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Anaerobic granulation from dispersed inoculum is recognized as a slow process. However, studies under saline conditions have shown that adding complex proteinaceous substrates can accelerate this process. To explore whether this holds true also under non-saline conditions, we conducted a 262-days experiment with four lab-scale upflow anaerobic sludge blanket reactors inoculated with digested sewage sludge. Each reactor received a synthetic feed containing varying amount of carbohydrate/protein substrate: glucose (R Glu ), acetate/tryptone (R Ac+Try ), glucose/tryptone (R Glu+Try ), and glucose/starch (R Glu+Sta ). Development of granules with different influent composition was monitored with macroscopy, analysis of the extracellular polymeric substances, and microbial diversity. Granulation was faster in reactors R Glu+Try and R Glu+Sta . Increasing granule diameters positively correlated with the occurrence of bacteria from Muribaculaceae and Lachnospiraceae families, suggesting their involvement in de novo granulation. Granules of R Glu+Try also had high relative abundances of both fermenting bacteria (e.g. Lactococcus, Streptococcus, Trichococcus) and bacteria involved in the oxidation of volatile fatty acids (Smithella, Acetobacteroides). The results of this study provide a basis for strategies to enhance the sludge granulation rate in practice when granular inoculum is not available. Specifically, supplementing small amounts of waste protein during reactor start-up can be effective., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

At the interface between an ion-exchange membrane and a multi-electrolyte solution, charged species redistribute themselves to minimize the free energy of the system. In this paper, we explore the Donnan equilibrium of membranes with quaternary electrolyte (Na + /Mg 2+ /K + /Ca 2+ /Cl - ) solutions, experimentally. The data was used to calculate the ion activity coefficients for six commercial cation-exchange membranes (CEMs). After setting one of the activity coefficients to an arbitrary value, we used the remaining (N-1) activity coefficients as fitting parameters to describe the equilibrium concentrations of (N) ionic species with a mean relative error of 3 %. At increasing solution ionic strengths, the equivalent ion fractions of monovalent counter-ions inside the membrane increased at the expense of the multivalent ones in alignment with the Donnan equilibrium theory. The fitted activity coefficients were employed in a transport model that simulated a Donnan dialysis experiment involving all four cations simultaneously. The arbitrary value assigned to one activity coefficient affects the calculated Donnan potential at the membrane interface. Nevertheless, this arbitrary value does not affect the prediction of the ion concentrations inside the membrane and consequently does not affect the modeled ion fluxes., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

Extracellular polymeric substances (EPS) are considered to play a pivotal role in shaping granules' physical properties. In this contribution, we characterized the viscoelastic properties of EPS from granules of 9 full-scale industrial anaerobic reactors; and quantitatively investigated whether these properties correlate with granules' resistance to compression (E granule ) and shear strength (S granule ). Most granules with a higher shear strength, also exhibited a stronger resistance to compression (r = 0.96, p = 0.002), except those granules that contained relatively more proteins in their EPS. Interestingly, these granules were also the most resistant to shear stress (S granule  ≥ 110 ± 40 h). Furthermore, the EPS hydrogels of these granules had slower softening rates (κ < 0.9) compared to the others (κ ranged between 0.95 and 1.20), indicating stronger gels were formed. These findings suggest that the EPS hydrogel softening rate could be a key parameter to explain granule's shear strength., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

The factors limiting micropollutant biodegradation in the environment and how to stimulate this process have often been investigated. However, little information is available on the capacity of microbial communities to retain micropollutant biodegradation capacity in the absence of micropollutants or to reactivate micropollutant biodegradation in systems with fluctuating micropollutant concentrations. This study investigated how a period of 2 months without the addition of micropollutants and other organic carbon affected micropollutant biodegradation by a micropollutant-degrading microbial community. Stimulation of micropollutant biodegradation was performed by adding different types of dissolved organic carbon (DOC)-extracted from natural sources and acetate-increasing 10 × the micropollutant concentration, and inoculating with activated sludge. The results show that the capacity to biodegrade 3 micropollutants was permanently lost. However, the biodegradation activity of 2,4-D, antipyrine, chloridazon, and its metabolites restarted when these micropollutants were re-added to the community. Threshold concentrations similar to those obtained before the period of no substrate addition were achieved, but biodegradation rates were lower for some compounds. Through the addition of high acetate concentrations (108 mg-C/L), gabapentin biodegradation activity was regained, but 2,4-D biodegradation capacity was lost. An increase of bentazon concentration from 50 to 500 µg/L was necessary for biodegradation to be reactivated. These results provide initial insights into the longevity of micropollutant biodegradation capacity in the absence of the substance and strategies for reactivating micropollutant biodegrading communities., (© 2024. The Author(s).)

The availability of suitable electron donors and acceptors limits micropollutant natural attenuation in oligotrophic groundwater. This study investigated how electron donors with different biodegradability (humics, dextran, acetate, and ammonium), and different oxygen concentrations affect the biodegradation of 15 micropollutants (initial concentration of each micropollutant = 50 μg/L) in simulated nitrate reducing aquifers. Tests mimicking nitrate reducing field conditions showed no micropollutant biodegradation, even with electron donor amendment. However, 2,4-dichlorophenoxyacetic acid and mecoprop were biodegraded under (micro)aerobic conditions with and without electron donor addition. The highest 2,4-dichlorophenoxyacetic acid and mecoprop biodegradation rates and removal efficiencies were obtained under fully aerobic conditions with amendment of an easily biodegradable electron donor. Under microaerobic conditions, however, amendment with easily biodegradable dissolved organic carbon (DOC) inhibited micropollutant biodegradation due to competition between micropollutants and DOC for the limited oxygen available. Microbial community composition was dictated by electron acceptor availability and electron donor amendment, not by micropollutant biodegradation. Low microbial community richness and diversity led to the absence of biodegradation of the other 13 micropollutants (such as bentazon, chloridazon, and carbamazepine). Finally, adaptation and potential growth of biofilms interactively determined the location of the micropollutant removal zone relative to the point of amendment. This study provides new insight on how to stimulate in situ micropollutant biodegradation to remediate oligotrophic groundwaters as well as possible limitations of this process., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Groundwater is the most important source for drinking water in The Netherlands. Groundwater quality is threatened by the presence of pesticides, and biodegradation is a natural process that can contribute to pesticide removal. Groundwater conditions are oligotrophic and thus biodegradation can be limited by the presence and development of microbial communities capable of biodegrading pesticides. For that reason, bioremediation technologies such as bioaugmentation (BA) can help to enhance pesticide biodegradation. We studied the effect of BA using enriched mixed inocula in two column bioreactors that simulate groundwater systems at naturally occurring redox conditions (iron and sulfate-reducing conditions). Columns were operated for around 800 days, and two BA inoculations (BA1 and BA2) were conducted in each column. Inocula were enriched from different wastewater treatment plants (WWTPs) under different redox-conditions. We observed a temporary effect of BA1, reaching 100% removal efficiency of the pesticide 2,4-D after 100 days in both columns. In the iron-reducing column, 2,4-D removal was in general higher than under sulfate-reducing conditions demonstrating the influence of redox conditions on overall biodegradation. We observed a temporary shift in microbial communities after BA1 that is relatable to the increase in 2,4-D removal efficiency. After BA2 under sulfate-reducing conditions, 2,4-D removal efficiency decreased, but no change in the column microbial communities was observed. The present study demonstrates that BA with a mixed inoculum can be a valuable technique for improving biodegradation in anoxic groundwater systems at different redox-conditions., (© 2023. The Author(s).)

Electrodialysis is a water desalination technology that enables selective separation of ions, making it a promising solution for sustainable water reuse. The selectivity of the process is mainly determined by the properties of ion exchange membranes that can vary depending on the composition of ions in water, such as water uptake and charge density. In this work, we studied selective adsorption of Na + and K + ions in various ion exchange membranes considering the effect of solution ion composition on membrane water volume fraction. For that purpose, we conducted membrane adsorption experiments using solutions with Na + and K + ions with different ion compositions including Li + , Ca 2+ or Mg 2+ ions at different concentrations (0.001 - 0.25 M). The experiments showed that with the total ion concentration and the amount of divalent ions in solution, the membrane water volume fraction decreases while the selective adsorption of the smaller (hydrated) K + ions over the Na + ions in the membrane increases. We developed a theoretical framework based on Boublik-Mansoori-Carnahan-Starling-Leland (BMCSL) theory to describe the effect of membrane water volume fraction on selective adsorption of the ions by including volumetric effects, such as size exclusion. The developed framework was used to describe ion partitioning results of the membrane adsorption experiments. In addition, the effect of solution ion composition on selective ion removal during electrodialysis operation was evaluated using experimental data and theoretical calculations. The results of this study show that considering volumetric effects can improve the ion partitioning description in ion exchange membranes for solutions with various ion compositions., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

