la Recherche Scientifique (1380) Harbin Institute of Technology (1255)
Denmark (15.13)
University of California System (1186)
7
United Kingdom (3831)
Brazil (410)
Greece (14.42)
Tsinghua University (1109)
8
Turkey (3827)
South Korea (409)
Brunei (14.37)
CSIC - Consejo Superior de Investigaciones Cientificas (1062)
Canada (386)
Switzerland (13.04)
Tongji University (1026)
National Basic Research Program of China (459)
Turkey (328)
Spain (12.83)
University of Queensland (815)
Spanish Autonomous Regions (437)
ro of
Spanish Ministries (897)
US National Science Foundation (828)
China Postdoctoral Science Foundation (598)
-p
NSERC - Natural Sciences & Engineering Research Council of Canada (587) CNPQ - Conselho Nacional de Desenvolvimento Científico e Tecnológico (498)
re
Jo
ur
na
10
South Korea (3818) Japan (3813)
lP
9
National Natural Science Foundation of China (10758) European Union (1521) Fundamental Research Funds for the Central Universities (1492)
66
PII:
S0304-3894(20)30127-8
DOI:
https://doi.org/10.1016/j.jhazmat.2020.122139
Reference:
HAZMAT 122139
To appear in:
Journal of Hazardous Materials
Received Date:
19 September 2019
Revised Date:
10 January 2020
Accepted Date:
18 January 2020
Please cite this article as: Villar´ın MC, Merel S, Assessment of current challenges and paradigm shifts in wastewater management, Journal of Hazardous Materials (2020), doi: https://doi.org/10.1016/j.jhazmat.2020.122139
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2020 Published by Elsevier.
Assessment of current challenges and paradigm shifts in wastewater management María C. Villarín1*, Sylvain Merel2,3*
1
Department of Human Geography, University of Seville, c/ Doña María de Padilla s/n, 41004, Sevilla, Spain
Institute of Marine Research (IMR), PO Box 1870 Nordnes, N-5817 Bergen, Norway
ro of
2
3
National Research Institute for Agriculture Food and Environment (INRAE), 5 rue de la Doua, CS 20244, 69625 Villeurbanne Cedex, France
Sylvain Merel
E-mail: [email protected]
María C. Villarín
E-mail: [email protected]
Jo
ur
na
lP
re
Graphical abstract
-p
* Corresponding authors:
1
Highlights The number of publication on wastewater is growing exponentially Paradigm shifts are water reuse, wastewater-based epidemiology, cradle to cradle Public acceptance, legislation and access to basic sanitation are social challenges Chemical and toxicological characterization of wastewater are technical challenges Contaminants of concern and treatments evolve with science and society
Jo
ur
na
lP
re
-p
ro of
2
Abstract Wastewater is a significant environmental and public health concern which management is a constant challenge since antiquity. Wastewater research has increased exponentially over the last decades. This paper provides a global overview of the exponentially increasing wastewater research in order to identify current challenges and paradigm shifts. Besides households, hospitals and typical industries, other sources of wastewater appear due to emerging activities like hydraulic fracturing. While the composition of wastewater needs
ro of
constant reassessment to identify contaminants of interest, the comprehensive chemical and toxicological analysis remains one of the main challenges in wastewater research. Moreover, recent changes in the public perception of wastewater has led to several paradigm shifts: i)
-p
water reuse considering wastewater as a water resource rather than a hazardous waste, ii) wastewater-based epidemiology considering wastewater as a source of information regarding
re
the overall health of a population through the analysis of specific biomarkers, iii) implementation of treatment processes aiming at harvesting valuable components such as
lP
precious metals or producing valuable goods such as biofuel. However, wastewater research should also address social challenges such as the public acceptance of water reuse or the access
na
to basic sanitation that is not available for nearly a third of the world’s population.
ur
Keywords: wastewater-based epidemiology, contaminants and transformation products,
Jo
microplastics, basic sanitation, water conflict and legislation, yuck factor
3
1. Introduction The amount and the composition of wastewater produced by households, hospitals and industries represent a major concern for human and environmental health. Therefore, an efficient management of wastewater, which involves collection, treatment and discharge with
ro of
the smallest possible environmental impact, is necessary. In fact, sanitation systems and wastewater management strategies were already developed by different ancient cultures (Lofrano and Brown, 2010). For instance, around the 6th century BC, in the Ancient Rome, the Cloaca Maxima was built as a large sanitation network and drainage system in case of flooding
-p
in the city (Hopkins, 2012). This characterizes a management strategy that was still largely
re
applied a few decades ago, and even remains in use in some countries, which consists in preserving public health by simply sending wastewater away from the population.
lP
Nowadays, wastewater management is still an issue and strategies evolve in order to protect public health while limiting the ecological impact on receiving waters. For instance,
na
ongoing research constantly adapts to new emerging contaminants generated by modern societies and aims at improving their attenuation through the development of new treatment
ur
processes. Moreover, this quick and recent evolution also results from the fact that wastewater management is no longer considered as a local issue faced by each municipality individually
Jo
but as a priority increasingly tackled globally. For example, communication on phenomena such as the “feminization” of fish population downstream of wastewater treatment plant due to endocrine disruptors discharged with wastewater effluents (Sumpter and Johnson, 2005) has created greater social and political awareness. As a consequence, the treatment of wastewater and the discharge of effluents are increasingly regulated at the country level and even at international level like in the European Union (EU) where a first common wastewater 4
regulation was established in the 1990s (EEC, 1991). However, some member states do not observe with the EU legislation (Voulvoulis et al., 2017) which must be enforced and updated periodically in order to ensure compliance and environmental protection while avoiding social conflicts. The current needs of modern societies also change the perception of wastewater and create paradigm shifts that drive wastewater research. For instance, the increase of population in urban agglomerations generates a growing water demand which worsens the water footprint
ro of
of major cities. This encourages the paradigm shift consisting in converting wastewater from an unwanted substance to a valuable resource (Grant et al., 2012; Pradel et al., 2016; Salgot and Folch, 2018).
-p
The simultaneous evolution of wastewater management, wastewater perception and new requirements of modern societies results in growing research. However, the large amount of
re
publications from different fields (analytical science, engineering, social sciences…) makes it
lP
more complex for the readers to have and keep a broad overview of recent evolution in a given topic. In this context, this paper aims to provide the expert as well as non-expert readers with a global and comprehensive view of wastewater research and its evolution. In particular, the
na
paper will present a bibliometric analysis leading to considerations on the sources of wastewater, the description of paradigm shifts, and the characterization of technical and social
Jo
ur
challenges (Fig. 1).
2. Bibliographic search and data collection The publications reflecting wastewater research were retrieved using the Web Of
Science (WOS) from Clarivate Analytics. As described in a previous bibliometric study (Merel et al., 2013a), an initial search by “topic” across all databases was performed in May 2018 using the word “wastewater”. The items retrieved were filtered according to the document type,
5
language and publication year in order to restrict the bibliometric study to articles and reviews published in English up to 2017. Among the remaining items, the “highly cited papers” were particularly considered as they represent recent research (published over the last ten years) which received enough citations to be placed in the top 1% of a relevant academic field. These highly cited papers were used as a basis to determine the most significant emerging challenges in wastewater research. The bibliometric overview of wastewater research worldwide was obtained from the
ro of
raw amount of publications retrieved as described previously. When an article was published by co-authors from different countries, the paper was counted only once to assess the overall amount of literature available but it was affected to the publication record of each contributing
-p
country. This allowed the accurate assessment of both the total amount of publication and the relative contribution of each country worldwide. In addition, for each country, the research
re
output was considered along with other parameters such as the population, the inequality-
lP
adjusted human development index (IHDI) and the percentage of the population with access to basic sanitation. Data related to population and basic sanitation were retrieved form the World Bank Group (WBG, 2018a, b) while the IHDI was obtained from the United Nations
na
Development Programme (UNDP, 2016).
ur
3. Bibliometric assessment of wastewater research
Jo
3.1. Overall bibliometric evolution of wastewater research The number of studies related to wastewater has strongly increased over the last decades
(Fig. 2). The total number of articles and reviews retrieved through WOS until December 2017 reached 126,765 items. Among them, 120,553 items (95%) were published in English and were considered in this study. The first four articles retrieved about wastewater were published in 1959. Since then, the number of yearly publications kept increasing with an exponential growth
6
from the 70s until today (Fig. 2). In fact, over 100 papers were published in the year 1975 while 13,612 papers were published in the year 2017. Similarly, the amount of publications on water reuse (today a significant field of wastewater research) have been increasing gradually (Fig. 2) since the first publication retrieved from 1959. The number of yearly publications remained below 12 until 1985 but progressively increased to 100 articles in the year 2000. Since then, the number of yearly publications kept growing exponentially to reach 1051 items in the year 2017. Overall, WOS sorted the publications into six general categories, allowing each
ro of
publication to be assigned several categories. The main categories were “Science Technology” with 99% of the publications, “Life Science Biomedicine” with 85% of the publications, “physical Sciences” with 77% of the publications and “Technology” with 71% of the
-p
publications. On the contrary, the categories “Social Sciences” with 20% of the publications and “Arts Humanities” with less than 1% of the publications were largely underrepresented.
re
This distribution tends to indicate that a major part of wastewater research focuses on improving
lP
treatment technology or assessing the toxicity of effluents while much less is done on areas such as the legal and economical aspect of wastewater treatment or the public perception of wastewater management. This observation is further sustained when refining the distribution of
na
the publications. For instance, WOS also sorted the publications into 150 research areas. Overall, “Environmental Sciences Ecology”, “Public Environmental Occupational Health”,
ur
“Water Resources” and “Engineering” were the main research areas with 56% to 84% of the
Jo
publications. Another height research areas including “Chemistry” or “Toxicology” also gathered 20% to 30% of the publications. However, research areas belonging to social sciences were much less significant. In fact, while the research area “Business Economics” still gathered 18% of the publications, the remaining research areas including “Public Administration”, “Geography” and “Government Law” gathered less than 1% of the publications.
7
3.2. Geography of wastewater research Besides the chronological trend described previously, the bibliometric assessment of wastewater research also reveals a heterogeneous spatial distribution. During the twentieth century, several countries changed their borders as a result of two World Wars, the dismantling of the USSR and Yugoslavia or the creation of new countries in Africa. Therefore, the overall
ro of
political stability that limited the alteration of borders worldwide only allowed the geography of wastewater research to be assessed over the last 25 years, which still reflects 94% of all publications.
-p
Overall, over the period 1993-2017, wastewater research was mostly dominated by China and the USA (Table 1), each of them accounting for more than 10% of the publications
re
(Fig.3). Next in the ranking are India and Spain representing between 5 and 10% of the
lP
publications. Finally, the ranking of countries with the highest amount of publication also included Canada, Germany, UK, Turkey, South Korea and Japan, each of them accounting for 3-5% of wastewater research. However, the geography of wastewater research is not rigid and
na
the progressive evolution across the period 1993-2017 is reflected by the relative distribution of yearly publications by continent (Fig.2). Indeed, while Africa and Oceania kept a steady
ur
relative scientific production around 4%, the relative contribution of Asia increased from 23%
Jo
in 1993 to 51% in 2017. In return this was compensated by the decreasing relative contribution of Europe and North America. This trend appears even more clearly when considering specifically the relative contribution of China, the EU and the USA (Fig.2). Additionally, as suggested in a previous bibliometric study (Merel et al., 2013a) and in order to account for the intrinsic possibilities of each country, wastewater research was also assessed after adjusting the number of publications to the population size. Such normalization
8
to the population size for the year 2015 changes considerably the geography of water research (Fig. 3) since China, India and USA no longer appear in the top ten ranking even though they were the countries with the largest raw number of publications (Table 1). On the contrary, the most productive countries based on their population size are Singapore, Finland, Australia, Cyprus, Portugal, Denmark, Greece, Brunei, Switzerland and Spain. Finally, in order to account for additional country-specific parameters such as the level of education and income, the scientific production adjusted to population size was also plotted
ro of
as a function of the inequality-adjusted human development index (IHDI). This revealed that the amount of publication/million inhabitant increased exponentially with the growing IHDI (Fig. 2), which was expected since a higher IHDI implies conditions that favor research
-p
(education, infrastructure and funding availability).
re
3.3. Major research institutions and funding bodies
lP
The main research institutions in the field of wastewater were rather representative of the country ranking over the period 1993-2017 (Table 1). The Chinese Academy of Sciences was the institution with the highest number of publications (3163 items) before the Indian
na
Institute of Technology (1548 items) and the Council of Scientific Industrial Research of India (1417 items). The French National Centre for Scientific Research (CNRS) was ranked as the
ur
fourth research institution with 1380 publications even though France was only the 12 th most
Jo
publishing country. Overall, the ranking of institutions mostly highlights a consortium of universities (for instance the University system of California) or large research entities with researchers extensively distributed nationwide and internationally (for instance, the Academy of Sciences in China, the CNRS in France or the CSIC in Spain). Similarly, the main funding bodies also reflected the most publishing countries over the period 1993-2017 (Table 1). The National Natural Science Foundation of China (10,758
9
articles) appeared as the main source of funding before the European Union (1521 articles) and the Chinese Fundamental Research Funds for the Central Universities (1492 articles). Spanish ministries represent the fourth source of funding (897 articles) before the US national Science Foundation (828 articles), which sustains the previously described and constantly good ranking of Spain according to wastewater research publications (Table 1). Moreover, wastewater research in Spain is also funded at the local level with autonomous regions (Andalusia, Catalonia, Galicia and Valencia) all together ranked as the tenth major funding source with 437
ro of
articles. However, it should be noticed that such ranking according to WOS is based on the assumption that each funding body was truthfully acknowledged in each article. While such assumption is likely to be accurate for publications released over the last few years because
-p
journals put a strong emphasis on mentioning all funding sources, it might be less accurate for the earliest publications. Moreover, it is also essential to recognize that the ranking of funding
re
bodies is only based on the number of publications that mentioned them, but the ranking does
usually not readily available.
na
4. Sources of wastewater
lP
not take into account at all the actual amount of funding provided since such information is
ur
Modern societies enclose a perpetually growing number of activities which generate waste and wastewater. Therefore, the accurate understanding of the multiple sources of
Jo
wastewater is a precondition for an optimal management at the local and global scale by determining the need for collection (where, when and how much?) and the most relevant treatment options (which treatment for which contaminant?). However, while some sources of wastewater are well identified and characterized, other sources are either emerging or remain largely overlooked.
10
4.1. Common sources of wastewater Statistics regarding the origin of wastewater and the volume discharged at the country level are scarce and incomplete (Eurostat, 2018). For instance, a yearly discharge of 1010 m3 of wastewater equivalent to 125 m3/inhabitant can be considered for Germany (Statista, 2013), a Western European country with high IHDI.
ro of
Households are well known contributors to the global amount of wastewater discharged each year worldwide. Indeed, human individuals use at least several liters of water per day in order to satisfy basic requirements such as drinking water for survival, hygiene, sanitation and
-p
food preparation (Gleick, 1996). While understanding the domestic water demand remains challenging (Villarín and Rodriguez-Galiano, 2019), several European capitals present an
re
average water consumption ranging from 136 to 289 L/day/inhabitant (Villarín, 2019). A large part of this domestic consumption will become wastewater carrying a large set of chemicals
lP
such as pharmaceuticals and their metabolites excreted after consumption or improperly disposed via the toilets (Mompelat et al., 2009), fungicides and flame retardants leaching from
na
cloths being washed (Merel et al., 2018), insect repellents and other personal care products removed from the skin when showering (Merel and Snyder, 2016), and compounds like
ur
denatonium used as additives to multiple consumer products (Lege et al., 2017).
Jo
Hospitals are other contributors to the amount of wastewater produced and treated each year (Mompelat et al., 2009). With a concentration of patients using water for personal hygiene, and additional water needs in order to keep the facilities clean, the actual volume of wastewater generated by hospitals is not well characterized. Such wastewater contains a wide range of pharmaceuticals which partially differ from those released by households since patients treated internally receive heavier treatments, for instance antineoplastics against cancer. Nevertheless, with the constant progress in medicine, a trend consists in increasing prescription to outpatients, 11
therefore progressively reducing the dissimilarity between pharmaceuticals in wastewater from households and hospitals (Mompelat et al., 2009). Rainfalls and subsequent runoff form another source of wastewater, particularly in urban areas largely impermeable and often equipped with a collection system. For instance, in Germany, the collection of water from rainfalls represent 26% of the overall wastewater discharged (Statista, 2013). Water collected after rainfalls may contain contaminants leaching from roofs and the facades of buildings, including pesticides such as diuron, terbutryn and
ro of
carbendazim (Burkhardt et al., 2011; Jungnickel et al., 2008; Merel et al., 2018; Schoknecht et al., 2009).
Industries are also well-known sources of wastewater due to their respective activities.
-p
However, since industrial wastewater effluents are usually treated internally before being discharged, assessing the actual volume of wastewater generated remains a challenge. The
re
composition of wastewater and related concerns will not be discussed in this paper as there are
lP
large differences between different industries. For instance, paper industries that produce a large amount of wastewater will mostly focus on removal of relevant contaminants (Ashrafi et al., 2015; Toczyłowska-Mamińska, 2017) while power production sites that generate large amount
na
of wastewater from their cooling operations will particularly care about the temperature of the
ur
effluent before discharge (Lee et al., 2018).
