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Former studies have shown that enhanced-zero valent iron (ZVI) could effectively remove various contaminants. The present study evaluates for the first time the long-term performance of enhanced-ZVI to remove natural organic matter (NOM), an important water quality parameter in drinking water. Lab-scale flow-through experiments showed that averagely 7–14% dissolved organic carbon (DOC) and 6–15% ultraviolet absorbance at 254 nm (UV 254 ) reduction could be achieved by enhanced-ZVI in the first 10,000 bed volumes filtration when a 0.36 or 1.8 mins empty bed contact time (EBCT) was applied. After 10,000-bed volumes, the enhanced-ZVI bed became passivated. However, sulphuric acid was able to regenerate the passivated enhanced-ZVI bed, recover the capacity of enhanced-ZVI in removing NOM, and hence make the best use of the available ZVI. The acidic rinsing solution containing dissolved iron was suitable as a supplemental source of iron for coagulation. In addition, during the long-term experiments, the biofilters following enhanced-ZVI (1.8 min EBCT) removed more NOM than biofilters without any pre-treatment. This could be explained by the formation of biodegradable organic matter (BDOC) during the enhanced-ZVI process and the precipitation of iron in the biofilters. Based on these findings, a novel water treatment train, incorporating enhanced-ZVI with periodical regeneration, biofiltration, and coagulation, was proposed and evaluated. [ABSTRACT FROM AUTHOR]

Chlorine demand of a water sample depends on the characteristics of dissolved organic matter (DOM). It is an important parameter for water utilities used to assess oxidant and/or disinfectant consumption of source waters during treatment and distribution. In this study, model compounds namely resorcinol, tannic acid, vanillin, cysteine, tyrosine, and tryptophan were used to represent the reactive moieties of complex DOM mixtures. The reactivity of these compounds was evaluated in terms of Cl 2 demand and electron donating capacity (EDC). The EDC was determined by mediated electrochemical oxidation (MEO) which involves the use of 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) as an electron shuttle. The Cl 2 demand of readily oxidizable compounds (resorcinol, tannic acid, vanillin, and cysteine) was found to correlate well with EDC (R 2 = 0.98). The EDC values (mol e − /mol C) of the model compounds are as follows: 1.18 (cysteine) > 0.77 (resorcinol) > 0.59 (vanillin) > 0.52 (tannic acid) > 0.36 (tryptophan) > 0.19 (tyrosine). To determine the effect of pre-oxidation on EDC, ozone was added (0.1 mol O 3 /mol C) into each model compound solution. Ozonation caused a general decrease in EDC (10–40%), chlorine demand (10–30%), and UV absorbance (10–40%), except for tyrosine which showed both increased UV 275 and EDC. Before and after ozonation, 24 h disinfection byproduct (DBP) formation potential tests (Cl 2 residual = 1.5 mg/L) were conducted to evaluate the use of EDC for DBP formation prediction. The results indicate that there was no significant correlation between the EDC of the model compounds and the formation potentials of adsorbable organic chlorine, trichloromethane, and trichloroacetic acid. This suggests that while EDC correlates with Cl 2 demand, chlorine consumption may not directly translate to DBP formation because oxidation reactions may dominate over substitution reactions. Overall, this study provides useful insights on the reactions of ABTS + and HOCl with model DOM compounds, and highlights the potential application of MEO for rapid determination of Cl 2 demand of a water sample. [ABSTRACT FROM AUTHOR]

Dissolved organic nitrogen (DON) is an emerging concern in oxidative water treatment because it exerts oxidant demand and may form nitrogenous oxidation/disinfection by-products. In this study, we investigated the reactions of ozone with DON with a special emphasis on the formation of nitrate (NO 3 − ) and ammonium ( NH 4 + ). In batch ozonation experiments, the formation of NO 3 − and NH 4 + was investigated for natural organic matter standards, surface water, and wastewater effluent samples. A good correlation was found between NO 3 − formation and the O 3 exposure (R 2 > 0.82) during ozonation of both model DON solutions and real water samples. To determine the main precursor of NO 3 − , solutions composed of tannic acid and model compounds with amine functional groups were ozonated. The NO 3 − yield during ozonation was significantly higher for glycine than for trimethylamine and dimethylamine. Experiments with glycine also showed that NO 3 − was formed via an intermediate with a second-order rate constant of 7.7 ± 0.1 M −1 s −1 while NH 4 + was formed by an electron-transfer mechanism with O 3 as confirmed from a hydroxyl radical ( OH) yield of 24.7 ± 1.9%. The NH 4 + concentrations, however, were lower than the OH yield (0.03 mol NH 4 + /mol OH) suggesting other OH-producing reactions that compete with NH 4 + formation. This study concludes that NO 3 − formation during ozonation of DON is induced by an oxygen-transfer to nitrogen forming hydroxylamine and oxime, while NH 4 + formation is induced by electron-transfer reactions involving C-centered radicals and imine intermediates. [ABSTRACT FROM AUTHOR]

Abstract: During the production of high quality recycled water by reverse osmosis membrane filtration secondary effluent must be disinfected to limit biofouling on the membrane surface. Advanced Water Treatment Plants in South East Queensland, Australia use disinfectant contact times ranging from 30 min up to 24 h. Disinfectants such as chlorine and chloramines react with effluent organic matter to generate disinfection by-products (DBPs) which could be potentially hazardous to human health if the water is destined for supplementing public water supplies. In this context, secondary effluents are of concern because of their high total organic carbon content which can act as DBP precursors. Also, effluent organic matter may form different DBPs to those formed from natural organic matter during conventional drinking water treatment, either in quantity, identity or simply in the abundance of different DBPs relative to each other. It cannot be assumed per se with certainty that DBP formation will be affected in the same way by operational changes as in drinking water production. Response surface modelling has been employed in this study at the bench scale to investigate the effect of reaction time (0–24 h), pH (5.5–8.5), temperature (23–35 °C), disinfection strategy (chlorine vs chloramines used prior to membrane treatment) and the interaction between these different parameters on DBP formation during disinfection of secondary effluent. The concentration of halogenated DBPs formed during the first 24 h of reaction with the different disinfectants followed the order chlorination >> in line-formed monochloramine > pre-formed monochloramine. Contact time with chlorine was the major influencing factor on DBP formation during chlorination, except for the bromine-containing trihalomethanes and dibromoacetonitrile for which pH was more significant. Chlorination at high pH led to an increased formation of chloral hydrate, trichloronitromethane, dibromoacetonitrile and the four trihalomethanes while the opposite effect was observed for the other targeted DBPs. Temperature was identified as the least influencing parameter compared to pH and reaction time for all DBPs in all the disinfection strategies, except for the formation of chloral hydrate where pH and temperature had a similar significance and bromoform that was similarly affected by temperature and reaction time. Chloramines employed at pH 8.5 reduced the concentration of all studied DBPs compared to pH 5.5. Furthermore, reaction time was the most significant factor for trichloronitromethane, chloroform, trichloroacetonitrile, dichloroacetonitrile and bromochloroacetonitrile formation while pH was the most influencing factor affecting the formation of the remaining DBPs. [Copyright &y& Elsevier]

The purpose of this work was to determine the degradation products and pathway of chlorfenvinphos (CFVP) in water treated by photo-Fenton driven by solar irradiation, as well as to develop an analytical procedure for the degradation experiments. Degradation products and pathway were determined in a laboratory experimental setup. Routine water sample analysis was done by standard laboratory wet chemistry procedures and the use of laboratory equipment such as HPLC–UV and ionic chromatography (IC). Solid-phase extraction (SPE) was used to extract analytes from an aqueous matrix, and GC–MS was used to identify intermediate degradation products. The use of an HPLC–TOF-MS provided more results on degradation products and more insight was gained into how degradation takes place. In all experiments, strong mineralisation and degradation of CFVP was observed. CFVP and its degradation products, like 2,4-dichlorophenol, 2,4-dichlorobenzoic acid and triethylphosphate were decomposed into organic substances like acetate, formate, maleate, and inorganic ions like chloride and phosphate, within the detection limits (12.5μg/L for CFVP in the GC–MS and 40μg/L in HPLC–UV) of the equipment used. In fact, Cl− emerges in nearly stoichiometric concentrations and PO4 3 − is precipitated as FePO4. The remarkably complete absence of chlorinated aliphatic substances and chlorinated acids leads to the conclusion that chlorine is removed very quickly, and that residual DOC does not correspond to any chlorinated compound. [Copyright &y& Elsevier]