The efficient utilization of food waste (FW) resources through Food Waste Valorization (FWV) has received increasing attention in recent years. Various decision-making studies have been undertaken to facilitate FWV implementation, such as the studies on decision-making framework and FWV technology assessment. Food waste hierarchy is a widely discussed framework in FW management, but it was found too simplified and does not always contribute positively to environmental sustainability. Moreover, decision-making studies in FWV often focus on specific aspects of the food system and employ distinctive decision-making approaches, making it difficult to compare the results from different studies. Therefore, our literature review is conducted to provide a comprehensive understanding of FWV decision-making. This study identifies what decisions are needed, and three levels of decisions are revealed: system-level, FW stream-level, and FWV option-level. The assessment approaches and criteria used to support decision-making in FWV are also collected and analyzed. Building upon these findings, an hourglass model is synthesized to provide a holistic illustration of decision-making in FWV. This study untangles the complexities of FWV decision-making and sheds light on the limitations of current studies. We anticipate this study will make more people realize that FWV is a multidisciplinary issue and requires the collective participation of researchers, practitioners, policymakers, and consumers. Such collective engagement is essential to effectively address practical challenges and propel the transition of the current food system toward a more resource-efficient paradigm., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Understanding the dynamic change in abundance of both fecal and opportunistic waterborne pathogens in urban surface water under different abiotic and biotic factors helps the prediction of microbiological water quality and protection of public health during recreational activities, such as swimming. However, a comprehensive understanding of the interaction among various factors on pathogen behavior in surface water is missing. In this study, the effect of salinity, light, and temperature and the presence of indigenous microbiota, on the decay/persistence of Escherichia coli and Pseudomonas aeruginosa in Rhine River water were tested during 7 days of incubation with varying salinity (0.4, 5.4, 9.4, and 15.4 ppt), with light under a light/dark regime (light/dark) and without light (dark), temperature (3, 12, and 20 °C), and presence/absence of indigenous microbiota. The results demonstrated that light, indigenous microbiota, and temperature significantly impacted the decay of E. coli. Moreover, a significant (p<0.01) four-factor interactive impact of these four environmental conditions on E. coli decay was observed. However, for P. aeruginosa, temperature and indigenous microbiota were two determinate factors on the decay or growth. A significant three-factor interactive impact between indigenous microbiota, temperature, and salinity (p<0.01); indigenous microbiota, light, and temperature (p<0.01); and light, temperature, and salinity (p<0.05) on the decay of P. aeruginosa was found. Due to these interactive effects, caution should be taken when predicting decay/persistence of E. coli and P. aeruginosa in surface water based on a single environmental condition. In addition, the different response of E. coli and P. aeruginosa to the environmental conditions highlights that E. coli monitoring alone underestimates health risks of surface water by non-fecal opportunistic pathogens, such as P. aeruginosa. KEY POINTS: Abiotic and biotic factors interactively affect decay of E. coli and P. aeruginosa E.coli and P.aeruginosa behave significantly different under the given conditions Only E. coli as an indicator underestimates the microbiological water quality., (© 2024. The Author(s).)

Unconventional substrata like activated carbon or clay beads can enhance micropollutant removal in constructed wetlands. However, hydroponic materials widely used in horticulture have not yet been investigated for their potential to remove micropollutants. In addition, potential effect of plant species other than reeds on micropollutant removal has not been sufficiently investigated. Therefore, a nature-based, post-treatment technology called improved vertical flow constructed wetlands (CW) with hydroponic (H) materials (CWH) was designed by employing cocopeat and mineral with ornamental plant species syngonium and periwinkle. A mesocosm CWH system was tested in a climate-controlled greenhouse for 550 days for its potential to remove frequently found micropollutants in wastewater, namely sulfamethoxazole, trimethoprim, diclofenac, erythromycin, carbamazepine, pyrimethanil, tebuconazole, pymetrozine, atrazine and DEET from wastewater effluent. The main focus was to understand the contribution of sorption, microbial degradation and phytoremediation on the removal of those micropollutants. It was found that cocopeat showed a capacity for sorbing micropollutants, ranging between 80 and 99% of the compounds added while less than 10% sorption was observed for mineral wool. Additionally moderate to high biological removal (25-60 μg of compound/kg dry weight of substratum/day) for most of the studied compounds was observed in all the cocopeat biotic groups. Furthermore, it could be stated that plants appear not to be an important factor for micropollutant removal. The observed differences in removal between the cocopeat and mineral wool systems could be explained by the difference in physico-chemical properties of the substrata, where cocopeat has a higher water holding capacity, moisture content, nutrient and organic matter content, and a higher intraparticle porosity and surface area. This study revealed notable removal of persistent and mobile micropollutants in cocopeat CWH, namely carbamazepine (80-86%) and diclofenac (97-100%). These results demonstrate the potential beneficial use of hydroponic materials as substratum in more advanced constructed wetlands designed to remove micropollutants., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Groundwater, a major source of drinking water worldwide, is often contaminated with micropollutants. Although microbial communities in aquifers and soils have the capability to biodegrade some micropollutants, this process is limited in situ. Biostimulation with dissolved organic carbon (DOC) is known to promote micropollutant biodegradation, but the role of DOC biodegradability is still poorly understood. This study investigated how three DOC types with different biodegradability (humics, dextran and acetate) affect the biodegradation of 15 micropollutants by aquifer and soil microbial communities under aerobic and nitrate reducing conditions. Although originating from different environments, both communities were able to biodegrade the same 4 micropollutants under aerobic conditions - 2,4-D, MCPP, chloridazon (CLZ) and chloridazon-desphenyl. However, DOC addition only affected MCPP biodegradation, promoting MCPP biodegradation regardless of DOC biodegradability. Biodegradation of 2,4-D, MCPP and CLZ under aerobic conditions was observed after a lag phase, whose duration differed per compound. 2,4-D was biodegraded first and fully. Aquifer community was able to degrade about half of the initial MCPP concentration (removal efficiency of 49.3 ± 11.7%). CLZ was fully biodegraded by the aquifer community, but not by the soil community, possibly due to substrate competition with organics originating from the inoculum. Therefore, the natural organic carbon present in the inocula and in environmental systems can influence micropollutant biodegradation. Under nitrate reducing conditions micropollutant biodegradation was not observed nor biostimulated by DOC addition. The results also highlight the importance of sufficient exposure time to trigger in situ micropollutant biodegradation., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Micropollutant biodegradation is selected by the interplay among environmental conditions and microbial community composition. This study investigated how different electron acceptors, and different inocula with varying microbial diversity, pre-exposed to distinct redox conditions and micropollutants, affect micropollutant biodegradation. Four tested inocula comprised of agricultural soil (Soil), sediment from a ditch in an agricultural field (Ditch), activated sludge from a municipal WWTP (Mun AS), and activated sludge from an industrial WWTP (Ind AS). Removal of 16 micropollutants was investigated for each inoculum under aerobic, nitrate reducing, iron reducing, sulfate reducing, and methanogenic conditions. Micropollutant biodegradation was highest under aerobic conditions with removal of 12 micropollutants. Most micropollutants were biodegraded by Soil (n = 11) and Mun AS inocula (n = 10). A positive correlation was observed between inoculum community richness and the number of different micropollutants a microbial community initially degraded. The redox conditions to which a microbial community had been exposed appeared to positively affect micropollutant biodegradation performance more than pre-exposure to micropollutants. Additionally, depletion of the organic carbon present in the inocula resulted in lower micropollutant biodegradation and overall microbial activities, suggesting that i) an additional carbon source is needed to promote micropollutant biodegradation; and ii) overall microbial activity can be a good indirect indicator for micropollutant biodegradation activity. These results could help to develop novel micropollutant removal strategies., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.)

