Engineered wetland reactors with different media types to treat drinking water contaminated by boron (B)

Accepted Manuscript Engineered wetland reactors with different media types to treat drinking water contaminated by boron (B) Onur Can Türker, Cengiz Türe, Anıl Yakar, Çağdaş Saz PII:

S0959-6526(17)32056-5

DOI:

10.1016/j.jclepro.2017.09.067

Reference:

JCLP 10572

To appear in:

Journal of Cleaner Production

Received Date: 14 March 2017 Revised Date:

6 September 2017

Accepted Date: 6 September 2017

Please cite this article as: Türker OC, Türe C, Yakar Anı, Saz Çğş, Engineered wetland reactors with different media types to treat drinking water contaminated by boron (B), Journal of Cleaner Production (2017), doi: 10.1016/j.jclepro.2017.09.067. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. 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.

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ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT Engineered wetland reactors with different media types to treat drinking water contaminated by boron (B) Onur Can TÜRKER1*, Cengiz TÜRE2, Anıl YAKAR2, Çağdaş SAZ2 1

Faculty of Science and Letters, Department of Biology, Aksaray University, Aksaray, TURKEY Faculty of Science, Department of Biology, Anadolu University, Eskişehir, TURKEY

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*Corresponding Author, Phone: +90 382 288 21 69, Fax: +90 382 280 12 46, e-mail: [email protected]

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Boron (B) removal is a difficult process, and techniques based on conventional methodology mostly remove little or no B from drinking water. Therefore, an attractive, low cost, and environmental friendly treatment method should be tested in order to recover B from

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drinking water, especially when instillation, operation, and maintenance costs limit treatment applications. Engineered wetland (EW) treatment technologies are effective, economical, and eco-friendly treatment options for wastewater treatment in semi-arid and arid areas in the world. This study presents four new up-flow engineered wetland (UEW) reactors tested with different media types for B removal from drinking water in 120 days treatment period. The

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results show that significant amount of B is removed from drinking water with UEW, suggesting that using an up-flow mode in EW treatment technology for B removal seems to be an option more effective than those of the other EW system modes. Using Typha latifolia, the present experiment chooses four different filling materials, namely peat, zeolite, volcanic

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cinder, and sand as media to design wetland reactors. We found that media type affects the removal capacities of wetland reactors and thus B removal efficiency of four reactors are

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ordered as peat reactor (91%)>volcanic cinder reactor (84%)>sand reactor (83%)>zeolite reactor (57%). Furthermore, results from the present experiment emphasize that the media type also affects the physicochemical parameter, plant uptake, and soil enzyme activities. Consequently, it can be suggested that a well-designed wetland treatment reactor with an upflow mode and peat media is an effective tool for drinking water treatment in order to obtain higher B removal efficiency.

Keywords: Boron removal, engineered wetlands, drinking water, media type, soil enzymes

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ACCEPTED MANUSCRIPT 1. Introduction Boron (B) removal from water environment is gaining increased attention worldwide due to threatening not only the aquatic ecosystems but also human beings through contamination of drinking water sources. Specifically, the experimental studies associated

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with the toxicology show that B has potential negative impacts on the male reproduction, especially low sperm count and birth size (Igra et al., 2016; Robbins et al., 2010). Hence, World Health Organization (WHO) recommended a safety limit of B in drinking water lower

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than 2.4 mg L-1 in 2011 (Guan et al., 2016; Gür et al., 2016; Hilal et al., 2011). However, B concentrations in the drinking water above the safety limit have been recorded in various

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countries such as Sweden (3 mg L-1), Argentina (6 mg L-1), Germany (11 mg L-1), Chile (11 mg L-1), as well as Turkey (29 mg L-1), and thus excessive B may endanger the drinking water supplies of at least 15 million people in these countries (Igra et al., 2016). Correspondingly, potential B toxicity threat in drinking water has come under the scientific spotlight for

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scientific researchers who evaluate, practice, and develop treatment techniques in order to remove or eliminate B from drinking water and asses its effects of toxicity on ecological components.

conventional

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To date, most treatment researches have focused on treating B in drinking water using treatment

techniques

such

as

membranes

processes,

coagulation-

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electrocoagulation, adsorption techniques, and ion exchange (Hilal et al., 2011). Correspondingly, the average B removals through these conventional treatment techniques can reach up to 90% for wastewater contain high concentration of B. Although such conventional methodologies can make wastewater meet acceptable standards for discharge (Wolska and Bryjak, 2013), unfortunately, the conventional techniques remove little or no B from aqueous solutions with low boron concentration such as drinking water, and they are not only costly and unsustainable but also produce secondary waste during the purification

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ACCEPTED MANUSCRIPT (Hasenmueller and Criss, 2013; Türker et al., 2016a; Türker et al., 2016d). Clearly, alternative, low cost, eco-friendly treatment methods in order to eliminate B from drinking water are imperative. Engineered or Constructed wetlands modules have been recognized as an attractive,

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cost-effective, less complex, and eco-friendly alternative treatment technology that mimics the function of natural wetland ecosystems including biological, chemical, and physical processes for treating wastewater (Gao et al., 2015; Vymazal, 2013; Wu et al., 2017). At

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present, EWs have been applied to remove contaminants from wastewater as they have high environmental effectiveness and economical or ecological efficiency that can particularly be

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used for B removal purposes in semi-arid and arid regions. (Schoderboeck et al., 2011; Türker et al., 2016b). Numerous researches have shown that EW systems which have surface, vertical, and horizontal flow types are seen as potentially attractive solutions to remove B from various types of wastewater (Allende et al., 2014; Turker et al., 2013; Ye et al., 2003);

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however, to our knowledge, an up-flow engineered wetland system (UEW) has not been tested for the removal of B from the contaminated water sources so far. In an UEW system, the contaminated water would be pumped into the base of the wetland matrix in an up-flow

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mode to increase the retention time of the water in the wetland bed (Huang et al., 2015). According to this, as the contaminated drinking water moves upwards, adsorption or sorption

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of B in filtration media would retard the movement of B resulting in longer detention times. This unique operational characteristic of an UEW may make an ideal approach to minimize land requirement and increase B removal performance for relatively low concentration of B in drinking water, especially when instillation, operation, and maintenance costs are limiting factors for applying other EW types. In this respect, it is important to note that an up-flow wetland treatment system with different media types was developed for the first to test B

