Conservation and improvements in water resource management: a global challenge

Journal of Cleaner Production xxx (2014) 1e9

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Conservation and improvements in water resource management: a global challenge Roberto Bagatin a, Ji
ri Jaromír Kleme
s b, Andrea Pietro Reverberi c, *, Donald Huisingh d a

ENI S.p.A., Research Centre for Unconventional Energies, via Giacomo Fauser 4, 28100 Novara, Italy } Centre for Process Integration and Intensification e CPI2, Research Institute of Chemical and Process Engineering e MUKI, Faculty of Information Technology, University of Pannonia, Egyetem u. 10, H-8200 Veszprém, Hungary c DCCI e Department of Chemistry and Industrial Chemistry, University of Genova, via Dodecaneso 31, 16146 Genova, Italy d The Institute for a Secure and Sustainable Environment, University of Tennessee, Knoxville, 311 Conference Center Building, Knoxville, TN 37996-4134, USA b

a r t i c l e i n f o

a b s t r a c t

Article history: Received 7 April 2014 Accepted 14 April 2014 Available online xxx

This Special Volume of the Journal of Cleaner Production focuses on “water Efficient Processes”. It highlights the issues of a global challenge to use water resources more efficiently and more effectively in various fields of human activity. For the process industry the new paradigm of profitable cleaner production means the adoption of complex strategies that are build upon the most advanced developments in several areas of science and technology: chemistry, physics, engineering, ecology and economics, which can and do provide essential contributions to better and cleaner production processes. Because of the sheer size of the problems involved, some issues of special relevance call for intensified efforts. The most significant topics are dealt with eleven contributors from ten countries in Europe, Asia and South America. In the first part of this paper, selected themes concerning the most pressing environmental challenges are reviewed, with particular attention to environmental remediation, pollution control and water decontamination. The second part, where the selected papers are presented and discussed, within the spirit of the making improvements in water resource management. Several novel technical solutions in terms of materials, processes and software are proposed and designed to achieve pollution prevention orientated methodologies with beneficial real-world applications. Ó 2014 Elsevier Ltd. All rights reserved.

Keywords: Responsible water resource management Global water challenges Improved water use efficiency Water sustainability Contaminated sites Water pinch analysis

1. Introduction The growing water scarcities at the global scale and the volume of wastewater effluents from industrial sites as well as from urban agglomerations are becoming of increasing environmental, economic and societal concern. The combined pressures of human population growth, climate changes, increased per capita wastage, combined with more stringent environmental regulations and intensifying market competition, makes it imperative that advanced technologies be developed and implemented for the conservation and the optimal management of hydric resources. To face an increasing freshwater demand, different strategies can/must be adopted, which are reviewed in the following

* Corresponding author. Tel.: þ39 10 3532927; fax: þ39 10 3532586. E-mail addresses: [email protected] (R. Bagatin), [email protected] (J.J. Kleme
s), [email protected] (A.P. Reverberi), donaldhuisingh@ comcast.net (D. Huisingh).

paragraphs. The first approach deals with the enhanced usage of produced water as a by-product of human activities related to hydrocarbons extraction. The second strategy refers to groundwater recovery/preservation by clean-up technologies and/or by preventative policies and procedures. Finally, a rational approach to the problem of improved efficiency water management within industrial facilities is explored, with particular attention to the recent developments in new computational algorithms for combined water/energy optimisation.

1.1. Produced water This is a critical issue involving both developing and developed countries. Produced water (sometimes referred to as brine or formation water) refers to the largest volume of wastewaters associated with oil and gas exploration and production (Produced Water, 2011). It is water trapped in underground formations, brought to the surface along with oil or gas. The main produced water pollutants are oil and grease, chemical additives used in drilling and

http://dx.doi.org/10.1016/j.jclepro.2014.04.027 0959-6526/Ó 2014 Elsevier Ltd. All rights reserved.

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exploitation activities, naturally occurring elemental, radioactive or organic contaminants (Ahmadun et al., 2009). During the production of crude oil, water-in-oil emulsions are formed owing to the mixing with naturally present surfactants enhancing the stability of the emulsions and posing serious problems of water purification. In fact, many chemical treatments are often prohibitively costly and may alter the water qualities. For this reason, a combination of biological and physical method of separation seems to be the preferable trend for future technologies (Utvik, 1999). As a rough estimate of the amount to be considered, approximately nine Gm3/d of produced water are generated in the USA from nearly one million wells. About 86% of this wastewater is managed by subsurface reinjection, while the remainder is discharged at the surface. Produced water/oil volumetric ratio depends on reservoir geology, age and exploitation technology. Ratios of produced water to materials recovered, ranged from two to three with some values as high as 50. The gigantic volumes of contaminated water involved makes production water not only a serious environmental concern but it can also be a potential source of freshwater for domestic or agricultural usage, once subjected to efficient and cost-effective cleaner production, prevention oriented approaches as well as, when needed, wastewater treatment methods (it should be recalled that many oil and gas producers are located in water-stressed countries). In the field of natural gas exploitation and technologies, the shale-gas industry, whose diffusion is an object of controversy and legal restrictions, is a recent and dramatic source of pollution in produced water. The fluids used in hydraulic fracking techniques contain suspended sand and many organic and inorganic compounds that can be grouped in several classes according to their specific function. Among the substances used in fracking fluids: a. Acids such as hydrochloric acid are used to promote fractures in the rocks by leaching minerals. b. Anti-bacterial agents such as glutaraldehyde or quaternary ammonium salts, are used to eliminate micro-organisms producing unwanted by-products. c. Friction-reducing additives such as hydrocarbons or polyacrylamide are used to reduce the fluid pumping work. d. Oxygen scavengers, such as sulphites or other reducing agents are used to limit pipe corrosion. e. Crosslinkers, such as boron compounds are used for fluid viscosity control. f. Scale inhibitors such as glycols are used to prevent scale deposits on the inner pipe walls (Schlumberger, 2008). The blend of these compound depends on specific company preferences according to the so-called “proprietary fracking fluids”. Many of the aforementioned constituents are highly toxic or are damaging to human and eco-system health. More than 650 compounds among 750 different additives used by fourteen hydraulic fracturing companies in the United States between 2005 and 2009 (Mahony, 2011), are suspected of carcinogenic activity on humans. The paper of Gordalla et al. (2013) is an interesting study on possible environmental impact of hydraulic fracking fluids adopted by the Exxon Mobil drilling company in Germany. Besides these toxic compounds present in produced waters by anthropic activities, dissolved salts are naturally present and their separation requires desalination plants, generally based on thermal or osmotic separation processes, such as mechanical vapour compression (MVC), forward osmosis (FO) and membrane distillation (MD) (Shaffer et al., 2013).