Ozonation is a viable option to improve the removal of micropollutants (MPs) in wastewater treatment plants (WWTPs). Nevertheless, the application of ozonation is hindered by its high energy requirements and by the uncertainties regarding the formation of toxic transformation products in the process. Energy requirements of ozonation can be reduced with a pre-ozone treatment, such as a biological activated carbon (BAC) filter, that removes part of the effluent organic matter before ozonation. This study investigated a combination of BAC filtration followed by ozonation (the BO 3 process) to remove MPs at low ozone doses and low energy input, and focused on the formation of toxic organic and inorganic products during ozonation. Effluent from a WWTP was collected, spiked with MPs (approximately 1 µg/L) and treated with the BO 3 process. Different flowrates (0.25-4 L/h) and specific ozone doses (0.2-0.6 g O 3 /g TOC) were tested and MPs, ecotoxicity and bromate were analyzed. For ecotoxicity assessment, three in vivo (daphnia, algae and bacteria) and six in vitro CALUX assays (Era, GR, PAH, P53, PR, andNrf2 CALUX) were used. Results show that the combination of BAC filtration and ozonation has higher MP removal and higher ecotoxicity removal than only BAC filtration and only ozonation. The in vivo assays show a low ecotoxicity in the initial WWTP effluent samples and no clear trend with increasing ozone doses, while most of the in vitro assays show a decrease in ecotoxicity with increasing ozone dose. This suggests that for the tested bioassays, feed water and ozone doses, the overall ecotoxicity of the formed transformation products during ozonation was lower than the overall ecotoxicity of the parent compounds. In the experiments with bromide spiking, relevant formation of bromate was observed above specific ozone doses of approximately 0.4 O 3 /g TOC and more bromate was formed for the samples with BAC pre-treatment. This indirectly indicates the effectivity of the pre-treatment in removing organic matter and making ozone more available to react with other compounds (such as MPs, but also bromide), but also underlines the importance of controlling the ozone dose to be below the threshold to avoid formation of bromate. It was concluded that treatment of the tested WWTP effluent in the BO 3 process at a specific ozone dose of 0.2 g O 3 /g TOC, results in high MP removal at limited energy input while no increase in ecotoxicity, nor formation of bromate was observed under this condition. This indicates that the hybrid BO 3 process can be implemented to remove MPs and improve the ecological quality of this WWTP effluent with a lower energy demand than conventional MP removal processes such as standalone ozonation., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Antibiotic resistance is a global public health concern. Antibiotic usage in pigs makes swine wastewater (SW) a reservoir for antibiotic resistance genes (ARGs). SW is usually stored and treated in a three-chamber anaerobic pond (3-CAP) in medium and small pig farms in northern China. However, the yet unexplored presence of ARGs in SW during 3-CAP treatment may result in ARGs spreading into the environment if farmers apply SW to farmland as a liquid organic fertilizer. This study investigated the profiles of and changes in ARGs in SW during its treatment in 3-CAP over four seasons and analyzed the correlation between ARGs and bacterial phenotypes, along with the physicochemical parameters of the water. The results revealed that ARG abundance decreased considerably after 3-CAP treatment in April (47%), October (47%), and December (62%) but increased in May (43%) and August (73%). The ARG copies in the influent and other SW samples increased significantly from 10 7 copies/mL in April to 10 9 copies/mL in October and were maintained in December. The increase in ARG abundance was not as rapid as the growth of the bacterial population, resulting in lower relative abundance in October and December. Bacterial communities possessed more sul1 and tetM genes, which were also positively correlated with mobile genetic elements. After the 3-CAP treatment, 16% of antibiotics and 60% of heavy metals were removed, and both had a weak correlation with ARGs. Predicted phenotypes showed that gram-positive (G + ) and gram-negative (G - ) bacteria have different capacities for carrying ARGs. G + bacteria carry more ARGs than G - bacteria. This study revealed the persistence of ARGs in SW after 3-CAP treatment over different seasons. Applying SW in the proper month will mitigate ARG dissemination to the environment., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Canals and canalized rivers form a major part of surface water systems in European delta cities and societal ambitions to use these waters increase. This is the first assessment of how suitability of these waters can improve for three important uses: transportation, thermal energy extraction (TEE) and recreation. We assess suitability with Suitability Indices (SIs) and identify which alterations in the water system are needed to improve SI scores in Amsterdam, The Netherlands, and Ghent, Belgium. The results show spatial variability in suitability scores. Current suitability for transportation is low (SI score = 1) to excellent (SI score = 4), for TEE fair (SI score = 2) to excellent (SI score = 4), and suitability for recreation is low (SI score = 1). Suitability could improve by enlarging specific waterway dimensions, increasing discharge and clarity, and by enhancing microbiological water quality. The same methodology can be applied to optimize designs for new water bodies and for more water uses., (© 2022. The Author(s).)

Organic matter (OM) is the most important factor influencing the effectivity and efficiency of micropollutant (MP) ozonation in wastewater effluents. The importance of the quantity of OM is known, because of this, total organic carbon (TOC) is generally used to determine the required ozone dose for any water sample. Still, the effect of OM type on MP ozonation is not well understood. In this study, effluents from five wastewater treatment plants were collected and the organic matter in these effluents was fractionated using membranes (F1-4) and resin (HI, HOA, HON and HOB). Fractions were diluted to the same TOC concentration, spiked with MPs and ozonated at three ozone doses. Our results show that all five effluents had comparable OM compositions and similar MP removal, confirming the suitability of OM quantity (TOC) to compare the ozone requirements for wastewater effluents. From the 19 analysed MPs, three groups were identified that showed similar removal behaviour. The strongest differences between the groups were observed around MP ozone reactivities of 10 2 , 10 4 and 10 6 M -1 s -1 . This indicates the presence of three OM groups in the samples that interfere with the removal of different MPs. MP removal in the resin fraction HON were higher for MPs with high and medium ozone reactivity, indicating a low interference of OM in this fraction with MP ozonation. OM in the resin fractions HOA and HI showed higher interference with MP ozonation. Therefore, removing the HOA and HI fractions prior to ozonation would result in a lower required ozone dose and a more efficient removal of the MPs. MP removal correlated with the OM characteristics A300, SR and fluorescence component comp 2. These characteristics can be used as inline tools to predict the required ozone dose in water treatment plants., (Copyright © 2022 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Electrochemical oxidation is an effective technique for treating persistent organic pollutants, which are hardly removed in conventional wastewater treatment plants. Sulfate and chloride salts commonly used and present in natural wastewater influence the electrochemical degradation process. In this study, the effect of electrolyte composition on the active sulfate species (SO 4 ● ⁻ and S 2 O 8 2 ⁻) formation, benzotriazole degradation-a model organic compound, and chlorinated by-products distribution have been investigated while using a boron-doped diamond (BDD) anode. Different Na 2 SO 4 :NaNO 3 and Na 2 SO 4 :NaCl ratios with constant conductivity of 10 mS/cm were used in the experiments and applied anode potential was kept constant at 4.3 V vs. Ag/AgCl. The electrogenerated SO 4 ● ⁻ and S 2 O 8 2 ⁻ formation were faster in 10:1 and 2:1 Na 2 SO 4 :NaNO 3 ratios than in the 1:0 ratio. The ● OH-mediated SO 4 ● ⁻ production has prevailed in 10:1 and 2:1 ratios. However, ● OH-mediated SO 4 ● ⁻ production has hindered the 1:0 ratio due to excess chemisorption of SO 4 2 ⁻ on the BDD anode. Similarly, the faster benzotriazole degradation, mineralization, and lowest energy consumption were achieved in the 10:1 Na 2 SO 4 :NaNO 3 and Na 2 SO 4 :NaCl ratio. Besides, chlorinated organic by-product concentration (AOX) was lower in the 10:1 Na 2 SO 4 :NaCl ratio but increased with the increasing chloride ratio in the electrolyte. LC-MS analysis shows that several chlorinated organic transformation products were produced in 0:1 to 2:1 ratio, which was not found in the 10:1 Na 2 SO 4 :NaCl ratio. A comparatively higher amount of ClO 4 ⁻ was formed in the 10:1 ratio than in 2:1 to 0:1 ratio. This ClO 4 ⁻ formation train evidence the effective ● OH generation in a sulfate-enriched condition because the ClO 4 ⁻ formation is positively correlated to ● OH concentration. Overall results show that sulfate-enriched electrolyte compositions are beneficial for electrochemical oxidation of biorecalcitrant organic pollutants., (Copyright © 2022 The Author(s). Published by Elsevier Inc. All rights reserved.)

Groundwater quality is crucial for drinking water production, but groundwater resources are increasingly threatened by contamination with pesticides. As pesticides often occur at micropollutant concentrations, they are unattractive carbon sources for microorganisms and typically remain recalcitrant. Exploring microbial communities in aquifers used for drinking water production is an essential first step towards understanding the fate of micropollutants in groundwater. In this study, we investigated the interaction between groundwater geochemistry, pesticide presence, and microbial communities in an aquifer used for drinking water production. Two groundwater monitoring wells in The Netherlands were sampled in 2014, 2015, and 2016. In both wells, water was sampled from five discrete depths ranging from 13 to 54 m and was analyzed for geochemical parameters, pesticide concentrations and microbial community composition using 16S rRNA gene sequencing and qPCR. Groundwater geochemistry was stable throughout the study period and pesticides were heterogeneously distributed at low concentrations (μg L -1 range). Microbial community composition was also stable throughout the sampling period. Integration of a unique dataset of chemical and microbial data showed that geochemical parameters and to a lesser extent pesticides exerted selective pressure on microbial communities. Microbial communities in both wells showed similar composition in the deeper aquifer, where pumping results in horizontal flow. This study provides insight into groundwater parameters that shape microbial community composition. This information can contribute to the future implementation of remediation technologies to guarantee safe drinking water production., (Copyright © 2022 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Several harmful or valuable ionic species present in seawater, brackish water, and wastewater are amphoteric, weak acids or weak bases, and, thus, their properties depend on local water pH. Effective removal of these species can be challenging for conventional membrane technologies, necessitating chemical dosing of the feedwater to adjust pH. A prominent example is boron, which is considered toxic in high concentrations and often requires additional membrane passes to remove during seawater desalination. Capacitive deionization (CDI) is an emerging membraneless technique for water treatment and desalination, based on electrosorption of salt ions into charging microporous electrodes. CDI cells show strong internally generated pH variations during operation, and, thus, CDI can potentially remove pH-dependent species without chemical dosing. However, development of this technique is inhibited by the complexities inherent to the coupling of pH dynamics and ion properties in a charging CDI cell. Here, we present a theoretical framework predicting the electrosorption of pH-dependent species in flow-through electrode CDI cells. We demonstrate that such a model enables insight into factors affecting species electrosorption and conclude that important design rules for such systems are highly counterintuitive. For example, we show both theoretically and experimentally that for boron removal, the anode should be placed upstream and the cathode downstream, an electrode order that runs counter to the accepted wisdom in the CDI field. Overall, we show that to achieve target separations relying on coupled, complex phenomena, such as in the removal of amphoteric species, a theoretical CDI model is essential., Competing Interests: The authors declare no competing interest.