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ACCEPTED MANUSCRIPT removal from drinking water and to decrease B below the value of 2.4 mg L-1 (a safety limit of B for drinking water) in terms of an eco-technological perspective. The active reaction zone of EWs is their supporting media where biological and biochemical processes happen through the complex interactions between substrates,

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microorganisms, plants, and contaminants (Vymazal, 2013). Each media used in EWs has its own physical and chemical specification, and these properties may directly affect the removal performance of the wetland treatment technology (Lu et al., 2016; Vymazal and Kröpfelová,

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2009). Therefore, the selection of the filtration media plays a critical role in the EW matrix to provide attractive water treatment. Specifically, media storage is the crucial removal process

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of B because B can remain in EW through adsorption, sorption, and precipitation, and a minor fraction of B is removed from water environment by plants. However, not many of the studies address the selection of the media type and employ alternative media in the EWs for B removal. In this case, the key motivation of the present experiment is to explore a well-

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designed wetland treatment reactor may combine the advantages of system type, such as an up-flow mode and effective filtration media selection, in order to obtain higher B treatment performance.

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In the present experiment, using the same macrophyte, four different filtration media of peat, zeolite, volcanic cinder, and sand were tested as substrates in designing UEW

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reactors, and drinking water contaminated with B is studied in order to assess their treatment performance. Consequently, we suggest that the results from the present study could be meaningful in assessing the potential of UEW for B removal and significance of the media type in EW systems while remediating drinking water sources contaminated with B. The objections of the present experiment are, therefore: (1) to test the up-flow EW systems with different media types to remediate drinking water contaminated with B; (2) to examine and compare B removal at different heights of the up-flow EW; (3) to determine the

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ACCEPTED MANUSCRIPT effect of media type on B removal, physicochemical parameters, plant uptake, and some important soil enzyme activities (dehydrogenase, urease, and phosphatase) while remediating

2. Material and methods 2.1. Design of wetland units and culture period

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drinking water contaminated with B.

The experiment was performed in the Anadolu University, Department of Biology,

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Eskişehir, Turkey. The climate of the research site is semi-arid Mediterranean that characterized by mean annual precipitation of 373.8 mm, average temperature 10.8 ºC.

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Four parallel up-flow engineered wetland (UEW) reactors (identified as R1, R2, R3, and R4) were fabricated and designed according to up-flow design parameter using polyester chambers with 65 cm length, 30 cm width, and 0.18 m2 total surface area for each reactor. The wetland reactors were placed outside and divided into four experimental groups employing

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either peat (R1), zeolite (R2), volcanic cinder (R3), or sand (R4) as the main media in their wetland matrix. Correspondingly, the peat (pH 4.8) was supplied from an agricultural company in Turkey, and two mineral materials including volcanic cinder and zeolite were

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supplied from various mine reserves in Western Anatolia, Turkey. Furthermore, sand and gravel which were used in this study were obtained from Porsuk River and washed prior to

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use in the treatment reactors. Each reactor had a 5 cm deep inlet section of 5-8 mm gravel at its base. The inlet section was overlain with a single 55 cm deep layer of the main media type (peat, zeolite, volcanic cinder, or sand), and 5 cm of gravel layer was also placed on the main media in outflow section, resulting in a total depth of 65 cm (the main media plus gravel layers). Three sampling points at the heights of 20 (S1), 40 (S2), and 60 (S3) cm from the bottom were tapped along the reactors according to Ong et al. (2010). In each reactor, Cattail (Typha latifolia L), a popular wetland macrophyte used as phytoremediation of B in EWs,

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ACCEPTED MANUSCRIPT was used as donor species in this study. Rhizomes of T.latifolia were collected from a wetland habitat located in Eskişehir, Turkey (39º17' N, 30º30' E), and the rhizomes were immediately transplanted in wetland reactors. Typha latifolia was chosen primarily due to its well documented tolerance to B toxicity, and it is also found in B rich habitat as a local native

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species (Turker et al., 2014). A detailed scheme of the UEW reactors is given in Fig 1.

All reactors were fed with Hoagland medium plus sludge (obtained from a treatment plant for industrial wastewater) for 60 days in order to support T.latifolia growth and establish

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microorganisms prior to commencement of the experimental period. The chemical composition of Hoagland medium is as follows (in mg L-1): KH2PO4, 0.5 mM; NH4Cl, 0.4

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mM; MgSO4.7H2O, 1.0 mM; CaCl2.H2O, 0.75 mM; H3BO3, 23 µM; MnCl2.4H2O, 4.5 µM; Na2MoO4.2H2O, 0.06 µM; ZnSO4.7H2O, 0.38 µM; CuSO4.5H2O, 0.16 µM; FeCl3.6H2O, 45 µM Na2-EDTA.2H2O, 1.4 µM.

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2.2. Boron dosage and operation of wetland reactors

After culture in a period of 60 days, the UEW reactors were fully established for B treatment facility. The investigations were carried out with simulated tap water samples

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contaminated with various levels of B obtained by dissolution of H3BO3 (Merck, purity>99) arranged in a range: 2.6-5.65 mg L-1. The reason of choosing this contaminated water range as

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study concentrations is due to the necessity of remaining as close as possible to natural and operational conditions because this range is higher than the safety limit of B for drinking water, in addition to being equivalent to the maximum concentrations of B found in drinking water in Western Anatolia (data not shown). This also indicates how we determined the range of B values studied in the present experiment. In the experiment period, the wastewater was stored in a 100 L polyethylene inflow tank which was continuously stirred. Furthermore, the wastewater was freshly prepared for

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ACCEPTED MANUSCRIPT each experimental group before the first dosing, and this wastewater was kept until the next dosing day on the same week (Allende et al., 2014). The simulated wastewater was supplied to each reactor by using a peristaltic pump which was controlled by a timer. Moreover, wetlands reactors were manually drained with a valve at the bottom of each EW every two

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weeks and then were refilled with fresh test solution containing different boron concentrations. Evaporation loss was also estimated and thus compensated with tap water for each reactor during the experiment. The reactors were operated under the same hydraulic

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loading rate of 83mL/h and dosed every 8 hours over the periods of 24 h, so the hydraulic retention times of the units were to set to 4 days. The wetland reactors operated continuously

2.3. Wastewater sampling and analysis

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for a period 120 days until the vegetation showed wilting at the end of November 2016.