The removal of persistent organic micropollutants (OMPs) from secondary effluent in wastewater treatment plants is critical for meeting water reuse standards. Traditional treatment methods often fail to adequately degrade these contaminants. This study explored the efficacy of a hybrid ozonation membrane filtration (HOMF) process using CeO2 and CeTiOx-doped ceramic crossflow ultrafiltration ceramic membranes for the degradation of OMPs. Hollow ceramic membranes (CM) with a 300 kDa molecular weight cut-off (MWCO) were modified to serve as substrates for catalytic nanosized metal oxides in a crossflow and inside-out operational configuration. Three types of depositions were tested: a single layer of CeO2, a single layer of CeTiOx, and a combined layer of CeO2 + CeTiOx. These catalytic nanoparticles were distributed uniformly using a solution-based method supported by vacuum infiltration to ensure high-throughput deposition. The results demonstrated successful infiltration of the metal oxides, although the yield permeability and transmembrane flow varied, following this order: pristine > CeTiOx > CeO2 > CeO2 + CeTiOx. Four OMPs were examined: two easily degraded by ozone (carbamazepine and diclofenac) and two recalcitrant (ibuprofen and pCBA). The highest OMP degradation was observed in demineralized water, particularly with the CeO2 + CeTiOx modification, suggesting O3 decomposition to hydroxyl radicals. The increased resistance in the modified membranes contributed to the adsorption phenomena. The degradation efficiency decreased in secondary effluent due to competition with the organic and inorganic load, highlighting the challenges in complex water matrices. [ABSTRACT FROM AUTHOR]

In summer 2019, a full-scale trial was carried out to investigate the effects in drinking water quality when tertiary treated wastewater was discharged into the Llobregat River upstream of the intake of one of the major drinking water treatment plants of Barcelona and its metropolitan area. Two scenarios were investigated, i.e. discharging the reclaimed water with and without chemical disinfection with chlorine. This study investigates the concentration of N-nitrosodimethylamine (NDMA) as the specific disinfection conditions employed in this trial may favor its formation. To this aim, both NDMA and NDMA formation potential, were measured. The river contained NDMA at very low concentrations, but the concentration of NDMA precursors was already high. The NDMA concentration was reduced from discharge to the river to drinking water intake probably due to a combined effect of dilution and photolysis. The formation potential was also reduced probably due to dilution and biodegradation. The concentration of NDMA in the drinking water was always low (<7.3 ng/L), although the formation potential was above 10 ng/L in one sample. Dissolved organic matter characterization by high resolution mass spectrometry revealed differences between the nature of the organic matter in the river before and after reclaimed water discharge. ga1 • Disinfection increased NDMA in comparison to the non-disinfected reclaimed water. • NDMA was reduced in the river probably due to both dilution and photolysis. • NDMA precursors were reduced in the river probably due to both dilution and biodegradation. • NDMA net removal at the drinking water treatment plant was 40 ± 20%. • Compounds with low O/C and H/C > 1.5 correlated with NDMA formation potential. [ABSTRACT FROM AUTHOR]

Conventional urban wastewater treatment plants (UWTPs) are poorly effective in the removal of most contaminants of emerging concern (CECs), including antibiotics, antibiotic resistant bacteria and antibiotic resistance genes (ARB&ARGs). These contaminants result in some concern for the environment and human health, in particular if UWTPs effluents are reused for crop irrigation. Recently, stakeholders' interest further increased in Europe, because the European Commission is currently developing a regulation on water reuse. Likely, conventional UWTPs will require additional advanced treatment steps to meet water quality limits yet to be officially established for wastewater reuse. Even though it seems that CECs will not be included in the proposed regulation, the aim of this paper is to provide a technical contribution to this discussion as well as to support stakeholders by recommending possible advanced treatment options, in particular with regard to the removal of CECs and ARB&ARGs. Taking into account the current knowledge and the precautionary principle, any new or revised water-related Directive should address such contaminants. Hence, this review paper gathers the efforts of a group of international experts, members of the NEREUS COST Action ES1403, who for three years have been constructively discussing the efficiency of the best available technologies (BATs) for urban wastewater treatment to abate CECs and ARB&ARGs. In particular, ozonation, activated carbon adsorption, chemical disinfectants, UV radiation, advanced oxidation processes (AOPs) and membrane filtration are discussed with regard to their capability to effectively remove CECs and ARB&ARGs, as well as their advantages and drawbacks. Moreover, a comparison among the above-mentioned processes is performed for CECs relevant for crop uptake. Finally, possible treatment trains including the above-discussed BATs are discussed, issuing end-use specific recommendations which will be useful to UWTPs managers to select the most suitable options to be implemented at their own facilities to successfully address wastewater reuse challenges. Unlabelled Image • This work gathers the efforts of international experts from NEREUS COST Action. • Advantages and drawbacks of BATs discussed according to CECs removal and AR control • Possible advanced treatment options to make wastewater reuse safer recommended • Smart combination of BATs and a suitable monitoring program necessary for a safe reuse • Further comparative studies among different advanced treatment methods recommended [ABSTRACT FROM AUTHOR]

Water bodies are being contaminated daily due to industrial, agricultural and domestic effluents. In the last decades, harmful organic micropollutants (OMPs) have been detected in surface and groundwater at low concentrations due to the discharge of untreated effluent in natural water bodies. As a consequence, aquatic life and public health are endangered. Unfortunately, traditional water treatment methods are ineffective in the degradation of most OMPs. In recent years, advanced oxidation processes (AOPs) techniques have received extensive attention for the mineralization of OMPs in water in order to avoid serious environmental problems. Cold atmospheric plasma discharge-based AOPs have been proven a promising technology for the degradation of non-biodegradable organic substances like OMPs. This paper reviews a wide range of cold atmospheric plasma sources with their reactor configurations used for the degradation of OMPs (such as organic dyes, pharmaceuticals, and pesticides) in wastewater. The role of plasma and treatment parameters (e.g. input power, voltage, working gas, treatment time, OMPs concentrations, etc.) on the oxidation of various OMPs are discussed. Furthermore, the degradation kinetics, intermediates compounds formed by plasma, and the synergetic effect of plasma in combination with a catalyst are also reported in this review. [ABSTRACT FROM AUTHOR]

N-nitrosamines (NAs), and N-nitrosodimethylamine (NDMA) in particular, are hazardous disinfection byproducts (DBPs) relevant when wastewater impacts drinking water sources and, in water reuse practices. Our study investigates the concentrations of NDMA and five additional NAs and their precursors in industrial wastewater effluents. Aiming to identify potential differences between industrial typologies, wastewaters from 38 industries belonging to 11 types of the UN International Standard Industrial Classification of All Economic Activities system (ISIC) were analysed. Results show that the presence of most NAs and their precursors cannot be linked to a specific industry type as these were in general very different within the classes. Nevertheless, N -nitrosomethylethylamine (NMEA) and N -nitrosopiperidine (NPIP) as well as precursors for N -nitrosodiethylamine (NDEA), NPIP and N -nitrosodibuthylamine (NDBA) could be rank with different concentrations between ISIC classes (p-value < 0.05). Specific industrial wastewater with notable high concentrations of NAs and their precursors were identified too. The effluents with the highest concentration of NDMA belong to the ISIC C2011 class (Manufacture of basic chemical), while the effluents with the highest concentration of NDMA precursors were from the ISIC C1511 class (Tanning and dressing of leather; dressing and dyeing of fur). Other relevant NAs found were NDEA in ISIC class B0810 (Quarrying of stone, sand, and clay) and ISIC class C2029 (Manufacture of other chemical products). [Display omitted] • Industrial effluents are important sources of nitrosamines and their precursors. • The highest N-nitrosodimethylamine conc. occurred in effluents of chemical industries. • The highest N-nitrosodiethylamine conc. was found in an effluent of stone quarrying. • Textile washing and dry cleaning is an important source of nitrosamine precursors. [ABSTRACT FROM AUTHOR]