Groundwater is the main source for drinking water production globally. Groundwater unfortunately can contain micropollutants (MPs) such as pesticides and/or pesticide metabolites. Biological remediation of MPs in groundwater requires an understanding of natural biodegradation capacity and the conditions required to stimulate biodegradation activity. Thus, biostimulation experiments are a valuable tool to assess pesticide biodegradation capacity of field microorganisms. To this end, groundwater samples were collected at a drinking water abstraction aquifer at two locations, five different depths. Biodegradation of the MPs BAM, MCPP and 2,4-D was assessed in microcosms with groundwater samples, either without amendment, or amended with electron acceptor (nitrate or oxygen) and/or carbon substrate (dissolved organic carbon (DOC)). Oxygen + DOC was the most successful amendment resulting in complete biodegradation of 2,4-D in all microcosms after 42 days. DOC was most likely used as a growth substrate that enhanced co-metabolic 2,4-D degradation with oxygen as electron acceptor. Different biodegradation rates were observed per groundwater sample. Overall, microorganisms from the shallow aquifer had faster biodegradation rates than those from the deep aquifer. Higher microbial activity was also observed in terms of CO 2 production in the microcosms with shallow groundwater. Our results seem to indicate that shallow groundwater contains more active microorganisms, possibly due to their exposure to higher concentrations of both DOC and MPs. Understanding field biodegradation capacity is a key step towards developing further bioremediation-based technologies. Our results show that biostimulation has real potential as a technology for remediating MPs in aquifers in order to ensure safe drinking production., (Copyright © 2021 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Additional treatment of wastewater, such as constructed wetlands (CWs), is a possible solution to reduce the discharge of antibiotics and antibiotic resistance genes (ARGs) from households and industry to the environment. This study aims to investigate the occurrence and removal of antibiotics and ARGs by two full scale CWs operated at different hydraulic retention times (HRT), namely 1 day and 3 days. Both CWs were receiving the same wastewater treatment plant (WWTP) effluent. Temporally and spatially distributed sampling of water and sediment was conducted for one year and samples were analyzed for antibiotics and ARGs by using LC-MS/MS and qPCR. Results showed that both CWs removed antibiotics significantly with a comparable overall removal of 28%-100%, depending on the type of antibiotics. However, some of the antibiotics showed higher concentration after the CW treatment. Five antibiotics (tiamulin, tylosin, oxytetracycline, sulfamethoxazole and trimethoprim) were the most abundant (>1500 ng/l on average) in winter. Meanwhile, ermB was the most abundant (average of 5.0 log) in winter compared to summer (average of 3.5 log). Other ARGs did not show a significant increase or decrease between winter and summer. ARGs were removed from the wastewater by 0.8 to 1.5 log. The HRT did not influence the removal of either the antibiotics or the ARGs. A strong correlation was found between sul genes and intI1. The results also revealed a positive and a negative relationship from sampling point 1 to sampling point 5: a positive relation between abundance of antibiotics, ARGs, and of NO 3 -N, NH 4 -N, TP, COD and a negative relation between antibiotics, ARGs and temperature. This relationship showed the effect between antibiotics and ARGs concentrations with physicochemical parameters and nutrients. The ability of CWs to reduce the input of micropollutants into the environment makes CWs a potential post treatment to WWTP., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 The Authors. Published by Elsevier B.V. All rights reserved.)

Water users can reduce their impact on scarce freshwater resources by using more abundant regional brackish or saline groundwater resources. Decentralized water supply networks (WSN) can connect these regional groundwater resources with water users. Here, we present WaterROUTE (Water Route Optimization Utility Tool & Evaluation), a model which optimizes water supply network configurations based on infrastructure investment costs while considering the water quality (salinity) requirements of the user. We present an example simulation in which we determine the optimal WSN for different values of the maximum allowed salinity at the demand location while supplying 2.5 million m 3 year -1 with regional groundwater. The example simulation is based on data from Zeeuws-Vlaanderen, the Netherlands. The optimal WSN configurations for the years 2030, 2045 and 2110 are generated based on the simulated salinity of the regional groundwater resources. The simulation results show that small changes in the maximum salinity at the demand location have significant effects on the WSN configuration and therefore on regional planning. For the example simulation, the WSN costs can differ by up to 68% based on the required salinity at the demand site. WaterROUTE can be used to design water supply networks which incorporate alternative water supply sources such as local brackish groundwater (this study), effluent, or rainwater., (Copyright © 2021. Published by Elsevier Ltd.)

While urban wastewater infrastructure is aging and no longer adequate, climate change and sustainability are urging the transition from pollution management to resource recovery. Lacking evidence-based quantitative evaluation of the potential benefits and consequences of resource recovery from wastewater hinders the negotiation amongst stakeholders and slows down the transition. This study proposes mathematical formulations for technical, environmental, economic, and social key performance indicators (KPIs) that can be used to quantify the benefits and the risks of resource recovery. The proposed formulations are derived from the literature and validated with stakeholders. Each KPI is mathematically formulated at treatment train level by considering: (1) the characteristics of individual unit processes (UPs) in the treatment train (TT), (2) the context in which the TT is installed, and (3) the resources to be recovered. The mathematical formulations of the KPIs proposed in this study enable a transparent, consistent and informative evaluation of existing treatment trains, as well as support the (computer aided) design of new ones. This could aid the transition from urban wastewater treatment to resource recovery from urban wastewater., (Copyright © 2021 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

DNA-stable isotope probing (SIP) with 13 C labeled phenanthrene (PHE) as substrate was used to identify specific bacterial degraders during natural attenuation (NA) and bioaugmentation (BA) in petroleum contaminated soil. BA, with the addition of a bacterial suspension mixture named GZ, played a significant role in PHE degradation with a higher PHE removal rate (∼90%) than that of NA (∼80%) during the first 3 days, and remarkably altered microbial communities. Of the five strains introduced in BA, only two genera, particularly, Ochrobactrum, Rhodococcus were extensively responsible for PHE-degradation. Six (Bacillus sp., Acinetobacter sp., Xanthomonas sp., Conexibacter sp., Acinetobacter sp. and Staphylococcus sp.) and seven (Ochrobactrum sp., Rhodococcus sp., Alkanindiges sp., Williamsia sp., Sphingobium sp., Gillisia sp. and Massilia sp.) bacteria responsible for PHE degradation were identified in NA and BA treatments, respectively. This study reports for the first time the association of Xanthomonas sp., Williamsia sp., and Gillisia sp. to PHE degradation., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Hypothesis: Cation exchange membranes (CEMs) are subject to fouling when utilized to desalinate wastewater from the oil and gas industry, hampering their performance. The kind and extent of the fouling are most likely dependent on the composition of the stream, which in practical applications can vary significantly., Experiments: Fouling experiments were performed on commercial cation exchange membranes, which were used in electrodialysis runs to desalinate solutions of varying composition. The variations included ionic strength, type of ions, amount of viscosifying polyelectrolyte (partially hydrolyzed polyacrylamide), presence of crude oil, and surfactants. Performance parameters, like electric potential and pH, were monitored during the runs, after which the membranes were recovered and analyzed., Findings: Fouling was detected on most CEMs and occurred mainly in the presence of the viscosifying polyelectrolyte. Under normal pH conditions (pH ~ 8), the polyelectrolyte fouled the concentrate side of the CEMs, as expected due to electrophoresis. However, by applying a current in the opposite direction, the polyelectrolyte layer could be removed. Precipitation occurred mostly on the opposite side of the membrane, with different morphology depending on the feed composition., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Published by Elsevier Inc.)