The water samples from inflow, outflow, different sampling points (S1, S2, and S3)

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were collected in order to evaluate treatment performance of four UEW reactors in removing B from drinking water. Wastewater samples were taken according to the hydraulic retention time of wetland units (4 days), and psychochemical parameters such as pH, electrical

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conductivity (EC), dissolved oxygen (DO), and redox potential (ORP) were measured with HACH HQ40D multi-parameter meter concurrent with sampling. Boron (B) concentrations

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were analyzed in the laboratory according to the standard methods (APHA, 1998). Correspondingly, water samples were put into polyethylene caps, and 2 drops (0.1 mL) of HCL was added. After that, 10 mL H2SO4 was carefully added, and the mixture was let to cool at room temperature. Then, 10 mL carmine solution was added and mixed well. After 45 to 60 min, the absorbance of the mixture was read at 585 nm for B determination.

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ACCEPTED MANUSCRIPT 2.4. Plant harvest, biomass production, and chemical analysis All T.latifolia biomass both aboveground and belowground was collected from each reactor to determine biomass production and chemical composition of T.latifolia plant at the end of the experiment. The harvested biomass was washed with tap water to remove

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undesirable sediment residue and rinsed with deionize water. Then, aboveground and belowground biomass was weighed in order to calculate biomass. Dry matter biomasses of T.latifolia were measured by drying the harvested biomass in an oven at 65°C for 48h.

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Afterwards, T.latifolia parts were separated into leaves, stems, and roots, and all the material were powdered and digested by HClO4:HNO3 acid at 1:3 proportion in a microwave digestion

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unit in order to determine B concentrations (Turker et al., 2013). The amount of B was determined with a high-resolution continuum source atomic absorption spectrometer (Analytikjena ContrAA 700).

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2.5. Media analysis and soil enzyme activities

The media samples from each wetland reactor were collected homogenously from different depths according to height of the bottom (0-20, 20-40, and 40-60) at the end of the

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experiments. The samples were collected using a 4-cm diameter PVC corer. Boron amount in filtration media was measured with a high-resolution continuum source atomic absorption

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spectrometer (Analytikjena ContrAA 700), N by Kjeldahl method (Turker et al., 2013). Furthermore, media samples were also collected from each reactor bed according to height of the bottom (0-20, 20-40, and 40-60) at the end of the experiment using hand-shaking method in order to determine some soil enzyme activities (dehydrogenase, urease, and phosphatase) while remediating drinking water sources contaminated with B. These enzymes have a crucial role associated with the cycling of carbon (dehydrogenase), nitrogen (urease), and phosphorus (phosphatase) (Zhang et al., 2010) in a wetland matrix. The collected media samples from

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ACCEPTED MANUSCRIPT each reactor were sieved and then stored in refrigerator at 4°C prior to analysis of enzyme activity within one week. The dehydrogenase, urease, and phosphatase enzyme activities in

2.6. Calculation and statistical analysis

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sediment of the reactors were determined according to (Kong et al., 2009).

The performance of Boron removal [%] from wastewater though reactors in the experiment period were calculated as follows:

(1)

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Boron removal performance [%] = [(C iVi − C eV e ) / C iVi ] × 100

where Ci and Ce are the average B concentrations of inflow and outflow samples from

collected and dosed into each reactor.

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different sampling points in mg L-1; Vi and Ve are the volumes of the outflow and the inflow

The mass removal rate (MRT) was calculated using the equation evaluated by (Türker et al., 2016a):

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Mass removal rate (mg m-2 d-1) = [(C iVi − C eV e ) / USA / HRT ] × 100

(2)

The unit surface area (USA) of each reactor was 0.18 m2, and Hydraulic retention time

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(HRT) was 4 days as described above.

Bioconcentration factor (BCF) of T.latifolia in different wetland reactors was

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calculated as described by Gao et al. (2015): BCF = (C1 / C 2 )

(3)

where C1 is B concentration in T.latifolia tissues both in aboveground or belowground parts (mg/kg), and C2 is B concentration in the wastewater (mg L-1) during the treatment period. In order to analyze the performance of the four wetland reactors, statistical tests were carried out with SPSS version 18.0 of the Statistical Software Package and a statistical confidence of p<0.05. The Shapiro-Wilks test was performed on the normality of the data. The statistical relations between inflow B level and outflow B concentrations from different 9

ACCEPTED MANUSCRIPT sampling points of each reactors were determined with a one-way ANOVA test (for example, in order to determine if the concentrations in the outflow are lower than those in the inflow). The same statistical relationships were also investigated for pH, EC, redox potential, and dissolved oxygen in effluent, as well as sediment enzyme activities. Tukey’s post hoc test was

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applied to elucidate mean differences between the treatment reactors.

3. Results and Discussion

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The major conventional treatment techniques or systems used for the removal of B from various aqueous solutions include adsorption on chelating resins, oxides or membrane filtration

such

as

reverse osmosis, and

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polysaccharides,

coagulation-

electrocoagulation (Wolska and Bryjak, 2013). In addition, many researchers found a B removal efficiency range between 5.1-93% for B removal using these conventional techniques in their experiment (Hilal et al., 2011; Wang et al., 2014). Although reverse osmosis is a best-

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known system for B purification from wastewater worldwide, adsorption technique seems to be the most effective treatment methods for B removal because the process requirements are relatively simple compare to other conventional techniques and can be used in various

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aqueous media which contaminated low B such as drinking water (Wang et al., 2014). However, adsorption processes for drinking water have many problems such as limited

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surface area, poor thermal and chemical stability, as well as unordered pore structure. Therefore, studies in finding new B removal methods with low cost, sustainable, and easy applicable should be evaluated.