Ozonation is known to generate biodegradable organic matter, which is typically reduced by biological filtration to avoid bacterial regrowth in distribution systems. Post-chlorination generates halogenated disinfection byproducts (DBPs) but little is known about the biodegradability of their precursors. This study determined the effect of ozonation and biofiltration conditions, specifically ozone exposure and empty bed contact time (EBCT), on the control of DBP formation potentials in drinking water. Ozone exposure was varied through addition of H 2 O 2 during ozonation at 1 mgO 3 /mgDOC followed by biological filtration using either activated carbon (BAC) or anthracite. Ozonation led to a 10% decrease in dissolved organic carbon (DOC), without further improvement from H 2 O 2 addition. Raising H 2 O 2 concentrations from 0 to 2 mmol/mmolO 3 resulted in increased DBP formation potentials during post-chlorination of the ozonated water (target Cl 2 residual after 24 h = 1–2 mg/L) as follows: 4 trihalomethanes (THM4, 37%), 8 haloacetic acids (HAA8, 44%), chloral hydrate (CH, 107%), 2 haloketones (HK2, 97%), 4 haloacetonitriles (HAN4, 33%), trichloroacetamide (TCAM, 43%), and adsorbable organic halogen (AOX, 27%), but a decrease in the concentrations of 2 trihalonitromethanes (THNM2, 43%). Coupling ozonation with biofiltration prior to chlorination effectively lowered the formation potentials of all DBPs including CH, HK2, and THNM2, all of which increased after ozonation. The dynamics of DBP formation potentials during BAC filtration at different EBCTs followed first-order reaction kinetics. Minimum steady-state concentrations were attained at an EBCT of about 10–20 min, depending on the DBP species. The rate of reduction in DBP formation potentials varied among individual species before reaching their minimum concentrations. CH, HK2, and THNM2 had the highest rate constants of between 0.5 and 0.6 min −1 followed by HAN4 (0.4 min −1 ), THM4 (0.3 min −1 ), HAA8 (0.2 min −1 ), and AOX (0.1 min −1 ). At an EBCT of 15 min, the reduction in formation potential for most DBPs was less than 50% but was higher than 70% for CH, HK2, and THNM2. The formation of bromine-containing DBPs increased with increasing EBCT, most likely due to an increase in Br − /DOC ratio. Overall, this study demonstrated that the combination of ozonation and biofiltration is an effective approach to mitigate DBP formation during drinking water treatment. [ABSTRACT FROM AUTHOR]

Former studies have shown that adding granular activated carbon (GAC) cathodes could enhance the overall performance of the zero valent iron (ZVI) process for organics removal. The present study evaluates for the first time the performance of such an enhanced ZVI process to remove natural organic matter (NOM), an important water quality parameter in drinking water. Lab-scale batch tests were conducted with surface reservoir feed water from a drinking water plant. In the GAC enhanced ZVI process dissolved organic carbon (DOC) and UV 254 were reduced by 61 ± 3% and 70 ± 2%, respectively, during 24 h treatment corresponding to 1.8 min empty bed contact time. The process was superior to ZVI alone, particularly during the earlier stages of the process due to the synergistically increased iron dissolution rate. Besides GAC, graphite and anthracite also prove to be suitable and potentially more cost-effective options as cathode materials for the enhanced ZVI process, whereby electrically conductive graphite clearly outperformed anthracite. The dominant mechanisms in terms of NOM removal from surface water were found to be coagulation following iron dissolution and adsorption in the case of employing GAC. Oxidation was also occurring to a lesser degree, converting some non-biodegradable into biodegradable DOC. [ABSTRACT FROM AUTHOR]

When ozonation is employed in advanced water treatment plants to produce drinking water, dissolved organic matter reacts with ozone (O 3 ) and/or hydroxyl radicals ( OH) affecting disinfection byproduct (DBP) formation with subsequently used chlorine-based disinfectants. This study presents the effects of varying exposures of O 3 and OH on DBP concentrations and their associated toxicity generated after subsequent chlorination. DBP formation potential tests and in vitro bioassays were conducted after batch ozonation experiments of coagulated surface water with and without addition of tertiary butanol (t-BuOH, 10 mM) and hydrogen peroxide (H 2 O 2 , 1 mg/mg O 3 ), and at different pH (6–8) and transferred ozone doses (0–1 mg/mg TOC). Although ozonation led to a 24–37% decrease in formation of total trihalomethanes, haloacetic acids, haloacetonitriles, and trihaloacetamides, an increase in formation of total trihalonitromethanes, chloral hydrate, and haloketones was observed. This effect however was less pronounced for samples ozonated at conditions favoring molecular ozone (e.g., pH 6 and in the presence of t-BuOH) over OH reactions (e.g., pH 8 and in the presence of H 2 O 2 ). Compared to ozonation only, addition of H 2 O 2 consistently enhanced formation of all DBP groups (20–61%) except trihalonitromethanes. This proves that OH-transformed organic matter is more susceptible to halogen incorporation. Analogously, adsorbable organic halogen (AOX) concentrations increased under conditions that favor OH reactions. The ratio of unknown to known AOX, however, was greater at conditions that promote direct O 3 reactions. Although significant correlation was found between AOX and genotoxicity with the p53 bioassay, toxicity tests using 4 in vitro bioassays showed relatively low absolute differences between various ozonation conditions. [ABSTRACT FROM AUTHOR]

Wastewater treatment plant (WWTP) discharges of microcontaminants negatively impact freshwater streams, underscoring the need for accurately mapping wastewater-derived contamination in water bodies across Europe (EU). In this study, we present a fast and open-source code for a microcontaminants fate and transport (MFT) model, capable of simulating contamination at a high resolution (15 arc second scale) across the EU. The model was developed using the best publicly available hydrological (HydroSHEDS) and sanitation (UWWTD) datasets and was rigorously calibrated, with a goodness of fit of 77.5% as measured by the R 2. Importantly, the model demonstrated the ability to predict wastewater-derived contamination in water bodies, making it a valuable tool for planning the upgrade of WWTPs and improving the ecological condition of freshwater streams in the EU. • A model is developed to simulate wastewater-based contamination in rivers. • Large-scale free hydrologic and sanitation layers are used. • The model is calibrated obtaining an R2 of 77.5%. • The model is open-source and has fast runtimes. [ABSTRACT FROM AUTHOR]

Abstract: The stability of five illicit drug markers in wastewater was tested under different sewer conditions using laboratory-scale sewer reactors. Wastewater was spiked with deuterium labelled isotopes of cocaine, benzoyl ecgonine, methamphetamine, MDMA and 6-acetyl morphine to avoid interference from the native isotopes already present in the wastewater matrix. The sewer reactors were operated at 20 °C and pH 7.5, and wastewater was sampled at 0, 0.25, 0.5, 1, 2, 3, 6, 9 and 12 h to measure the transformation/degradation of these marker compounds. The results showed that while methamphetamine, MDMA and benzoyl ecgonine were stable in the sewer reactors, cocaine and 6-acetyl morphine degraded quickly. Their degradation rates are significantly higher than the values reportedly measured in wastewater alone (without biofilms). All the degradation processes followed first order kinetics. Benzoyl ecgonine and morphine were also formed from the degradation of cocaine and 6-acetyl morphine, respectively, with stable formation rates throughout the test. These findings suggest that, in sewage epidemiology, it is essential to have relevant information of the sewer system (i.e. type of sewer, hydraulic retention time) in order to accurately back-estimate the consumption of illicit drugs. More research is required to look into detailed sewer conditions (e.g. temperature, pH and ratio of biofilm area to wastewater volume among others) to identify their effects on the fate of illicit drug markers in sewer systems. [Copyright &y& Elsevier]

UV–C radiation is the U.S. EPA recommended technology to remove N-nitrosodimethylamine (NDMA) during drinking and recycled water production. Frequently, H2O2 is added to the treatment to remove other recalcitrant compounds and to prevent NDMA reformation. However, the transformation of NDMA precursors during the UV and UV/H2O2 process and the consequences for NDMA formation potential are currently not well understood, in particular in the presence of monochloramine. In this study, doxylamine has been chosen as a model compound to elucidate its degradation byproducts in the UV and UV/H2O2 process and correlate those with changes to the NDMA formation potential. This study shows that during UV treatment in the presence and absence of monochloramine, NDMA formation potential can be halved. However, an increase of more than 30% was observed when hydrogen peroxide was added. Ultrafast liquid chromatography coupled to quadrupole-linear ion trap mass spectrometer was used for screening and structural elucidation of degradation byproducts identifying 21 chemical structures from the original parent compound. This work shows that further oxidation of NDMA precursors does not necessarily lead to a decrease in NDMA formation potential. Degradation byproducts with increased electron density in the vicinity of the dimethylamino moiety, for example induced by hydroxylation, may have a higher yield of nucleophilic substitution and subsequent NDMA formation compared to the parent compound during chloramination. This work demonstrates the need to consider the formation of oxidation byproducts and associated implications for the control and management of NDMA formation in downstream processes and distribution when integrating oxidative treatments into a treatment train generating either drinking water or recycled water for potable reuse. [ABSTRACT FROM AUTHOR]