Coal bed natural gas (CBNG), generally known as the Australian coal seam gas (CSG), is a gas adsorbed in the pores of coal deposits from which it can be extracted by steel-encased holes together with a considerable amount of produced water. The amount of worldwide coal bed methane is estimated at 140 Tm3, and therefore, it has the potential of playing an increasing role both as an energy source and in the future balance of the produced water (Hamawand et al., 2013). Unfortunately, the water obtained by CBNG technologies is rich in dissolved salts and generally contains undesired cations from which it can be set free by means of membrane separation systems (Nghiem et al., 2011). For this reason, CBNG plants may represent a serious threat for environmental equilibria and in particular for fish ecosystems. In a different context, fish breeding can be seriously endangered by pollution deriving from the aforementioned extraction activities (Davis et al., 2009). 1.2. Groundwater pollution Groundwater pollution is a rapidly increasing global emergency (Grotenhuis and Rijnaarts, 2011), frequently related to the concentration of chemical-intensive industries. It is appropriate to underscore that approximately 500 Mt/y of hazardous wastes are produced by industry, which negatively affect global water resources (UNESCO, 2014). Giant reductions in volume and in degree of toxicity of such hazardous wastewaters can be accomplished by utilization of cleaner production concepts, tools approaches management, monitoring and other ways of designing and implementing preventive approaches to reduce the production of so much hazardous wastes. A survey of accidents in the oil industry during the years 1930e 2010 highlighted that losses of piping containment accounted for 21.9% of the direct causes of accidents, whose effects were mainly related to the consequent water/soil pollution (Fabiano and Currò, 2012) and to the related fire hazards of the leaked materials (Palazzi and Fabiano, 2012). Other contaminant sources were related to natural releases of noxious compounds, ineffective waste management (Sullivan et al., 2010), impacts of nutrient discharges from wastewater treatment plants (Carey and Migliaccio, 2009) and from urban activities often related to limited municipal infrastructures. Urban areas are recipients of agricultural and food commodities, whose wastes are a sources of anthropogenic nitrogen and phosphorous-containing compounds as important causes of groundwater and surfacewater contamination (Bernhardt et al., 2008). Many countries depend essentially on groundwater resources for water supply. As an example, groundwater pollution in Greece is often related to the use or abuse of fertilisers, which diffuse into soils and contaminate the aquifers. Additionally, coastal aquifers are subject to a negative water balance, owing to their overexploitation that triggers saline water intrusions (Daskalaki and Voudoris, 2008). Furthermore, percolation of landfill leachates may dramatically affect the quality of groundwater reservoirs, but the criticality of the situation in most developed and developing countries, alike is usually underestimated. Adsorption techniques based on activated carbon may be a valid alternative to the traditional wet chemical pollution abatement processes (Foo and Hameed, 2009), despite their drawbacks in terms of high costs and limited stability. Up to this point, many have primarily dealt with postcontamination clean-up technologies, but preventative approaches should be used so we do not have to depend totally upon post-contamination clean-up. For example, groundwater contaminations are frequently related to leaking events of toxic and/or combustible agents from containers. In this case, prevention strategies should be based on:

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i) A proper choice of materials for containers with good corrosion resistance. ii) The use of the most advanced sensors and transducers to monitor the concentrations of pollutants in the area surrounding the reservoir. iii) A careful attention to the combined effects of humidity and polar solvents producing galvanic couples in junctions or welding between different metals or alloys with rapid unexpected corrosion events. iv) Careful control of the formation of reactive by-products that may alter some physicalechemical parameters inside the container, such as the pressure. v) The installation of devices for the dispersion of electrostatic charges that may accumulate during filling/emptying operations. vi) The use of qualified and experienced personnel. Polluted groundwater can be pumped to surface treatment facilities using a pump and treat (P&T) approach. Alternatively, use of permeable reactive barriers (PRBs) has been suggested (EPA, 2011) to take advantage of research in the 1990s (Henderson and Demond, 2007). In this case, walls of sorbent materials (usually mixed with gravel in order to assure adequate permeability) are sunk directly into the plume of polluted groundwater through trenches or funnels (generally, no deeper than 15 m). Then, these structures are covered with clean soil (Di Molfetta and Sethi, 2006). The abatement of contaminants proceeds according to two mechanisms, namely immobilization or transformation. In the first case, the pollutant is captured at the surface of the sorbent by different processes according to the chemical nature of the pollutant and the substrate. For example, hydrated lime, ferric oxides, peat, inorganic phosphates, calcite and siderite minerals have been used to retain both anionic and cationic pollutants from a water-bearing stratum. In the second case, which typically refers to the abatement of saturated or unsaturated chlorinated hydrocarbons, the barrier dehalogenates the pollutant without retaining its non-toxic reaction products, such as alkanes or alkenes (Powell et al., 1998). The performance monitoring of PRBs is realised by monitoring wells, typically bundled tubes, from which samples of the substrate are periodically drawn to check the pH and other physicalechemical parameters as indicators of the barrier ageing process. If the barrier has been used to immobilize inorganic pollutants, it is removed and the substrate is post-processed as an inorganic solid waste. If the barrier has been used for pollutant transformation without immobilization, it undergoes a regeneration process without being removed, for example by means of an in-situ injection of steam. Biobarriers are promising variants of PRBs; in this case, the polluting species are decomposed by a biomass immobilised on a suitable support such as nylon sponge or some other synthetic materials on which the bacterial colonies grow. In some cases, biobarriers have been proven to be useful in the abatement of polycyclic aromatic hydrocarbons (PAHs), such as phenanthrene, benzoanthracene and pyrene in a wide range of concentrations (Cobas et al., 2013). However, the use of biobarriers is subject to limitations related to several critical steps, namely the inoculation of the microorganisms, the stable growth of the colony and the supply of specific nutrients to ensure satisfactory colony growth (Careghini et al., 2013). 1.2.1. Water management within industrial facilities Water management aims at optimising the efficiency of water use in industrial processes that include heating, cooling, processing, cleaning and rinsing, so that operating costs and risks are reduced (Kleme
s et al., 2013). The concept of risk minimisation can be

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addressed by promoting the application of inherent safety criteria, as recently proposed in well-established processes (Fabiano et al., 2012). Besides, effluent water from one process might be perfectly suitable for reuse in another process somewhere else at the same site. With the proper treatment, a significant portion of industrial on-site wastewater can be reused multiple times. This can save money in three ways: lower charges for water purchases, lower charges for smaller volume of effluent water discharged (Kleme
s and Huisingh, 2008) and lower energy cost due to heat recovery from recycled wastewater. The strategies designed for rational use of water in industrial plants are hundreds and depend on the specific plant in question. The protocol edited by The New Hampshire Department of Environmental Sciences (Water Efficiency, 2013) is an important reference document which reviews the basic rules to be adopted by industrial and civil water users in matter of water use efficiency. Its cornerstones refer to rinsing and cleaning, non-contact cooling water, hot water, steam systems and finally outdoor water usage efficiency practices. From a computational point of view, many algorithms have been developed to facilitate the reduction of water wastage singly or combined with heat network management (Kleme
s, 2012) in continuous and batch processes (Su et al., 2012). By using game theory (Chew et al., 2009) and a hybrid approach (Statyukha et al., 2008) combining insight-based techniques with a mathematical programming method, several process design and water use optimisation techniques were developed to effectively manage water quantity and water quality in the presence of single or multiple contaminants. Process synthesis with uncertainties represents one of the most challenging aspects of optimal water networks related to unpredictable oscillations in water costs and variations in the performances of regenerators, often based on membrane operations. As a general trend, the optimisation techniques were initially limited to a single aspect of a process, but they have been extended to include all issues for improving process profitability. This is due to the development and usage of sophisticated algorithmic tools. The most important questions addressed by the Authors of this Special Supplemental Volume included: i) Why is the use of iron nanoparticles more and more promising in terms of slurry decontamination and groundwater remediation? ii) How can industrialists choose the optimal materials as substrates to maximize the sorption of pollutants produced by petrochemical activities? iii) What aspects should be taken into account for a correct and reliable modelling of an adsorption column for removal of toxic cations from process wastewaters? iv) Why is the In-Situ Chemical Oxidation technology the reference point in regard to pollutant abatement for water and soil decontamination? v) Why is boron removal an important aspect of water decontamination and what are the most recent technological options for boron capture? vi) How can we develop an algorithmic tool designed to minimise freshwater consumption and wastewater production in the presence of multiple contaminants? vii) How can we introduce stochastic constraints related to unpredictable factors in the determination of an optimal water network? viii) What benefits can be obtained by the incorporation of water sensible heat into the ‘Total Site Heat Integration’ method?

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ix) What strategies can be adopted for a simultaneous minimisation of water consumption and a maximisation of production in a batch process? x) How can we optimise water network configuration and heat integration simultaneously in an algorithm designed to minimise variable annual costs of plant? xi) What are the most promising strategies in terms of phosphorus recovery from wastewaters and how can we realise an optimal match between electrodialysis and crystallization approaches? Eleven papers were selected for this Special Supplemental Volume. Their main contributions are reviewed to provide answers to these questions. 2. Research opportunities highlighted in this Special Supplemental Volume All the papers presented in this Volume highlight recent developments and innovative technologies that are being operated in real-world, complex systems and in situations of high environmental significance. The article’s authors focussed upon key aspects, which are instrumental to achieving conservation, decontamination and efficient use of water. In the specific context of decontamination, these aspects are summarised as: - Selectivity, for the reduction of the effects of interfering adsorbates, such as unwanted ionic species and humic compounds. - Rapid kinetics, with the objective of obtaining high yields in short times, independently of rapid variations in the pollutant flow rates & concentrations. - Good specific capacity of the sorbent is particularly required when the costs per unit mass of the sorbent are high. - Easy regeneration of the sorbent is a basic item for the minimisation of operating costs. - Stability, for the attainment of high decontamination yields during long time cycles. The topics addressed by the articles in this Special Volume were grouped into three broad areas, each of which is characterised by the following keywords:

total annual cost (Chaturvedi and Bandyopadhyay, 2014), maximum production, Pareto optimal point, flexible schedule (Ibric et al., 2014), pellet reactor, selectrodialysis, phosphate recovery, crystallisation (Tran et al., 2014). 3. An overview of papers in this special volume i) The first thematic section is focused on adsorption technology, with particular attention to the choice of new materials and their topological structure as an important parameter for characterising their adsorption properties. Optimal design and operation regime of adsorption columns for the removal of toxic cations from aqueous dispersions are considered as well. ii) The second thematic section addresses advanced technologies for removal of high levels of contamination. This topic is focussed upon critical situations, when the toxic agent is particularly stable with respect to biodegradation or when a combination of effectiveness and rapidity are required to avoid an environmental disaster. iii) The third thematic section addresses the management of produced water. The paper included in this section is focused upon the presence of a specific element (boron), the human and environmental effects of which have often been underestimated in the literature. Boron removal requires unconventional water treatment approaches and its effective removal continues to be a challenge. iv) The fourth thematic section focuses upon simulation and optimisation of industrial plants. Some algorithmic tools are proposed for the determination of an optimal water network in the presence of multiple contaminants and of statistical uncertainties or fluctuations affecting the variables of the system. Additionally, computational schemes concerning heat integrated water networks, Total Site Heat Integration incorporating water sensible heat and an optimal combination of minimum water consumption with optimum production are considered. Finally, a new, integrated and technological approach using a combined selectrodialysiscrystallisation process is proposed.

3.1. Adsorption technologies 2.1. Environment decontamination/remediation Nanoscale materials, chlorinated hydrocarbons (Tosco et al., 2014), Micro- and meso-porous materials, heavy metal removal, hydrocarbon adsorption (Maretto et al., 2014), activated carbon, transport modelling, adsorption kinetics, wastewater remediation (Vocciante et al., 2014), groundwater remediation, soil remediation (Baciocchi et al., 2014), clean-up technologies, membrane separation, ion exchange (Tagliabue et al., 2014). 2.2. Water network design optimisation Water management, minimum water network, multiple contaminants (Lee et al., 2014), mixed-integer nonlinear programming (MINLP), risk management, conditional Value-at-Risk, mixedinteger quadratically-constrained quadratic program (MIQCQP) (Khor et al., 2014). 2.3. Multiobjective optimisation and process integration Total Site, Pinch Analysis, Heat Integrated water networks (Liew et al., 2014), heat exchanger networks, mathematical programming,

The first paper of this section, titled “Nanoscale zerovalent iron particles for groundwater remediation: a review”, by Tosco et al. (2014) from Italy, is based upon an exhaustive review on the use of zerovalent iron in permeable reactive barriers and described methods for the synthesis and characterisation of nanoscale zerovalent iron particles (nZVI). The authors discussed the roles of the preparation techniques in determining size, stability and chemical reactivity of nZVI particles with particular attention to reactivity, because it may severely condition the decontamination yield in practical uses. Indeed, a wide variety of reaction mechanisms of degradation, such as dichloro-elimination, hydrogenolysis, reduction, adsorption, oxidation/reoxidation, precipitation and coprecipitation are considered for organic and inorganic pollutants, respectively. Many strategies to improve nanoparticles stability, which is a compulsory constraint to be fulfilled in view of a further nZVI injection in aqueous slurries for remediation of contaminated areas, are reviewed: anionic surfactants, oil-in-water emulsions, polyelectrolytes, polymers and biopolymers represent the most promising additives for electrosteric or kinetic stabilisation. In the final part, nZVI transport in porous media is investigated by laboratory tests and numerical simulations, where specific strategies for