3.1. Boron treatment performance of UEW reactors from drinking water Boron concentrations in the inflow and outflow samples of each wetland reactors with three sampling points, as well as total B removal performance of the each treatment reactors

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ACCEPTED MANUSCRIPT over the entire experiment period are shown in Fig 2. Correspondingly, the concentration of B in the inflow ranged from 2.65 to 5.65 mg L-1 during the experiment period, and the final outflow samples (S3) taken from the reactors were much lower than the inflow samples most of the time. In addition, one-way ANOVA statistical analysis indicated significant statistical

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differences between the inflow B concentrations in the synthetic drinking water samples and the final outflow samples from the reactors (p<0.05). These results demonstrate that UEW treatment reactors with different media types are capable of removing B from drinking water,

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and thus such UEW reactors could be developed and used as an alternative, eco-friendly, and cost effective treatment option for the removal of B contamination from drinking water.

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On the other hand, boron removal rates were significantly different among four treatment reactors (R1>R3>R4>R2) in the experiment period (Supplementary materials), and the average B removal efficiencies were recorded as 91%, 58%, 84%, and 83% for R1, R2, R3, and R4, respectively (Fig 2). These B removal performances of UEW reactors were found to

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be relatively higher than efficiencies of other types of EW systems which were designed to remediate various wastewaters. Accordingly, Ye et al. (2003) found 32% B treatment efficiency for electric utility wastewater (collected from the sour water stripper of a coal

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gasification plant) in a surface flow EW with supporting media (mixture of colma sand plus organic-based potting medium). Kröpfelová et al. (2009) reported 22.5% B removal

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efficiency for full scale EWs while remediating municipal wastewater in Czech Republic. Allende et al. (2012) determined 12.5% B removal performance at the end of 7 weeks through vertical flow type EWs with coco-peat media type. The removal of B in horizontal subsurface EW amounted to 64% B removal rate reported by Türker et al. (2016a), a performance relatively close to what observed in the present experiment. It can be clearly inferred from the present experiment that using an up-flow mode EW treatment technology for B removal seems to be a more effective option in order to increase B removal efficiency as it provides

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ACCEPTED MANUSCRIPT longer detention time for wastewater in wetland bed compared to the horizontal and surface flow modes. Furthermore, the higher B removal efficiencies which were obtained in the present experiment verifies that an up-flow system mode is an ideal approach for increased metal and metalloid removal efficiency such as B in wastewater, especially when land

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requirement, operation, and maintenance costs are limiting factors for applying other EW types.

As seen in Fig 2, B concentration in the final outflow (S3) from R1, R3, and R4 was

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always stable below 2.4 mg L-1 during the experiment period with an inflow range from 2.65 to 5.65 B / mg L-1, whereas the outflow concentrations from the wetland reactor with zeolite

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(R2) was found to be mostly higher than 2.4 mg L-1 after the 48th treatment day. Therefore, it can be suggested that excessive B in the drinking water samples were disposed below the drinking water safety limit (as 2.4 mg L-1) through R1, R3, and R4 reactors during the remedial process and that effluents from R1, R3, and R4 can be used for drinking purpose as well.

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However, the effluent from zeolite wetland reactor (R2) mostly had concentration of B higher than recommended by the drinking water safety limit, so the effluent from (R2) cannot be used as a drinking water source. These results suggested that the selection of peat, volcanic cinder,

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and sand substrates in B-contaminated drinking water treatment with up-flow EW reactors were feasible, and the treatment efficiency of peat wetland reactor is the best for B

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purification. This finding is in good agreement with the results of Allende et al. (2012) and (2014), indicating that zeolite, gravel, and limestone wetland systems had poor B removal performance, whereas the wetland system with organic based media such as coco-peat had higher B removal performance for contaminated water.

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ACCEPTED MANUSCRIPT 3.2. The effect of media type on B removal efficiency in UEW reactors In the literature, boron removal mechanisms or pathways in a wetland matrix are basically accumulation in media or sediment, sorption on filtration materials, plant uptake, as well as sedimentation, and the main B removal pathway was found as sediment storage

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(Allende et al., 2014; Turker et al., 2014). Therefore, it can be concluded that the key element in the wetland treatment application for B removal is the media type, which plays the role of filtration. Retained B amount in different media types and other parameters (such as pH, EC,

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and redox values) of media types at the end of the study are shown in Table 1. Retained B amount in R1, R2, R3, and R4 ranged from 46.8, 2.03, 2.2, and 2.45 mg/kg B to 86.8, 3.9, 4.7,

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6.32 mg/kg B, respectively, and retained B amount varied among the depths of wetland reactors. These results indicate that the media type and wetland depth clearly affects the amount of B retained in sediment of UEW during B remediation process, and it is mostly related to physical and chemical characteristics of the media such as affinity, porosity, and

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particle size.

The average B concentrations in the inflow and outflow from different sampling points are shown in Fig 3a. It can be seen that B concentrations in the treatment reactors gradually

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decreased along the media bed and the lowest B concentrations were recorded as 0.394±0.44, 1.986±0.925, 0.718±0.541, and 0.775±0.643 mg L-1 for R1, R2, R3, and R4, respectively, at the

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upper sampling point of the treatment reactors. In parallel with this result, a higher B removal performance was also determined at the upper layers of all reactors (Fig 3b). This phenomenon is seen very often while removing contaminants through an up-flow mode because more pollutant is retained in bottom layer of the up-flow wetland during the remedial process, so less pollutant have reached at upper layer of the wetland system (Huang et al., 2015; Ong et al., 2010). Therefore, B removal rate at the top layer of the treatment reactors was higher because the surface area of sorption or the accumulation site increased with height

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ACCEPTED MANUSCRIPT of the bottom, thus the upper layers of UEW provide more sorption and accumulation sites in order to take up B from drinking water compared to bottom layer. Moreover, another important reason associated with higher B removal in upper parts of the treatment reactors is related to the presence of T.latifolia near the final sampling point (S3). According to this,

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T.latifolia’s roots/rhizomes in the upper section of the treatment reactors reduced the hydraulic conductivity and increased water duration for adsorption of B from drinking water at the top layer of the treatment reactors hence provided better B removal.