This study evaluates the effect of UV-C and UV-C/H2O2 in the presence of chloramines on the N-nitrosodimethylamine formation potential (NDMA FP) of tramadol as a model precursor. The experiments were performed at high initial concentrations of TMDL (i.e., 20 mg/L) in order to elucidate the structures of TMDL byproducts. Twenty-four byproducts were identified in UV-C, UV-C/monochloramine, and UV/H2O2/monochloramine oxidation of tramadol using MS3 capabilities of a hybrid quadrupole-linear ion trap mass spectrometer, combined with online hydrogen/deuterium (H/D) exchange experiments. Oxidative cleavage of methoxy and methoxybenzene moiety, O-demethylation, hydroxylation, and cyclohexane ring-opening were identified as major reaction mechanisms of tramadol in UV oxidation. Addition of monochloramine decreased the degradation rates of tramadol and its byproducts and yielded several monochlorinated derivatives. The oxidation rates were significantly enhanced in the presence of H2O2, and byproducts of oxidative benzene ring-opening were detected. The majority of the identified byproducts are likely to have a higher NDMA FP than the parent compound due to a reduced steric hindrance and/or insertion of electron-donating hydroxyl groups in the N,N-dimethylamine side chain. This was confirmed by the results of NDMA FP tests, which showed that the formation of NDMA was enhanced up to four times depending on the process conditions in UV alone and in UV and UV/H2O2 in the presence of monochloramine. Prolonged oxidation by hydroxyl radicals in UV/H2O2/monochloramine process mineralized some of the byproducts and slightly reduced the NDMA FP at the end of the treatment. The obtained degradation pathway of tramadol allowed the correlation of changes in NDMA FP during oxidation with its major oxidative transformation reactions. This manuscript demonstrates the significance of oxidation byproducts as NDMA precursors and emphasizes the need for their consideration when evaluating the evolution of NDMA FP during oxidative treatment. [ABSTRACT FROM AUTHOR]

Abstract: Direct photolysis of flumequine (FLU, 20mgL−1) in different types of water (demineralised water (DW) and synthetic seawater (SW)), was conducted in a Suntest CPS+solar simulator to evaluate its persistence and toxicity, and to identify the major phototransformation products (PTPs) generated during photolysis in DW. It was observed that FLU is susceptible to transformation when subjected to direct solar radiation. The composition of the water affects the FLU degradation kinetics, which is slower in SW. Photolytic transformation products generated during direct photolysis were identified by liquid chromatography–time of flight–mass spectrometry (LC–TOF–MS). Fourteen PTPs generated in DW were identified. The transformation of FLU begins with the opening of the heterocyclic ring by oxidation of the double bond. Loss of the fluorine atom and the hydroxylation of the aromatic ring also appear as the majority, especially in the early stages. Comparative acute toxicity evaluation by Vibrio fischeri and Daphnia magna bioassays was performed for the first and last irradiated solutions in both matrices studied. These bioassays demonstrated that in the SW matrix, the most persistent PTPs are highly toxic to D. magna but less so to V. fischeri. [Copyright &y& Elsevier]

Abstract: The interaction of organic micropollutants with dissolved organic carbon (DOC) can influence their transport, degradation and bioavailability. While this has been well established for natural organic carbon, very little is known regarding the influence of DOC on the fate of micropollutants during wastewater treatment and water recycling. Dissolved organic carbon–water partition coefficients (K DOC) for wastewater derived and reference DOC were measured for a range of micropollutants using a depletion method with polydimethylsiloxane disks. For micropollutants with an octanol–water partition coefficient (log K OW) greater than 4 there was a significant difference in K DOC between reference and wastewater derived DOC, with partitioning to wastewater derived DOC over 1000 times lower for the most hydrophobic micropollutants. The interaction of nonylphenol with wastewater derived DOC from different stages of a wastewater and advanced water treatment train was studied, but little difference in K DOC was observed. Organic carbon characterisation revealed that reference and wastewater derived DOC had very different properties due to their different origins. Consequently, the reduced sorption capacity of wastewater derived DOC may be related to their microbial origin which led to reduced aromaticity and lower molecular weight. This study suggests that for hydrophobic micropollutants (log K OW > 4) a higher concentration of freely dissolved and thus bioavailable micropollutants is expected in the presence of wastewater derived DOC than predicted using K DOC values quantified using reference DOC. The implication is that naturally derived DOC may not be an appropriate surrogate for wastewater derived DOC as a matrix for assessing the fate of micropollutants in engineered systems. [Copyright &y& Elsevier]

This work assessed the solar photo-Fenton degradation of nalidixic acid (NXA), a quinolone antibacterial agent, in several different aqueous solutions. It has been proven that the composition of the water clearly affects the efficiency of the photo-Fenton process. The presence of chlorine ions induces the concurrence of different mechanisms involving Cl· and Cl2·- radicals, which slow down the process. Up to 35 transformation products (TPs) were identified and their structures characterized by accurate LC–TOF-MS mass measurements during treatment of the different model waters. Photocatalytic degradation was thus observed to proceed mainly through the attack of the hydroxyl radicals on the double bond C(2)=C(3) which induce further ring opening. All the TPs identified persisted after total degradation of NXA. NXA in real pharmaceutical effluent was treated by photo-Fenton as a first stage before biological treatment. As NXA has been demonstrated to be recalcitrant to biological treatment, photo-Fenton treatment of the effluent was continued until its total degradation. Although NXA was efficiently degraded, LC–MS analyses demonstrated that some of the TPs identified after the photo-Fenton treatment were also recalcitrant to biological treatment, persisting after the combined treatment. These results show that analytical assessment of photocatalytic water treatments is essential to assure they are functioning as intended. [ABSTRACT FROM AUTHOR]

Abstract: Direct photolysis and solar TiO2 photocatalysis of Trimethoprim (TMP) in different water matrices (demineralised and simulated seawater) have been studied. Direct photolysis yielded a similar, slow TMP degradation rate in both water matrices, and the formation of very stable photo-transformation products. Dissolved organic carbon decreased slightly after prolonged irradiation. The main intermediate identified was a ketone derivative (trimethoxybenzoylpyrimidine), which was proved to be a photosensitizer of TMP degradation. During TiO2 photocatalysis, TMP was completely eliminated in both water matrices at a similar rate, however, the mineralization rate was appreciably reduced in seawater, which can be explained by the presence of inorganic species acting as hydroxyl radical scavengers, and directly affecting photocatalytic efficiency. Identification of intermediates showed differences between the two processes but hydroxylation, demethylation and cleavage of the original drug molecule were observed in both. [Copyright &y& Elsevier]

A coupled solar photo-Fenton (chemical) and biological treatment has been used to remove biorecalcitrant diuron (42mgl−1) and linuron (75mgl−1) herbicides from water at pilot plant scale. The chemical process has been carried out in a 82l solar pilot plant made up by four compound parabolic collector units, and it was followed by a biological treatment performed in a 40l sequencing batch reactor. Two Fe(II) doses (2 and 5mgl−1) and sequential additions of H2O2 (20mgl−1) have been used to chemically degrade the initially polluted effluent. Next, biodegradability at different oxidation states has been assessed by means of BOD/COD ratio. A reagent dose of Fe=5mgl−1 and H2O2 =100mgl−1 has been required to obtain a biodegradable effluent after 100min of irradiation time. Finally, the organic content of the photo-treated solution has been completely assimilated by a biomass consortium in the sequencing batch reactor using a total suspended solids concentration of 0.2gl−1 and a hydraulic retention time of 24h. Comparison between the data obtained at pilot plant scale (specially the one corresponding to the chemical step) and previously published data from a similar system performing at laboratory scale, has been carried out. [Copyright &y& Elsevier]

Abstract: A multivariate analysis using experimental design techniques was performed to determine the effect of iron, hydrogen peroxide and titanium dioxide in the solar photodegradation of dichloroacetic acid in a combined TiO2/photo-Fenton process. The study was carried out at pilot-plant scale, using TiO2 supported on silica as the heterogeneous photocatalyst to facilitate separation of the solids after the reaction, and iron concentrations of less than 3mgL−1 to avoid removal of iron from the effluent. The results show that iron is the most important factor influencing the reaction rate, which suggests that in strongly acidic solutions, the Fenton mechanism controls the process even at such low iron concentrations. Under these conditions, the expected synergism between TiO2 and iron degradation pathways seems to be negligible compared to the antagonistic effect between hydrogen peroxide and TiO2, which reduces the activity of the combined system. However, in the absence of hydrogen peroxide, the activity achieved by the combined Fe/TiO2 system is similar to that of the photo-Fenton process, with the advantage that H2O2 is replaced by a reusable TiO2-based catalytic material. Consequently, the analysis of pilot-plant operation economics took not only the degradation rate, but also the cost of chemicals into account. [Copyright &y& Elsevier]