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solving advection-dispersion partial differential equations are required. The second paper, titled “Microporous and mesoporous materials for the treatment of wastewater produced by petrochemical activities”, by Maretto et al. (2014) from Italy, includes two parts. In the introduction, the authors present a thorough review of applied adsorption technologies. They specifically focus on zeolites as one of the most versatile, stable and regenerable cation-exchange adsorbents. The subsequent sections of their paper study, which represents the innovative content of the article, are related to the use of three different materials, namely clinoptilolite, a polymeric synthetic resin and a mesoporous siliceous material (MSA) for removal of dissolved heavy metals and the sequestration of hydrocarbons from polluted water. The authors present results of experimental investigations to determine adsorption times and adsorption isotherms for those substances using i) three different toxic cations, namely Pb2þ, Cd2þ and Ni2þ as target elements and ii) benzene and toluene as target organic contaminants. Additionally, the effects of mixed organic-inorganic contaminants were evaluated together with the assessing the competing impacts of mixed cations. In conclusion, their results with microporous materials are promising and they suggested a potential use of them for full industrial-scale applications. Thus, the MSA were proven to be highly efficient for hydrocarbon removal, and had a lower but useful cation uptake. The last paper of this section, titled, “A rigorous procedure for the design of adsorption units for the removal of cadmium and nickel from process wastewaters”, by Vocciante et al. (2014) from Italy and Columbia, is comprised of the experimental part in which two polluting cations were adsorbed onto activated carbon (AC) in single compound and in binary systems. The sorbent substrate is pre-treated with oxidizing agents or by heating at 900  C to enhance its uptake capacity and the relevant adsorption isotherms were obtained by experimental runs run in batch mode. The physicalechemical characteristics of the sorbent were determined and the Langmuir parameters for single and binary systems were obtained by data regression. The second part of this study is devoted to the mathematical modelling of a fixed-bed column dynamics, and the coupled partial differential equations for the pollutant concentrations in the liquid and solid phases were solved by a finite difference code. The transport parameters contained in the dynamic model were calculated by semi-empirical correlations, while the thermodynamic parameters were obtained in the previous experimental runs. A fully predictive and robust modelling for column design allowed the authors to anticipate the single and combined effects of pollutant concentrations, inlet flow rates and geometrical characteristics of the fixed bed. Finally, optimal operating conditions for particle dimensions of the fixed bed were developed. In summary, the practical benefits of this study are i) the development of a reliable tool for the design and optimization of adsorption columns and ii) the prediction of column performances even in case of non-nominal operating regimes. The robustness and efficiency of this software makes it particularly useful for process control. 3.2. Advanced technologies for water and soil decontamination In the paper of this section, titled “Development of technical guidelines for the application of in-situ chemical oxidation to groundwater remediation”, by Baciocchi et al. (2014) from Italy, the authors proposed a new protocol for the rational use of an In-Situ Chemical Oxidation (ISCO) of pollutants dispersed in contaminated soils.

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ISCO, as a form of advanced oxidation process and advanced oxidation technology, is an environmental technique used for groundwater remediation to reduce the concentrations of targeted environmental contaminants to acceptable levels. The remediation of several organic substances such as chlorinated solvents and gasoline-related compounds (benzene, toluene, ethyl benzene, MTBE and xylenes) was accomplished by ISCO in contaminated sites. Over the last ten years, a significant development of ISCO has remarkably advanced the state of the science, state of the practice, and the effectiveness of this technology. ISCO has been used at thousands of hazardous waste sites and it is the fastest growing subsurface remedial technology used today. Many real world examples of successful applications of ISCO include: the treatment of a gasoline and waste oil contaminated groundwater in New Jersey (Greenberg et al., 1998), the abatement of chlorinated solvents dispersed by a dry-cleaning facility in Florida (Kakarla et al., 2002) and the use of sodium permanganate for the abatement of trichloroethylene contamination in Wyoming’s groundwater (Lowe et al., 2002). In which study, the authors reviewed a wide array of oxidizing agents according to their efficiency, stability and selectivity with respect to different contaminants, such as volatile organic compounds (VOC), chlorinated aryl compounds, polycyclic aromatic hydrocarbons (PAH), polychlorinated biphenyls and waste oils. Potassium permanganate, sodium persulfate and hydrogen peroxide are the most efficient oxidizing agents; the last two reactants are generally used in a catalysed or activated form by mixing them with ferrous ions. The new protocol is divided into the following sections: i) The first one was focused on the national legislative constraints to be fulfilled for the application of the ISCO technology. For example, the injection of chemicals used for remediation is subject to permission given by the environmental control authorities. ii) The second one refers to constraints to be considered according to the hydro-geological properties of soils, the chemical properties of the aquifer and the choice of the specific oxidising agent according to the relevant contaminants. iii) The third one focuses on the assessment of the time required for remediation. Then, a feasibility study is done to analyse different aspects, such as site characterisation, lab-scale and pilot-scale feasibility tests. The subsequent step was based upon an evaluation of the previous feasibility study results, namely an assessment of the applicability of the ISCO technique to the site in question. This decision depended on a number of side effects mainly related to the release of gases as by-products of the oxidation process and to the modifications of the physicalechemical characteristics of the aquifer. In the appendix, the authors proposed three practical applications in which a feasibility test procedure was applied. Two of them were pilot tests. In a contaminated refinery site (Baciocchi et al., 2010) treated with hydrogen peroxide, the concentration of total petroleum hydrocarbons in the groundwater was decreased by more than one order of magnitude, proving the real effectiveness of the ISCO technology. 3.3. Produced water management The article titled “Boron removal from water: needs, challenges and perspectives” by Tagliabue et al. (2014) from Italy [32], is a review paper concerning boron decontamination in water streams