Jo
4.2. Examples of overlooked and emerging sources of wastewater 4.2.1. Hydraulic fracturing Nowadays, hydraulic fracturing, also referred to as fracking, is mostly associated with
unconventional gas production such as shale gas extraction. While combining vertical and horizontal drilling enhances access to gas-containing shale matrices, injecting under high pressure a large volume of water mixed with sand and various chemicals into the borehole
12
allows fracturing the shale. Once the fracturing fluid is removed, shale gas can flow through the cracks to the well and be collected. However, there is a growing concern regarding the production and fate of wastewater related to such process. In fact, 209 publications associated with the topics “wastewater” AND “hydraulic fracturing” could be retrieved in WOS, over twenty of them being “highly cited”. While the first publication was from the year 2000, the amount of yearly publications strongly increased since 2012 and reached 66 for the year 2017. Shale gas extraction through hydraulic fracturing generates three types of wastewater: Wastewater from drilling operations. Because drilling wastewater conveys
ro of
drilling waste, it contains high levels of suspended and dissolved solids in addition to a range of chemicals used to lubricate the drilling equipment (Lutz et
-p
al., 2013).
Wastewater from the hydraulic fracturing operation itself. After fracturing the
re
shale, the mixture of water, sand and chemicals injected under high pressure is
lP
removed from the borehole and referred to as flowback water (Lutz et al., 2013). A recent study performed on a well located in Colorado in the USA revealed that flowback water contained 22,500 mg/L total dissolved solids and a high amount
na
(590 mg/L) of dissolved organic carbon (Lester et al., 2015). The elemental analysis also revealed the occurrence of metals such as sodium, calcium and
ur
magnesium while heavy metals were detected at levels similar to those usually
Jo
observed in municipal wastewater or not detected. In addition, high resolution mass spectrometry showed the occurrence of numerous trace organic contaminants including the surfactant cocamidopropyl dimethylamine and multiple linear alkyl ethoxylates also used to improve surfactant properties of the fracturing fluids (Lester et al., 2015; Thurman et al., 2014). Finally, another study reported high concentration of ammonium (reaching 420 mg/L) chloride
13
(reaching over 100 g/L), bromide (reaching over 1 g/L) and iodide (reaching over 50 g/L) in flowback water (Harkness et al., 2015).
Wastewater from the operation of the well which are referred to as brine. Along with gas production, wells usually produce brine water coming from the shale matrices which might contain residuals of the fracturing fluid, metals, trace organic contaminants and halides (Harkness et al., 2015; Lutz et al., 2013).
Overall, the volume of wastewater generated by shale gas extraction through hydraulic
ro of
fracturing remains imprecise, particularly since drilling fluids are often neglected while flowback water is not clearly distinguished from the brine. For instance, some estimations report that wastewater represent 10% to 70% of the volume of fracking fluid injected per well,
-p
which itself varies between 11,000 to 19,000 m3 (Lutz et al., 2013). Another study indicates that 1,788,000 m3 of wastewater were generated for the year 2013 in the state of Pennsylvania
re
(USA), out of which 5% were drilling fluids, 23% were flowback water and 72% were brine
lP
(Harkness et al., 2015). However, with the growing number of operating wells and future drillings, the volume of wastewater associated with shale gas production is likely to increase therefore causing significant challenges as well as environmental and health concerns.
na
The major concern associated with wastewater from shale gas extraction is the potential contamination of local groundwater and surface water. In theory, this can occur through
ur
different circumstances including leaks through fractured rock (no evidence found so far) or
Jo
well casing, discharge at the drilling site, spills during transportation, and wastewater disposal (Rozell and Reaven, 2012; Vengosh et al., 2014). On the first hand, direct groundwater contamination have scarcely been reported (Llewellyn et al., 2015; Vidic et al., 2013) and the constant progress in drilling techniques and well casing will further help preventing such environmental issue. On the other hand, concerns related to the contamination of surface water is growing as the discharge of treated wastewater from shale gas production would increase the
14
concentration of halides (I-, Br-) and of the non-ionized form of nitrogen (NH3) in the receiving waters (Harkness et al., 2015; Warner et al., 2013). Such increase in halide concentration could impact the drinking water treatment located further downstream by enhancing the formation of toxic iodinated and brominated disinfection by-products while (NH3) could also have deleterious effects on aquatic species (Harkness et al., 2015). In order to avoid the discharge of wastewater into the environment, some areas rely on deep-well injection to place the liquid into geologic formations that prevent potential migration towards aquifers. However, deep-well
ro of
injection is also subject to discussion since several studies have linked this practice with an increase in seismicity (Keranen et al., 2014; Weingarten et al., 2015; Yeck et al., 2017). Therefore, in this context of quickly growing shale gas extraction by hydraulic fracturing, the
-p
management of related wastewater requires further research aiming at achieving a full characterization of chemical composition, evaluating the efficacy as well as the affordability of
lP
re
potential treatments, and assessing the toxicity of the effluents for the environment and human.
4.2.2. Fire extinguishing operations
The extinguishment of wildfires, urban fires and industrial fires often relies on applying
na
large amount of water. This water is usually not retained nor treated after the fire has been extinguished and becomes wastewater that reaches the nearby river or the local treatment plant
ur
if a precipitation runoff collection system exists. Because such source of wastewater shows a
Jo
random spatial distribution with a short time span, no estimation of volume could be found. However, a brief calculation indicates that the fire extinguishing process would generate several cubic meters of wastewater for operations lasting only a few minutes to thousands of cubic meters or more for operations lasting hours and even days. Indeed, fire trucks used in France are commonly equipped with fire hoses delivering a flow of water ranging from 0.1 to 1 m3/min with sometimes several of them operated for hours in parallel.
15
The composition of wastewater from fire extinguishing operations depends on the material burning. For instance, wildfires or fire in compost production sites would result in wastewater with a high content of natural organic matter. Moreover, wastewater might also contain fire suppressants (Plucinski et al., 2017) often used in aerial firefighting. On the other hand, urban fire would result in wastewater containing substances like fungicides leaching from construction materials (Burkhardt et al., 2011; Merel et al., 2018). Finally, other extinguishing operations specific to means of transport (aircraft, car, trucks…) and industrial sites like oil
ro of
refineries rely on the application of foam. Therefore, related wastewater would contain high amount of proteins or surfactants such as perfluorinated compounds (PFCs) frequently used in
-p
the composition of firefighting foam (Moody and Field, 2000; Moody et al., 2003).
4.2.3. Other examples
re
Overlooked sources of wastewater also include landfills. Lixiviation of materials buried
lP
in landfills through the infiltration of water from rainfall leads to the production of leachate containing high concentrations of a wide range of chemicals including pharmaceuticals, personal care products, brominated flame retardants, pesticides, endocrine disruptors, and
na
perfluorinated compounds (Clarke et al., 2015). Ships transporting passengers and those transporting cargo also generate wastewater in the form of bilge water usually containing oil,
ur
polycyclic aromatic hydrocarbons (PAHs), surfactants and heavy metals (Magnusson et al.,
Jo
2018). Finally, other overlooked sources of wastewater might also include municipalities through the cleaning of streets and market places with water later collected by the sewer system; ski resorts through the production of artificial snow which reaches nearby streams when melting; public services through the prevention of icing on the streets by the application of salty water which later reach the sewer system or a nearby watercourse; desalination plants which
16
produce drinking water from sea water but generate concentrated brines; local business such as laundry services and car wash stations…
5. Current technical challenges 5.1. Contaminants to remove Wastewater carries a wide range of contaminants that reflect the society and which need to be removed. The peer-reviewed literature offers multiple reviews on the occurrence and fate
ro of
of specific contaminants. Consequently, this article will provide an overview of wastewater contaminants associated with highly cited papers and therefore of particular interest but without
-p
entering in the details of their attenuation.
5.1.1. Chemical contaminants
re
Nutrients represent the first and potentially the oldest class of wastewater contaminant.
lP
Indeed, nutrients such has ammonium and phosphate are constituents of urine, which therefore already occurred when wastewater was first collected in 3500-2500 BC in the Mesopotamian
na
Empire (Lofrano and Brown, 2010). When released in the receiving water, nutrients increase the eutrophication process and favor the formation of potentially toxic blooms of algae or
ur
cyanobacteria (Merel et al., 2013b; Paerl et al., 2016; Watson et al., 2016). Therefore, processes to improve the removal of nutrients are still a major research focus (Cao et al., 2017; Desmidt
Jo
et al., 2015; Garcia et al., 2017; Guaya et al., 2015; Kelly and He, 2014). Pharmaceuticals and personal care products represent a second but major class of
wastewater contaminant (Petrie et al., 2015). As new molecules are regularly authorized while other are progressively withdrawn, the suite of pharmaceuticals detectable in wastewater varies over the years and from a country to another. Therefore, compound libraries used with high resolution mass spectrometry should be regularly updated to include new chemicals of interest 17
and assess their occurrence and fate in wastewater. Overall, the attenuation of pharmaceuticals is an important research focus since their biological activity is a major environmental health concern with residuals of antibiotics favoring the development of resistant bacteria (Novo et al., 2013; Rizzo et al., 2013; Sousa et al., 2017) and hormones causing endocrine disruption (Huerta et al., 2016; Liu et al., 2009; Samaras et al., 2013). Poly- and perfluoroalkyl substances (PFASs) that were developed for their stability are commonly used in multiple consumer products since the 1950s (Richardson and Kimura, 2017)
ro of
and represent a third class of major wastewater contaminant (Ahrens, 2011; Zareitalabad et al., 2013). In the literature, perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) are the most commonly reported PFAS in wastewater. However, wastewater is likely to contain
-p
many other PFASs that might remain unnoticed due to the lack of specific monitoring. For instance, with the growing application of high resolution mass spectrometry, 455 new PFASs
re
have been characterized in a wide range of matrices over the period 2009-2017 (Xiao, 2017).
lP
As preliminary evidence suggests significant health effects associated with exposure to emerging PFASs (Sunderland et al., 2019), the occurrence of such chemicals in wastewater is of particular interest, particularly when implementing water reuse strategies.
na
Biocides are often associated with agriculture and multiple molecules are currently authorized as plant protection products by the European Union. However, pesticides are also a
ur
significant class of wastewater contaminants. For instance, wastewater effluent from food
Jo
processing industry has been shown to contain 20 pesticides along with 14 of their transformation products (Campos-Mañas et al., 2019). In addition, some biocides like carbendazim that might be used to protect cloths as well as the facades of buildings against fungi growth also occur in municipal wastewater after progressive leaching (Merel et al., 2018). Some pesticides also occur in wastewater effluent without satisfactory explanation, therefore revealing an unknown input source. For instance, in France, atrazine could still be detected in
18
wastewater effluent collected by dry weather several years after prohibiting the commercialization and use of this pesticide for agricultural purpose (Becouze-Lareure et al., 2016). Due to their biological properties, the occurrence of biocides in wastewater effluent represents a significant environmental health concern. Heavy metals enclose a wide range of chemicals among which cadmium, chromium, copper, iron, lead, mercury, selenium or zinc. Since several heavy metals have been associated with human health issues, their occurrence and fate in wastewater is greatly studied. However,
ro of
while the concentration of heavy metal in the treated effluent is a concern for the implementation of water reuse strategies, a major concerns relates to their concentration in wastewater sludge which have to be disposed or reused. Nowadays, beyond attenuating the
-p
concentration of heavy metals in wastewater, a growing trend consist in harvesting them as a valuable good from wastewater (Westerhoff et al., 2015), as described in the following sections.
re
Dyes gather chemicals that also represent a major focus in wastewater treatment. Over
lP
the last decade, the removal of dyes from wastewater related to the textile industry was the topic multiples papers including several reviews (Bilal et al., 2017; Raman and Kanmani, 2016; Singh et al., 2015). However, it should also be considered that dyes might leach from cloths over
na
subsequent wash, therefore becoming also compounds of concern in domestic wastewater generated by households. These chemicals such as azo dyes and their cleaved products could
ur
be carcinogenic (Chung, 2016) and therefore represent a public health concern, particularly in
Jo
the context of water reuse.
Another group of chemicals of concern in wastewater are radionuclides. These are
radioactive isotopes of elements including strontium, selenium or uranium. They might occur in laundry wastewater from nuclear power plants (Park et al., 2010) but they might also occur in regular wastewater treatment plants (Montaña et al., 2013), and hospital wastewater due to the application of specific treatments for certain diseases (Verlicchi et al., 2010). Measures such
19
as the separated collection and treatment of discharges from toilets of patients receiving nuclear medicine therapy prevents elevated level of radionuclides in public sewer. However, radionuclides should remain carefully monitored. In additions to the main groups of chemicals mentioned previously, transformation products (TPs) should also be considered very carefully, particularly after disinfection processes (Le Roux et al., 2017). Indeed, while some TPs formed during wastewater treatment have a chemical structure closely related to that of their parent compound, they might remain
ro of
biologically active. In addition, most of the TPs remain unknown. Therefore, the chemical and toxicological characterization of TPs in wastewater is a major environmental and public health
-p
concern.
5.1.2. Non-chemical contaminants
re
Among non-chemical contaminants, microplastics have been reported in wastewater by
lP
multiple studies (Carr et al., 2016; Dris et al., 2015; Mintenig et al., 2017) therefore gaining increasing attention over the last decade. Microplastics, defined as polymer particles smaller than 5 mm, can be intentionally produced with a size of 60-800 μm to enter the composition of
na
personal care products (Chang, 2015). Therefore, microplastics are collected by the sewer system and sent to local wastewater treatment plants which are usually not designed to ensure
ur
their retention. Thus the discharge of treated wastewater is often considered as a major source
Jo
of microplastics in the aqueous environment. Nanoparticles, which are often described as particles with a diameter in the range 1-100
nm (Richardson and Kimura, 2017), have also become a significant concern for wastewater treatment. Engineered nanomaterials include for instance silver (Ag), titanium dioxide (TiO2), zinc oxide (ZnO), silicon dioxide (SiO2) or carbon nanotubes. Nanoparticles are used in the composition of personal care products, paints, food packaging and therefore reach the local
20
wastewater treatment plant (Zhang et al., 2015) which might not be designed to ensure their removal. However, nanomaterials also have a role in wastewater treatment where they can be employed in order to enhance the removal of other contaminants of concern (Santhosh et al., 2016). Consequently, a major challenge consists in designing treatment plants able to retain nanoparticles from wastewater while using the properties of immobilized nanomaterials to achieve an enhanced attenuation of trace organic contaminants. Finally, pathogens represent another class of contaminants of concern that wastewater
ro of
treatment should aim to remove. While providing an exhaustive overview of pathogens in wastewater is a complex task that is not the aim of the current study, it should be noticed that common wastewater pathogens can be distributed into several categories. A first category of
-p
pathogens gathers viruses, including the human adenovirus, JC polyomavirus, norovirus and rotaviruses (Eftim et al., 2017; Prado et al., 2019) as well as enterovirus, hepatitis A and E viruses
re
(Hellmér et al., 2014). A second category of pathogens gathers parasites, including helminths
lP
which eggs have been reported in wastewater effluent (Ajonina et al., 2015) and protozoa such as Cryptosporidium and Giardia (Adeyemo et al., 2019; Moutinho et al., 2019) which are well known to cause diarrhea when reaching and contaminating drinking water (Daniels et al., 2018).
na
Finally, a third category of wastewater pathogens gathers bacteria such as Legionella, Clostridium perfringens and the well-known diarrhea causing agent Escherichia coli (Ajonina
ur
et al., 2015; Caicedo et al., 2019; Paulshus et al., 2019). In addition, Vibrio cholera is another
Jo
wastewater bacteria responsible for cholera epidemic occurrence like in Yemen where the contamination of water wells by wastewater and the use of untreated wastewater for irrigation caused 500,000 individuals to be infected resulting in 2,000 deaths (Al-Gheethi et al., 2018). Overall, when considering the population of bacteria in wastewater, a study based on gene fingerprinting revealed that 0.06% and up to 3.20% were pathogenic (Cai and Zhang, 2013). Therefore, due the related consequences for human health, the attenuation of wastewater
21
pathogens during wastewater treatment is of high importance, more particularly when considering water reuse strategies. In practice and according to local legislation, treated wastewater discharged in the environment is not necessarily disinfected, which leaves to any entity (usually a drinking water treatment plant) using river water further downstream the responsibility of ensuring its own disinfection. However, when implementing potable or nonpotable water reuse, treated effluent must be carefully disinfected in order to ensure the removal of pathogens below guidelines set by local authorities. In fact, treatment plants aiming at water
ro of
reuse usually rely on the successive application of several disinfection processes. For instance, a facility in North Carolina provides a dual disinfection with a UV irradiation step followed by chlorination (Bailey et al., 2018) and consistently achieves log 10 removals up to 6 for bacteria,
-p
4 for virus and 4 for protozoan parasite surrogates. However, while chlorination is often selected as the last treatment step in order to ensure a residual of free chlorine that prevents the regrowth
re
of pathogens in the distribution network (Whitton et al., 2018), it is also well known that
lP
chemical oxidants including chlorine form a large amount of unknown disinfection by-products which should also be investigated (Postigo and Richardson, 2014; Richardson et al., 2007).
na
5.2. Treatment of wastewater
Wastewater management strategies were already implemented by ancient civilizations
ur
(Lofrano and Brown, 2010). Throughout the centuries and mostly over the last decades,
Jo
wastewater treatment technology has dramatically improved and current research keeps developing new processes. Since the recent literature offers reviews for most treatment technologies (Roccaro, 2018), providing a detailed examination of each process is not in the scope of this study. However this paper will rely on bibliometry to provide a brief overview of current wastewater treatment strategies and research.