In recent years, the presence of pharmaceuticals in the aquatic environment has been of growing interest. These new contaminants are important because many of them are not degraded under the typical biological treatments applied in the wastewater treatment plants and represent a continuous input into the environment Thus, compounds such as diclofenac are present in surface waters in all Europe and a crucial need for more enhanced technologies that can reduce its presence in the environment has become evident In this sense, advanced oxidation processes (AOPs) represent a good choice for the treatment of hazardous nonbiodegradable pollutants. This work deals with the solar photodegradation of diclofenac, an antiinflammatory drug, in aqueous solutions by photo-Fenton reaction. A pilot- scale facility using a compound parabolic collector (CPC) reactor was used for this study. Results obtained show rapid and complete oxidation of diclofenac after 60 mm, and total mineralization (disappearance of dissolved organic carbon, DOC) after 100 mm of exposure to sunlight Although diclofenac precipitates during the process at low pH, its degradation takes place in the homogeneous phase governed by a precipitation-redissolution- degradation process. Establishment of the reaction pathway was made possible by a thorough analysis of the reaction mixture identifying the main intermediate products generated. Gas chromatography–mass spectrometry (GC/MS) and liquid chromatography coupled with time-of-flight mass spectrometry (LC/TOF-MS) were used to identify 18 intermediates, in two tentative degradation routes. The main one was based on the initial hydroxylation of the phenylacetic acid moiety in the C-4 position and subsequent formation of a quinoneimine derivative that was the starting point for further multistep degradation involving hydroxylation, decarboxylation, and oxidation reactions. An alternative route was based on the transient preservation of the biphenyl amino moiety that underwent a similar oxidative process of C–N bond cleavage. The proposed degradation route differs from those previously reported involving alternative degradation processes (ozonization, UV/H2O2, or photolysis), indicating that diclofenac degradation follows different pathways, depending on the treatment applied. [ABSTRACT FROM AUTHOR]

• EU Rivers' capacity to dilute wastewater treatment plants discharges is assessed • Climate change will lead to a dilution factor decrease for 11% of the EU rivers • 42% of the rivers will downgrade their ecological status due to climate change • More vulnerable sites are located in the Mediterranean countries Impacts from urban wastewater treatment plants (WWTP) to receiving riverine surface water bodies (SWBs) depend on the load of contaminants discharged, as well as on their dilution capacity. Yet, climate change impacts on such dilution capacity and ultimately on the SWBs ecological status remain unclear. Here, we assess SWBs dilution capacity across the European continent to identify most vulnerable areas using information from centralized European databases. SWBs´ future dilution factor values are estimated based on representative concentration pathway scenarios impacts on rivers flow, and likely changes in European SWBs´ ecological status foretold. Results show that dilution factor in Europe increases by 5.4% in average. Yet, climate change effects are found to lead to a consistent dilution factor decrease for 11% of the 40074 European SWBs receiving WWTP discharge for the early century. This share reaches 17% for the midcentury period. We estimate that up to 42% of the SWBs receiving WWTP discharges and currently reaching a good ecological status show a 0.7 probability to have their ecological status downgraded due to climate change. Sites more vulnerable are located in the Mediterranean countries. Our findings highlight that climate change mitigation is essential for maintaining good ecological status in European SWBs. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract Urban wastewater treatment plants (WWTPs) are among the main anthropogenic sources for the release of contaminants of emerging concern (CECs) into the environment, which can result in toxic and adverse effects on aquatic organisms and consequently on humans. Unfortunately, WWTPs are not designed to remove CECs and secondary (e.g., conventional activated sludge process, CAS) and tertiary (such as filtration and disinfection) treatments are not effective in the removal of most CECs entering WWTP. Accordingly, several advanced treatment methods have been investigated for the removal of CECs from wastewater, including consolidated (namely, activated carbon (AC) adsorption, ozonation and membranes) and new (such as advanced oxidation processes (AOPs)) processes/technologies. This review paper gathers the efforts of a group of international experts, members of the NEREUS COST Action ES1403 who for three years have been constructively discussing the state of the art and the best available technologies for the advanced treatment of urban wastewater. In particular, this work critically reviews the papers available in scientific literature on consolidated (ozonation, AC and membranes) and new advanced treatment methods (mainly AOPs) to analyse: (i) their efficiency in the removal of CECs from wastewater, (ii) advantages and drawbacks, (iii) possible obstacles to the application of AOPs, (iv) technological limitations and mid to long-term perspectives for the application of heterogeneous processes, and (v) a technical and economic comparison among the different processes/technologies. Graphical abstract Unlabelled Image Highlights • Adsorption, O 3 , NF and RO membranes filtration can effectively remove CECs. • (Solar driven) AOPs appear competitive for CECs removal from urban wastewater. • When applying O 3 or AOPs ecotoxicological studies should be performed. • Lack of comparative investigations between consolidated and new processes • Conclusive evaluation of the most suitable and cost effective solution/s not yet possible [ABSTRACT FROM AUTHOR]

Forward osmosis (FO) offers to be a very promising technology for the removal of trace organic compounds (TrOCs) from contaminated wastewater, and with the recent developments in FO membranes, the effect of both a higher water flux and reverse salt flux on the rejection of TrOCs needs to be explored. In this study two novel thin-film composite (TFC) membranes with greater water permeability and selectivity than the benchmark cellulose tri-acetate (CTA) membrane were compared at bench-scale in terms of TrOCs permeability. By probing the solute-membrane interactions that dictate the transport of TrOCs through the two membranes in the absence and presence of a draw solution, several conclusions were drawn. Firstly, steric hindrance is the main TrOCs transport -limiting mechanism through TFC membranes unless the negative membrane surface charge is significant, in which case, electrostatic interactions can dominate over steric hindrance. Secondly, the increase in ionic strength induced by the draw solution in the vicinity of and perhaps inside the membrane seems to favour the rejection of TrOCs by “shrinking” the membrane pores or by “shielding” the negative surface charge. Lastly, during FO operation, solute concentration polarisation becomes detrimental when working at high water fluxes, whereas the reverse solute flux has no direct impact on the transport of TrOCs through the membrane. [ABSTRACT FROM AUTHOR]

The European Union is determined to address the problem of contaminants of emerging concern (CEC) occurrence in natural water bodies. However, if a broad range of possible advanced treatment technological solutions exists as well as a variety of possible future conditions, then emission and consequently strategies for wastewater treatment plan (WWTP) upgrade and operation are not easy to anticipate. Here, a strategic foresight exercise was carried out to support decision-making matching anticipated future conditions toward the goal of finding suitable treatment upgrades to control CECs release in the environment. As a result, a roadmap and strategic routes were developed based on the interpretation of drivers for the EU region in the context of Shared Socioeconomic Pathways (SSPs) global change narratives. Screening and ranking of WWTP tertiary and advanced treatment technology upgrades were performed. Analysis of the resulting envisioned strategic routes allowed identifying and confronting core challenges such as the CEC removal agenda, technologies' performance, requirements for CEC removal and water scarcity. The results also underline opportunities to shape WWTP technological upgrade planning such as: enhancing circular economy solutions in WWTP, water reclamation, and accelerated increase of the technology readiness level of hybrid and nature-based solutions. • Assessment of individual performance of advanced WWTP processes. • Development of a roadmap framework based on SSP narratives for CEC removal. • Development of strategic routes for WWTP technology upgrade for each selected SSP. • Uptake of mature, combined or hybrid solutions require a SSP that favours innovation. • Achieving CEC related EU water quality goals is unlikely before 2040 in all SSPs. [ABSTRACT FROM AUTHOR]

Climate change and socioeconomic factors have increased the complexity of urban water supply systems. Thus, fresh water sources are being gradually diversified to improve the reliability and resilience of the systems. However, as the number of source blending options grows, optimization tools are needed to design drinking water supply systems that comply with indicators of cost, resilience, and water quality. This paper proposes a pioneering methodological approach, based on an ant-colony-optimization (ACO) algorithm, to optimize the blending of drinking water from different sources to minimize operational costs of a given system originating from a number of impaired water sources while complying with water quality standards. To evidence the potential of the ACO algorithm to solve such a system, a virtual case study was designed that considers eight fresh water sources, including seawater desalination and potable reuse. Seven scenarios were developed with different weightings to service outage, water conveyance and treatment costs while complying with water quality goals in regard to total organic carbon, nitrates, and total dissolved solids. It was shown that the cost per volumetric unit of water can vary considerably depending on the weightings of the three cost items. This paper provides a rigorous scientific approach to propose a methodology supporting the decision-making process of selecting a mixture of different sources to achieve the overall lowest system cost. Hence, this work contributes to improving the resilience and sustainability of urban water supplies. [ABSTRACT FROM AUTHOR]