Petroleum-industry wastewater (PI-WW) is a potential source of water that can be reused in areas suffering from water stress. This water contains various fractions that need to be removed before reuse, such as light hydrocarbons, heavy metals and conditioning chemicals. Constructed wetlands (CWs) can remove these fractions, but the range of PI-WW salinities that can be treated in CWs and the influence of an increasing salinity on the CW removal efficiency for abovementioned fractions is unknown. Therefore, the impact of an increasing salinity on the removal of conditioning chemicals benzotriazole, aromatic hydrocarbon benzoic acid, and heavy metal zinc in lab-scale unplanted and Phragmites australis and Typha latifolia planted vertical-flow CWs was tested in the present study. P. australis was less sensitive than T. latifolia to increasing salinities and survived with a NaCl concentration of 12 g/L. The decay of T. latifolia was accompanied by a decrease in the removal efficiency for benzotriazole and benzoic acid, indicating that living vegetation enhanced the removal of these chemicals. Increased salinities resulted in the leaching of zinc from the planted CWs, probably as a result of active plant defence mechanisms against salt shocks that solubilized zinc. Plant growth also resulted in substantial evapotranspiration, leading to an increased salinity of the CW treated effluent. A too high salinity limits the reuse of the CW treated water. Therefore, CW treatment should be followed by desalination technologies to obtain salinities suitable for reuse. In this technology train, CWs enhance the efficiency of physicochemical desalination technologies by removing organics that induce membrane fouling. Hence, P. australis planted CWs are a suitable option for the treatment of water with a salinity below 12 g/L before further treatment or direct reuse in water scarce areas worldwide, where CWs may also boost the local biodiversity. Graphical abstract.

Information on the removal of antibiotics and ARGs in full-scale WWTPs (with or without additional treatment technology) is limited. However, it is important to understand the efficiency of full-scale treatment technologies in removing antibiotics and ARGs under a variety of conditions relevant for practice to reduce their environmental spreading. Therefore, this study was performed to evaluate the removal of antibiotics and ARGs in a conventional wastewater treatment plant (WWTP A) and two full-scale combined with additional treatment technologies. WWTP B, a conventional activated sludge treatment followed by an activated carbon filtration step (1-STEP® filter) as a final treatment step. WWTP C, a treatment plant using aerobic granular sludge (NEREDA®) as an alternative to activated sludge treatment. Water and sludge were collected and analysed for 52 antibiotics from four target antibiotic groups (macrolides, sulfonamides, quinolones, tetracyclines) and four target ARGs (ermB, sul 1, sul 2 and tetW) and integrase gene class 1 (intI1). Despite the high removal percentages (79-88%) of the total load of antibiotics in all WWTPs, some antibiotics were detected in the various effluents. Additional treatment technology (WWTP C) showed antibiotics removal up to 99% (tetracyclines). For ARGs, WWTP C reduced 2.3 log followed by WWTP A with 2.0 log, and WWTP B with 1.3 log. This shows that full-scale WWTP with an additional treatment technology are promising solutions for reducing emissions of antibiotics and ARGs from wastewater treatment plants. However, total removal of the antibiotics and ARGS cannot be achieved for all types of antibiotics and ARGs. In addition, the ARGs were more abundant in the sludge compared to the wastewater effluent suggesting that sludge is an important reservoir representing a source for later ARG emissions upon reuse, i.e. as fertilizer in agriculture or as resource for bioplastics or bioflocculants. These aspects require further research., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 The Authors. Published by Elsevier B.V. All rights reserved.)

The presence of contaminants of emerging concern (CECs) in various water bodies and the associated threats to eco-system and human society have raised increasing concerns. To fight against such a problem, TiO 2 photocatalysis is considered to be a powerful tool. In recent decades, TiO 2 nanotube array (TNA) fabricated by electrochemical anodization emerged as a viable immobilized catalyst and its applications on CECs removal have gained a considerable amount of research interest. We herein present a critical review on the development of TNA and its applications on the removal of aqueous CECs. In this work, the CECs removal in different TNA based processes, the CECs removal mechanisms, the role of TNA properties, the role of operational parameters, and the role of water matrices are discussed. Moreover, perspectives on the current research progress are presented and recommendations on future research are elaborated., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

The reuse of cooling tower blowdown (CTBD) in the cooling tower itself requires CTBD deionization and a pre-treatment before deionization to remove organic compounds (OCs) that induce membrane fouling. This study assesses the potential of electrochemical oxidation (EO) with a boron-doped diamond (BDD) and a Ti/RuO 2 mixed-metal oxide (MMO) anode for CTBD pre-treatment. Also, the influence of the applied current density (j), initial pH, hydrodynamic conditions, and supporting electrolyte on the process performance was evaluated. Results show that COD and TOC removal were 85 and 51%, respectively, with the BDD-anode; however, they were 50 and 12% with MMO-anode at a j-value of 8.7 mA cm -2 and neutral pH. An increased j-value increased the COD and TOC removal; however, different pHs, hydrodynamic conditions, and the addition of supporting electrolytes had a minor impact on the removal with both anodes. Liquid chromatography-organic carbon detection analysis showed that the OC in CTBD mainly consisted of humic substances (HS). EO with the BDD-anode resulted in 35% HS mineralization, while the rest of the HS were partially oxidized into low molecular weight compounds and building blocks. However, HS mineralization was limited with the MMO-anode. The mineralization and oxidation were accompanied by the formation of organic and inorganic chlorinated species. These species increased the toxicity to Vibrio fischeri 20-fold compared to the initially low-toxic CTBD. Thus, EO with a BDD-anode is a promising pre-treatment technology for the removal of OCs before CTBD deionization, but measures to minimize the chlorinated species formation are required before its application., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Cooling towers are responsible for a large part of the industrial fresh water withdrawal, and the reuse of cooling tower water (CTW) effluents can strongly lower industrial fresh water footprints. CTW requires desalination prior to being reused, but various CTW components, such as total organic carbon (TOC), conditioning chemicals and total suspended solids (TSS) hamper physico-chemical desalination technologies and need to be removed from the CTW. A cost-efficient and robust pre-treatment is thus required, which can be provided by constructed wetlands (CWs). The present study is the first study that determined the CTW pre-treatment efficiency of hybrid-CWs and the impact of winter season and biocides in the CTW on the pre-treatment efficiency. The most efficient CW flow type and dominant removal mechanisms for CW components hampering physico-chemical desalination were determined. Subsurface flow CWs removed PO 4 3- , TSS and TOC as a result of adsorption and filtration. Vertical subsurface flow CWs (VSSF-CW) excelled in the removal of benzotriazole as a result of aerobic biodegradation. Horizontal subsurface flow CWs (HSSF-CW) allowed the denitrification of NO 3 - due to their anaerobic conditions. Open water CWs (OW-CWs) did not contribute to the removal of components that hamper physico-chemical desalination technologies, but do provide water storage options and habitat. The biological removal processes in the different CW flow types were negatively impacted by the winter season, but were not impacted by concentrations of the biocides glutaraldehyde and DBNPA that are relevant in practice. For optimal pre-treatment, a hybrid-CW, consisting of an initial VSSF-CW followed by an OW-CW and HSSF-CW is recommended. Future research should focus on integrating the hybrid-CW with a desalination technology, e.g. reverse osmosis, electrodialysis or capacitive ionization, to produce water that meets the requirements for use as cooling water and allow the reuse of CTW in the cooling tower itself., (Copyright © 2020 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Granule-based immobilization of anammox biomass assisted by polyvinyl alcohol/chitosan (PVA/CS) and PVA/CS/Fe gel beads was studied, via the operation of three identical up-flow reactors (R1 without gel beads, R2 with PVA/CS, R3 with PVA/CS/Fe) for 203 days. In the end, the nitrogen removal rates (NRR) were 5.3 ± 0.4, 10.0 ± 0.3 and 13.9 ± 0.5 kg-N m -3  d -1 for R1, R2 and R3, respectively. The porous PVA/CS and PVA/CS/Fe created a suitable eco-niche for anammox bacteria to grow and attach, thus being retained in the reactor. The EPS entangles newly grown cells within the gel beads, resulting in compact aggregation. The interaction between Fe ions added to PVA/CS/Fe gel beads and negatively charged EPS groups strongly promoted granule strength and compactness. The immobilization method proposed by this study was found to effectively improve biomass retention in the reactors, which is promising for advanced anammox process applications., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