22
Nowadays, conventional wastewater treatment consists in a combination of physical, chemical and biological processes that allow removing solids, organic matter and sometimes nutrients. Currently, the literature survey on wastewater reveals a significant amount of research on membrane bioreactor (MBR) to improve treatment efficacy (Krzeminski et al., 2017; Neoh et al., 2016; Skouteris et al., 2012). However, with MBR and other treatment processes, a major issue is the production of sludge which require specific management. Therefore, current wastewater research also aims at reducing sludge production and improving their handling
ro of
(Cieslik et al., 2015; Kelessidis and Stasinakis, 2012; Wang et al., 2017). In addition, the publication of several recent papers (Cao et al., 2017; Du et al., 2017; Garcia et al., 2017) also indicates that the removal of nutrients from wastewater remains a major research interest since
-p
the discharge of nitrogen and phosphorus aggravates the eutrophication of receiving waters (Paerl et al., 2016; Watson et al., 2016) and related issues such as the occurrence of harmful
re
blooms (Merel et al., 2013b).
lP
Improvement of wastewater treatment is also achieved through the application of processes based on the retention of contaminants. In recent years, several publications (Fane et al., 2015; Lee et al., 2016; Mohammad et al., 2015; Park et al., 2017a) show significant
na
investigation in the field of membranes in order to maximize the attenuation of contaminants. Filtration processes include ultrafiltration, nanofiltration but also osmosis (Chekli et al., 2016;
ur
Luo et al., 2017). While improving the retention of contaminants, research also focuses on the
Jo
mitigation of fouling (Perreault et al., 2016; Tijing et al., 2015), an issue inherent to membrane processes. Beyond membrane technology, the retention of contaminants in wastewater treatment also relies on processes based on sorption (Hai Nguyen et al., 2017; Khan et al., 2013). Over the last years, sorption research intensified with a focus on the application of biochar (Tan et al., 2016; Thines et al., 2017), an adsorbent produced by pyrolysis of agricultural waste such as coconut shell, empty fruit bunch and rice husk.
23
Finally, the attenuation of trace organic contaminants during wastewater treatment is also improved through the application of advanced oxidation processes (Asghar et al., 2015; Boczkaj and Fernandes, 2017; Roccaro, 2018) referred to as AOPs. The high reactivity of oxidants like ozone or radical species allows transforming contaminants not removed by conventional treatments, therefore reducing the impact of the discharge in receiving waters. Currently, the amount of literature indicates that a strong research effort is made on AOPs, which enclose multiple approaches (Oturan and Aaron, 2014) such as TiO2-based processes
ro of
(Wei et al., 2017), Fenton-related processes (Amor et al., 2015; Bokare and Choi, 2014), and ozone-based processes (Gomes et al., 2017) which have shown promising results for the attenuation of pharmaceuticals for many years (Snyder et al., 2006; Zwiener and Frimmel,
-p
2000). However, as implementing AOPs infer an additional cost, short term upgrading of conventional wastewater treatment plants with ozonation for instance might be limited to
re
countries like Switzerland that impose newer and stricter water protection acts (Bourgin et al.,
lP
2018). Nonetheless, even though AOPs significantly reduce the amount of known contaminants discharged in the environment, a major drawback is the production of new and unknown transformation products (Merel et al., 2017; Richardson and Kimura, 2016; Sgroi et al., 2018c;
na
Wert et al., 2007). Indeed, water contaminants are not removed by AOPs but rather transformed
ur
into multiple by-products the chemistry and toxicity of which remain largely unknown.
Jo
5.3. Analysis of wastewater samples Wastewater samples of different kinds (influent, primary, secondary or tertiary effluent)
are commonly analyzed for multiple purposes. These can include the detection of known compounds in order to assess treatment efficiency, the analysis of unknown components in order to identify transformation products, or the toxicity assessment through multiple endpoints.
24
However, the results do not only depend on the analytical technique used but also on how the sample was collected, preserved and prepared (Fig. 4).
5.3.1. Sample collection, preservation and preparation Overall, samples can be collected according to the three different approaches of which the most relevant is determined by the question to be addressed. The first approach, which consists in collecting a single sample at a specific time and location (grab sample), would
ro of
provide a punctual assessment of wastewater composition and properties. The second approach, which consists in collecting multiple samples across a given period of time (often 12 or 24 hours) and combining them before analysis (composite sample), would provide a representative
-p
average sample accounting for the temporal variation in the concentration of chemicals. The third approach, which consists in the continuous collection of chemicals by sorption on a
re
sorbent (passive sampling), would provide a time-integrated average over long periods (days or weeks) particularly useful to assess long term exposure.
lP
Sample preservation is critical in order to avoid any alteration of the composition (oxidation microbial degradation…) between collection and the analysis. Typical procedures
na
usually rely on storage at 4 °C, acidification (Trenholm et al., 2006) or addition of azide to limit biological activity (Anumol et al., 2013; Anumol and Snyder, 2015). However, in the absence
ur
of a detailed study on the most suitable preservation method for wastewater samples, two other
Jo
studies related to surface water but focusing on relevant contaminants could be considered (Mompelat et al., 2013; Vanderford et al., 2011). Overall, surface water samples collected in amber bottle to prevent photodegradation, quenched with ascorbic acid and spiked with sodium azide could be stored at 4 °C for up to 28 days with less than 15% loss for the pharmaceuticals and personal care products tested (Vanderford et al., 2011). Nonetheless, these results should
25
be considered with caution since they concern a limited set of test compounds and wastewater matrix is more complex than surface water. Sample preparation before analysis also largely evolved over the last decades. Initially, enrichment of the analytes was a pre-requisite often achieved by liquid-liquid extraction (LLE) but progressively replaced by solid phase extraction (SPE) more easily automated and allowing to extract a larger amount of contaminants (Merel and Snyder, 2016). With technological improvement, the sample volume required to performed SPE also decreased from several liters
ro of
(Snyder et al., 2001) to only a few milliliters with the development of online-SPE (Anumol and Snyder, 2015). In the recent years, wastewater analysis could even be performed without previous extraction, through the direct injection of 80-100 μL while achieving limit of
-p
quantification in the ng/L range (Anumol et al., 2015b). However, despite these major improvements, sample preparation remains challenging. For instance, the potential loss of
re
analytes inherent to sample preparation can be assessed and corrected by the addition of internal
lP
standards (isotope dilution) for known compounds of interest (Vanderford and Snyder, 2006) but it is still a major concern when assessing the fate of unknown contaminants. Moreover, sample preparation also remains a complex task for toxicity assessment which often requires a
na
higher enrichment factor than chemical analysis with a much lower fraction of organic solvent
ur
that could disrupt the normal activity of the organism/tissue/cell tested.
Jo
5.3.2. Analysis of known and unknown components Overall, high specificity and high sensitivity made mass spectrometry rather essential
for the detection of contaminants in wastewater through two different approaches. The first approach, referred to as “targeted analysis”, consists in selecting chemicals of interest in order to detect them and only them in a sample. The second approach, referred to as “untargeted
26
analysis”, consists in detecting all chemicals that can be ionized in the mass spectrometer while their tentative identification is carried out afterwards. Targeted analysis relies on chromatographic separation coupled to tandem mass spectrometry. Each compound is identified according to its retention time and its specific fragments with respect to an analytical standard which also allows an accurate quantification. When using isotope dilution, quantification can also include a correction factor accounting for any loss of analyte during sample preparation and ion suppression in the mass spectrometer
ro of
(Vanderford and Snyder, 2006). Nowadays, routine methods can often quantify several dozens of compounds for a measurement time below 30 minutes (Anumol et al., 2013; Anumol and Snyder, 2015). While data processing offers limited difficulty (Merel et al., 2015a), the results
-p
of target analysis still lead to some interrogations and new findings regarding the origin of contaminants in wastewater. For instance, the detection of the insect repellent DEET in
re
wastewater is commonly attributed to the dermal application of the molecule which is
lP
subsequently washed from the skin when showering and collected by the sewer system. However, the common detection of DEET in wastewater during the winter period, in dry areas that are not associated with the abundance of mosquitoes, together with the detection of the
na
insect repellent in blank samples (Anumol et al., 2013; Kolpin et al., 2013; Wode et al., 2015) has led to suspect the occurrence of potential analytical interferences or an uncharacterized
ur
source of DEET (Merel et al., 2015b; Merel and Snyder, 2016). Similarly, recent studies using
Jo
targeted analysis to monitor biocides identified households and paper production industries as previously unknown sources of the fungicide carbendazim in wastewater and the environment (Bollmann et al., 2014; Merel et al., 2018; Singer et al., 2010). On the contrary, compounds not considered in the targeted analysis cannot be detected with the consequence that some wastewater contaminants might remain unnoticed despite their potential ubiquity. For instance, a recent study suggested the potential ubiquity of denatonium (Lege et al., 2017), a bitter
27
substance added to certain products like detergents in order to prevent their ingestion. Yet the overall absence of targeted analysis for this compound excludes it and probably many other relevant chemicals from further research on occurrence, fate and environmental health risk assessment. The untargeted analysis relies on chromatographic separation coupled to high resolution mass spectrometry (HRMS), which allows detecting all chemicals within a given range of mass to charge ratio and without preliminary consideration as long as they can be ionized. This
ro of
approach has gained significance in the last decade, particularly due to the necessity to fully characterize wastewater samples and treatment efficacy when trying to reduce environmental impact and promoting water reuse. However, with untargeted analysis, each compound detected
-p
is initially an unknown chemical characterized by a retention time, an accurate mass, and potential fragment ions. Therefore, the first challenge associated with untargeted analysis
re
consists in identifying the compounds detected. This is often achieved by performing a “suspect
lP
screening” that matches the acquired data with a compound library. Thus, developing compound libraries and efficient algorithms are crucial needs to improve the identification rate (Zedda and Zwiener, 2012). In addition, new mass spectrometers that include ion mobility
na
separation allow a better compound characterization by providing their collision cross section (CCS) value which can be used to improve data processing (Bijlsma et al., 2019) and lower the
ur
rate of false positive (Regueiro et al., 2016). The second challenge with untargeted analysis
Jo
consists in identifying new compounds such as transformation products formed during wastewater treatment. For instance, while some studies rely on external software that predict potential transformation products for a given compound (Bijlsma et al., 2019), other studies identify transformation products according to the specific fragments (Hernández et al., 2015; Negreira et al., 2017) or the Kendrick mass defect (Merel et al., 2017) they share with the native compound. Nonetheless, the identification of a compound based on accurate mass, fragments
28
and retention time remains tentative until a standard can be procured. Therefore, the third challenge with untargeted analysis consists in communicating the confidence for each compound tentatively identified. Currently, a scale containing five confidence levels based on specific HRMS criteria has been proposed (Schymanski et al., 2014) and becomes commonly used even though periodic revisions might be required in order to incorporate constant progress in analytical science.
ro of
5.3.3. Development of alternative to mass spectrometry The development of alternative to mass spectrometry for the analysis of wastewater contamination can be observed in recent publications (Korshin et al., 2018; Park et al., 2017b;
-p
Sgroi et al., 2018a; Ziska et al., 2016). The aim is to enable on-site measurement in order to obtain simpler, near real-time and more affordable results. Instead of detecting specific
re
compounds, the approach consists in measuring bulk parameters of water contamination such
lP
as UV absorbance and fluorescence in order to estimate the occurrence of some pollutants. For instance, it is now well established that an excitation-emission matrix obtained from fluorescence measurement can be divided into several areas that characterize the presence of
na
compounds like proteins, fulvic acid, humic acid and soluble microbial by-products (Chen et al., 2003; Merel et al., 2015a). In particular, the measurement of bulk parameters is particularly
ur
useful when monitoring the efficacy of wastewater treatment. Indeed, several studies were able
Jo
to use fluorescence and UV absorbance to characterize the breakthrough of contaminants from activated carbon filters (Anumol et al., 2015a; Sgroi et al., 2018a; Ziska et al., 2016). In addition, using the attenuation of fluorescence during full scale wastewater treatment was also shown to be a successful surrogate to assess the removal of emerging contaminants (Huang et al., 2019; Park et al., 2017b; Sgroi et al., 2017a). Consequently, developing the continuous measurement of fluorescence and UV absorbance directly at the wastewater treatment plant for
29
real-time monitoring of water composition would allow designing “smart treatment plants” able to detect any potential failure or decreased efficiency without delay, triggering the automatic adjustment of the treatment (increase of reagent dose) and alerting the operator in charge. Such application of fluorescence and UV absorbance measurement would require further research but shows particular significance in the context of water reuse (Yu et al., 2015) and could be extended to assess potential contamination of surface water (Sgroi et al., 2017b).
ro of
5.3.4. Toxicity assessment The potential toxicity of wastewater effluent has always been and remains a major public concern, particularly when trying to reduce the environmental impact of wastewater
-p
discharge or implementing water reuse strategies. With the changes in society and the constant progress in science, the approach to toxicity assessment permanently evolves in order to face
re
new challenges. A first evolution in toxicity assessment is the shift from in-vivo methods to in-
lP
vitro methods that are not only more specific and more sensitive but also more acceptable from the current ethical perspective. However, while in-vivo methods could assess the overall toxicity of a sample for a complex organism, specific in-vitro methods assess the toxicity of wastewater
na
effluent with respect to specific biological endpoints. In order to cover several relevant endpoints, a single sample requires evaluation using numerous in-vitro assays (Escher et al.,
ur
2014), therefore increasing the need for techniques allowing high throughput.
Jo
A second evolution in toxicity assessment is the growing synergy with the chemical characterization of wastewater samples. Initially, bioassays were often used to complement mass spectrometry results by characterizing individually the biological relevance of new contaminants or transformation products. In recent years, the opposite approach has also been applied with bioassays used to monitor the overall biological activity of complex mixtures like wastewater samples and mass spectrometry used as a supporting tool in order to identify the
30
compounds responsible for a positive biological response (Jia et al., 2016; König et al., 2017; Leusch et al., 2014; Neale et al., 2017). For instance, this approach allowed proving that the glucocorticoid activity in treated wastewater was entirely due to the remaining occurrence of several known synthetic glucocorticoid compounds (Jia et al., 2016). Similarly, another study showed that endocrine disruption due to wastewater discharge was in agreement with concentrations of detected hormones (König et al., 2017). However, when monitoring other parameters such as the xenobiotic metabolism and the adaptive stress response, the chemicals
ro of
detected could explain only a limited fraction of the observed effects (König et al., 2017; Neale et al., 2017), corroborating the importance of the dual chemical and toxicological characterization of wastewater.
-p
Finally, besides considering the toxicity of mixtures instead of individual compounds, another challenge in toxicity assessment is to consider the effect of chronic exposure in addition
re
to acute toxicity. This is particularly relevant in order to assess potential effects on aquatic
lP
organisms exposed continuously to the chemicals discharged by wastewater treatment plants as well as on humans who might be exposed for years when implementing water reuse strategies. However, nowadays data remain scarce when it comes to the chronic effect of chemicals and
na
mixture of chemicals and future research should aim at filling this gap.
ur
6. Paradigm shifts
Jo
After several decades of constant technological and population growth resulting in the ever increasing demand in energy and in all kinds of natural resources (water, nutrients…), there is now a global awareness that these natural resources are limited since the negative consequences of their past/current overexploitation are becoming more and more palpable. Therefore, in an attempt to limit the human footprint on the Earth, a circular economy is being developed worldwide. Overall, the circular economy aims at avoiding as much as possible the
31
constant extraction of natural resources leading to waste production and disposal (also known as the chain: take, make, use, dispose and pollute) by favoring the full valorization of any residual (also known as the cycle: make, use, reuse, remake and recycle). This concept of circular economy together with social awareness and environmental issues have led to several paradigm shifts in wastewater management.