Stormwater is a major driving factor of aquatic ecosystem degradation as well as one of the largest untapped urban freshwater resources. We present results from a long-term, multi-catchment study of urban stormwater pesticides across Australia that addresses this dichotomous identity (threat and resource), as well as dominant spatial and temporal patterns in stormwater pesticide composition. Of the 27 pesticides monitored, only 19 were detected in Australian stormwater, five of which (diuron, MCPA, 2,4-D, simazine, and triclopyr) were found in >50% of samples. Overall, stormwater pesticide concentrations were lower than reported in other countries (including the United States, Canada and Europe), and exceedances of public health and aquatic ecosystem standards were rare (<10% of samples). Spatio-temporal patterns were investigated with principal component analysis. Although stormwater pesticide composition was relatively stable across seasons and years, it varied significantly by catchment. Common pesticide associations appear to reflect 1) user application of common registered formulations containing characteristic suites of active ingredients, and 2) pesticide fate properties (e.g., environmental mobility and persistence). Importantly, catchment-specific occurrence patterns provide opportunities for focusing treatment approaches or stormwater harvesting strategies. [ABSTRACT FROM AUTHOR]

The UV/chlorine system has become an attractive alternative Advanced Oxidation Process (AOP) for the removal of recalcitrant pollutants in the last decade due to the simultaneous formation of chlorine and hydroxyl radicals. However, there is no consensus regarding the results and trends obtained in previous micropollutant removal studies by AOPs, highlighting the complexity of the UV/chlorine process and the need for further research. This study investigates the degradation of acetaminophen (ACTP) by UV/chlorine and the effects of the water matrix in the reaction kinetics. In particular, the effects of natural organic matter (NOM), alkalinity and mineral salts on the kinetics and reactive species were elucidated. The complexity of the system was revealed by the analysis of the radical generation and transformation in different water matrices, applying the kinetic modelling approach to complement the scavenger tests. The higher kinetic rates of ACTP at alkaline pH provided new insights into the chlorine reactions under UV radiation, where secondary and tertiary reactive oxygen species including ozone were proven to play the major role in degradation. On the contrary, at acidic pH, reaction kinetic modelling demonstrated that ClO• radical occurs at high concentrations in the order of 10−10 M, being therefore the main oxidant, followed by other chlorine radicals. It is noteworthy that at alkaline pH the presence of typical inorganic ions such as carbonate had little impact on ACTP degradation, contrary to the observed reduction of degradation rates at acidic pH. The expected detrimental effect of the NOM in AOPs was also evidenced, although the use of chlorine as radical source reduces the relevance of the inner filter effect in comparison to UV/H 2 O 2. [ABSTRACT FROM AUTHOR]

Riverbank filtration (RBF) with days to months of residence time has been successfully used as treatment or pre-treatment process to improve water quality for decades. However, its feasibility depends on the local hydrogeological conditions. Therefore, for sites unsuitable to traditional RBF, a smaller engineered RBF may be an option. This study evaluates the performance of engineered short residence time RBF on improving water quality, focusing on the removal of natural organic matter (NOM) and the reduction of precursors of carbon and nitrogen disinfection by-products (DBP). Lab-scale experiments were conducted with surface feed water from a drinking water plant. The results showed that within 6 days hydraulic retention time (HRT), 60–70% dissolved organic carbon (DOC) and 70–80% ultraviolet absorbance at 254 nm (UV 254 ) could be removed. During the whole filtration process, biodegradation was responsible for the removal of organic matter, and it was found that alternating redox condition between oxic and anoxic was beneficial for the overall performance of the RBF. Dissolved oxygen (DO) had a substantial impact on the removal of DBP precursors. For carbon-containing DBP (C-DBP) precursors' removal, re-aeration after a sequence of oxic and anoxic conditions could further increase the removal efficiencies from 50%, 60%, and 60% to 80%, 90%, and 80% for trihalomethanes (THMs), chloral hydrate (CH), and haloketones (HKs). Prolonged anoxic conditions were however beneficial for the removal of nitrogen-containing DBP (N-DBP) precursors. [ABSTRACT FROM AUTHOR]

• Data-driven analysis of micropollutants in 77 wet-weather discharge sites. • Top list of micropollutants with high occurrence and risk for surface waters. • Combined sewer overflows, stormwater outlets and all chemical classes show risk. • Minimum number of required events and sites predicted by concentration variability. • Discussion of learnings for future wet-weather flow monitoring. Urban wet-weather discharges from combined sewer overflows (CSO) and stormwater outlets (SWO) are a potential pathway for micropollutants (trace contaminants) to surface waters, posing a threat to the environment and possible water reuse applications. Despite large efforts to monitor micropollutants in the last decade, the gained information is still limited and scattered. In a metastudy we performed a data-driven analysis of measurements collected at 77 sites (683 events, 297 detected micropollutants) over the last decade to investigate which micropollutants are most relevant in terms of 1) occurrence and 2) potential risk for the aquatic environment, 3) estimate the minimum number of data to be collected in monitoring studies to reliably obtain concentration estimates, and 4) provide recommendations for future monitoring campaigns. We highlight micropollutants to be prioritized due to their high occurrence and critical concentration levels compared to environmental quality standards. These top-listed micropollutants include contaminants from all chemical classes (pesticides, heavy metals, polycyclic aromatic hydrocarbons, personal care products, pharmaceuticals, and industrial and household chemicals). Analysis of over 30,000 event mean concentrations shows a large fraction of measurements (> 50%) were below the limit of quantification, stressing the need for reliable, standard monitoring procedures. High variability was observed among events and sites, with differences between micropollutant classes. The number of events required for a reliable estimate of site mean concentrations (error bandwidth of 1 around the "true" value) depends on the individual micropollutant. The median minimum number of events is 7 for CSO (2 to 31, 80%-interquantile) and 6 for SWO (1 to 25 events, 80%-interquantile). Our analysis indicates the minimum number of sites needed to assess global pollution levels and our data collection and analysis can be used to estimate the required number of sites for an urban catchment. Our data-driven analysis demonstrates how future wet-weather monitoring programs will be more effective if the consequences of high variability inherent in urban wet-weather discharges are considered. [Display omitted] [ABSTRACT FROM AUTHOR]

A reverse osmosis (RO) process is often included in the treatment train to produce high quality reuse water from treated effluent for potable purposes because of its high removal efficiency for salinity and many inorganic and organic contaminants, and importantly, it also provides an excellent barrier for pathogens. In order to ensure the continued protection of public health from pathogen contamination, monitoring RO process integrity is necessary. Due to their small sizes, viruses are the most difficult class of pathogens to be removed in physical separation processes and therefore often considered the most challenging pathogen to monitor. To-date, there is a gap between the current log credit assigned to this process (determined by integrity testing approved by regulators) and its actual log removal capability as proven in a variety of laboratory and pilot studies. Hence, there is a challenge to establish a methodology that more closely links to the theoretical performance. In this review, after introducing the notion of risk management in water reuse, we provide an overview of existing and potentially new RO integrity monitoring techniques, highlight their strengths and drawbacks, and debate their applicability to full-scale treatment plants, which open to future research opportunities. [ABSTRACT FROM AUTHOR]

Membrane ageing reduces the quality of the filtered water. Therefore, in order to warrant public health, monitoring membrane performances are of utmost importance. Reverse osmosis (RO) membranes are generally used to remove viruses and salt. However, there is no detailed study demonstrating the impact of aged membrane on the rejection of viruses and of membrane integrity indicators. In this paper, the impact of hypochlorite induced RO ageing on the rejection of a virus surrogate (MS2 phage) and four membrane integrity indicators (salt, dissolved organic matter, rhodamine WT and sulphate) was evaluated. Hypochlorite exposure was either active (under filtration) or passive (soaking), and the changes of the membrane surface chemistry were characterised using several autopsy techniques. Under this accelerated ageing condition, the introduction of chlorine in the membrane chemistry and the breakage of amide bonds caused an increase of the water permeability and a decrease of the virus surrogate's and indicators' rejection. Ageing resulted in a more negatively charged membrane and also in a higher hydrophobicity, which lead to the adsorption of MS2 phage. Despite severe physical membrane damage leading to a reduction of salt rejection to 1.2 log (94%), the minimum rejection of MS2 phage stayed on or above 4 log. [ABSTRACT FROM AUTHOR]