This paper aims to elucidate the role of extracellular polymeric substances (EPS) in regulating anion and cation concentrations and toxicity towards microorganisms in anaerobic granular sludges adapted to low (0.22 M of Na + ) and high salinity (0.87 M of Na + ). The ion exchange properties of EPS were studied with a novel approach, where EPS were entangled with an inert binder (PVDF-HFP) to form a membrane and characterized in an electrodialysis cell. With a mixture of NaCl and KCl salts the EPS membrane was shown to act as a cation exchange membrane (CEM) with a current efficiency of ∼80%, meaning that EPS do not behave as ideal CEM. Surprisingly, the membrane had selectivity for transport of K + compared to Na + with a separation factor ( [Formula: see text] ) of 1.3. These properties were compared to a layer prepared from a model compound of EPS (alginate) and a commercial CEM. The alginate layer had a similar current efficiency (∼80%.), but even higher [Formula: see text] of 1.9, while the commercial CEM did not show selectivity towards K + or Na + , but exhibited the highest current efficiency of 92%. The selectivity of EPS and alginate towards K + transport has interesting potential applications for ion separation from water streams and should be further investigated. The anion repelling and cation binding properties of EPS in hydrated and dehydrated granules were further confirmed with microscopy (SEM-EDX, epifluorescence) and ion chromatography (ICP-OES, IC) techniques. Results of specific methanogenic activity (SMA) tests conducted with 0.22 and 0.87 M Na + adapted granular sludges and with various monovalent salts suggested that ions which are preferentially transported by EPS are also more toxic towards methanogenic cells., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Pharmaceuticals in water have adverse effects on aquatic environment. Anaerobic pharmaceutical biodegradation coupled to dissimilatory manganese(Mn) (IV)- or iron(Fe) (III)-oxides reduction is potentially efficient but unexplored. In this study, batch experiments were performed using different Mn(IV) and Fe(III) species with a microbial inoculum pre-cultivated with 15 mM chemically-synthesized Mn(IV) and 10 mg L -1 metoprolol. Results show 26% caffeine and 52% naproxen are degraded with Mn(IV) as terminal electron acceptor and insignificant biodegradation for other pharmaceuticals tested. Reduction of Mn(IV) from drinking water treatment is coupled to anaerobic biodegradation of metoprolol and propranolol, resulting in removal efficiencies of 96% and 31%, respectively. The results indicate that adsorption contributes to the pharmaceutical removal during the first 10 days of incubation, while biodegradation is the main removal mechanism in the whole period. Fe(III) can also be used as electron acceptor in anaerobic pharmaceutical biodegradation. Over half of the added metoprolol is degraded with both chemically-synthesized Fe(III) and Fe(III)-citrate as terminal electron acceptors. However, this process did not occur when using Fe(III) from drinking water treatment or Fe(III)-based sorbents. This study indicates that anaerobic pharmaceutical biodegradation coupled to dissimilatory Mn(IV) or Fe(III) reduction is possible, and promising for application to cleaning wastewater treatment plant effluents., (Copyright © 2018. Published by Elsevier B.V.)

Agriculture in delta areas of emerging economies is highly reliant on the provision of water with adequate quality. This quality is often under pressure by season-related saltwater intrusion and poor domestic or industrial wastewater management. Methods to separate these two negative impacts on water quality for the delta areas are lacking but essential for proper management and supply of irrigation water. Therefore, the main aim of this research is to propose a method that maps salt and wastewater impacts on seasonal water quality and relate that to different land uses. Khulna, a delta city of Bangladesh was taken as a representative case study. Surface water samples have been collected from different city locations in winter, summer and monsoon seasons, and were analyzed for a variety of chemical-physical water quality parameters. Spatio-temporal variation maps were generated using Inverse Distance Weighted (IDW) interpolation method, and weighted overlay method was employed to map the current irrigation water use suitability based on FAO guidelines for the interpretations of water quality for irrigation. The influence of land-use on water quality was assessed by correlation analysis followed by bi-variate linear regression analysis. Analysis indicated significant (p < 0.05) seasonal dependent variation in water quality parameters, especially for saltwater influenced and generic water quality parameters. Also, the land-use percentage within 500 m radii to the sampling stations had a significant positive correlation with several parameters indicating saltwater and urban wastewater influences. Weighted overlay analysis revealed that during summer, approximately 1/3rd of the total studied area has a severe restriction for irrigation water use. The method presented here was shown to be effective in presenting variabilities on the effects of salinization and wastewater discharge on water quality in urbanized deltas and can be used as a knowledge base for formulating and implementing future urban infrastructure planning to improve irrigation water quality., (Copyright © 2019 Elsevier B.V. All rights reserved.)

The desalination and reuse of discharged cooling tower water (CTW) as feed water for the cooling tower could lower the industrial fresh water withdrawal. A potential pre-treatment method before CTW desalination is the use of constructed wetlands (CWs). Biodegradation is an important removal mechanism in CWs. In the present study, the impact of the biocides 2,2-dibromo-2-cyanoacetamide (DBNPA) and glutaraldehyde on the biodegradation process by CW microorganisms was quantified in batch experiments in which benzoic acid was incubated with realistic CTW biocide concentrations. DBNPA had a stronger negative impact on the biodegradation than glutaraldehyde. The combination of DBNPA and glutaraldehyde had a lower impact on the biodegradation than DBNPA alone. UHPLC-qTOF-MS/MS non-target screening combined with data-analysis script 'patRoon' revealed two mechanisms behind this low impact. Firstly, the presence of glutaraldehyde resulted in increased DBNPA transformation to the less toxic transformation product 2-bromo-2-cyanoacetamide (MBNPA) and newly discovered 2,2-dibromopropanediamide. Secondly, the interaction between glutaraldehyde and DBNPA resulted in the formation of new products that were less toxic than DBNPA. The environmental fate and toxicity of these products are still unknown. Nevertheless, their formation can have important implications for the simultaneous use of the biocides DBNPA and glutaraldehyde for a wide array of applications., Competing Interests: Declaration of Competing Interest The authors declare that there are no conflicts of interest., (Copyright © 2019 Elsevier B.V. All rights reserved.)

The reuse of discharged cooling tower water (CTW) in the cooling tower itself could reduce fresh water intake and help mitigating fresh water scarcity problems. However, this requires desalination prior to its reuse, and hindering fractions, such as conditioning chemicals, should be removed before desalination to obtain a higher desalination efficiency. Constructed wetlands (CWs) can provide such a pre-treatment. In this study, the mechanisms underlying the removal of conditioning chemical benzotriazole (BTA) in CWs was studied using an innovative approach of differently designed pilot-scale CWs combined with batch removal experiments with substrate from these CWs. By performing these combined experiments, it was possible to determine the optimal CW design for BTA removal and the most relevant BTA removal processes in CWs. Adsorption yielded the highest contribution, and the difference in removal between different CW types was linked to their capability to aerobically biodegrade BTA. This knowledge on the main removal mechanisms for BTA allows for a CW design tailored for BTA removal. In addition, the outcomes of this research show that performing batch experiments with CW substrate allows one to determine the relevant removal mechanisms for a given compound which results in a better understanding of CW removal processes., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Retention soil filters (RSFs) are vertical flow constructed wetlands. They are mainly used for the treatment of combined sewer overflow or stormwater, and not operated during dry weather conditions. However, RSFs have been successfully tested as continuous post treatment for sewage treatment plant effluents. In this paper we present a new approach, namely dual usage of the retention soil filter. During dry weather the RSF is used for the polishing treatment of sewage treatment plant effluent and during overflow events, the retention soil filter treats the combined sewer overflow. This study was conducted at two pilot RSFs that were fed with sewage treatment effluent for four years. Removal of TOC, DOC, nutrients and 21 organic micropollutants was determined during six months at different sequences of regular effluent and overflow treatment conditions. TOC, DOC and nutrients, appearing in high concentration in combined sewer overflow, were effectively removed, and metformin and caffeine micropollutants showed >99% removal. Residues from this combined sewer treatment that were sorbed on filter material or stored in pore water were washed out directly after treatment when STP effluent infiltration was initiated. This effect declined within 20 h after combined sewer overflow treatment. Dry periods of 18 h between combined sewer and sewage treatment plant effluent feeding counteracted the wash out effects. The highest removal efficiency was found in the beginning of the feeding time of 28 h, indicating that shorter feeding cycles enhance the overall efficiency of the RSF. Finally, the results show that a single RSF system can successfully reduce emissions of TOC, DOC, nutrients and micropollutants to surface waters from two different emission pathways, i.e. from regular treated effluents and storm related sewer overflows. In conclusion, the dual usage of RSF is a promising approach and ready for upscaling and implementation., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Hypothesis: Anion exchange membranes (AEMS) are particularly prone to fouling when employed to desalinate polymer flooding produced water (PFPW), an abundant sub-product from the oil and gas industry. The formation of fouling on an AEM will be affected by the composition of the solution, which includes various dissolved salts, partially hydrolyzed polyacrylamide (HPAM), crude oil, and surfactants., Experiments: Electrodialysis experiments were performed to desalinate feed solutions with different compositions, aiming to distinguish between their individual and combined effects. The solutions contained diverse mono- and divalent ions. The analysis included data collected during the desalination and characterization of the fouled AEMs by diverse analytical techniques., Findings: HPAM produced the most severe effects in terms of visible fouling and increase of resistance. This polyelectrolyte fouls the AEM by adsorbing on its surface and by forming a viscous gel layer that hampers the replenishment of ions from the bulk solution. Ca and Mg have a large influence on the formation of thick HPAM gel layers, while the oily compounds have only a minimal influence acting mainly as a destabilizing agent. The membranes also presented scaling consisting of calcium precipitates. The effects of the gel layer were minimized by applying current reversal and foulant-free solution., (Copyright © 2019 The Author(s). Published by Elsevier Inc. All rights reserved.)