6.1. Water reuse
ro of
The world´s population has been rapidly increasing, particularly in urban areas. For instance, only around 1 billion people (30% of the population) lived in urban areas in 1950 but it steadily increased until reaching over 4 billion people (55% of the population) in 2018. In
-p
fact, 68% of the world´s population is projected to be urban in 2050 (United Nations, 2018). In addition, the increase of extreme droughts due to climate change will worsen existing troubles
re
to satisfy water demand in growing urban areas (Pedrero et al., 2010). The lack of water has
lP
been avoided with traditional models based on increasing the resources available through dams or artificial canals like in Arizona (Chowdhury et al., 2013). However, these alternatives tend to be insufficient, costly and environmentally unsustainable. Conversely, reusing adequately
na
treated wastewater (water reuse) could ensure the supply and regular distribution of water to the population (Fig. 5). The quality of treated wastewater will determine if it can be classified
ur
as non-potable or potable and therefore the potential application of reclaimed water. According
Jo
to the literature (Bixio et al., 2008; Michael-Kordatou et al., 2015), non-potable water reuse can be grouped into four categories based on its application: i) agricultural irrigation; ii) industrial activities such as cooling; iii) urban and environmental uses (including recreational use and aquifer recharge), and iv) the combination of all activities mentioned previously. Using reclaimed water for agricultural irrigation is a common practice worldwide. Such water reuse requires more specific treatment to attenuate the contaminants described previously and limit
32
the exposure for the population and the environment. In particular, there is a need to accurately characterize the water composition in heavy metals, pharmaceuticals, pesticides and transformation products (Le Roux et al., 2017; Qadir et al., 2010; Singh et al., 2010) to assess how those components can be taken up by plants and if they can be transferred to fruits and vegetables. Potable water reuse can be classified into “direct” and “indirect” (Fig. 5) respectively if water is consumed by the population directly after treatment (known as pipe to pipe), or after
ro of
using an environmental buffer like in the case of aquifer recharge (Gerrity et al., 2013; US EPA, 2012). Direct potable reuse (DPR) is defined as purified water which is directly discharged into a municipal water supply system (Leverenz et al., 2011). The first DPR scheme was established
-p
in Windhoek (Namibia) and dates back to 1968 but only an handful of plants have been built since then, including those in Cloudcroft (New Mexico, USA) operating since 2007, Western
re
Cape (South Africa) operating since 2010, and Big Spring (Texas, USA) operating since 2014
lP
(Warsinger et al., 2018). Despite the implementation of advanced wastewater treatment and monitoring to ensure that water quality requirements are fulfilled, direct potable reuse implies direct human exposure and therefore a high level of public concerns. One concern is the
na
exposure to some well-known wastewater contaminants such as pharmaceuticals, personal care products or artificial sweetener (acesulfame and sucralose among others) which were not fully
ur
removed during wastewater treatment (Bottoni et al., 2010; Dias and Petit, 2015; Malchi et al.,
Jo
2014; Richardson and Ternes, 2018). Indeed, little is known regarding how human health may be affected due to the chronic exposure to low doses and to a mixture of components (potential antagonism, addition or synergistic effect). Another concern is the fraction of water composition that is not known (unknown molecules or biological agents) and how advanced treatments can protect consumer’s health from that perspective. Finally, a major concern is the very short time available to detect any potential treatment failure and prevent water
33
consumption. Due to this, most country require indirect potable water reuse with an environmental buffer. This might be implemented as aquifer recharge or discharge in rivers with increased residence time through damns (Michael-Kordatou et al., 2015). The aim is to delay human exposure in order to take corrective measure and avoid health issue in case of treatment failure. Nowadays, in order to develop potable water reuse, many studies are carried out to improve treatment technology but also public acceptance as described in subsequent
ro of
sections.
6.2. Wastewater-based epidemiology
Traditionally, many organic compounds are contained in municipal wastewater
-p
including pharmaceuticals, personal care products (PPCPs) and illicit drugs (Carballa et al., 2004; Ort et al., 2010). However, the occurrence of these substances and their metabolites
re
reflects human habits and lifestyle, providing information about both the exposure to specific
lP
chemicals and the prevalence of certain diseases (Castiglioni et al., 2015; Kasprzyk-Hordern et al., 2014; Thomas and Reid, 2011). The advanced analysis of wastewater in order to assess the exposure and health status of a population (Fig. 5) is referred to as wastewater-based
na
epidemiology (WBE). Over the last decades, this approach has increasingly focused on the detection of illicit drugs in order to estimate their consumption at the population level
ur
(Daughton, 2001; Daughton, 2011; McCall et al., 2016). In addition, the geographic and
Jo
temporal analysis of drug residuals matched with the related population according to age, economic level or spatial distribution can help understanding and discriminating the different use of drugs. For instance, some studies revealed an increase in the use of cocaine and 3,4methylenedioxymethamphetamine (MDMA) for recreational purposes during the weekends while for methadone and 3,4-methylenedioxypyrovalerone (MDPV) there were no variations patterns depending on the day of the week (Kankaanpää et al., 2014; Ort et al., 2014).
34
Similarly, WBE also includes the detection of biomarkers which can quantify the health status of the population (Thomas and Reid, 2011). The biomarkers can be grouped into two categories: i) biomarkers of exposure; ii) biomarkers of effect. On the first hand, biomarkers of exposure are chemicals excreted by human and resulting from the detoxification process after exposure to xenobiotics such as pesticides or illicit drugs mentioned previously. Knowing their excretion rate and their concentration in wastewater, these biomarkers allow to back calculate the exposure of the population. On the other hand, biomarkers of effect are molecules secreted
ro of
by the body when developing a disease. For instance, isoprostanes would reflect the level of oxidative stress in the population while other biomarkers of effect could reflect the incidence of diabetes or cancer. However, compounds of interest are usually at low level in very complex
-p
matrices and extensive sample preparation is necessary before their accurate quantification. In addition, in order to obtain meaningful data, the stability of biomarkers in wastewater should
re
be determined thoroughly in order to avoid any underestimation.
lP
Overall, WBE allows obtaining information about the health status of a complete population instead of analyzing urine samples of specific individuals. However, WBE can be conducted with more or less resolution according to the sampling area. For instance, collecting
na
samples at the entrance of the wastewater treatment plant will average the entire city but collecting samples at different places in the sewer network would allow isolating specific
ur
districts or neighborhoods in order to carry out a geographical and socio-demographic
Jo
comparison. The results obtained can be compared with population surveys or even used to create estimates where such data does not exist, for instance regarding the consumption of illicit drugs (Castiglioni et al., 2015; Ort et al., 2014; Senta et al., 2015; Zuccato et al., 2008). WBE carried out on well characterized substances (known excretion rate, stability…) in accurately defined sewer systems (knowledge of total population concerned, fraction of households vs offices…) and with robust analytical methods (suitable sample preparation, accurate
35
quantification with internal standards…) might provide better estimates than anonymous surveys in which candidates might not always disclose the complete information. Moreover, WBE is also a non-invasive approach in comparison to collection of blood or urine samples from individuals, and there is no need to obtain personal consent. Only the consent of the entity in charge of wastewater collection and treatment is necessary but this is also problematic since municipalities could be prone to refuse wastewater sampling in order to avoid bad press. Despite this latter limitation, WBE could help to better design prevention campaigns by
ro of
focusing on the most relevant geographic areas and population groups. This could be an important tool in addition to conventional socio-epidemiological studies (Castiglioni et al.,
-p
2015; Thomas and Reid, 2011; van Nuijs et al., 2011).
6.3. Recovery of valuable components
re
Traditionally, wastewater treatment has been focusing on improving water quality by
lP
removing components like pathogens or micro-pollutants that can be a threat for the environment and human health. However, with the concept of circular economy, a major paradigm shift consists in turning wastewater components such as nutrients which were
na
historically considered as pollutants to be removed into valuable components to recover. For instance, nitrogen, ammonium, phosphorus and potassium occurring in wastewater might be
ur
valuable since they can be used as fertilizers for agriculture (Randall and Naidoo, 2018; Simha
Jo
and Ganesapillai, 2017). On its own, this sole paradigm shift provides a new resource of nutrients while avoiding the release of chemicals responsible for eutrophication of natural waters, the energy consumption and the emission of greenhouse gases traditionally associated with the biological nutrient removal. Similarly, rare-earth elements and metals such as Y, La, Ce, Pr can have industrial applications (Peccia and Westerhoff, 2015).
36
Therefore, recent research has been focusing on developing cost-efficient and implementable technologies to concentrate, recover and recycle (Fig. 5) those valuable components from wastewater (Ganesapillai et al., 2016). For instance, several recovery processes can be used for P and N, including adsorption, electrodialysis or struvite precipitation, although only few can produce a fertilizer with minimal post-processing (Perera et al., 2019). Likewise, as progress in science and technology rapidly increments the use of rare-earth elements and precious metals in several electronics and communication applications (He and
ro of
Kappler, 2017), their amount in wastewater becomes increasingly valuable. Therefore, harvesting metals (Ag, Au, Ni, Cu, Zn, Pb or Cd), rare-earth elements and other less-studied elements, such as Nb, Ta, Ga, Ge, In, Tl, and Te (Vriens et al., 2017) prevents the negative
-p
impacts for human and the environment but also provides a new source to obtain these materials at lower cost. For instance, while wastewater production in the U.S. is decreasing due to water
re
conservation measures, metal concentration in related biosolids remains stable and may
lP
increase in the future, which would convert biosolids into a more economical and sustainable source of valuable metals (Westerhoff et al., 2015). Overall, wastewater treatment should not only focus on achieving water reuse but also
na
on harvesting components to be recycled as raw material for different purposes (Puyol et al., 2017). This concept is known as cradle-to-cradle cycle (McDonough and Braungart, 2002), and
ur
encourages the manufacture of products that have a better environmental quality or value
Jo
(upcycling or creative reuse).
6.4. Lowering the carbon footprint Although it is often neglected in the non-expert community, the activity of wastewater treatment plant can be examined in term of carbon footprint since every treatment step requires energy (Mannina et al., 2019). For instance, the traditional biological removal of nutrients
37
requires energy for aeration, and so does the treatment of sludge which relies on drying before exportation by trucks. Therefore, another paradigm shift in wastewater treatment is to lower the carbon footprint through the reduction of energy consumption. In order to reduce the consumption of energy, several strategies can be employed. For instance, wastewater treatment plant and incineration plants can be integrated (Montorsi et al., 2018; Nakatsuka et al., 2020) in order to achieve the self-production of up to 25% of the electric energy required for the operation of the facilities while decreasing the dramatically the final amount of residues sent to
ro of
landfill. Another approach consists in installing treatment processes that can achieve similar removal capacity with lower energy demand, for instance using the Anammox process instead of the conventional biological removal of nutrients (Larsen, 2015). However, in the case of
-p
nutrient removal, the benefit from lower energy consumption should not be overcome by an increase in the inherent generation of greenhouse gases (Fenu et al., 2019). Indeed, the emission
re
of nitrous oxide (N2O) during nutrient removal contributes significantly to the total carbon
lP
footprint of wastewater treatment plants (Zaborowska et al., 2019). Therefore, in addition to developing more energy-efficient treatment and processes limiting the emission of greenhouse gases, numerous studies are also carried out to monitor, model and assess the carbon footprint
na
of wastewater treatment plants (Gruber et al., 2020; Mannina et al., 2016).
ur
6.5. Production of valuable goods
Jo
Wastewater treatment is rapidly evolving from simply ensuring public sanitation and environmental protection to allowing water reuse while harvesting valuable components. However, in order to optimize the benefit of wastewater, another approach consists in developing treatment technologies that will not only attenuate contaminants but also produce valuable goods (Fig. 5). For instance, wastewater can contribute to the production of biofuels which have the potential to replace a part of fossil fuels (Lin et al., 2012). Anaerobic digestion
38
is the typical process to achieve the biological production of energy and biofuel like methane from organic products (Batstone and Virdis, 2014). However, several technologies are currently under development to convert organic matter to bioenergy (Puyol et al., 2017). Thereby, an upgrade of conventional wastewater treatment could achieve an additional attenuation of contaminants while producing valuable material. For instance, wastewater could be used to grow certain types of algae which will extract and fix some metals and nutrients like phosphorous and nitrogen (Chen et al., 2015; de-Bashan and Bashan, 2010). The algal biomass
6.6. Segregation at source and decentralized treatment
ro of
produced might then be used for biofuel production.
-p
The implementation of collective wastewater treatment in urban and semi urban areas is undoubtedly recognized as a major step in wastewater management and environmental
re
protection (Roccaro et al., 2014). Indeed, when the aim is to attenuate specific contaminants,
lP
small facilities designed to treat wastewater at the households scale tend to achieve lower removal rate and it is more efficient to collect and convey all types of wastewater together to large centralized facilities with treatment processes specifically designed to achieve legal
na
requirements before discharge. However, with the concept of circular economy, a potentially upcoming paradigm shift consists in promoting decentralized treatment that tend to be more
ur
sustainable than centralized systems (Diaz-Elsayed et al., 2019; Sgroi et al., 2018b) while
Jo
offering a lower cost (Jung et al., 2018). This approach often adopted in developing countries can also be implemented in industrialized countries through a major change in the modus vivendi (Tchnobanoglous and Leverenz, 2013). In addition, with the circular economy the aim of wastewater treatment is no longer solely to remove contaminants but to recover valuable components as mentioned previously. In this context, segregation at source followed by immediate decentralized treatment would likely be more beneficial. For instance, when
39
considering nutrients cycle, those nutrients which must not be discharged into the environment but recovered from wastewater largely originate from urine excretion. Therefore, collecting urine together with water resulting from shower, washing machine and rain water to a centralized treatment plant result in a severe dilution of nutrients which will difficult their recovery. On the contrary, segregation of urine at the household scale would prevent issues related to dilution and allow developing efficient decentralized nutrient recovery units (Almeida et al., 2019). For instance, a complete nutrient recovery from source-separated urine could be
ro of
achieved by nitrification and distillation (Udert and Wächter, 2012). In fact, a study showed that a wide range of technical options are available for the on-site collection and treatment of urine but none of them was yet able to fulfill all purposes of hygienisation, volume reduction,
-p
stabilization recovery of nutrients and attenuation of trace organic contaminants (Maurer et al., 2006). Consequently, even though it is currently not well developed (Sgroi et al., 2018b),
re
segregation of organic waste, feces, urine, graywater and rainwater at source for decentralized
lP
valorization treatment might be an upcoming trend.
na
7. Current social challenges 7.1. Access to basic sanitation
ur
In the last census of 2018 the world population was estimated to 7.7 billion people.
Jo
However, only approximately 5.4 billion people have access to basic sanitation defined as facilities such as pit latrine, composting toilets and amenities connected to piped sewer or septic tanks that are not shared with other households. The general assembly of the United Nations, through the resolution 64/292 of 2010 (United Nations, 2010), recognized sanitation as a human right that is essential to prevent mortal diseases but 2.3 billion people still live without access to a basic sanitation service (UNICEF and WHO, 2017).
40
Despite the high number of people without access to basic sanitation, the worldwide status has steadily improved over the last decades. In fact, the world population with access to basic sanitation increased from 58% in the year 2000 to 68% in the year 2015 (Fig. 6). Although, the trend might differ according to the country, for instance with France showing a status quo and limited room for improvement, Laos showing dramatic improvement and the Gambia showing a constant worsening (Fig. 6). For the year 2015, up to 148 countries could provide basic sanitation to more than 80% of their population, whereas only 16 countries ensured basic
ro of
sanitation to less than 20% of their population (Fig. 7). In particular, some countries such as Ethiopia, Madagascar and South Sudan provided basic sanitation to less than 10% of their population. Overall, access to basic sanitation improves with the human development index and
-p
countries of highest concern are mainly located in Africa and Asia (Fig. 6 and Fig. 7).
In the next decades, projections indicate a population growth worldwide, so improving
re
and maintaining the requirement of sanitation services will imply a large investment for the
lP
countries. Nowadays, in the countries where the access to basic sanitation is mainly limited by the high cost of sanitation facilities, low-cost solutions based on ecological sanitation that are safe for health and the environment should be engineered. This involves for instance the
na
conservation of water (dry sanitation), the treatment of human excreta to prevent environmental contamination and disease transmission while recycling nutrients for agriculture or home
Jo
ur
gardens among others (Moe and Rheingans, 2006).
7.2. Legal aspects Water resources are often shared between riparian countries. Therefore, many
hydropolitical tensions and conflicts around the world might arise from water scarcity and water quality. Indeed, with climate change, arid and semi-arid regions of the world already face difficulties to meet the rapidly increasing water demand for more than a decade (Swain, 2001).