Adsorbable organic halogens (AOX) were measured at the outlet (AOXo) and after 24 h contact time with residual disinfectant (AOX24 h) for 10 samples obtained from 7 drinking water treatment plants (WTPs) that employ chlorine-based disinfectants. AOXo ranged from 0.75 to 7.60 µM (26.2-266.0 µgCl=L) and increased by up to 170% after 24 h contact time. The results were also compared with AOX formation potential (AOXFP) measured in the laboratory for the samples collected prior to disinfection at the same WTPs. In general, AOX24 h and AOXFP values varied by less than ±20%. A suite of disinfection byproducts (DBPs) were individually measured to elucidate the AOX composition. Trihalomethanes and haloacetic acids explained the largest fraction of AOX; however, the percentage of AOX not accounted for by measured DBPs varied greatly between samples (14.5-62.0%). Additionally, the fate of AOXFP was assessed across the seven WTPs. On average, coagulation removed 67 ± 7% of AOXFP across the WTPs, while dual media filtration did not substantially remove AOXFP. The effect of ozone on AOXFP varied between WTPs, while biological activated carbon filtration removed 33 ± 13% AOXFP. The ratio of known versus unknown AOXFP did not change across the WTPs. [ABSTRACT FROM AUTHOR]

Biofouling is generally regarded as a major issue in reverse osmosis (RO) membrane filtration. Two-step chemical cleanings with alkaline and acidic agents are typically applied to restore the treatment capacity. In this study, the feasibility of one-step cleaning using free nitrous acid (FNA) was investigated as a novel low cost cleaning agent. The FNA cleaning solution was prepared by acidification of a sodium nitrite solution with hydrochloric acid. Seven fouled RO membranes collected from full-scale wastewater recycling and desalination plants were used to perform lab-scale cleaning trials. Membrane fouling characterisation revealed six of out of seven membranes were mainly bio-fouled, while one membrane was severely fouled by calcium carbonate. This study showed the feasibility of using FNA at pH 3.0 for biomass removal as well as for calcium carbonate scaling removal. The results from the lab-scale cleaning tests suggested that FNA can be used as a single cleaning agent for both biofouling and scaling removal. Cost analysis showed that FNA is a cost-effective solution for biofouling and scaling removal in RO filtration applications. [ABSTRACT FROM AUTHOR]

The objective of this study was to determine the influence of solute properties and operational parameters on disinfection by-product (DBP) rejection by reverse osmosis (RO) and nanofiltration (NF) membranes. This was achieved by assessing the removal efficiency for 29 DBPs likely to be formed during disinfection of secondary effluents. The DBPs investigated were trihalomethanes, iodinated-trihalomethanes, haloacetonitriles, chloral hydrate, haloketones, halonitromethanes and haloacetamides. The performance of a NF and a low pressure RO membrane was investigated within a range of different pHs, temperatures, transmembrane fluxes, crossflow velocities and ionic strengths. Rejection decreased significantly with increasing temperature and decreasing transmembrane flux, while the influence of the other operational parameters was minimal with a few exceptions detailed in the manuscript. Multiple linear regression was used to determine the physico-chemical solute properties contributing significantly to DBP rejection. For NF, geometric parameters were revealed to be the dominant molecular descriptors influencing rejection, whereas for RO, besides size exclusion, solute-membrane interaction played an important role. A predictive model based on multiple linear regression was established that could forecast rejection of DBPs as a function of membrane operation parameters and DBP properties. [ABSTRACT FROM AUTHOR]

Abstract: Creatinine was proposed to be used as a population normalising factor in sewage epidemiology but its stability in the sewer system has not been assessed. This study thus aimed to evaluate the fate of creatinine under different sewer conditions using laboratory sewer reactors. The results showed that while creatinine was stable in wastewater only, it degraded quickly in reactors with the presence of sewer biofilms. The degradation followed first order kinetics with significantly higher rate in rising main condition than in gravity sewer condition. Additionally, daily loads of creatinine were determined in wastewater samples collected on Census day from 10 wastewater treatment plants around Australia. The measured loads of creatinine from those samples were much lower than expected and did not correlate with the populations across the sampled treatment plants. The results suggested that creatinine may not be a suitable biomarker for population normalisation purpose in sewage epidemiology, especially in sewer catchment with high percentage of rising mains. [Copyright &y& Elsevier]

Abstract: Stormwater harvesting has become an attractive alternative strategy to address the rising demand for urban water supply due to limited water sources and population growth. Nevertheless, urban stormwater is also a major source of surface water pollution. Runoff from different urban catchments with source contributions from anthropogenic activities and various land uses causes variable contaminant profiles, thus posing a challenging task for environmental monitoring and risk assessment. A thorough understanding of raw stormwater quality is essential to develop appropriate treatment facilities for potential indirect potable reuse of stormwater. While some of the key chemical components have previously been characterized, only scarce data are available on stormwater toxicity. We benchmarked stormwater samples from urban, residential and industrial sites across various Australian capital cities against samples from the entire water cycle, from sewage to drinking water. Six biological endpoints, targeting groups of chemicals with modes of toxic action of particular relevance for human and environmental health, were investigated: non-specific toxicity (Microtox and combined algae test), the specific modes of action of phytotoxicity (combined algae test), dioxin-like activity (AhR-CAFLUX), and estrogenicity (E-SCREEN), as well as reactive toxicity encompassing genotoxicity (umuC) and oxidative stress (AREc32). Non-specific toxicity was highly variable across sites. The baseline toxicity equivalent concentrations of the most polluted samples were similar to secondary treated effluent from wastewater treatment plants. Phytotoxicity results correlated well with the measured herbicide concentrations at all sites. High estrogenicity was found in two sampling events and could be related to sewage overflow. Genotoxicity, dioxin-like activity, and oxidative stress response were evident in only three of the samples where the stormwater drain was beside a heavy traffic road, confirming that road runoff is the potential source of contaminants, while the bioanalytical equivalent concentrations (BEQ) of these samples were similar to those of raw sewage. This study demonstrates the benefit of bioanalytical tools for screening-level stormwater quality assessment, forming the basis for the evaluation of future stormwater treatment and reuse schemes. [Copyright &y& Elsevier]

Abstract: This paper evaluated dissolved organic matter (DOM) rejection by reverse osmosis (RO) membranes employed in full-scale water reclamation plants with two techniques based on fluorescence to assess its suitability as a novel method for verification of membrane process integrity. Excitation–emission matrices (EEM) of feed and permeate samples from individual pressure vessels, complete stages and RO trains of two full scale plants were analysed with a fluorescence regional integration technique. Depending on the excitation–emission region quantified, DOM rejection up to around 99.5% was regularly measured and fluorescence measurements could be used as more sensitive tool compared to conductivity profiling when assessing membrane installations. A blue-shift in the fluorescence of the humic substances peak was observed and could be explained by determining size distribution of organic matter by size exclusion chromatography (SEC) with fluorescence detection. The results demonstrated that the size distribution of fluorescent DOM changed towards lower molecular weight from feed to permeate due to increased rejection of high molecular weight compounds. Preliminary trials showed rejection of high molecular weight substances and consequentially membrane integrity beyond 99.9%. We conclude that fluorescence coupled with regional integration techniques and potentially SEC is a promising sensitive technique to assess RO membrane integrity. [Copyright &y& Elsevier]

Abstract: The declining functionality associated with membranes ageing includes changes in physical parameters, such as, thickness, roughness and density of defects, but also in chemical structure. All these factors impact synergistically on the major performance indicators: permeability and salt rejection. In this study, three types of commercially available RO membranes were statically exposed to hypochlorite solutions and analysed by Fourier transform infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) in conjunction with performance tests. IR data support the chemical structure alteration for samples aged at pHs 7 and 4, where hypochlorous acid (HOCl) is the main oxidant. For two of the membranes, AFM results indicate increasing roughness at pH 4. Performance tests show a reduction of de-ionised (DI) water and brackish water permeability at pH 7 and pH 4, while at pH 10, where hypochlorite ion (ClO−) is abundant, permeability increases. Salt rejection results vary in a narrow interval of 5% and depend on the type of membrane. Based on these results the ppm∙h concept appears to fail to express a simple ageing kinetic over the entire range of pH, owing to the competing mechanisms of ring chlorination and surface hydrolysis of amide groups. [Copyright &y& Elsevier]