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based upon recently developed technologies. A preliminary survey dealing with the chemical behaviour of boron, its anthropogenic sources related to agrochemicals and detergents, its natural presence in groundwater and in produced water streams was developed. An important aspect to be considered is the fragmentary and often contradictory literature on the physio-pathological effects of boron on humans, animals and plants. Short and long-term tests concerning oral exposures to soluble boron compounds in rats, mice, dogs and rabbits have proven that the male reproductive system is a consistent target of toxicity. A provisional maximal safe concentration has been established fixed at 0.5 mg/L in drinking water according to the World Health Organization Guidelines for drinking water quality (WHO, 2003). The most reliable technological options for dissolved boron removal are based on i) sorption on solids; ii) ionic exchange; iii) membrane filtration and iv) hybrid methods. The first one, despite the relatively low cost and high specific capacity of many sorbing substrates, has several drawbacks related to the non-regenerability of the sorbents. A typical example is magnesium oxide, with specific capacity of 102 g/kg. The list of sorbents investigated in literature is very wide and includes anionic clays, cationic clays, carbon, alumina, and bauxite in activated forms. Ionic exchange resins, generally containing poly-alcohol or amino-saccharide functional groups, proved to have a satisfactory specific capacity with range spans between 2.3 g/kg and a maximum of 36 g/kg for polymers carrying hydroxylamine moieties. Boron separation by membrane filtration is essentially based on reverse osmosis (RO) and nanofiltration (RF). The former has a higher rejection with respect to the latter, but it requires high operating pressures and it supplies low permeate flow rates. The latter has symmetrical characteristics. Control of the solution pH is an essential aspect in membrane filtration technology. At high pH values, boron is present mainly as borate anion, while, at lower pHs, the equilibrium is shifted towards undissociated boric acid, which behaves similarly to water owing to the absence of free charges in its molecular structure and to its tendency to establish hydrogen bonds with the membrane. For these reasons, a multi-step RO with an intermediate correction of pH is a promising solution in order to combine good yields of boron separation with a minimum of scale production. Other separation techniques such as electrocoagulation, polymer-assisted ultrafiltration (PAUF), adsorption membrane filtration (AMF) and electro-dialysis (ED), were reviewed. Some of the other techniques have not yet been applied at industrial scale. 3.4. Industrial plants simulation and optimisation The last group of papers includes a contribution titled “Minimum water network design for fixed schedule and cyclic operation batch processes with minimum storage capacity and inter-connections”, by Lee et al. (2014) from Malaysia, where the authors proposed a mathematical programming technique to minimise freshwater and wastewater consumption in the presence of multiple contaminants. They considered process changes according to a water management hierarchy (WMH) scheme including water source elimination or reduction, reuse, recycling and regeneration using a mixed integer linear and non-linear programming to find the minimum water utilisation network for their system. The model is comprised of four stages: i) The determination of minimum freshwater flow rates considering water reuse/recycle options. ii) The minimum freshwater consumption when all WMH options are explored.

iii) Minimisation of the number of storage tanks using the total freshwater target from stage ii). iv) Minimisation of the number of interconnections between the elements of the structure using the minimum number of storage tanks determined at stage iii). To check the validity of the method, the authors considered two case studies concerning an urban building and a literature example. In the first one, the water distribution network of the Sultan Ismail Mosque, located at the centre of Universiti Teknologi Malaysia (UTM) in Johor Bahru was optimised; in the second one, the optimisation procedure was applied to a system of five water sources and eight water sinks adapted from the paper of Shoaib et al. (2008). In the first case study, the freshwater-wastewater savings were 65.7e99.9% while, in the second case, the corresponding reductions were 16.4e59.5%. These results demonstrated the effectiveness of the algorithms outlined. The second paper in this group, titled “Fixed-flowrate total water network synthesis under uncertainty with risk management” by Khor et al. (2014) from the United Kingdom and Malaysia, dealt with the determination of an optimal water network that was subject to stochastic constraints. In fact, market fluctuations, water scarcity and apportionment strategies related to unforeseeable political and environmental reasons may introduce a remarkable variability of water prices, with a dramatic influence on many industrial sectors. A classical approach in the literature to such uncertainties has been based on the assumption of deterministic values of all model parameters. In this paper, instead, the authors underscored the need to consider the stochastic character of many parameters, namely the water source flow rates, the contaminant concentrations and the regenerator efficiencies. For example, the removal ratio of a membrane regeneration unit is subject to daily fluctuations that cannot be neglected. The model was based on a recourse-based two-stage stochastic programming scheme by which discrete scenarios were adopted to capture the probability distribution of the uncertain parameters. Essentially, the proposed solution for water network synthesis was comprised of five sequential steps. In the first one, the scenarios were produced with the aid of the Monte Carlo technique relying upon a random number generation. In the second one, the optimal risk-neutral solution was found for each scenario. If the number of scenarios required an excessive computational burden, a third step was started, to determine the minimum number of scenarios to reduce the computational burden. In the fourth step, a Value-at-Risk was estimated and an initial guess for the fifth step was determined. In the last step, the optimal risk-adverse solution was computed for a desired confidence level. The model was then applied to a real-life case study for the determination of an optimal water network in a petroleum refinery according to a risk-neutral model and a risk-averse model. A comparison between the two model solutions revealed an increase of the expected total annualized costs for the risk-averse model, with a difference of about $15,000 between the two approaches. The third paper in this section was titled “Total Site Heat Integration incorporating the water sensible heat”, by Peng Yen Liew et al. (2014) from Malaysia and Hungary. The authors describe a technique to improve the energy efficiency of the heat exchanger network of large industrial sites. Specifically, the authors proposed an improvement of the numerical tool, the Total Site Problem Table Algorithm (TS-PTA), to exploit the sensible heat present in the condensate of the steam used for factory operations. The authors showed that in a typical steam cycle configuration, the boiler feed water (BFW) is heated to its equilibrium temperature using an energy contribution which has not been taken into account by any