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The results from the present experiment have also shown that B removal performance of R1 was higher than those of the other treatment reactors (Fig 3b), indicating that the

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removal of B in UEWs was primarily affected by the type of the media. The reasonable explanation might be that, among the filtration media, peat has a small particle size, relatively softer properties, and irregular shape; consequently the efficiency of the interception, filtration, and adsorption of B was better in peat wetland bed compared to zeolite, volcanic

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cinder, and sand. Allende et al. (2012) and Türker et al. (2016a) demonstrated similar types of observation while removing B from wastewater by EWs. Furthermore, the result could be also related to high affinity of B to peat compared to other materials which were used in the

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present experiment. It is well known that B adsorption increases with increasing affinity of material against B and it can be retained in the organic based materials such as peat through a

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ligand exchange mechanism related to diol or cis-diol complexes (Allende et al., 2012; Sartaj and Fernandes, 2005). In this respect, the adsorptivity of peat for B can be much stronger and higher than those of zeolite, volcanic cinder, and sand. Furthermore, the data obtained from the present study verified that more B is retained in peat reactor compared to other reactors, and it can be seen in Fig 3c that UEW with peat media removed more than 0.002 mg m-2 d-1 B from the drinking water under the conditions of the same water loads. The results from the literature are also in good agreement with our findings as peat media had stronger B

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ACCEPTED MANUSCRIPT adsorption capacity in wetland matrix. Allende et al. (2012) have compared the removal efficiencies of various fillers including coco-peat, zeolite, and limestone, concluding that B removal efficiency of coco-peat wetland unit was significantly higher than those of zeolite and limestone, however with B removal efficiency of only 12.5% for coco-peat wetland.

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Kuyucak and Zimmer (2004) use peat as substrate filler in a wetland system to carry out an experimental research on B-rich wastewater and compare their results with the operation conditions of gravel fillers. The results suggested that the removal efficiency of a peat

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wetland system for removal of B in sewage was good, with B removal by peat clearly much

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higher than the gravel wetland unit.

3.3. The effect of media type on physicochemical parameter in UEW reactors As seen in Table 2, pH values of the outflow samples from different sampling points for each reactor were mostly alkaline during the experiment period, and with the increase of

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height to the bottom, pH value increased in the reactor beds. In this case, pH values of the final outflow samples from R1, R2, R3, and R4 were found as 7.58, 7.75, 7.86, and 7.73, respectively. However, one way ANOVA analysis concluded no significant differences

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among the outflow samples from the treatment reactors, indicating that pH levels were not significantly affected by media type used in the present experiment (p>0.05). Moreover, it

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can be seen in Table 2 that pH value of the outflow from the peat reactor (R1) was relatively more neutral than those of zeolite, volcanic cinder, and sand in all sampling points during the experiment period. This behavior can also affect the removal efficiency of the treatment reactors because the media type itself does not only adsorb B but also has its own special properties which can effect environmental parameters such as pH, so that it can more efficiently carry out B removal from drinking water. Correspondingly, B adsorption increases with the near neutral pH in a wetland matrix, thus B is more available in peat wetland for

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ACCEPTED MANUSCRIPT adsorption process due to boric acid predominant in water environment rather than borate ions (Allende et al., 2014; Türker et al., 2014; Wolska and Bryjak, 2013). Various researchers have found similar observations associated with pH effect on B adsorption for different media types (Allende et al., 2012; Sartaj and Fernandes, 2005).

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Electrical conductivity (EC) of the final outflow samples obtained from different reactors was lower than those of the inflow during the experiment period (Table 2), and the average EC values in the final effluent were determined as 1265 µS cm-1, 1266 µS cm-1, 1283

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µS cm-1, and 1303 µS cm-1 for R1, R2, R3, and R4, respectively. These results indicated that many anionic and cationic ions in drinking water were reduced by the treatment reactors

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during B purification process, however this reduction was not significant among media types (p>0.05).

The redox parameter indicates that the concentration of dissolved oxygen, activity of organisms in the wetland matrix, and redox value less than -100 reflect an anaerobic

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environment (Ong et al., 2010). The distribution of average redox and dissolved oxygen (DO) along UEW reactors are illustrated in Table 2. Redox and DO distribution were different between the final outflow and the other sampling points for each reactor, and these

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distributions were significant as well (p<0.05). The redox at the top layer of the treatment reactors ranged between 36.14 and 49.5 mV, whereas they were in the ranges of (-105.5) to

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(0.26) mV in the lower sections of the reactors. Furthermore, it can be seen in Table 2 that DO at the top layers of the wetland reactors were in the ranges of 5.09-6.53 mg L-1 and less than 1 mg L-1 in the lower sections of the reactors. These results indicated that anaerobic environment developed at the lower parts of all reactors, whereas upper parts of the reactors were mostly aerobic. Accordingly, the aerobic and anaerobic environments in up-flow wetland beds would influence B removal efficiency because studies in the recent past indicated that B removal dynamics in a wetland matrix are mostly related to aerobic

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ACCEPTED MANUSCRIPT environment, and presence of oxygen in the environment has more positive effects improving B removal (Türker et al., 2016c). Thus, it can be concluded that high redox potential value and DO levels also catalyzed B removal from drinking water in the upper sections of the treatment reactors because we found higher B removal performance in the upper sections

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during the experiment period (Fig 3b). On the other hand, it can be seen in the Table 2 that redox and DO value of the peat reactor are mostly lower than the values in other treatment reactors, suggesting that organic based media such as peat effects the redox profile in the

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wetland bed and creates a more anaerobic environment, especially in the lower section of the wetland reactor, compared to other filling material types used in this study. Therefore, experts

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should consider this phenomenon when they design their own wetland reactors.

3.4. The effect of the media type on B uptake by plants in UEW reactors The uptake of B by plants in a wetland matrix is mostly controlled by pH, wastewater

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composition, amount of organic matter, and climatic conditions. Among these parameters, the pH values of water environment and organic matter content in the filtration materials are the most crucial factors affecting uptake of B from water environment. (Allende et al., 2012;

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Nable et al., 1997; Turker et al., 2014).