Abstract: Electrochemical processes have been widely investigated for degrading organic contaminants present in wastewater. This study evaluated the performance of electrochemical oxidation using boron-doped diamond (BDD) electrodes by forming OH for the treatment of reverse osmosis concentrate (ROC) from secondary-treated wastewater effluents. Since oxidation by OH and active chlorine species (HClO/ClO−) is influenced by pH, the electrochemical oxidation of ROC was evaluated at controlled pH 6–7 and at pH 1–2 (no pH adjustment). A high concentration of chloride ions in the ROC enhanced the oxidation, and 7–11% of Coulombic efficiency for chemical oxygen demand (COD) removal was achieved with 5.2 Ah L−1 of specific electrical charge. Complete COD removal was observed after 5.2 and 6.6 Ah L−1, yet the corresponding dissolved organic carbon (DOC) removal was only 48% (at acidic pH) and 59% (at circumneutral pH). Although a higher operating pH seemed to enhance the participation of OH in oxidation mechanisms, high concentrations of chloride resulted in the formation of significant concentrations of adsorbable organic chlorine (AOCl) after electrochemical oxidation at both pH. While adsorbable organic bromine (AOBr) was degraded at a higher applied electrical charge, a continuous increase in AOCl concentration (up to 0.88 mM) was observed until the end of the experiments (i.e. 10.9 Ah L−1). In addition, total trihalomethanes (tTHMs) and total haloacetic acids (tHAAs) were further degraded with an increase in electrical charge under both pH conditions, to final total concentrations of 1 and 4 μM (tTHMs), and 12 and 22 μM (tHAAs), at acidic and circumneutral pH, respectively. In particular, tHAAs were still an order of magnitude above their initial concentration in ROC after further electrooxidation. Where high chloride concentrations are present, it was found to be necessary to separate chloride from ROC prior to electrochemical oxidation in order to avoid the formation of chlorinated by-products. [Copyright &y& Elsevier]

Abstract: Long-term exposure to low concentrations of disinfection byproducts (DBPs) in drinking water has been associated with increased human-health risks of bladder cancer and adverse reproductive outcomes. In this study, we investigated electrochemical reduction utilizing a resin-impregnated graphite cathode for the degradation of 17 DBPs (i.e. halomethanes, haloacetonitriles, halopropanones, chloral hydrate and trichloronitromethane) at low μg L−1 concentration levels. The reduction experiments were potentiostatically controlled at cathode potentials −700, −800 and −900 mV vs Standard Hydrogen Electrode (SHE) during 24 h. At the lowest potential applied (i.e. −900 mV vs SHE), the disappearance of DBPs from the solution after 24 h of reduction was >70%, except for chloroform (32%), 1,1-dichloropropanone (48%), and chloral hydrate (31%). Due to the participation of several removal mechanisms (e.g. electrochemical reduction, adsorption, volatilization and/or hydrolysis) it was not possible to distinguish the removal efficiencies of electrochemical reduction of individual compounds. Adsorption of the more hydrophilic DBPs (i.e. haloacetonitriles, chloral hydrate, and 1,1-dichloropropanone) onto the electrode seems to be affected by the cathode polarization, as the removals observed in the open circuit experiments were significantly higher than the ones obtained in electrochemical reduction under the same conditions. The overall efficiency of reduction was estimated based on the analyses of the released Cl−, Br− and I− ions. Nearly complete C–I bond cleavage was achieved at all three potentials applied, and from the theoretically predicted release of I− ions, calculated based on the removed DBPs, 86 ± 9 to 92 ± 1% was measured in the catholyte solution at −700 to −900 mV vs SHE. Debromination efficiencies obtained were 74 ± 3, 79 ± 6 and 68 ± 4% at −700, −800 and −900 mV vs SHE, while for C–Cl bond cleavage the obtained values were 69 ± 1, 72 ± 1 and 76 ± 4%, respectively. Nevertheless, dechlorination efficiencies are to be considered as approximate, since an increase in Cl− concentration was observed in the open circuit experiments due to the hydrolysis of some of the chlorine-containing DBPs. Although the Coulombic efficiencies for DPBs dehalogenation were only 1.9 ± 0.3 (−900 mV vs SHE) –4.1 ± 0.2% (−700 mV vs SHE), relatively low energy consumption of the process was observed, estimated at 72 ± 2 Wh m−3 at −900 mV vs SHE for the concentration range of DBPs in this study (i.e. 65.3–129.7 μg L−1). The study demonstrated that reductive electrochemical treatment has the potential to be a modern remediation technology for the removal of low concentrations of halogenated DBPs in water. [Copyright &y& Elsevier]

Abstract: The presence of disinfection by-products (DBPs) such as trihalomethanes (THMs), haloacetic acids (HAAs) and N-nitrosamines in water is of great concern due to their adverse effects on human health. In this work, the removal of N-nitrosodimethylamine (NDMA), total THM and five HAA precursors from secondary effluent by biological activated carbon (BAC) is investigated at full and pilot scale. In the pilot plant two filter media, sand and granular activated carbon, are tested. In addition, we evaluate the influence of ozonation prior to BAC filtration on its performance. Among the bulk of NDMA precursors, the fate of four pharmaceuticals containing a dimethylamino moiety in the chemical structure are individually investigated. Both NDMA formation potential and each of the studied pharmaceuticals are dramatically reduced by the BAC even in the absence of main ozonation prior to the filtration. The low removal of NDMA precursors at the sand filtration in comparison to the removal of NDMA precursors at the BAC suggests that adsorption may play an important role on the removal of NDMA precursors by BAC. Contrary, the precursors for THM and HAA formation are reduced in both sand filtration and BAC indicating that the precursors for the formation of these DBPs are to some extent biodegradable. [Copyright &y& Elsevier]

Abstract: A solar desalination system based on membrane distillation (MD) is presented and evaluated. In the context of a European project, the MEDESOL project, a pilot plant was built to evaluate the system, which consists of three commercial MD modules coupled with a static solar collector''s field. The MD modules employed have been developed and manufactured by the Swedish company Scarab AB. They have a flat sheet air gap membrane distillation (AGMD) configuration with a total membrane surface area per module of 2.8m2. The MD system is intended to be technically simple to operate, robust and able to cover water demands of small settlements. It also contemplates the use of a multi-stage layout to minimize energy consumption. Experiments were run during solar hours (the layout didn’t include heat storage) and addressed to characterize the performance of the system (i.e. distillate production and quality, thermal efficiency and recovery ratio) as a function of operation variables and salt concentration, as well as to identify the operating capacities and the potential improvements of the MD technology. Aqueous NaCl solutions of 1 and 35g/l concentration were used as feed. Temperatures up to 85°C in the feed and up to 75°C in the refrigeration were employed. Maximum specific distillate flux values registered were in the range of 7l/hm2. Multi-stage layouts were tested in order to evaluate the improvement of the system''s thermal efficiency and recovery ratio. The MD technology assessed proved to be suitable for coupling with transient solar thermal energy but inefficiencies inherent to scaling-up compared to laboratory experiences reported in literature were also identified, namely affecting specific distillate production and thermal consumption. The results of the characterization, performance assessment and operational issues description of the pilot plant are shown. [Copyright &y& Elsevier]

Advanced water treatment of secondary treated effluent requires stringent quality control to achieve a water quality suitable for augmenting drinking water supplies. The removal of micropollutants such as pesticides, industrial chemicals, endocrine disrupting chemicals (EDC), pharmaceuticals, and personal care products (PPCP) is paramount. As the concentrations of individual contaminants are typically low, frequent analytical screening is both laborious and costly. We propose and validate an approach for continuous monitoring by applying passive sampling with Empore disks in vessels that were designed to slow down the water flow, and thus uptake kinetics, and ensure that the uptake is only marginally dependent on the chemicals' physicochemical properties over a relatively narrow molecular size range. This design not only assured integrative sampling over 27 days for a broad range of chemicals but also permitted the use of a suite of bioanalytical tools as sum parameters, representative of mixtures of chemicals with a common mode of toxic action. Bioassays proved to be more sensitive than chemical analysis to assess the removal of organic micropollutants by reverse osmosis, followed by UV/H2O2 treatment, as many individual compounds fell below the quantification limit of chemical analysis, yet still contributed to the observed mixture toxicity. Nonetheless in several cases, the responses in the bioassays were also below their quantification limits and therefore only three bioassays were evaluated here, representing nonspecific toxicity and two specific end points for estrogenicity and photosynthesis inhibition. Chemical analytical techniques were able to quantify 32 pesticides, 62 PCPPs, and 12 EDCs in reverse osmosis concentrate. However, these chemicals could explain only 1% of the nonspecific toxicity in the Microtox assay in the reverse osmosis concentrate and 0.0025% in the treated water. Likewise only 1% of the estrogenic effect in the E-SCREEN could be explained by the quantified EDCs after reverse osmosis. In comparison, >50% of the estrogenic effect can typically be explained in sewage. Herbicidal activity could be fully explained by chemical analysis as the sampling period coincided with an illegal discharge and two herbicides dominated the mixture effect. The mass balance of the reverse osmosis process matched theoretical expectations for both chemical analysis and bioanalytical tools. Overall the investigated treatment train removed >97% estrogenicity, >99% herbicidal activity, and >96% baseline toxicity, confirming the suitability of the treatment train for polishing water for indirect potable reuse. The product water was indistinguishable from local tap water in all three bioassays. This study demonstrates the suitability and robustness of passive sampling linked with bioanalytical tools for semicontinuous monitoring of advanced water treatment with respect to micropollutant removal. [ABSTRACT FROM AUTHOR]