Organic micropollutants (OMPs) are widely detected in surface waters. So far, the removal processes of these compounds in situ in river systems are not yet totally revealed. In this study, a combined monitoring and modelling approach was applied to determine the behaviour of 1-H benzotriazole, carbamazepine, diclofenac and galaxolide in a small river system. Sewage treatment plant effluents and the receiving waters of the river Swist were monitored in 9 dry weather sampling campaigns (precipitation < 1 mm on the sampling day itself and <5 mm total precipitation two days before the sampling) during different seasons over a period of 3 years. With the results gained through monitoring, mass balances have been calculated to assess fate in the river. With the DWA Water Quality Model, OMP concentrations in the river were successfully simulated with OMP characteristics gained through literature studies. No removal was determined for 1-H benzotriazole and carbamazepine, whereas diclofenac showed removal that coincided with light intensity. Moreover, modelling based on light sensitivity of diclofenac also suggested relevant degradation at natural light conditions. These two approaches suggest removal by photodegradation. The highest removal in the river was detected for galaxolide, presumably due to volatilisation, sorption and biodegradation. Furthermore, short-term concentration variability in the river was determined, showing that daily concentration patterns are influenced by dynamics of sewage treatment plant effluent volumes and removal processes in the river., (Copyright © 2019 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Insights into the influence of redox conditions, that is the availability of electron acceptors, and dissolved organic matter (DOM) on pesticide biodegradation in groundwater are key to understanding the environmental fate of pesticides in natural groundwater systems. Here, the influence of redox conditions and supplemental DOM addition on biodegradation of pesticides, 2,4-dichlorophenoxyacetic acid (2,4-D), 2,6-dichlorobenzamide (BAM), mecoprop-p (MCPP) and bentazone, was tested in microcosm and subsequent column experiments. Pesticide degradation, functional genes and changes in specific fractions and quantity of DOM were systematically quantified. In aerobic microcosm experiments, the highest 2,4-D degradation rate was obtained with the presence of more assimilable DOM. In column experiments, minimal pesticide degradation (≤33.77%) in any anaerobic redox conditions was observed in the absence of DOM. However, in the presence of DOM, 2,4-D biodegradation was considerably enhanced under nitrate-reducing conditions (from 23.5 ± 10.2% to 82.3 ± 11.6%) and in a column without external electron acceptor amendment (from -6.3 ± 12.6% to 31.1 ± 36.3%). Observed preferential depletion of the fulvic acid fraction of DOM provides indications for specific functional DOM properties. The qPCR results show an increase in microbial biomass and functional genes (tfdA) in liquid phase after DOM addition. The results of this work provide insights into the interplays among DOM, redox geochemistry, and pesticide biodegradation, and show the potential of a novel approach - DOM addition to groundwater systems - for in situ biostimulation technology to remove pesticides from groundwater systems., (Copyright © 2019. Published by Elsevier B.V.)

The potential water demand for fracturing fluids along with the possible flowback and produced water production is assessed for the Dutch Posidonia shale. Total water demand estimated for 25 years of the field development using historic data from the U.S. plays varies between 12.2 and 36.9 Mm 3 . The maximal annual water consumption of 0.95-2.88 Mm 3 is expected in the peak years of shale gas production. These figures are much lower than the availability of any potential water sources, which include drinking water, fresh and brackish groundwater, river water, effluents of wastewater treatment plants (WWTP) and sea water. River water is considered the most promising water source for fracturing fluids in the Dutch Posidonia shale based on its availability (>6·10 4  Mm 3 /year) and quality (only bacterial composition needs to be controlled). Total wastewater production for the whole period of the field development is estimated between 6.6 and 48.0 Mm 3 . Wastewater recycling can cover significant part of the source water demand for fracturing fluid. However, high mineral content of the wastewater as well as temporal and spatial discrepancies between wastewater production and water demand will form obstacles for wastewater recycling. The assessment framework developed in this study may be applied for other shale gas fields with high uncertainties regarding subsurface properties, connate formation water characteristics and future legislative framework., (Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Increasing amounts of saline (waste)water with high concentrations of organic pollutants are generated globally. In the anaerobic (waste)water treatment domain, high salt concentrations are repeatedly reported to inhibit methanogenic activity and strategies to overcome this toxicity are needed. Current research focuses on the use of potential osmolyte precursor compounds for osmotic stress alleviation in granular anaerobic sludges upon exposure to hypersalinity shocks. Glutamic acid, aspartic acid, lysine, potassium, gelatine, and tryptone were tested for their potential to alleviate osmotic stress in laboratory grown and full - scale granular sludge. The laboratory grown granular sludge was adapted to 5 (R5) and 20 (R20) g Na + /L. Full-scale granular sludge was obtained from internal circulation reactors treating tannery (waste)water with influent conductivity of 29.2 (Do) and 14.1 (Li) mS/cm. In batch experiments which focused on specific methanogenic activity (SMA), R5 granular sludge was exposed to a hypersalinity shock of 20 g Na + /L. The granular sludge of Do and Li was exposed to a hypersalinity shock of 10 g Na + /L with sodium acetate as the sole carbon source. The effects on R20 granular sludge were studied at the salinity level to which the sludge was already adapted, namely 20 g Na + /L. Dosing of glutamic acid, aspartic acid, gelatine, and tryptone resulted in increased SMA compared to only acetate fed batches. In batches with added glutamic acid, the SMA increased by 115% (Li), 35% (Do) and 9% (R20). With added aspartic acid, SMA increased by 72% (Li), 26% (Do), 12% (R5) and 7% (R20). The addition of tryptone resulted in SMA increases of 36% (R5), 17% (R20), 179% (Li), and 48% (Do), whereas added gelatine increased the SMA by 30% (R5), 14% (R20), 23% (Li), and 13% (Do). The addition of lysine, meanwhile, gave negative effects on SMA of all tested granular sludges. Potassium at sea water Na/K ratio (27.8 w/w) had a slight positive effect on SMA of Do (7.3%) and Li (10.1%), whereas at double the sea water ratio (13.9% w/w) had no pronounced positive effect. R20 granular sludge was also exposed to hyposalinity shock from 20 down to 5 g Na + /L. Glutamate and N-acetyl-β-lysine were excreted by microbial consortium in anaerobic granular sludge adapted to 20 g Na + /L upon this exposure to hyposalinity. A potential consequence when applying these results is that saline streams containing specific and hydrolysable proteins can be anaerobically treated without additional dosing of osmolytes., (Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Applying manganese(IV)- or iron(III)-(hydr)oxides to remove pharmaceuticals from water could be attractive, due to the capacity of these metal oxides to remove pharmaceuticals and be regenerated. As pharmaceutical removal under anaerobic conditions is foreseen, Mn(IV) or Fe(III) regeneration under anaerobic conditions, or with minimum oxygen dosage, is preferred. In this study, batch experiments are performed to investigate (1) Mn(IV) and Fe(III) regeneration from Mn(II) and Fe(II); (2) the pharmaceutical removal during biological Mn(IV) and Fe(III) regeneration; and (3) anaerobic abiotic pharmaceutical removal with different Mn(IV) or Fe(III) species. Results show that biological re-oxidation of reduced Mn(II) to Mn(IV) occurs under oxygen-limiting conditions. Biological re-oxidation of Fe(II) to Fe(III) is obtained with nitrate under anaerobic conditions. Both bio-regenerated Mn(IV)-oxides and Fe(III)-hydroxides are amorphous. The pharmaceutical removal is insignificant by Mn(II)- or Fe(II)-oxidizing bacteria during regeneration. Finally, pharmaceutical removal is investigated with various Mn(IV) and Fe(III) sources. Anaerobic abiotic removal using Mn(IV) produced from drinking water treatment plants results in 23% metoprolol and 44% propranolol removal, similar to chemically synthesized Mn(IV). In contrast, Fe(III) from drinking water treatment plants outperformed chemically or biologically synthesized Fe(III); Fe (III) from drinking water treatment can remove 31-43% of propranolol via anaerobic abiotic process. In addition, one of the Fe(III)-based sorbents tested, FerroSorp ® RW, can also remove propranolol (20-25%). Biological regeneration of Mn(IV) and Fe(III) from the reduced species Mn(II) and Fe(II) could be more effective in terms of cost and treatment efficiency., (Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Retention soil filters (RSFs) are a specific form of vertical flow constructed wetlands for the treatment of rain water and/or wastewater. We have tested 3 pilot RSFs to investigate removal of dissolved organic carbon (DOC) and 14 different organic micropollutants (OMPs) from the effluent of a large scale sewage treatment plant (STP). Two of them were operated as conventional RSF with material (sand with CaCO 3 and organic matter) from two different full-scale RSFs. The third pilot RSF contained filter material (sand with CaCO 3 ) with additional biochar in the upper layer (0-10 cm) and granulated activated carbon (GAC) in the lower layer (60-90 cm). The filters were planted with Phragmites australis. The RSFs were operated and monitored for 3 years, and water samples were taken regularly at inflow, outflows and in 3 depths within the filters. In total 523 samples were taken. In the conventional RSF, best median removal was detected for galaxolide, diclofenac 4-hydroxy, metoprolol and clarithromycin (75-79%). No removal was seen for sulfamethoxazole and carbamazepine. The DOC and OMP removal in the conventional RSFs was best in the upper layer with highest organic matter content, increased in time over the three years of operation and also with extended contact time. In the effluent of the RSF with GAC, 10 out of the 14 OMPs could not be detected; 4 OMPs were detected, but only metformin with removal < 80%, thus showing a more efficient removal than the conventional RSF. A decrease in DOC removal was detected in the GAC layer (>88% to 60%) over the 2.5 years of operation. Biochar was most effective in OMP removal in the first operational year. It can be concluded that the increasing removal efficiency of the conventional RSF material - also present in the RSF with biochar and GAC - might mitigate the reduced efficiency of the sorbent additives biochar and GAC. This enables to extend the operational lifetime of the filters with acceptable removal rates. Finally, our study demonstrates that an RSF with GAC shows an enhanced removal of OMPs, which is a suitable post-treatment step for STPs., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Removal of pharmaceutically active compounds (PhACs) in constructed wetlands (CWs) is a complex interplay of different processes. We studied fate and distribution of seven PhACs (caffeine, CAF; naproxen, NAP; metoprolol, MET; propranolol, PRO; ibuprofen, IBP; carbamazepine, CBZ; diclofenac, DFC) in mesocosm CWs and effects of irradiation via pre-photocatalysis, substrate composition (mainly sediment) through addition of litter (dead plant biomass), and plants. CWs showed high removal of CAF, NAP, MET, PRO, and IBP (79-99%). All seven PhACs were detected in substrate and plant tissues as well as IBP intermediates. Estimated PhAC mass balance showed that sorption dominated PRO removal in CWs while other PhACs were mainly removed by biodegradation and/or phytodegradation. Pre-photocatalysis significantly increased removal of PhACs except for CAF and IBP, and decreased accumulation of PhACs in substrate and plant tissues of the following wetland compartment. Litter addition in CW significantly enhanced removal of PRO and CBZ via biodegradation and/or phytodegradation. Plants played an essential and positive role in removing PhACs, resulting from direct phytoremediation and indirectly enhancing sorption and biodegradation. Our study provides knowledge to understand removal mechanisms of PhACs in CWs and to potentially enhance PhAC removal by developing pre-photocatalysis, adding dead plant biomass, and optimizing vegetation., (Copyright © 2018 Elsevier B.V. All rights reserved.)