41
A recent study (De Stefano et al., 2017) reveals that very high risk of potential hydropolitical tension exists for instance between China and Vietnam (Bei Jiang/Hsi basin), Lesotho and South Africa (Thukela basin), Colombia and Ecuador (Mira basin) and even between countries within the European Union. In order to lower the risk of hydropolitical tension and since wastewater can spread diseases all along the river basins from upstream towns to the mouth (Salgot and Folch, 2018), the disposal of wastewater in the environment and water reuse should be regulated through
ro of
national and international legislation in the case of watershed shared by different countries. In United States, The Federal Water Pollution Control Act (known as Clean Water Act) of 1948 revised in 1972 (US Congress, 1972) was the first enacted law to address water pollution and
-p
included funding to improve wastewater treatment. In 1978, the United States and Canada agreed to reduce certain toxic pollutants in the Great Lakes. In 1980, the U.S. Environmental
re
Protection Agency released guidelines to assist municipalities in planning for the
lP
implementation of programs on the non-potable reuse of municipal wastewater (US EPA, 1980). Similarly, in 1991, the European Union adopted the Directive 91/271/EEC (under revision since 2017) which specifies the requirements concerning the collection, treatment and
na
discharge of urban wastewater and certain industrial sectors (EEC, 1991). This Directive also considers the eventuality that wastewater discharge from a member State would adversely
ur
contaminate waters from another member State. However, in 2014, while 18 countries fully
Jo
complied with the requirements related to wastewater collection (article 3), 7 countries complied with the obligation of secondary treatment (article 5) and only 4 countries complied with the necessity of more stringent treatment for discharge in sensitive areas (article 5). Overall, only Austria, Germany and the Netherlands fully complied with all requirements (European Commission, 2017). Failure to comply might result in financial consequences as in the case of Spain condemned by the European Court of Justice to pay 12 M€ to the European
42
Commission for 17 urban agglomerations of more than 15.000 inhabitants without adequate wastewater collection and treatment systems (European Court of Justice, 2018). In parallel, the European Union also strengthened the engagement to preserve water quality through the Water Framework Directive adopted in the year 2000 (European Parliament, 2000) and now completed by guidelines on Integrating Water Reuse into Water Planning and Management, taking into account underlying environmental and socio-economic benefits. Finally, since 2017, a proposal for a Regulation on minimum requirements for water reuse within the European
ro of
Union has been drafted (Council of the European Union, 2019). This proposal covers the obligations regarding reclaimed water permit, risk management, compliance check, information to the public, cooperation between states and reclaimed water quality requirements which
-p
include maximum values for E. coli number, biological oxygen demand and turbidity. However, a critical evaluation of the regulation proposal highlighted that it did not sufficiently address
re
some key points of interest such as the contaminants of emerging concern as well as the
lP
antibiotic resistance spread via the treated effluent of wastewater treatment plants (Rizzo et al., 2018). Moreover, it should be noticed that the scope of such regulation refers to agricultural irrigation without considering potential potable water reuse.
na
Despite the increasing efforts to implement global regulations aiming at preserving water quality by imposing standards for wastewater treatment, new paradigm shifts presented
ur
previously might bring new legal challenges and concerns. For instance, in countries where
Jo
water is not considered as public domain, cities implementing extensive water reuse would dramatically decrease their discharge of wastewater effluent with the potential to impair the water resources and therefore the economy of downstream cities. Similarly, as wastewater becomes a resource from which to extract valuable content (nutrients, metals, energy, and information related to public health), future regulation might need to address more specifically the right to access and use wastewater.
43
7.3. Social acceptance The concept of water reuse presented previously is overall well understood in the context of increasing awareness with respect to water poverty and growing water demand. However, the implementation of water reuse as a drinking water source is less likely to be accepted by society in comparison to non-potable purposes such as irrigation of parks (Rodriguez et al., 2009). Negative emotional reactions gathered under the term “yuck factor”
ro of
are important obstacles to social acceptance which reflect the visceral disgust and fear associated with recycled wastewater (Smith et al., 2018). Overall, the variables explaining the yuck factor include trust, subjective social norms, perceived control and emotional aversion
-p
(Wester et al., 2015). However, reducing the yuck factor in order to increase the acceptance of water reuse is possible, for instance using suitable vocabulary (Rock et al., 2012). Indeed, an
re
experiment showed a significant improvement in public perception when the term “recycled water” was used instead of “treated wastewater” (Menegaki et al., 2009) or when “purified
lP
water” was used instead of “effluent” (Furlong et al., 2019). Similarly, the case of Singapore which strongly avoids using the term “wastewater” and called recycled water “NEWater” is
na
usually given as an example of water reuse with a large (74%) social acceptance (Lee and Tan, 2016; Timm and Deal, 2018). In addition, communication and public dialogue in order to build
ur
and maintain trust (Rodriguez et al., 2009) while educating the population around treatment
Jo
technologies and safety (Stenekes et al., 2006) will further strengthen social acceptance of water reuse to augment drinking water resources. Therefore, water reuse shows important advantages for the environment and to satisfy human requirements but future research should not only focus on improving treatment technologies but also include more social sciences and outreach in order to convince the public. More particularly, public institutions should involve stakeholders and
44
include public participation in decision-making while promoting active communication programs on water reuse. Similarly to water reuse, it should be noticed that public acceptance is a key factor for most of the previously mentioned paradigm shifts. Indeed, after decades of communication aiming at promoting centralized wastewater treatment reinforcing the idea of the necessity to send away wastewater effluents, the implementation of urine separation at source for better recovery of nutrient meets social resistance. As for water reuse, reluctance is mostly due to
ro of
concerns regarding hygiene and safety, as well as the necessity to adapt housing buildings.
8. Conclusion
-p
The bibliometric assessment of wastewater research indicates that the amount of publication has been growing exponentially over the last decades. The examination of the
Identifying the sources of wastewater. While households, hospitals and
lP
re
literature reveals multiple technical challenges:
industries are the main producers of wastewater, new activities like hydraulic
na
fracturing are now emerging or growing and generate large volumes of wastewater which need to be accurately characterized and treated. In addition,
ur
unpredictable activities such as that of fire departments are also often overlooked even though they can generate a large amount of wastewater with specific
Jo
contaminants.
Assessing the composition of wastewater. Despite the tremendous progress in analytical science, wastewater analysis often consists in quantifying known chemicals. However, with the growing application of high resolution mass spectrometry over the last decade, the identification of new contaminants and their transformation products has become a major research focus. 45
Removing trace contaminants. Modern societies often generate wastewater containing new contaminants that conventional treatment were not designed to remove. While recent research focuses on the development of advanced oxidation processes or retention processes to remove such contaminants, another trend consists in developing treatments also able to harvest or generate valuable goods from wastewater.
The examination of the literature also evidenced several paradigm shifts related to
ro of
wastewater: Water reuse. With the growing water demand and the growing hydric stress worldwide, wastewater effluents progressively cease to be a substance that needs
-p
to be disposed to become a valuable water resource that can be used for multiple purposes including irrigation or even the production of drinking water. Wastewater based epidemiology. Collecting both environmental contaminants
re
lP
and urinary metabolites, wastewater is a mirror of the population from which many information can be extracted in order to assess the exposure to certain
na
chemicals or even the prevalence of some diseases. Recovery and production of valuable goods. More than removing contaminants from wastewater, new treatment options tend to harvest valuable components
ur
such as rare-earth elements and precious metals in order reuse them. In addition,
Jo
new treatment options also intend to produce valuable goods from wastewater, for instance by growing certain algae species that will remove nutrients and which could be used subsequently for the production of biofuel.
The multiple challenges and paradigm shifts revealed by the peer-reviewed literature also imply some social impacts which are yet poorly investigated. For instances, while technological progress allows converting wastewater to high quality water suitable for human
46
consumption, heavy efforts in social research and outreach are required to ensure public acceptance. Moreover, even though paradigm shifts such as water reuse and wastewater based epidemiology are increasingly promoted and gain in popularity due to their undoubtable contribution to a more sustainable development of communities, it must be noticed that the peer-reviewed literature has not considered their potential drawbacks on a global level. Indeed, with the large application of water reuse the discharge of wastewater might strongly decrease, which could affect the ecosystem of receiving waters but also the economy of downstream
ro of
cities. For instance, a scenario where several cities upstream reduce their discharge should be simulated in order to assess the subsequent restriction in water resources for downstream cities which might progressively struggle to meet the water demand and therefore have their growth
-p
(population and industries) impaired. In addition, this scenario should also evaluate the ecological impact of a widespread water reuse considering that the fraction of wastewater still
re
discharged (from cities not implementing water reuse, or from households not connected to the
lP
sewer network) might have a lower dilution factor that could induce an increased concentration of contaminants in the receiving water. Finally, considering wastewater as something valuable will imply competition and potential conflict to access it. Therefore, legislation should be
na
drafted at the local and international level and further research is required in order to assess and anticipate the social outcome of progress in wastewater management.
ur
Credit Author Statement
Jo
María C. Villarín: Data Curation, Writing - Original Draft, Writing - Review & Editing, Visualization, Project administration Sylvain Merel: Conceptualization, Data Curation, Writing - Original Draft, Writing - Review & Editing, Supervision
Conflict of interest
47
The authors declare no conflict of interest. The authors declare that they have no known competing financial interests or personal relationships that could have influenced the work reported in this paper.
Acknowledgements María C. Villarín is grateful to Åse Åtland from the Norwegian Institute of Water Research
ro of
(NIVA) for allowing her to join the group located in Bergen as visiting scientist.
References
Jo
ur
na
lP
re
-p
Adeyemo, F.E., Singh, G., Reddy, P., Bux, F., Stenstrom, T.A., 2019. Efficiency of chlorine and UV in the inactivation of Cryptosporidium and Giardia in wastewater. Plos One 14. Ahrens, L., 2011. Polyfluoroalkyl compounds in the aquatic environment: a review of their occurrence and fate. Journal of Environmental Monitoring 13, 20-31. Ajonina, C., Buzie, C., Rubiandini, R.H., Otterpohl, R., 2015. Microbial pathogens in Wastewater Treatment Plants (WWTP) in Hamburg. Journal of Toxicology and Environmental Health - Part A: Current Issues 78, 381-387. Al-Gheethi, A., Noman, E., David, B.J., Mohamed, R., Abdullah, A.H., Nagapan, S., Mohd, A.H., 2018. A review of potential factors contributing to epidemic cholera in Yemen. Journal of Water and Health 16, 667-680. Almeida, J.A.S., Azevedo, A.L., Brett, M., Tadeu, A., Silva-Afonso, A., Costa, A., Rufo, E., Além, S., 2019. Urine recovery at the building level. Building and Environment 156, 110-116. Amor, C., De Torres-Socias, E., Peres, J.A., Maldonado, M.I., Oller, I., Malato, S., Lucas, M.S., 2015. Mature landfill leachate treatment by coagulation/flocculation combined with Fenton and solar photoFenton processes. Journal of Hazardous Materials 286, 261-268. Anumol, T., Merel, S., Clarke, B.O., Snyder, S.A., 2013. Ultra high performance liquid chromatography tandem mass spectrometry for rapid analysis of trace organic contaminants in water. Chemistry Central Journal 7, 104. Anumol, T., Sgroi, M., Park, M., Roccaro, P., Snyder, S.A., 2015a. Predicting trace organic compound breakthrough in granular activated carbon using fluorescence and UV absorbance as surrogates. Water Research 76, 76-87. Anumol, T., Snyder, S.A., 2015. Rapid analysis of trace organic compounds in water by automated online solid-phase extraction coupled to liquid chromatography–tandem mass spectrometry. Talanta 132, 77-86. Anumol, T., Wu, S., Marques dos Santos, M., Daniels, K.D., Snyder, S.A., 2015b. Rapid direct injection LC-MS/MS method for analysis of prioritized indicator compounds in wastewater effluent. Environmental Science: Water Research & Technology 1, 632-643. Asghar, A., Raman, A.A.A., Daud, W.M.A.W., 2015. Advanced oxidation processes for in-situ production of hydrogen peroxide/hydroxyl radical for textile wastewater treatment: a review. Journal of Cleaner Production 87, 826-838.
48
Jo
ur
na
lP
re
-p
ro of
Ashrafi, O., Yerushalmi, L., Haghighat, F., 2015. Wastewater treatment in the pulp-and-paper industry: A review of treatment processes and the associated greenhouse gas emission. Journal of Environmental Management 158, 146-157. Bailey, E.S., Casanova, L.M., Simmons, O.D., Sobsey, M.D., 2018. Tertiary treatment and dual disinfection to improve microbial quality of reclaimed water for potable and non-potable reuse: A case study of facilities in North Carolina. Science of The Total Environment 630, 379-388. Batstone, D.J., Virdis, B., 2014. The role of anaerobic digestion in the emerging energy economy. Current Opinion in Biotechnology 27, 142-149. Becouze-Lareure, C., Dembélé, A., Coquery, M., Cren-Olivé, C., Barillon, B., Bertrand-Krajewski, J.L., 2016. Source characterisation and loads of metals and pesticides in urban wet weather discharges. Urban Water Journal 13, 600-617. Bijlsma, L., Berntssen, M.H.G., Merel, S., 2019. A Refined Nontarget Workflow for the Investigation of Metabolites through the Prioritization by in Silico Prediction Tools. Analytical Chemistry 91, 6321-6328. Bilal, M., Asgher, M., Parra-Saldivar, R., Hu, H., Wang, W., Zhang, X., Iqbal, H.M.N., 2017. Immobilized ligninolytic enzymes: An innovative and environmental responsive technology to tackle dye-based industrial pollutants - A review. Science of The Total Environment 576, 646-659. Bixio, D., Thoeye, C., Wintgens, T., Ravazzini, A., Miska, V., Muston, M., Chikurel, H., Aharoni, A., Joksimovic, D., Melin, T., 2008. Water reclamation and reuse: implementation and management issues. Desalination 218, 13-23. Boczkaj, G., Fernandes, A., 2017. Wastewater treatment by means of advanced oxidation processes at basic pH conditions: A review. Chemical Engineering Journal 320, 608-633. Bokare, A.D., Choi, W., 2014. Review of iron-free Fenton-like systems for activating H2O2 in advanced oxidation processes. Journal of Hazardous Materials 275, 121-135. Bollmann, U.E., Tang, C., Eriksson, E., Jönsson, K., Vollertsen, J., Bester, K., 2014. Biocides in urban wastewater treatment plant influent at dry and wet weather: Concentrations, mass flows and possible sources. Water Research 60, 64-74. Bottoni, P., Caroli, S., Caracciolo, A.B., 2010. Pharmaceuticals as priority water contaminants. Toxicological and Environmental Chemistry 92, 549-565. Bourgin, M., Beck, B., Boehler, M., Borowska, E., Fleiner, J., Salhi, E., Teichler, R., von Gunten, U., Siegrist, H., McArdell, C.S., 2018. Evaluation of a full-scale wastewater treatment plant upgraded with ozonation and biological post-treatments: Abatement of micropollutants, formation of transformation products and oxidation by-products. Water Research 129, 486-498. Burkhardt, M., Zuleeg, S., Vonbank, R., Schmid, P., Hean, S., Lamani, X., Bester, K., Boller, M., 2011. Leaching of additives from construction materials to urban storm water runoff. Water Science and Technology 63, 1974-1982. Cai, L., Zhang, T., 2013. Detecting Human Bacterial Pathogens in Wastewater Treatment Plants by a High-Throughput Shotgun Sequencing Technique. Environmental Science & Technology 47, 54335441. Caicedo, C., Rosenwinkel, K.H., Exner, M., Verstraete, W., Suchenwirth, R., Hartemann, P., Nogueira, R., 2019. Legionella occurrence in municipal and industrial wastewater treatment plants and risks of reclaimed wastewater reuse: Review. Water Research 149, 21-34. Campos-Mañas, M.C., Plaza-Bolaños, P., Martínez-Piernas, A.B., Sánchez-Pérez, J.A., Agüera, A., 2019. Determination of pesticide levels in wastewater from an agro-food industry: Target, suspect and transformation product analysis. Chemosphere 232, 152-163. Cao, Y., van Loosdrecht, M.C.M., Daigger, G.T., 2017. Mainstream partial nitritation-anammox in municipal wastewater treatment: status, bottlenecks, and further studies. Applied Microbiology and Biotechnology 101, 1365-1383. Carballa, M., Omil, F., Lema, J.M., Llompart, M., García-Jares, C., Rodríguez, I., Gómez, M., Ternes, T., 2004. Behavior of pharmaceuticals, cosmetics and hormones in a sewage treatment plant. Water Research 38, 2918-2926. Carr, S.A., Liu, J., Tesoro, A.G., 2016. Transport and fate of microplastic particles in wastewater treatment plants. Water Research 91, 174-182. 49
Jo
ur
na
lP
re
-p
ro of