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of the existing Total Site Heat Integration methods. So, the essential feature of this work is the inclusion of the sensible heats both for BFW preheating and steam superheating. A new algorithmic code, named Extended TS-PTA,was developed and tested by a graphical and analytical approach. In the former, the method introduced new steps for the compilation of the Extended Site Composite Curves (ESCC) configuration and a comparison between the traditional Site Composite Curve scheme (SCC) and the new ESCC variant was proposed. Additionally, two types of targeting methodologies were investigated for BFW preheating and steam superheating and two case studies were discussed. The first one was applied to two hypothetical process plants, while the second one was a simplified industrial process taken from the real world. In the latter, the application of the methods described in this paper determined a 100% deviation in the hot utility requirement and a 10.9% deviation in the cold utility requirement with respect to the traditional methods that do not consider the water sensible heat. The fourth paper, titled “Simultaneous targeting for the minimum water requirement and the maximum production in a batch process”, by Chaturvedi and Bandyopadhyay (2014) from India, addressed the problem of the simultaneous freshwater requirement minimisation and production maximisation in a batch process. Multi-objective optimisation is easier in continuous processes than in batch processes. Indeed, in addition to pollutant concentrations in wastewater recovery, batch processes were subjected to time constraints. As a rough classification, batch process optimisation can be realised in a fixed or variable schedule approach. The choice of the optimum production policy in multi-objective optimisation is generally considered as a crucial problem. Infrastructure costs for network construction, operating costs for water piping and environmental impact were the most commonly adopted objective functions to be minimised together with the water consumption. In essence, the primary task of this work was to determine the Pareto optimal front for minimizing the water requirements and maximizing production, using the epsilonconstraint algorithm. The minimisation proceeded in two steps, where the objective functions were interchanged with one another. Firstly, the freshwater requirement was minimised while fixing the production at a lower bound. Then, the production was maximised by fixing the water requirement at an upper bound. The intersections of the solutions obtained by both steps supplied the Pareto optimal front of the feasible solutions. The method was applied to a literature example where two products were obtained from three raw materials. Several Pareto-optimal points documented a trade-off between minimum water requirement and production. In particular, for a fixed time horizon of 8 h, the maximum production was calculated at 149.86 kg, with a corresponding minimum water requirement of 280 kg. The fifth paper, authored by Ibri c et al. (2014) from Bosnia e Herzegovina and Slovenia, is titled “Two-step mathematical programming synthesis of pinched and threshold heat-integrated water networks”. This work addressed the synthesis of heatintegrated process water networks (HIPWNs) at a minimum total annual cost (TAC). The global system was represented by a network superstructure including mixers, splitters, water-using units together with freshwater and wastewater heating and cooling units. The overall model was comprised of two different steps. In the first one, a non-linear programming technique (NLP) was adapted to determine the optimal combined water network-heat integration. The relevant solution, which supplied an optimal configuration with minimum freshwater, flow-rates, utility consumption and contaminant concentrations, provided the starting point for the second step. This solution identified an upper bound for water and utility consumption in the second step, where a mixed-integer nonlinear

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programming technique (MINLP) led to the minimisation of the TAC of the overall network. The authors validated their method by considering three examples at a growing level of complexity. In the first one, based upon a literature study, the optimal network consisted of one heater and one heat exchanger, thus saving one heat exchanger with respect to the solution previously proposed by other authors. The second one, which focussed upon multiple contaminants, resulted in a TAC reduction of about 28,000 $ when compared with the optimal solution obtained by another recent model. Finally, in the last example, this method allowed to save even ten heat exchangers with a total heat recovery of 17,088 kW. The last paper, titled “P-recovery as calcium phosphate from wastewater using an integrated selectrodialysis-crystallisation process”, by Tran et al. (2014) from Belgium and Malaysia, concluded the list of the articles of this section. The authors considered the problem of phosphorus recovery from wastewater as a valid alternative to the use of phosphate rock as a primary source of this element. A novel industrial process based on a matching between a selective dialysis and crystallisation of calcium phosphate was proposed and several operating conditions were investigated. The selective dialysis (selectrodialysis) was adopted as a wastewater pre-treatment to increase the concentration at the inlet of the following pellet reactor, where calcium phosphate separates out in the form of a crystalline phase. Based on considerable experimental work on a lab-scale, the authors discussed the performance of the selectrodialysis section for different values of phosphate and chloride anions concentrations in the feed stream to find reciprocal synergies or inhibitions between the anions. Furthermore, the effects of the current density at the electrodes and the role of pH are investigated. The remaining part of the study was focused on the operating regimes of the pellet reactor, where a sandbed served as the substrate for calcium phosphate crystal growth and deposition. It was found that there was a threshold concentration (4 mM of phosphate anion at the selectrodialysis exit), which was the minimum recommended concentration at the pellet reactor inlet to ensure a process yield very close to the theoretical one. Lastly, the economics of phosphorus recovery based on traditional processes were compared with the one of the new approaches. Despite the fact that the initial costs of a combined selectrodialysis-crystallisation process is actually higher than a cost of a traditional process, the authors documented that the high efficiency of phosphorus removal of this approach (up to 82.7%) makes it a very promising technique even in the treatment of low phosphorus concentration effluents due to increasing price of phosphorus.

4. Conclusions From a methodological point of view, the thematic contents of the papers selected led to a global scenario with the key findings summarized as: - The exponentially increasing demand of energy sources does not generally correspond to a proportional increase in the exploitation of renewable energies. This trend is particularly remarkable for countries of recent industrialization (Manenti and Ravaghi-Ardebili, 2013). - As a consequence, the oil and/or gas extraction remains a serious environmental threat as a source of water and air pollution. Not surprisingly, approximately half of the selected contributions to this special issue were devoted to environmental remediation and decontamination techniques. To this purpose, a highly interdisciplinary character of the research was required, as clearly shown in the articles of this special volume.