The boron content in the organs of T.latifolia growing in the different treatment

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reactors at the end of the experiment period are shown in Fig 4a. The highest B concentrations were determined as 181 mg/kg, 54 mg/kg, 127 mg/kg, and 66 mg/kg in leaves of T.latifolia growing in R1, R2, R3, and R4, respectively. The concentration of B in roots/rhizomes was higher than stems, and B concentrations in root/rhizome of T.latifolia were recorded as 142 mg/kg, 38 mg/kg, 99 mg/kg, and 45 mg/kg for R1, R2, R3, and R4 treatment reactors, respectively. Moreover, the lowest B concentrations were found as 45 mg/kg, 31 mg/kg, 32 mg/kg, and 16 mg/kg in the stems of T.latifolia growing in R1, R2, R3, and R4, respectively.

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ACCEPTED MANUSCRIPT These results indicate that the media type in EWs affects B accumulation capacity of the same plant species growing in different substrates and B amount which is transported from roots/rhizomes to leaves in T.latifolia’s tissues. On the other hand, it could be inferred from the present results that the presence of organic based media such as peat in the wetland bed

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greatly affects B uptake ability of T.latifolia. As seen in Table 2, peat reactor (R1) has more neutral pH than those of the other reactors, and it might help to increase the uptake of B and lead to incorporate higher B removal in the wetland matrix. It is well known that B uptake by

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plants increases with neutral pH, and the decreasing pH in a wetland matrix with use of the peat substrate may be attributed to binding of B by plants (Allende et al., 2014). If this

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phenomenon is the case, it can also explain why there is a greater B concentration in the T.latifolia grown in the peat media during the treatment period compared to other media types.

The uptake rate of B by plants from their surrounding environment can be described

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better by the bioconcentration factor (BCF), and this factor was determined as the ratio between B amount in T.latifolia tissue and average B concentration in the drinking water in the present experiment. As seen in the Fig 4b, the BCF of T.latifolia growing in R1, R2, R3,

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and R4 were calculated as 26.7, 8.95, 18.7, and 9.29, respectively after the treatment period. This result also clearly indicates that B accumulation capacity of T.latifolia growing in peat

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media is higher than the same individual species growing in zeolite, volcanic cinder, and sand media and that bioavailability of B to T.latifolia is high in the peat reactors. The results from the dry matter biomass content assessments of T.latifolia growing in

the different reactors are shown Fig 4c. According to these results, the biomass content of T.latifolia was calculated as 274.02, 159.71, 178.16, and 170.37 DW g for R1, R2, R3, and R4, respectively. Moreover, above ground parts including leaves and stems had more biomass than below ground parts such as roots/rhizomes after the experiment period. These results

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ACCEPTED MANUSCRIPT indicated that media type clearly effects the biomass production of T.latifolia growing in different media and using peat substrate in a wetland matrix increased the biomass production more compared to zeolite, volcanic cinder, and sand media. It was an expected result because peat in wetland reactor presents micro and macro elements, as well as carbon source, for

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T.latifolia for plant growth, and it catalyzed the growth of T.latifolia’ organs more compared to zeolite, volcanic cinder, and sand media during the remediation period. In this respect, it is recommended that experts should take into consideration the advantages of an organic based

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media type such as peat on plant growth and biomass production for an UEW reactor in their

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experiment plans.

3.5. The effect of media type on soil enzyme activity in UEW reactors The soil enzymes activities in a wetland matrix present crucial information associated with living dynamics such as microbial compositions and activity (Zhang et al., 2010).

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Measurement of some soil enzyme activities including dehydrogenase, urease, and phosphatase is one way of describing the cycling of carbon (dehydrogenase), nitrogen (urease), phosphorus (phosphatase), and the general condition of microbial populations in the

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wetland environment. Moreover, the enzymes activities in a wetland matrix are affected by various soil parameters such as pH, organic matter content, depth profile, and texture (Zhang

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et al., 2010). In the present experiment, the activities of some important enzymes (dehydrogenase, urease, and phosphatase) are also measured in order to understand the effect of media type on soil enzymes during B remediation from drinking water in the UEW reactors. In this respect, we suggested that the results from enzyme activities could be meaningful in assessing the treatment performance of UEWs and importance of media type in such systems while remediating drinking water.

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ACCEPTED MANUSCRIPT The activity of dehydrogenase, urease, and phosphatase in different wetland reactors in the experiment period are shown in Fig 5. Correspondingly, the highest dehydrogenase activity was determined at 0-20 cm wetland depth as 367.3, 26.8, 19.8, 30.7 µg TPF g

-1

h-1

for R1, R2, R3, and R4, respectively. Moreover, the highest urease enzyme activity was also -1

48 h-1 for R1, R2, R3,

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observed at 0-20 cm depth as 4895, 1367, 1095, and 548 µg NH4+ g

and R4, respectively. The phosphatase activity decreased with increasing reactor depth, and the highest enzyme activity was measured as 16.5, 2.71, 0.179, and 2.9 µg p-nitrophenol g-1 hfor R1, R2, R3, and R4, respectively. These results indicate that adequate microbial population

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1

necessary for biochemical purification reaction in the wetland matrix was observed in all of

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the treatment reactors during B remediation process. The result also shows that the soil enzymes had different activities in the different media types during B remediation period, and soil enzymes in the peat wetland were found to be higher than those of other wetland reactors. One way ANOVA statistical analysis also indicates that soil enzyme activities in the peat

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wetland were significantly higher than other media types (p<0.05). It was an expected result because peat substrate is organic-based, and it presents more available environment associated with organic carbon availability and soil nutrients for soil microorganisms compared to other

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reactors. In the peat reactor, soil microorganisms were exposed to more nutrients and organic carbon in the wetland bed, and thus these organisms could have increased the rate of

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microbial growth and soil enzyme activities including dehydrogenase, urease, and phosphatase during B remediation process. Lower soil enzyme activities in other wetland reactors may be related to the decrease in the synthesis of enzymes associated with changes in microbial population in these reactors. Unfortunately, there is no information in literature about soil enzyme activities in different media types while remediating B from wastewater, thus it is not possible to make any comparisons. Nevertheless, it can be suggested that the monitoring of dehydrogenase, urease, and phosphatase activities in UEW reactors could

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ACCEPTED MANUSCRIPT provide information regarding the improvement of matrix quality and overall microbial activity or growth during B remediation from drinking water.