Castiglioni, S., Senta, I., Borsotti, A., Davoli, E., Zuccato, E., 2015. A novel approach for monitoring tobacco use in local communities by wastewater analysis. Tobacco Control 24, 38-42. Chang, M., 2015. Reducing microplastics from facial exfoliating cleansers in wastewater through treatment versus consumer product decisions. Marine Pollution Bulletin 101, 330-333. Chekli, L., Phuntsho, S., Kim, J.E., Kim, J., Choi, J.Y., Choi, J.-S., Kim, S., Kim, J.H., Hong, S., Sohn, J., Shon, H.K., 2016. A comprehensive review of hybrid forward osmosis systems: Performance, applications and future prospects. Journal of Membrane Science 497, 430-449. Chen, G., Zhao, L., Qi, Y., 2015. Enhancing the productivity of microalgae cultivated in wastewater toward biofuel production: A critical review. Applied Energy 137, 282-291. Chen, W., Westerhoff, P., Leenheer, J.A., Booksh, K., 2003. Fluorescence Excitation−Emission Matrix Regional Integration to Quantify Spectra for Dissolved Organic Matter. Environmental Science & Technology 37, 5701-5710. Chowdhury, F., Lant, C., Dziegielewski, B., 2013. A century of water supply expansion for ten U.S. cities. Applied Geography 45, 58-76. Chung, K.T., 2016. Azo dyes and human health: A review. Journal of Environmental Science and Health Part C-Environmental Carcinogenesis & Ecotoxicology Reviews 34, 233-261. Cieslik, B.M., Namiesnik, J., Konieczka, P., 2015. Review of sewage sludge management: standards, regulations and analytical methods. Journal of Cleaner Production 90, 1-15. Clarke, B.O., Anumol, T., Barlaz, M., Snyder, S.A., 2015. Investigating landfill leachate as a source of trace organic pollutants. Chemosphere 127, 269-275. Council of the European Union, 2019. Interinstitutional File: 2018/0169(COD). Daniels, M.E., Smith, W.A., Jenkins, M.W., 2018. Estimating Cryptosporidium and Giardia disease burdens for children drinking untreated groundwater in a rural population in India. PLOS Neglected Tropical Diseases 12, e0006231. Daughton, C.G., 2001. Illicit Drugs in Municipal Sewage, Pharmaceuticals and Care Products in the Environment. American Chemical Society, pp. 348-364. Daughton, C.G., 2011. Illicit drugs: Contaminants in the environment and utility in forensic epidemiology, Reviews of Environmental Contamination and Toxicology, pp. 59-110. de-Bashan, L.E., Bashan, Y., 2010. Immobilized microalgae for removing pollutants: Review of practical aspects. Bioresource Technology 101, 1611-1627. De Stefano, L., Petersen-Perlman, J.D., Sproles, E.A., Eynard, J., Wolf, A.T., 2017. Assessment of transboundary river basins for potential hydro-political tensions. Global Environmental Change 45, 3546. Desmidt, E., Ghyselbrecht, K., Zhang, Y., Pinoy, L., Van der Bruggen, B., Verstraete, W., Rabaey, K., Meesschaert, B., 2015. Global Phosphorus Scarcity and Full-Scale P-Recovery Techniques: A Review. Critical Reviews in Environmental Science and Technology 45, 336-384. Dias, E.M., Petit, C., 2015. Towards the use of metal-organic frameworks for water reuse: A review of the recent advances in the field of organic pollutants removal and degradation and the next steps in the field. Journal of Materials Chemistry A 3, 22484-22506. Diaz-Elsayed, N., Rezaei, N., Guo, T., Mohebbi, S., Zhang, Q., 2019. Wastewater-based resource recovery technologies across scale: A review. Resources, Conservation and Recycling 145, 94-112. Dris, R., Gasperi, J., Rocher, V., Saad, M., Renault, N., Tassin, B., 2015. Microplastic contamination in an urban area: a case study in Greater Paris. Environmental Chemistry 12, 592-599. Du, R., Cao, S., Li, B., Niu, M., Wang, S., Peng, Y., 2017. Performance and microbial community analysis of a novel DEAMOX based on partial-denitrification and anammox treating ammonia and nitrate wastewaters. Water Research 108, 46-56. EEC, 1991. Council Directive 91 /271 /EEC concerning urban waste water treatment, p. 13. Eftim, S.E., Hong, T., Soller, J., Boehm, A., Warren, I., Ichida, A., Nappier, S.P., 2017. Occurrence of norovirus in raw sewage - A systematic literature review and meta-analysis. Water Research 111, 366374. Escher, B.I., Allinson, M., Altenburger, R., Bain, P.A., Balaguer, P., Busch, W., Crago, J., Denslow, N.D., Dopp, E., Hilscherova, K., Humpage, A.R., Kumar, A., Grimaldi, M., Jayasinghe, B.S., Jarosova, B., Jia, A., 50
Jo
ur
na
lP
re
-p
ro of
Makarov, S., Maruya, K.A., Medvedev, A., Mehinto, A.C., Mendez, J.E., Poulsen, A., Prochazka, E., Richard, J., Schifferli, A., Schlenk, D., Scholz, S., Shiraishi, F., Snyder, S., Su, G., Tang, J.Y.M., Burg, B.v.d., Linden, S.C.v.d., Werner, I., Westerheide, S.D., Wong, C.K.C., Yang, M., Yeung, B.H.Y., Zhang, X., Leusch, F.D.L., 2014. Benchmarking Organic Micropollutants in Wastewater, Recycled Water and Drinking Water with In Vitro Bioassays. Environmental Science & Technology 48, 1940-1956. European Commission, 2017. Ninth Report on the implementation status and the programmes for implementation (as required by article 17) of Council Directive 91/271/EEC concerning urban waste water treatment. European Court of Justice, 2018. European Commission v Kingdom of Spain, Case C-205/17. European Parliament, 2000. Directive 2000/60/EC of the European Parliament and of the Council of 23 October 2000 establishing a framework for Community action in the field of water policy. Eurostat, 2018. Generation and discharge of wastewater in volume. Fane, A.G., Wang, R., Hu, M.X., 2015. Synthetic Membranes for Water Purification: Status and Future. Angewandte Chemie-International Edition 54, 3368-3386. Fenu, A., Smolders, S., De Gussem, K., Weemaes, M., 2019. Conflicting carbon footprint and energy saving in a side-stream Anammox Process. Biochemical Engineering Journal 151, 107336. Furlong, C., Jegatheesan, J., Currell, M., Iyer-Raniga, U., Khan, T., Ball, A.S., 2019. Is the global public willing to drink recycled water? A review for researchers and practitioners. Utilities Policy 56, 53-61. Ganesapillai, M., Simha, P., Gupta, K., Jayan, M., 2016. Nutrient Recovery and Recycling from Human Urine: A Circular Perspective on Sanitation and Food Security, pp. 346-353. Garcia, D., Alcantara, C., Blanco, S., Perez, R., Bolado, S., Munoz, R., 2017. Enhanced carbon, nitrogen and phosphorus removal from domestic wastewater in a novel anoxic-aerobic photobioreactor coupled with biogas upgrading. Chemical Engineering Journal 313, 424-434. Gerrity, D., Pecson, B., Shane Trussell, R., Rhodes Trussell, R., 2013. Potable reuse treatment trains throughout the world. Journal of Water Supply: Research and Technology - AQUA 62, 321-338. Gleick, P.H., 1996. Basic Water Requirements for Human Activities: Meeting Basic Needs. Water International 21, 83-92. Gomes, J., Costa, R., Quinta-Ferreira, R.M., Martins, R.C., 2017. Application of ozonation for pharmaceuticals and personal care products removal from water. Science of The Total Environment 586, 265-283. Grant, S.B., Saphores, J.-D., Feldman, D.L., Hamilton, A.J., Fletcher, T.D., Cook, P.L.M., Stewardson, M., Sanders, B.F., Levin, L.A., Ambrose, R.F., Deletic, A., Brown, R., Jiang, S.C., Rosso, D., Cooper, W.J., Marusic, I., 2012. Taking the “Waste” Out of “Wastewater” for Human Water Security and Ecosystem Sustainability. Science 337, 681-686. Gruber, W., Villez, K., Kipf, M., Wunderlin, P., Siegrist, H., Vogt, L., Joss, A., 2020. N2O emission in fullscale wastewater treatment: Proposing a refined monitoring strategy. Science of The Total Environment 699, 134157. Guaya, D., Valderrama, C., Farran, A., Armijos, C., Luis Cortina, J., 2015. Simultaneous phosphate and ammonium removal from aqueous solution by a hydrated aluminum oxide modified natural zeolite. Chemical Engineering Journal 271, 204-213. Hai Nguyen, T., You, S.-J., Hosseini-Bandegharaei, A., Chao, H.-P., 2017. Mistakes and inconsistencies regarding adsorption of contaminants from aqueous solutions: A critical review. Water Research 120, 88-116. Harkness, J.S., Dwyer, G.S., Warner, N.R., Parker, K.M., Mitch, W.A., Vengosh, A., 2015. Iodide, Bromide, and Ammonium in Hydraulic Fracturing and Oil and Gas Wastewaters: Environmental Implications. Environmental Science & Technology 49, 1955-1963. He, J., Kappler, A., 2017. Recovery of precious metals from waste streams. Microbial Biotechnology 10, 1194-1198. Hellmér, M., Paxéus, N., Magnius, L., Enache, L., Arnholm, B., Johansson, A., Bergström, T., Norder, H., 2014. Detection of Pathogenic Viruses in Sewage Provided Early Warnings of Hepatitis A Virus and Norovirus Outbreaks. Applied and Environmental Microbiology 80, 6771. 51
Jo
ur
na
lP
re
-p
ro of
Hernández, F., Ibáñez, M., Botero-Coy, A.-M., Bade, R., Bustos-López, M.C., Rincón, J., Moncayo, A., Bijlsma, L., 2015. LC-QTOF MS screening of more than 1,000 licit and illicit drugs and their metabolites in wastewater and surface waters from the area of Bogotá, Colombia. Analytical and Bioanalytical Chemistry 407, 6405-6416. Hopkins, J., 2012. The ‘sacred sewer’: Tradition and religion in the Cloaca Maxima, Rome, Pollution and Propriety: Dirt, Disease and Hygiene in the Eternal City from Antiquity to Modernity, pp. 81-102. Huang, Y., Cheng, S., Wu, Y.-P., Wu, J., Li, Y., Huo, Z.-L., Wu, J.-C., Xie, X.-C., Korshin, G.V., Li, A.-M., Li, W.-T., 2019. Developing surrogate indicators for predicting suppression of halophenols formation potential and abatement of estrogenic activity during ozonation of water and wastewater. Water Research 161, 152-160. Huerta, B., Rodriguez-Mozaz, S., Nannou, C., Nakis, L., Ruhi, A., Acuna, V., Sabater, S., Barcelo, D., 2016. Determination of a broad spectrum of pharmaceuticals and endocrine disruptors in biofilm from a waste water treatment plant-impacted river. Science of The Total Environment 540, 241-249. Jia, A., Wu, S., Daniels, K.D., Snyder, S.A., 2016. Balancing the Budget: Accounting for Glucocorticoid Bioactivity and Fate during Water Treatment. Environmental Science & Technology 50, 2870-2880. Jung, Y.T., Narayanan, N.C., Cheng, Y.L., 2018. Cost comparison of centralized and decentralized wastewater management systems using optimization model. Journal of Environmental Management 213, 90-97. Jungnickel, C., Stock, F., Brandsch, T., Ranke, J., 2008. Risk assessment of biocides in roof paint. Environmental Science and Pollution Research 15, 258. Kankaanpää, A., Ariniemi, K., Heinonen, M., Kuoppasalmi, K., Gunnar, T., 2014. Use of illicit stimulant drugs in Finland: A wastewater study in ten major cities. Science of The Total Environment 487, 696702. Kasprzyk-Hordern, B., Bijlsma, L., Castiglioni, S., Covaci, A., de Voogt, P., Emke, E., Hernández, F., Ort, C., Reid, M., van Nuijs, A.L.N., Thomas, K.V., 2014. Wastewater-based epidemiology for public health monitoring. Water & Sewerage Journal 4, 25-26. Kelessidis, A., Stasinakis, A.S., 2012. Comparative study of the methods used for treatment and final disposal of sewage sludge in European countries. Waste Management 32, 1186-1195. Kelly, P.T., He, Z., 2014. Nutrients removal and recovery in bioelectrochemical systems: A review. Bioresource Technology 153, 351-360. Keranen, K.M., Weingarten, M., Abers, G.A., Bekins, B.A., Ge, S., 2014. Sharp increase in central Oklahoma seismicity since 2008 induced by massive wastewater injection. Science 345, 448-451. Khan, N.A., Hasan, Z., Jhung, S.H., 2013. Adsorptive removal of hazardous materials using metalorganic frameworks (MOFs): A review. Journal of Hazardous Materials 244, 444-456. Kolpin, D.W., Blazer, V.S., Gray, J.L., Focazio, M.J., Young, J.A., Alvarez, D.A., Iwanowicz, L.R., Foreman, W.T., Furlong, E.T., Speiran, G.K., Zaugg, S.D., Hubbard, L.E., Meyer, M.T., Sandstrom, M.W., Barber, L.B., 2013. Chemical contaminants in water and sediment near fish nesting sites in the Potomac River basin: Determining potential exposures to smallmouth bass (Micropterus dolomieu). Science of The Total Environment 443, 700-716. König, M., Escher, B.I., Neale, P.A., Krauss, M., Hilscherová, K., Novák, J., Teodorović, I., Schulze, T., Seidensticker, S., Kamal Hashmi, M.A., Ahlheim, J., Brack, W., 2017. Impact of untreated wastewater on a major European river evaluated with a combination of in vitro bioassays and chemical analysis. Environmental Pollution 220, 1220-1230. Korshin, G.V., Sgroi, M., Ratnaweera, H., 2018. Spectroscopic surrogates for real time monitoring of water quality in wastewater treatment and water reuse. Current Opinion in Environmental Science & Health 2, 12-19. Krzeminski, P., Leverette, L., Malamis, S., Katsou, E., 2017. Membrane bioreactors - A review on recent developments in energy reduction, fouling control, novel configurations, LCA and market prospects. Journal of Membrane Science 527, 207-227. Larsen, T.A., 2015. CO2-neutral wastewater treatment plants or robust, climate-friendly wastewater management? A systems perspective. Water Research 87, 513-521. 52
Jo
ur
na
lP
re
-p
ro of
Le Roux, J., Plewa, M.J., Wagner, E.D., Nihemaiti, M., Dad, A., Croué, J.-P., 2017. Chloramination of wastewater effluent: Toxicity and formation of disinfection byproducts. Journal of Environmental Sciences 58, 135-145. Lee, A., Elam, J.W., Darling, S.B., 2016. Membrane materials for water purification: design, development, and application. Environmental Science-Water Research & Technology 2, 17-42. Lee, H., Tan, T.P., 2016. Singapore’s experience with reclaimed water: NEWater. International Journal of Water Resources Development 32, 611-621. Lee, P.-W., Tseng, L.-C., Hwang, J.-S., 2018. Comparison of mesozooplankton mortality impacted by the cooling systems of two nuclear power plants at the northern Taiwan coast, southern East China Sea. Marine Pollution Bulletin 136, 114-124. Lege, S., Guillet, G., Merel, S., Yanez Heras, J.E., Zwiener, C., 2017. Denatonium – A so far unrecognized but ubiquitous water contaminant? Water Research 112, 254-260. Lester, Y., Ferrer, I., Thurman, E.M., Sitterley, K.A., Korak, J.A., Aiken, G., Linden, K.G., 2015. Characterization of hydraulic fracturing flowback water in Colorado: Implications for water treatment. Science of The Total Environment 512, 637-644. Leusch, F.D.L., Khan, S.J., Gagnon, M.M., Quayle, P., Trinh, T., Coleman, H., Rawson, C., Chapman, H.F., Blair, P., Nice, H., Reitsema, T., 2014. Assessment of wastewater and recycled water quality: A comparison of lines of evidence from in vitro, in vivo and chemical analyses. Water Research 50, 420431. Leverenz, H.L., Tchobanoglous, G., Asano, T., 2011. Direct potable reuse: A future imperative. Journal of Water Reuse and Desalination 1, 2-10. Lin, C.Y., Lay, C.H., Sen, B., Chu, C.Y., Kumar, G., Chen, C.C., Chang, J.S., 2012. Fermentative hydrogen production from wastewaters: A review and prognosis. International Journal of Hydrogen Energy 37, 15632-15642. Liu, Z.-h., Kanjo, Y., Mizutani, S., 2009. Removal mechanisms for endocrine disrupting compounds (EDCs) in wastewater treatment - physical means, biodegradation, and chemical advanced oxidation: A review. Science of The Total Environment 407, 731-748. Llewellyn, G.T., Dorman, F., Westland, J.L., Yoxtheimer, D., Grieve, P., Sowers, T., Humston-Fulmer, E., Brantley, S.L., 2015. Evaluating a groundwater supply contamination incident attributed to Marcellus Shale gas development. Proceedings of the National Academy of Sciences of the United States of America 112, 6325-6330. Lofrano, G., Brown, J., 2010. Wastewater management through the ages: A history of mankind. Science of The Total Environment 408, 5254-5264. Luo, W., Phan, H.V., Xie, M., Hai, F.I., Price, W.E., Elimelech, M., Nghiem, L.D., 2017. Osmotic versus conventional membrane bioreactors integrated with reverse osmosis for water reuse: Biological stability, membrane fouling, and contaminant removal. Water Research 109, 122-134. Lutz, B.D., Lewis, A.N., Doyle, M.W., 2013. Generation, transport, and disposal of wastewater associated with Marcellus Shale gas development. Water Resources Research 49, 647-656. Magnusson, K., Jalkanen, J.-P., Johansson, L., Smailys, V., Telemo, P., Winnes, H., 2018. Risk assessment of bilge water discharges in two Baltic shipping lanes. Marine Pollution Bulletin 126, 575-584. Malchi, T., Maor, Y., Tadmor, G., Shenker, M., Chefetz, B., 2014. Irrigation of root vegetables with treated wastewater: Evaluating uptake of pharmaceuticals and the associated human health risks. Environmental Science and Technology 48, 9325-9333. Mannina, G., Ekama, G., Caniani, D., Cosenza, A., Esposito, G., Gori, R., Garrido-Baserba, M., Rosso, D., Olsson, G., 2016. Greenhouse gases from wastewater treatment — A review of modelling tools. Science of The Total Environment 551-552, 254-270. Mannina, G., Rebouças, T.F., Cosenza, A., Chandran, K., 2019. A plant-wide wastewater treatment plant model for carbon and energy footprint: Model application and scenario analysis. Journal of Cleaner Production 217, 244-256. Maurer, M., Pronk, W., Larsen, T.A., 2006. Treatment processes for source-separated urine. Water Research 40, 3151-3166. 53
Jo
ur
na
lP
re
-p
ro of
McCall, A.K., Bade, R., Kinyua, J., Lai, F.Y., Thai, P.K., Covaci, A., Bijlsma, L., van Nuijs, A.L.N., Ort, C., 2016. Critical review on the stability of illicit drugs in sewers and wastewater samples. Water Research 88, 933-947. McDonough, W., Braungart, M., 2002. Cradle to Cradle: Remaking the Way We Make Things. North Point Press. Menegaki, A.N., Mellon, R.C., Vrentzou, A., Koumakis, G., Tsagarakis, K.P., 2009. What’s in a name: Framing treated wastewater as recycled water increases willingness to use and willingness to pay. Journal of Economic Psychology 30, 285-292. Merel, S., Anumol, T., Park, M., Snyder, S.A., 2015a. Application of surrogates, indicators, and highresolution mass spectrometry to evaluate the efficacy of UV processes for attenuation of emerging contaminants in water. Journal of Hazardous Materials 282, 75-85. Merel, S., Benzing, S., Gleiser, C., Di Napoli-Davis, G., Zwiener, C., 2018. Occurrence and overlooked sources of the biocide carbendazim in wastewater and surface water. Environmental Pollution 239, 512-521. Merel, S., Lege, S., Yanez Heras, J.E., Zwiener, C., 2017. Assessment of N-Oxide Formation during Wastewater Ozonation. Environmental Science & Technology 51, 410-417. Merel, S., Nikiforov, A.I., Snyder, S.A., 2015b. Potential analytical interferences and seasonal variability in diethyltoluamide environmental monitoring programs. Chemosphere 127, 238-245. Merel, S., Snyder, S.A., 2016. Critical assessment of the ubiquitous occurrence and fate of the insect repellent N,N-diethyl-m-toluamide in water. Environment International 96, 98-117. Merel, S., Villarín, M.C., Chung, K., Snyder, S., 2013a. Spatial and thematic distribution of research on cyanotoxins. Toxicon 76, 118-131. Merel, S., Walker, D., Chicana, R., Snyder, S., Baurès, E., Thomas, O., 2013b. State of knowledge and concerns on cyanobacterial blooms and cyanotoxins. Environment International 59, 303-327. Michael-Kordatou, I., Michael, C., Duan, X., He, X., Dionysiou, D.D., Mills, M.A., Fatta-Kassinos, D., 2015. Dissolved effluent organic matter: Characteristics and potential implications in wastewater treatment and reuse applications. Water Research 77, 213-248. Mintenig, S.M., Int-Veen, I., Loeder, M.G.J., Primpke, S., Gerdts, G., 2017. Identification of microplastic in effluents of waste water treatment plants using focal plane array-based micro-Fourier-transform infrared imaging. Water Research 108, 365-372. Moe, C.L., Rheingans, R.D., 2006. Global challenges in water, sanitation and health. J Water Health 4 Suppl 1, 41-57. Mohammad, A.W., Teow, Y.H., Ang, W.L., Chung, Y.T., Oatley-Radcliffe, D.L., Hilal, N., 2015. Nanofiltration membranes review: Recent advances and future prospects. Desalination 356, 226-254. Mompelat, S., Jaffrezic, A., Jardé, E., Le Bot, B., 2013. Storage of natural water samples and preservation techniques for pharmaceutical quantification. Talanta 109, 31-45. Mompelat, S., Le Bot, B., Thomas, O., 2009. Occurrence and fate of pharmaceutical products and byproducts, from resource to drinking water. Environment International 35, 803-814. Montaña, M., Camacho, A., Devesa, R., Vallés, I., Céspedes, R., Serrano, I., Blàzquez, S., Barjola, V., 2013. The presence of radionuclides in wastewater treatment plants in Spain and their effect on human health. Journal of Cleaner Production 60, 77-82. Montorsi, L., Milani, M., Venturelli, M., 2018. Economic assessment of an integrated waste to energy system for an urban sewage treatment plant: A numerical approach. Energy 158, 105-110. Moody, C.A., Field, J.A., 2000. Perfluorinated surfactants and the environmental implications of their use in fire-fighting foams. Environmental Science & Technology 34, 3864-3870. Moody, C.A., Hebert, G.N., Strauss, S.H., Field, J.A., 2003. Occurrence and persistence of perfluorooctanesulfonate and other perfluorinated surfactants in groundwater at a fire-training area at Wurtsmith Air Force Base, Michigan, USA. Journal of Environmental Monitoring 5, 341-345. Moutinho, G.M., dos Santos, I., Matos, M., Auxtero, M.D., 2019. Research and identification of Cryptosporidium and Giardia lamblia in wastewater treatment plants. Annals of Medicine 51, S73-S73.