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- The effects of on-going micro and macroclimatic changes may aggravate the aforementioned trends determining local critical situations as far as freshwater availability and apportionment are concerned. Therefore, the development of sophisticated strategies for combined water/energy savings is essential, decisive and indispensable. This is precisely the goal of approximately another half of the articles in this special volume. Acknowledgements The editors are deeply grateful to the following reviewers who dedicated so much time and efforts to the papers selected for this issue: AJE Language Editor, Donald Huisingh, Marianne Boix, Chun Deng, Luciana Savulescu, Petar Sabev Varbanov, Hon Loong Lam, Peter Glavic, Igor Bulatov, Mikiya Tanaka, Linyu Xu, Vincenzo Giorgio Dovì, Valentin L. Plesu, Jin-Kuk Kim, Milica Velimirovic, Julian Bosch, Alberto Tiraferri, Roberto Bagatin, Alberto Alberti, Thokozani Majozi, Santanu Bandyopadhyay, Raymond R. Tan, Dominic Chwan Yee Foo, Siyu Yang, Douglas Lambert, Sharifah Rafidah Wan Alwi, Gaetano D’Avino, Guillaume Habert, Chen Li, Bart Van der Bruggen, Idil Yilmaz Ipek, Nour Fahim, Merv Fingas, Nagaraj H.B., Mamun Habib. References Ahmadun, F.R., Pendashteh, A., Abdullah, L.C., Biak, D.R.A., Madaeni, S.S., Abidin, Z.Z., 2009. Review of technologies for oil and gas produced water treatment. J. Hazard. Mater. 170 (2e3), 530e551. Baciocchi, R., Ciotti, C., Cleriti, G., Innocenti, I., Nardella, A., 2010. Design of in situ Fenton oxidation based on the integration of experimental and numerical modelling. J. Adv. Oxid. Technol. 13 (2), 153e216. Baciocchi, R., D’Aprile, L., Innocenti, I., Massetti, F., Verginelli, I., 2014. Development of technical guidelines for the application of in-situ chemical oxidation to groundwater remediation. J. Clean. Prod. http://dx.doi.org/10.1016/ j.jclepro.2013.12.016. Bernhardt, E.S., Band, L.E., Walsh, C.J., Berke, P.E., 2008. Understanding, managing, and minimizing urban impacts on surface water nitrogen loading. Ann. N.Y. Acad. Sci. 1134, 61e96. Careghini, A., Saponaro, S., Sezenna, E., 2013. Biobarriers for groundwater treatment: a review. Water Sci. Technol. 67 (3), 453e468. Carey, R.O., Migliaccio, K.W., 2009. Contribution of wastewater treatment plant effluents to nutrient dynamics in aquatic systems: a review. Environ. Manag. 44 (2), 205e217. Chaturvedi, N.D., Bandyopadhyay, S., 2014. Simultaneous targeting for the minimum water requirement and the maximum production in a batch process. J. Clean. Prod. http://dx.doi.org/10.1016/j.jclepro.2013.11.079. Chew, I.M.L., Tan, R.R., Foo, D.C.Y., Chiu, A.S.F., 2009. Game theory approach to the analysis of inter-plant water integration in an eco-industrial park. J. Clean. Prod. 17 (18), 1611e1619. Cobas, M., Ferreira, L., Tavares, T., Sanromán, M.A., Pazos, M., 2013. Development of permeable reactive biobarrier for the removal of PAHs by Trichoderma longibrachiatum. Chemosphere 91, 711e716. Daskalaki, P., Voudoris, K., 2008. Groundwater quality of porous aquifers in Greece: a synoptic review. Environ. Geol. 54 (3), 505e513. Davis, W.N., Bramblett, R.G., Zale, A.V., Endicott, C.L., 2009. A review of the potential effects of coal bed natural gas development activities on fish assemblages of the Powder River geologic basin. Rev. Fish. Sci. 17 (3), 402e422. Di Molfetta, A., Sethi, R., 2006. Clamshell excavation of a permeable reactive barrier. Environ. Geol. 50 (3), 361e369. EPA, 2011. A Citizen’s Guide to Permeable Reactive Barriers. US Environmental Protection Agency (EPA), Washington (DC). www.epa.gov (accessed 16.02.11.). Fabiano, B., Currò, F., 2012. From a survey on accidents in the downstream oil industry to the development of a detailed near-miss reporting system. Process Saf. Environ. Prot. 90 (5), 357e367. Fabiano, B., Reverberi, A.P., Del Borghi, A., Dovì, V.G., 2012. Biodiesel production via transesterification: process safety insights from kinetic modeling. Theor. Found. Chem. Eng. 46 (6), 673e680. Foo, K.Y., Hameed, B.H., 2009. An overview of landfill leachate treatment via activated carbon adsorption process. J. Hazard. Mater. 171 (1e3), 54e60. Schlumberger, 2008. Fracturing. Available from: www.slb.com/services/ stimulation/reservoir.aspx (accessed 12.03.13.). Gordalla, B.C., Ewers, U., Frimmel, F.H., 2013. Hydraulic fracturing: a toxicological threat for groundwater and drinking water? Environ. Earth Sci. 70, 3875e3893. Greenberg, R.S., Andrews, T., Kakarla, P.K., Watts, R.J., 1998. In-situ Fenton-like oxidation of volatile organics: laboratory, pilot and full-scale demonstrations. Remediat. J. 8 (2), 29e42.

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