The performance of constructed wetlands (CWs) in the removal of pharmaceutically active compounds (PhACs) is generally evaluated on the basis of chemical analysis. In this work, we used a combination of chemical, toxicological, and molecular analyses to assess the attenuation of PhACs, toxic potency and antibiotic resistance genes (ARGs) in a field study of three CWs serving as tertiary treatment of wastewater treatment plants. First, 17 PhACs were analysed chemically, of which 14 were detected and seven at concentrations >0.1μg/l. Even though some of the individual PhACs were moderately or highly removed in the CWs investigated, median removal of overall PhACs was approximately 50% in the vertical subsurface flow CW (VSF-CW) with a lower hydraulic loading rate while the removal in the other two free water surface flow CWs (SF-CWs) was negligible. Second, toxic potency of wastewater extracts was assessed in a range of bioassays. Estrogenicity was overall attenuated in CWs, while the neurotoxic potency of wastewater extracts did not decrease after passage through the two CWs investigated. Third, the VSF-CW and one of the SF-CW showed a positive removal of an integrase gene and three ARGs tested. The increased concentrations of ARGs in the other SF-CW, as well as the increase of total bacteria in all CWs, may relate to regrowth of resistance-carrying bacteria. Finally, multivariate analysis shows that most PhACs are positively correlated to the observed toxic potency. Additionally, low removal of organics and nutrients seems to parallel with low removal of PhACs. ARGs positively correlated with organics, nutrients and some PhACs, and the integrase gene but not to the respective antibiotics. The insufficient removal of PhACs, toxic potency, and ARGs indicates the need of an optimal design of CWs as tertiary treatment facilities., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Natural dissolved organic matter (DOM) and nitrification can play an important role in biodegradation of pharmaceutically active compounds (PhACs) in aerobic zones of constructed wetlands (CWs). This study used an enrichment culture originating from CW sediment to study the effect of DOM and nitrification on aerobic biodegradation of seven PhACs. The enriched culture degraded caffeine (CAF), metoprolol (MET), naproxen (NAP), and ibuprofen (IBP) with a consistent biodegradability order of CAF>MET>NAP>IBP. Biodegradation of propranolol, carbamazepine, and diclofenac was insignificant (<15%). CAF biodegradation was inhibited by the easily biodegradable DOM. Conversely, DOM enhanced biodegradation of MET, NAP, and IBP, potentially by contributing more biomass capable of degrading PhACs. Nitrification enhanced biodegradation of NAP and IBP and mineralization of the PhAC mixture as well as less biodegradable DOM, which may result from co-metabolism of ammonia oxidizing bacteria or enhanced heterotrophic microbial activity under nitrification. MET biodegradation was inhibited in the presence of nitrification. DOM and nitrification effects on PhAC biodegradation in CWs gained from this study can be used in strategies to improve CW operation, namely: designing hydraulic retention times based on the biodegradability order of specific PhACs; applying DOM amendment; and introducing consistent ammonium streams to increase removal of PhACs of interest., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Ozonation, sorption to granular activated carbon and aerobic degradation were compared as potential treatment methods for removal of dissolved organic carbon (DOC) fractions and selected organic compounds from shale gas flowback water after pre-treatment in dissolved air flotation unit. Flowback water was characterised by high chemical oxygen demand and DOC. Low molecular weight (LMW) acids and neutral compounds were the most abundant organic fractions, corresponding to 47% and 35% of DOC respectively. Ozonation did not change distribution of organic carbon fractions and concentrations of detected individual organic compounds significantly. Sorption to activated carbon targeted removal of individual organic compounds with molecular weight >115 Da, whereas LMW compounds remained largely unaffected. Aerobic degradation was responsible for removal of LMW compounds and partial ammonium removal, whereas formation of intermediates with molecular weight of 200-350 Da was observed. Combination of aerobic degradation for LMW organics removal with adsorption to activated carbon for removal of non-biodegradable organics is proposed to be implemented between pre-treatment (dissolved air floatation) and desalination (thermal or membrane desalination) steps., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

This is the first study examining pharmaceutical removal under anoxic conditions with MnO 2 . This study compares the abiotic removal of seven pharmaceuticals with reactive MnO 2 particles in the presence of oxygen (oxic conditions) and in the absence of oxygen (anoxic conditions). Due to the novelty of pharmaceutical removal under anoxic conditions, the influence of phosphate buffer, pH, and MnO 2 morphologies is also examined. Results show that over 90% of diclofenac is removed under anoxic conditions. Additionally, we found that (1) anoxic conditions are beneficial for diclofenac removal with MnO 2 , (2) phosphate buffer affects the pharmaceutical removal efficiencies, (3) higher pharmaceutical removal is obtained at acidic pH compared to that at neutral or alkaline conditions, and (4) amorphous MnO 2 removes pharmaceuticals better than crystalline MnO 2 . The pharmaceutical molecular structure and properties, MnO 2 properties especially reactive sites of the MnO 2 surface, are important for degradation kinetics. This study provides a fundamental basis towards understanding pharmaceutical degradation with MnO 2 under anoxic conditions, and development of a cost-effective, sustainable technology for removal of pharmaceuticals from water.

Biodegradation of pharmaceutically active compounds (PhACs) in the subsurface layer of constructed wetlands (CWs) under various anaerobic redox conditions is rarely studied. In this study, CW sediment microbial populations were enriched for PhAC biodegrading organisms. Biodegradation effectivity of a mixture of six PhACs (caffeine, CAF; naproxen, NAP; metoprolol, MET; propranolol, PRO; ibuprofen, IBP; carbamazepine, CBZ) and single compounds (CAF, NAP) was investigated under nitrate reducing, sulfate reducing, and methanogenic conditions using chemical and toxicological analyses. Biodegradation efficiencies varied strongly among the six PhACs and three redox conditions chosen. CAF and NAP were completely biodegraded under sulfate reducing and methanogenic conditions whereas biodegradation efficiencies of the other PhACs were much less (MET, PRO <20%; IBP, CBZ, negligible). CAF and NAP showed significantly lower biodegradation under nitrate reducing conditions than under the other two redox conditions. No difference was found in biodegradation efficiencies of CAF and NAP when present as single compound, or as a mixture with other PhACs. Different intermediates were observed, indicating different biodegradation pathways under different redox conditions and when the PhACs were present as single compound or in a mixture. From toxicological perspective, toxicity of PhACs and/or their intermediates to Vibrio fischeri was attenuated during the biodegradation process. Chemical and toxicological data showed positive correlations in principle component analysis, by which potentially toxic PhACs and intermediates are indicated for further ecotoxicological hazard assessment., (Copyright © 2017 Elsevier B.V. All rights reserved.)