54
Jo
ur
na
lP
re
-p
ro of
Nakatsuka, N., Kishita, Y., Kurafuchi, T., Akamatsu, F., 2020. Integrating wastewater treatment and incineration plants for energy-efficient urban biomass utilization: A life cycle analysis. Journal of Cleaner Production 243, 118448. Neale, P.A., Munz, N.A., Aїt-Aїssa, S., Altenburger, R., Brion, F., Busch, W., Escher, B.I., Hilscherová, K., Kienle, C., Novák, J., Seiler, T.-B., Shao, Y., Stamm, C., Hollender, J., 2017. Integrating chemical analysis and bioanalysis to evaluate the contribution of wastewater effluent on the micropollutant burden in small streams. Science of The Total Environment 576, 785-795. Negreira, N., Regueiro, J., Valdersnes, S., Berntssen, M.H.G., Ørnsrud, R., 2017. Comprehensive characterization of ethoxyquin transformation products in fish feed by traveling-wave ion mobility spectrometry coupled to quadrupole time-of-flight mass spectrometry. Analytica Chimica Acta 965, 72-82. Neoh, C.H., Noor, Z.Z., Mutamim, N.S.A., Lim, C.K., 2016. Green technology in wastewater treatment technologies: Integration of membrane bioreactor with various wastewater treatment systems. Chemical Engineering Journal 283, 582-594. Novo, A., Andre, S., Viana, P., Nunes, O.C., Manaia, C.M., 2013. Antibiotic resistance, antimicrobial residues and bacterial community composition in urban wastewater. Water Research 47, 1875-1887. Ort, C., Lawrence, M.G., Rieckermann, J., Joss, A., 2010. Sampling for pharmaceuticals and personal care products (PPCPs) and illicit drugs in wastewater systems: Are your conclusions valid? A critical review. Environmental Science and Technology 44, 6024-6035. Ort, C., van Nuijs, A.L.N., Berset, J.D., Bijlsma, L., Castiglioni, S., Covaci, A., de Voogt, P., Emke, E., FattaKassinos, D., Griffiths, P., Hernández, F., González-Mariño, I., Grabic, R., Kasprzyk-Hordern, B., Mastroianni, N., Meierjohann, A., Nefau, T., Östman, M., Pico, Y., Racamonde, I., Reid, M., Slobodnik, J., Terzic, S., Thomaidis, N., Thomas, K.V., 2014. Spatial differences and temporal changes in illicit drug use in Europe quantified by wastewater analysis. Addiction 109, 1338-1352. Oturan, M.A., Aaron, J.-J., 2014. Advanced Oxidation Processes in Water/Wastewater Treatment: Principles and Applications. A Review. Critical Reviews in Environmental Science and Technology 44, 2577-2641. Paerl, H.W., Scott, J.T., McCarthy, M.J., Newell, S.E., Gardner, W.S., Havens, K.E., Hoffman, D.K., Wilhelm, S.W., Wurtsbaugh, W.A., 2016. It Takes Two to Tango: When and Where Dual Nutrient (N & P) Reductions Are Needed to Protect Lakes and Downstream Ecosystems. Environmental Science & Technology 50, 10805-10813. Park, H.B., Kamcev, J., Robeson, L.M., Elimelech, M., Freeman, B.D., 2017a. Maximizing the right stuff: The trade-off between membrane permeability and selectivity. Science 356. Park, M., Anumol, T., Daniels, K.D., Wu, S., Ziska, A.D., Snyder, S.A., 2017b. Predicting trace organic compound attenuation by ozone oxidation: Development of indicator and surrogate models. Water Research 119, 21-32. Park, Y., Lee, Y.-C., Shin, W.S., Choi, S.-J., 2010. Removal of cobalt, strontium and cesium from radioactive laundry wastewater by ammonium molybdophosphate-polyacrylonitrile (AMP-PAN). Chemical Engineering Journal 162, 685-695. Paulshus, E., Kühn, I., Möllby, R., Colque, P., O'Sullivan, K., Midtvedt, T., Lingaas, E., Holmstad, R., Sørum, H., 2019. Diversity and antibiotic resistance among Escherichia coli populations in hospital and community wastewater compared to wastewater at the receiving urban treatment plant. Water Research 161, 232-241. Peccia, J., Westerhoff, P., 2015. We Should Expect More out of Our Sewage Sludge. Environmental Science and Technology 49, 8271-8276. Pedrero, F., Kalavrouziotis, I., Alarcón, J.J., Koukoulakis, P., Asano, T., 2010. Use of treated municipal wastewater in irrigated agriculture-Review of some practices in Spain and Greece. Agricultural Water Management 97, 1233-1241. Perera, M.K., Englehardt, J.D., Dvorak, A.C., 2019. Technologies for Recovering Nutrients from Wastewater: A Critical Review. Environmental Engineering Science 36, 511-529.
55
Jo
ur
na
lP
re
-p
ro of
Perreault, F., Jaramillo, H., Xie, M., Ude, M., Nghiem, L.D., Elimelech, M., 2016. Biofouling Mitigation in Forward Osmosis Using Graphene Oxide Functionalized Thin-Film Composite Membranes. Environmental Science & Technology 50, 5840-5848. Petrie, B., Barden, R., Kasprzyk-Hordern, B., 2015. A review on emerging contaminants in wastewaters and the environment: Current knowledge, understudied areas and recommendations for future monitoring. Water Research 72, 3-27. Plucinski, M.P., Sullivan, A.L., Hurley, R.J., 2017. A methodology for comparing the relative effectiveness of suppressant enhancers designed for the direct attack of wildfires. Fire Safety Journal 87, 71-79. Postigo, C., Richardson, S.D., 2014. Transformation of pharmaceuticals during oxidation/disinfection processes in drinking water treatment. Journal of Hazardous Materials 279, 461-475. Pradel, M., Aissani, L., Villot, J., Baudez, J.-C., Laforest, V., 2016. From waste to added value product: towards a paradigm shift in life cycle assessment applied to wastewater sludge – a review. Journal of Cleaner Production 131, 60-75. Prado, T., de Castro Bruni, A., Barbosa, M.R.F., Garcia, S.C., de Jesus Melo, A.M., Sato, M.I.Z., 2019. Performance of wastewater reclamation systems in enteric virus removal. Science of The Total Environment 678, 33-42. Puyol, D., Batstone, D.J., Hülsen, T., Astals, S., Peces, M., Krömer, J.O., 2017. Resource recovery from wastewater by biological technologies: Opportunities, challenges, and prospects. Frontiers in Microbiology 7. Qadir, M., Wichelns, D., Raschid-Sally, L., McCornick, P.G., Drechsel, P., Bahri, A., Minhas, P.S., 2010. The challenges of wastewater irrigation in developing countries. Agricultural Water Management 97, 561-568. Raman, C.D., Kanmani, S., 2016. Textile dye degradation using nano zero valent iron: A review. Journal of Environmental Management 177, 341-355. Randall, D.G., Naidoo, V., 2018. Urine: The liquid gold of wastewater. Journal of Environmental Chemical Engineering 6, 2627-2635. Regueiro, J., Negreira, N., Berntssen, M.H.G., 2016. Ion-Mobility-Derived Collision Cross Section as an Additional Identification Point for Multiresidue Screening of Pesticides in Fish Feed. Analytical Chemistry 88, 11169-11177. Richardson, S.D., Kimura, S.Y., 2016. Water Analysis: Emerging Contaminants and Current Issues. Analytical Chemistry 88, 546-582. Richardson, S.D., Kimura, S.Y., 2017. Emerging environmental contaminants: Challenges facing our next generation and potential engineering solutions. Environmental Technology & Innovation 8, 4056. Richardson, S.D., Plewa, M.J., Wagner, E.D., Schoeny, R., DeMarini, D.M., 2007. Occurrence, genotoxicity, and carcinogenicity of regulated and emerging disinfection by-products in drinking water: A review and roadmap for research. Mutation Research - Reviews in Mutation Research 636, 178-242. Richardson, S.D., Ternes, T.A., 2018. Water Analysis: Emerging Contaminants and Current Issues. Analytical Chemistry 90, 398-428. Rizzo, L., Krätke, R., Linders, J., Scott, M., Vighi, M., de Voogt, P., 2018. Proposed EU minimum quality requirements for water reuse in agricultural irrigation and aquifer recharge: SCHEER scientific advice. Current Opinion in Environmental Science & Health 2, 7-11. Rizzo, L., Manaia, C., Merlin, C., Schwartz, T., Dagot, C., Ploy, M.C., Michael, I., Fatta-Kassinos, D., 2013. Urban wastewater treatment plants as hotspots for antibiotic resistant bacteria and genes spread into the environment: A review. Science of The Total Environment 447, 345-360. Roccaro, P., 2018. Treatment processes for municipal wastewater reclamation: The challenges of emerging contaminants and direct potable reuse. Current Opinion in Environmental Science & Health 2, 46-54. Roccaro, P., Santamaria, A.E., Vagliasindi, F.G.A., 2014. Historical development of sanitation from the 19th century to nowadays: centralized vs decentralized wastewater management systems, in: 56
Jo
ur
na
lP
re
-p
ro of
Angelakis, A., Rose, J. (Eds.), Evolution of sanitation and wastewater technologies through the centuries. IWA Publishing, pp. 437-456. Rock, C., Solop, F.I., Gerrity, D., 2012. Survey of statewide public perceptions regarding water reuse in Arizona. Journal of Water Supply: Research and Technology-Aqua 61, 506-517. Rodriguez, C., Van Buynder, P., Lugg, R., Blair, P., Devine, B., Cook, A., Weinstein, P., 2009. Indirect potable reuse: a sustainable water supply alternative. International journal of environmental research and public health 6, 1174-1209. Rozell, D.J., Reaven, S.J., 2012. Water Pollution Risk Associated with Natural Gas Extraction from the Marcellus Shale. Risk Analysis 32, 1382-1393. Salgot, M., Folch, M., 2018. Wastewater treatment and water reuse. Current Opinion in Environmental Science & Health 2, 64-74. Samaras, V.G., Stasinakis, A.S., Mamais, D., Thomaidis, N.S., Lekkas, T.D., 2013. Fate of selected pharmaceuticals and synthetic endocrine disrupting compounds during wastewater treatment and sludge anaerobic digestion. Journal of Hazardous Materials 244, 259-267. Santhosh, C., Velmurugan, V., Jacob, G., Jeong, S.K., Grace, A.N., Bhatnagar, A., 2016. Role of nanomaterials in water treatment applications: A review. Chemical Engineering Journal 306, 11161137. Schoknecht, U., Gruycheva, J., Mathies, H., Bergmann, H., Burkhardt, M., 2009. Leaching of biocides used in façade coatings under laboratory test conditions. Environmental Science & Technology 43, 9321-9328. Schymanski, E.L., Jeon, J., Gulde, R., Fenner, K., Ruff, M., Singer, H.P., Hollender, J., 2014. Identifying Small Molecules via High Resolution Mass Spectrometry: Communicating Confidence. Environmental Science & Technology 48, 2097-2098. Senta, I., Gracia-Lor, E., Borsotti, A., Zuccato, E., Castiglioni, S., 2015. Wastewater analysis to monitor use of caffeine and nicotine and evaluation of their metabolites as biomarkers for population size assessment. Water Research 74, 23-33. Sgroi, M., Anumol, T., Roccaro, P., Vagliasindi, F.G.A., Snyder, S.A., 2018a. Modeling emerging contaminants breakthrough in packed bed adsorption columns by UV absorbance and fluorescing components of dissolved organic matter. Water Research 145, 667-677. Sgroi, M., Roccaro, P., Korshin, G.V., Greco, V., Sciuto, S., Anumol, T., Snyder, S.A., Vagliasindi, F.G.A., 2017a. Use of fluorescence EEM to monitor the removal of emerging contaminants in full scale wastewater treatment plants. Journal of Hazardous Materials 323, 367-376. Sgroi, M., Roccaro, P., Korshin, G.V., Vagliasindi, F.G.A., 2017b. Monitoring the Behavior of Emerging Contaminants in Wastewater-Impacted Rivers Based on the Use of Fluorescence Excitation Emission Matrixes (EEM). Environmental Science & Technology 51, 4306-4316. Sgroi, M., Vagliasindi, F.G.A., Roccaro, P., 2018b. Feasibility, sustainability and circular economy concepts in water reuse. Current Opinion in Environmental Science & Health 2, 20-25. Sgroi, M., Vagliasindi, F.G.A., Snyder, S.A., Roccaro, P., 2018c. N-Nitrosodimethylamine (NDMA) and its precursors in water and wastewater: A review on formation and removal. Chemosphere 191, 685-703. Simha, P., Ganesapillai, M., 2017. Ecological Sanitation and nutrient recovery from human urine: How far have we come? A review. Sustainable Environment Research 27, 107-116. Singer, H., Jaus, S., Hanke, I., Lück, A., Hollender, J., Alder, A.C., 2010. Determination of biocides and pesticides by on-line solid phase extraction coupled with mass spectrometry and their behaviour in wastewater and surface water. Environmental Pollution 158, 3054-3064. Singh, A., Sharma, R.K., Agrawal, M., Marshall, F.M., 2010. Health risk assessment of heavy metals via dietary intake of foodstuffs from the wastewater irrigated site of a dry tropical area of India. Food and Chemical Toxicology 48, 611-619. Singh, R.L., Singh, P.K., Singh, R.P., 2015. Enzymatic decolorization and degradation of azo dyes - A review. International Biodeterioration & Biodegradation 104, 21-31. Skouteris, G., Hermosilla, D., Lopez, P., Negro, C., Blanco, A., 2012. Anaerobic membrane bioreactors for wastewater treatment: A review. Chemical Engineering Journal 198, 138-148. 57
Jo
ur
na
lP
re
-p
ro of