4. Conclusions

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Up-flow engineered wetland (UEW) reactors with different media types (peat, zeolite, volcanic cinder, and sand) were the first tested for the first time in an eco-technology experiment to remediation of drinking water contaminated B. Correspondingly, the four types

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of media in wetland reactor can effectively remove B from drinking water, and more than 90% B removal was achieved with peat-based UEW. This result suggests that the applications

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of these four media types in B drinking water treatment by UEW reactors are feasible. The removal of B by peat (which is based on organic matter) reactor is the highest, and it can also reach the drinking water standards (2.4 mg L-1) recommended by WHO at all of the sampling points during B remediation process. We also found that media type affected the soil enzyme

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activities associated with cycling of carbon, nitrogen, as well as phosphorus in wetland matrix, and soil enzyme activities in the peat wetland were significantly higher than other media types. Therefore it can be concluded that B treatment efficiency of peat wetland reactor

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is the best. Consequently, we suggest that engineers choose organic based media such as peat

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in order to obtain better B removal performance in their experimental wetland reactors.

Acknowledgements

This research did not receive any specific grant from funding agencies in the public,

commercial, or not-for-profit sectors.

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ACCEPTED MANUSCRIPT References Allende, K.L., Fletcher, T., Sun, G., 2012. The effect of substrate media on the removal of arsenic, boron and iron from an acidic wastewater in planted column reactors. Chemical Engineering Journal 179, 119-130.

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Allende, K.L., McCarthy, D., Fletcher, T., 2014. The influence of media type on removal of arsenic, iron and boron from acidic wastewater in horizontal flow wetland microcosms planted with Phragmites australis. Chemical Engineering Journal 246, 217-228.

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APHA, A., 1998. WEF (American Public Health Association, American Water Works Association, and Water Environment Federation). 1998. Standard methods for the

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Gao, J., Zhang, J., Ma, N., Wang, W., Ma, C., Zhang, R., 2015. Cadmium removal capability and growth characteristics of Iris sibirica in subsurface vertical flow constructed wetlands. Ecological Engineering 84, 443-450.

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Guan, Z., Lv, J., Bai, P., Guo, X., 2016. Boron removal from aqueous solutions by adsorption—A review. Desalination 383, 29-37. Gür, N., Türker, O.C., Böcük, H., 2016. Toxicity assessment of boron (B) by Lemna minor L.

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and Lemna gibba L. and their possible use as model plants for ecological risk assessment of aquatic ecosystems with boron pollution. Chemosphere 157, 1-9.

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Hasenmueller, E.A., Criss, R.E., 2013. Multiple sources of boron in urban surface waters and groundwaters. Science of the total environment 447, 235-247. Hilal, N., Kim, G., Somerfield, C., 2011. Boron removal from saline water: a comprehensive review. Desalination 273, 23-35. Huang, X., Liu, C., Li, K., Su, J., Zhu, G., Liu, L., 2015. Performance of vertical up-flow constructed wetlands on swine wastewater containing tetracyclines and tet genes. Water research 70, 109-117.

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ACCEPTED MANUSCRIPT Igra, A.M., Harari, F., Lu, Y., Casimiro, E., Vahter, M., 2016. Boron exposure through drinking water during pregnancy and birth size. Environment International 95, 54-60. Kong, L., Wang, Y.-B., Zhao, L.-N., Chen, Z.-H., 2009. Enzyme and root activities in surface-flow constructed wetlands. Chemosphere 76, 601-608.

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Lu, S., Zhang, X., Wang, J., Pei, L., 2016. Impacts of different media on constructed wetlands for rural household sewage treatment. Journal of Cleaner Production 127, 325-330.

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Ong, S.-A., Uchiyama, K., Inadama, D., Ishida, Y., Yamagiwa, K., 2010. Performance evaluation of laboratory scale up-flow constructed wetlands with different designs and

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emergent plants. Bioresource technology 101, 7239-7244.

Robbins, W.A., Xun, L., Jia, J., Kennedy, N., Elashoff, D.A., Ping, L., 2010. Chronic boron exposure and human semen parameters. Reproductive Toxicology 29, 184-190. Sartaj, M., Fernandes, L., 2005. Adsorption of boron from landfill leachate by peat and the

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effect of environmental factors. Journal of Environmental Engineering and Science 4, 19-28. Schoderboeck, L., Mühlegger, S., Losert, A., Gausterer, C., Hornek, R., 2011. Effects assessment: Boron compounds in the aquatic environment. Chemosphere 82, 483-487.

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Turker, O.C., Bocuk, H., Yakar, A., 2013. The phytoremediation ability of a polyculture constructed wetland to treat boron from mine effluent. J Hazard Mater 252-253, 132-141.

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Turker, O.C., Ture, C., Bocuk, H., Yakar, A., 2014. Constructed wetlands as green tools for management of boron mine wastewater. Int J Phytoremediation 16, 537-553. Türker, O.C., Türe, C., Böcük, H., Çiçek, A., Yakar, A., 2016a. Role of plants and vegetation structure on boron (B) removal process in constructed wetlands. Ecological Engineering 88, 143-152.

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ACCEPTED MANUSCRIPT Türker, O.C., Türe, C., Böcük, H., Yakar, A., 2016b. Phyto-management of boron mine effluent using native macrophytes in mono-culture and poly-culture constructed wetlands. Ecological Engineering 94, 65-74. Türker, O.C., Türe, C., Böcük, H., Yakar, A., Chen, Y., 2016c. Evaluation of an innovative

effluent pollution. Environ Sci Pollut R 23, 19302-19316.

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approach based on prototype engineered wetland to control and manage boron (B) mine

Türker, O.C., Vymazal, J., Türe, C., 2014. Constructed wetlands for boron removal: A

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review. Ecological Engineering 64, 350-359.

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irrigation water contaminated with boron (B) using duckweed (Lemna gibba L.) in a batch reactor system. Journal of Hazardous Materials.

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407, 3911-3922.

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horizontal sub-surface flow: a review of the field experience. Science of the total environment

Wang, B., Guo, X., Bai, P., 2014. Removal technology of boron dissolved in aqueous

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solutions–a review. Colloids and Surfaces A: Physicochemical and Engineering Aspects 444, 338-344.