Smith, H.M., Brouwer, S., Jeffrey, P., Frijns, J., 2018. Public responses to water reuse – Understanding the evidence. Journal of Environmental Management 207, 43-50. Snyder, S.A., Villeneuve, D.L., Snyder, E.M., Giesy, J.P., 2001. Identification and Quantification of Estrogen Receptor Agonists in Wastewater Effluents. Environmental Science & Technology 35, 36203625. Snyder, S.A., Wert, E.C., Rexing, D.J., Zegers, R.E., Drury, D.D., 2006. Ozone Oxidation of Endocrine Disruptors and Pharmaceuticals in Surface Water and Wastewater. Ozone: Science & Engineering 28, 445-460. Sousa, J.M., Macedo, G., Pedrosa, M., Becerra-Castro, C., Silva, S.C., Pereira, M.F.R., Silva, A.M.T., Nunes, O.C., Manaia, C.M., 2017. Ozonation and UV254 nm radiation for the removal of microorganisms and antibiotic resistance genes from urban wastewater. Journal of Hazardous Materials 323, 434-441. Statista, 2013. Discharge of wastewater in 2013 in Germany. Stenekes, N., Colebatch, H.K., Waite, T.D., Ashbolt, N.J., 2006. Risk and Governance in Water Recycling:Public Acceptance Revisited. Science, Technology, & Human Values 31, 107-134. Sumpter, J.P., Johnson, A.C., 2005. Lessons from Endocrine Disruption and Their Application to Other Issues Concerning Trace Organics in the Aquatic Environment. Environmental Science & Technology 39, 4321-4332. Sunderland, E.M., Hu, X.C., Dassuncao, C., Tokranov, A.K., Wagner, C.C., Allen, J.G., 2019. A review of the pathways of human exposure to poly- and perfluoroalkyl substances (PFASs) and present understanding of health effects. Journal of Exposure Science & Environmental Epidemiology 29, 131147. Swain, A., 2001. Water wars: fact or fiction? Futures 33, 769-781. Tan, X.-f., Liu, Y.-g., Gu, Y.-l., Xu, Y., Zeng, G.-m., Hu, X.-j., Liu, S.-b., Wang, X., Liu, S.-m., Li, J., 2016. Biochar-based nano-composites for the decontamination of wastewater: A review. Bioresource Technology 212, 318-333. Tchnobanoglous, G., Leverenz, H., 2013. The rationale for decentralization of wastewater infrastructure, in: Larsen, T., Udert, K., Lienert, J. (Eds.), Source separation and decentralization for wastewater management. IWA Publishing, pp. 101-115. Thines, K.R., Abdullah, E.C., Mubarak, N.M., Ruthiraan, M., 2017. Synthesis of magnetic biochar from agricultural waste biomass to enhancing route for waste water and polymer application: A review. Renewable & Sustainable Energy Reviews 67, 257-276. Thomas, K.V., Reid, M.J., 2011. What else can the analysis of sewage for urinary biomarkers reveal about communities? Environmental Science and Technology 45, 7611-7612. Thurman, E.M., Ferrer, I., Blotevogel, J., Borch, T., 2014. Analysis of Hydraulic Fracturing Flowback and Produced Waters Using Accurate Mass: Identification of Ethoxylated Surfactants. Analytical Chemistry 86, 9653-9661. Tijing, L.D., Woo, Y.C., Choi, J.-S., Lee, S., Kim, S.-H., Shon, H.K., 2015. Fouling and its control in membrane distillation-A review. Journal of Membrane Science 475, 215-244. Timm, S.N., Deal, B.M., 2018. Understanding the behavioral influences behind Singapore's water management strategies. Journal of Environmental Planning and Management 61, 1654-1673. Toczyłowska-Mamińska, R., 2017. Limits and perspectives of pulp and paper industry wastewater treatment – A review. Renewable and Sustainable Energy Reviews 78, 764-772. Trenholm, R.A., Vanderford, B.J., Holady, J.C., Rexing, D.J., Snyder, S.A., 2006. Broad range analysis of endocrine disruptors and pharmaceuticals using gas chromatography and liquid chromatography tandem mass spectrometry. Chemosphere 65, 1990-1998. Udert, K.M., Wächter, M., 2012. Complete nutrient recovery from source-separated urine by nitrification and distillation. Water Research 46, 453-464. UNDP, 2016. Human Development Report, New York, USA. UNICEF, WHO, 2017. Progress on Drinking Water, Sanitation and Hygiene: 2017 Update and SDG Baselines, Geneva. 58
Jo
ur
na
lP
re
-p
ro of
United Nations, 2010. The human right to water and sanitation. Resolution 64/292 adopted by the General Assembly on 28 July 2010. . United Nations, 2018. The World's Cities in 2018 - Data Booklet US Congress, 1972. Public Law 92-500 to amend the Federal Water Pollution Control Act. US EPA, 1980. Guidelines for water reuse. EPA-600/8-80-036. US EPA, 2012. Guidelines for water reuse. EPA/600/R-12/618. van Nuijs, A.L.N., Castiglioni, S., Tarcomnicu, I., Postigo, C., de Alda, M.L., Neels, H., Zuccato, E., Barcelo, D., Covaci, A., 2011. Illicit drug consumption estimations derived from wastewater analysis: A critical review. Science of The Total Environment 409, 3564-3577. Vanderford, B.J., Mawhinney, D.B., Trenholm, R.A., Zeigler-Holady, J.C., Snyder, S.A., 2011. Assessment of sample preservation techniques for pharmaceuticals, personal care products, and steroids in surface and drinking water. Analytical and Bioanalytical Chemistry 399, 2227-2234. Vanderford, B.J., Snyder, S.A., 2006. Analysis of Pharmaceuticals in Water by Isotope Dilution Liquid Chromatography/Tandem Mass Spectrometry. Environmental Science & Technology 40, 7312-7320. Vengosh, A., Jackson, R.B., Warner, N., Darrah, T.H., Kondash, A., 2014. A Critical Review of the Risks to Water Resources from Unconventional Shale Gas Development and Hydraulic Fracturing in the United States. Environmental Science & Technology 48, 8334-8348. Verlicchi, P., Galletti, A., Petrovic, M., Barceló, D., 2010. Hospital effluents as a source of emerging pollutants: An overview of micropollutants and sustainable treatment options. Journal of Hydrology 389, 416-428. Vidic, R.D., Brantley, S.L., Vandenbossche, J.M., Yoxtheimer, D., Abad, J.D., 2013. Impact of Shale Gas Development on Regional Water Quality. Science 340. Villarín, M.C., 2019. Methodology based on fine spatial scale and preliminary clustering to improve multivariate linear regression analysis of domestic water consumption. Applied Geography 103, 22-39. Villarín, M.C., Rodriguez-Galiano, V.F., 2019. Machine learning for modelling water demand in Seville city (Spain). Journal of Water Resources Planning and Management (Article in press). Voulvoulis, N., Arpon, K.D., Giakoumis, T., 2017. The EU Water Framework Directive: From great expectations to problems with implementation. Science of The Total Environment 575, 358-366. Vriens, B., Voegelin, A., Hug, S.J., Kaegi, R., Winkel, L.H.E., Buser, A.M., Berg, M., 2017. Quantification of Element Fluxes in Wastewaters: A Nationwide Survey in Switzerland. Environmental Science and Technology 51, 10943-10953. Wang, Q., Wei, W., Gong, Y., Yu, Q., Li, Q., Sun, J., Yuan, Z., 2017. Technologies for reducing sludge production in wastewater treatment plants: State of the art. Science of The Total Environment 587, 510-521. Warner, N.R., Christie, C.A., Jackson, R.B., Vengosh, A., 2013. Impacts of Shale Gas Wastewater Disposal on Water Quality in Western Pennsylvania. Environmental Science & Technology 47, 1184911857. Warsinger, D.M., Chakraborty, S., Tow, E.W., Plumlee, M.H., Bellona, C., Loutatidou, S., Karimi, L., Mikelonis, A.M., Achilli, A., Ghassemi, A., Padhye, L.P., Snyder, S.A., Curcio, S., Vecitis, C.D., Arafat, H.A., Lienhard, J.H., 2018. A review of polymeric membranes and processes for potable water reuse. Progress in Polymer Science 81, 209-237. Watson, S.B., Miller, C., Arhonditsis, G., Boyer, G.L., Carmichael, W., Charlton, M.N., Confesor, R., Depew, D.C., Hook, T.O., Ludsin, S.A., Matisoff, G., McElmurry, S.P., Murray, M.W., Richards, R.P., Rao, Y.R., Steffen, M.M., Wilhelm, S.W., 2016. The re-eutrophication of Lake Erie: Harmful algal blooms and hypoxia. Harmful Algae 56, 44-66. WBG, 2018a. People using at least basic sanitation services. World Bank Group. WBG, 2018b. Total population. World Bank Group. Wei, Z., Liang, F., Liu, Y., Luo, W., Wang, J., Yao, W., Zhu, Y., 2017. Photoelectrocatalytic degradation of phenol-containing wastewater by TiO2/g-C3N4 hybrid heterostructure thin film. Applied Catalysis BEnvironmental 201, 600-606. Weingarten, M., Ge, S., Godt, J.W., Bekins, B.A., Rubinstein, J.L., 2015. High-rate injection is associated with the increase in US mid-continent seismicity. Science 348, 1336-1340. 59
Jo
ur
na
lP
re
-p
ro of
Wert, E.C., Rosario-Ortiz, F.L., Drury, D.D., Snyder, S.A., 2007. Formation of oxidation byproducts from ozonation of wastewater. Water Research 41, 1481-1490. Wester, J., Timpano, K.R., Çek, D., Lieberman, D., Fieldstone, S.C., Broad, K., 2015. Psychological and social factors associated with wastewater reuse emotional discomfort. Journal of Environmental Psychology 42, 16-23. Westerhoff, P., Lee, S., Yang, Y., Gordon, G.W., Hristovski, K., Halden, R.U., Herckes, P., 2015. Characterization, Recovery Opportunities, and Valuation of Metals in Municipal Sludges from US Wastewater Treatment Plants Nationwide. Environmental Science & Technology 49, 9479-9488. Whitton, R., Fane, S., Jarvis, P., Tupper, M., Raffin, M., Coulon, F., Nocker, A., 2018. Flow cytometrybased evaluation of the bacterial removal efficiency of a blackwater reuse treatment plant and the microbiological changes in the associated non-potable distribution network. Science of The Total Environment 645, 1620-1629. Wode, F., van Baar, P., Dünnbier, U., Hecht, F., Taute, T., Jekel, M., Reemtsma, T., 2015. Search for over 2000 current and legacy micropollutants on a wastewater infiltration site with a UPLC-high resolution MS target screening method. Water Research 69, 274-283. Xiao, F., 2017. Emerging poly- and perfluoroalkyl substances in the aquatic environment: A review of current literature. Water Research 124, 482-495. Yeck, W.L., Hayes, G.P., McNamara, D.E., Rubinstein, J.L., Barnhart, W.D., Earle, P.S., Benz, H.M., 2017. Oklahoma experiences largest earthquake during ongoing regional wastewater injection hazard mitigation efforts. Geophysical Research Letters 44, 711-717. Yu, H.-W., Anumol, T., Park, M., Pepper, I., Scheideler, J., Snyder, S.A., 2015. On-line sensor monitoring for chemical contaminant attenuation during UV/H2O2 advanced oxidation process. Water Research 81, 250-260. Zaborowska, E., Lu, X., Makinia, J., 2019. Strategies for mitigating nitrous oxide production and decreasing the carbon footprint of a full-scale combined nitrogen and phosphorus removal activated sludge system. Water Research 162, 53-63. Zareitalabad, P., Siemens, J., Hamer, M., Amelung, W., 2013. Perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) in surface waters, sediments, soils and wastewater - A review on concentrations and distribution coefficients. Chemosphere 91, 725-732. Zedda, M., Zwiener, C., 2012. Is nontarget screening of emerging contaminants by LC-HRMS successful? A plea for compound libraries and computer tools. Analytical and Bioanalytical Chemistry 403, 2493-2502. Zhang, Y., Leu, Y.-R., Aitken, R.J., Riediker, M., 2015. Inventory of Engineered Nanoparticle-Containing Consumer Products Available in the Singapore Retail Market and Likelihood of Release into the Aquatic Environment. International journal of environmental research and public health 12, 8717-8743. Ziska, A.D., Park, M., Anumol, T., Snyder, S.A., 2016. Predicting trace organic compound attenuation with spectroscopic parameters in powdered activated carbon processes. Chemosphere 156, 163-171. Zuccato, E., Chiabrando, C., Castiglioni, S., Bagnati, R., Fanelli, R., 2008. Estimating community drug abuse by wastewater analysis. Environmental Health Perspectives 116, 1027-1032. Zwiener, C., Frimmel, F.H., 2000. Oxidative treatment of pharmaceuticals in water. Water Research 34, 1881-1885.
60
Figure Caption
-p
ro of
Fig. 1: Overview of the study on wastewater research.
Jo
ur
na
lP
re
Fig. 2: Bibliometric overview of wastewater research.
Fig. 3: Worldwide distribution of scientific publications related to wastewater.
61
ro of -p
Jo
ur
na
lP
re
Fig. 4: Steps of wastewater analysis and related challenges.
Fig. 5: Paradigm shift in wastewater management.
62
ro of -p re lP
Jo
ur
na
Fig. 6: Percentage of population with access to basic sanitation.
63
ro of -p
Jo
ur
na
lP
re
Fig. 7: Worldwide access to basic sanitation for the year 2015.
64
65
ro of
-p
re
lP
na
ur
Jo
Table 1: Ranking of countries, research institutions and funding bodies with respect to publications in the field of wastewater research Country
Institutions
Funding bodies Publications (1993-2017)
Ra nk
Publicati ons (19932017)
Public ations (2015)
Publications/I nhabitant (2015)
Publications (1993-2017)
1
China (22903)
China (3149)
Singapore (22.04)
Chinese Academy of Sciences (3163)
2
USA (15357)
USA (1315)
Finland (18.25)
3
India (7327)
India (917)
Australia (18.03)
4
Spain (6559)
Spain (596)
Cyprus (17.23)
5
Canada (4400)
Portugal (15.54)
6
Germany (4091)
Iran (495) Austral ia (430)
Indian Institute of Technology (1548) CSIR - Council of Scientific Industrial Research of India (1417) CNRS - Centre National de la Recherche Scientifique (1380) Harbin Institute of Technology (1255)
Denmark (15.13)
University of California System (1186)
7
United Kingdom (3831)
Brazil (410)
Greece (14.42)
Tsinghua University (1109)
8
Turkey (3827)
South Korea (409)
Brunei (14.37)
CSIC - Consejo Superior de Investigaciones Cientificas (1062)
Canada (386)
Switzerland (13.04)
Tongji University (1026)
National Basic Research Program of China (459)
Turkey (328)
Spain (12.83)
University of Queensland (815)
Spanish Autonomous Regions (437)
ro of
Spanish Ministries (897)
US National Science Foundation (828)
China Postdoctoral Science Foundation (598)
-p
NSERC - Natural Sciences & Engineering Research Council of Canada (587) CNPQ - Conselho Nacional de Desenvolvimento Científico e Tecnológico (498)
re
Jo
ur
na
10
South Korea (3818) Japan (3813)
lP
9
National Natural Science Foundation of China (10758) European Union (1521) Fundamental Research Funds for the Central Universities (1492)
66