Wolska, J., Bryjak, M., 2013. Methods for boron removal from aqueous solutions—A review. Desalination 310, 18-24. Wu, H., Zhang, J., Ngo, H.H., Guo, W., Liang, S., 2017. Evaluating the sustainability of free water surface flow constructed wetlands: Methane and nitrous oxide emissions. Journal of Cleaner Production 147, 152-156.

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ACCEPTED MANUSCRIPT Ye, Z., Lin, Z.-Q., Whiting, S., De Souza, M., Terry, N., 2003. Possible use of constructed wetland to remove selenocyanate, arsenic, and boron from electric utility wastewater. Chemosphere 52, 1571-1579. Zhang, C.-B., Wang, J., Liu, W.-L., Zhu, S.-X., Liu, D., Chang, S.X., Chang, J., Ge, Y., 2010.

constructed wetland. Bioresource technology 101, 1686-1692.

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Figure Captions

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Effects of plant diversity on nutrient retention and enzyme activities in a full-scale

media.

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Fig. 1. The detailed scheme of the up-flow engineered wetlands (UEWs) with different

Fig. 2. Boron (B) concentrations in inflow and outflow properties for R1, R2, R3, and R4 during the experiment period.

Fig. 3. Boron (B) concentrations profile in UEW reactors (a), B removal performance of

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reactors during the experiment period (b), and mass removal rate of treatment reactors (c). Fig. 4. Boron (B) amount in Typha latifolia grown in different reactors (a), Bioconcentration factors (BCF) of Typha latifolia in different reactors (b), Dry matter biomass content in UEW

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reactors at the end of the experiment period (c). Fig. 5. The activities of dehydrogenase (a), urease (b), and phosphatase (c) enzymes in UEW

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reactors in the experiment period. Error bars indicate standard deviation.

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Table 1. Chemical and physical analyzes of media from different depth in the treatment reactors at the end of the experiment. Reactor Number

0-20 cm

20-40 cm

40-60 cm

R1

46.8±12.1

46.6±10.8

86.87±12.7

R2

2.03±0.8

2.6±.0.4

3.9±0.8

R3

2.28±0.5

3.3±1.6

4.7±1.8

R4

2.45±1.2

3.48±1.3

6.32±2.1

7.83±0.09

7.81±0.02

7.75±0.07

8.14±0.04

8.15±0.19

8.2±0.06

8.2±0.005

8.16±0.07

8.16±0.03

8.05±0.107

8.06±0.25

7.93±0.18

1485±176

1566±196

1750±177

1142±95

906±105

1081±137

R3

688±85

779±121

636±89

R4

737±27

750±30

730±14

R1

102.7±1.8

90.7±9.3

79.6±2.6

R2

100±2.5

63±1.53

76.5±15.8

R3

91.4±2.7

95.4±9.2

101.6±3.19

R4

73.3±6.6

69.3±4.2

100.6±24.3

R1

1.11±0.16

1.07±0.05

1.38±0.14

R2

0.24±0.04

0.16±0.01

0.19±0.02

R3

0.1106±0.03

0.112±0.01

0.115±0.01

R4

0.125±0.01

0.159±0.01

0.145±0.01

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Parameters

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Boron (B) concentration (mg/kg)

R2 pH (-log[H+]) R3 R4 R1

Nitrogen (%)

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Redox (mV)

R2

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EC (µS cm-1)

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R1

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Table 2. Average pH, electrical conductivity (EC), redox, and dissolved oxygen (DO) values in inflow and outflow for treatment reactors during the experiment period.

Redox (mV)

S1

R1

7.81±0.26

R2

S3 (Final outflow)

7.06±0.2

7.17±0.19

7.58±0.2

7.81±0.26

7.41±0.12

7.51±0.13

7.75±0.21

R3

7.81±0.26

7.50±0.15

7.58±0.16

7.76±0.25

R4

7.81±0.26

7.42±0.12

7.50±0.13

7.73±0.21

R1

1419±498

1527±425

1836±538

1265±538

R2

1419±498

1345±409

1309±359

1266±449

R3

1419±498

1352±452

1379±427

1283±515

R4

1419±498

1412±455

1417±353

1303±526

R1

107.3±47.5

-105.5±42

-55.02±37

40.23±20.1

R2

107.3±47.5

-19.24±63

0.26±51.2

43.05±13.2

R3

107.3±47.5

-69.76±57.1

-36.53±47.9

49.59±14.4

107.3±47.5

-65.21±46.1

-27.74±40.4

36.14±13.1

8.05±0.9

0.96±0.28

1.79±0.64

5.09±1.87

8.05±0.9

2.13±0.82

2.97±1.12

6.53±2.76

R3

8.05±0.9

1.85±0.75

2.86±1.14

5.94±2.3

R4

8.05±0.9

1.92±0.74

2.66±1.04

5.7±2.35

R4 R1

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R2

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Dissolved oxygen (mg/L)

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S2

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EC (µS cm-1)

Inflow

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pH (-log[H+])

Reactor Number

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Parameters

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Fig. 1. The detailed scheme of the up-flow engineered wetlands (UEWs) with different media.

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Fig. 2. Boron (B) concentrations in inflow and outflow properties for R1, R2, R3, and R4 during the experiment period.

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Fig. 3. Boron (B) concentrations profile in UEW reactors (a), B removal performance of reactors during the experiment period (b), and mass removal rate of treatment reactors (c).

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Fig. 4. Boron (B) amount in Typha latifolia grown in different reactors (a), Bioconcentration factors (BCF) of Typha latifolia in different reactors (b), Dry matter biomass content in UEW reactors at the end of the experiment period (c).

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Fig. 5. The activities of dehydrogenase (a), urease (b), and phosphatase (c) enzymes in UEW reactors in the experiment period. Error bars indicate standard deviation.

ACCEPTED MANUSCRIPT Highlights •

Up-flow EW reactors were used to treat boron removal from drinking water for 120 days Average 91% boron removal was achieved by peat wetland reactor

•

Peat substrate was higher B adsorption capacity than zeolite, volcanic cinder, and sand

•

Media type affected physicochemical parameters, plant uptake, and soil enzymes.

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•