This work evaluated different advanced oxidation processes (AOPs) operated at pilot-scale as tertiary treatment of municipal wastewater in terms of energy efficiency, disinfection by-products ...formation and pathogens inactivation. Investigated AOPs included UV/H2O2, UV/Cl2, O3, O3/UV, H2O2/O3/UV, Cl2/O3/UV. AOPs were operated using various ozone doses (1.5–9 mg L−1), and UV fluences (191–981 mJ cm−2). Electrical energy costs necessary for the oxidation of contaminants of emerging concern (CEC) (i.e., carbamazepine, fluoxetine, gemfibrozil, primidone, sulfamethoxazole, trimethoprim) were calculated using the electrical energy per order (EEO) parameter. Ozonation resulted by far the most energy efficient process, whereas UV/H2O2 and UV/Cl2 showed the highest energy costs. Energy costs for AOPs based on the combination of UV and ozone were in the order O3/UV ≈ Cl2/O3/UV > H2O2/O3/UV, and they were significantly lower than energy costs of UV/H2O2 and UV/Cl2 processes. Cl2/O3/UV increased bromate formation, O3/UV and O3 had same levels of bromate formation, whereas H2O2/O3/UV did not form bromate. In addition, UV photolysis resulted an effective treatment for NDMA mitigation even in combination with ozone and chlorine in AOP technologies. Ozonation (doses of 1.5–6 mg L−1) was the least effective process to inactivate somatic coliphages, total coliform, escherichia coli, and enterococci. UV irradiation was able to completely inactivate somatic coliphages, total coliform, escherichia coli at low fluence (191 mJ cm−2), whereas enterococci were UV resistant. AOPs that utilized UV irradiation were the most effective processes for wastewater disinfection resulting in a complete inactivation of selected indicator organisms by low ozone dose (1.5 mg L−1) and UV fluence (191–465 mJ cm−2).
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•Ozonation was the most energy efficient AOP for micro-pollutants degradation.•Energy costs for O3/UV, H2O2/O3/UV, Cl2/O3/UV were lower than UV/H2O2 and UV/Cl2.•Bromate formation was highest in Cl2/O3/UV, whereas it was similar in O3 and O3/UV.•UV was effective for NDMA mitigation even in combination with ozone and chlorine.•AOPs using UV irradiation were the most effective processes for pathogens removal.
The adsorption breakthrough behavior of nine perfluoroalkyl substances (PFAS) in groundwaters by four bituminous coal-based granular activated carbons (F400, Carbsorb 40, HPC and CMR400) was studied ...using rapid small-scale column tests (RSSCTs). The half breakthrough bed volume (BV50), an indicator of apparent adsorption capacity, correlated with the hydrophobicity of PFAS at a given pH (i.e., Log Dow) for F400, indicating that hydrophobic interaction is important for apparent adsorption capacity of PFAS in groundwater with low dissolved organic concentrations (DOC < 1 mg C/L) and low specific UV absorbances at 254 nm (SUVA254 < 2 L mg−1m−1). Higher empty bed contact time (EBCT) caused steeper PFAS breakthrough curves with respect to throughput, but did not affect apparent adsorption capacity. Three different sizes of F400 (0.13, 0.17, and 0.20 mm) exhibited similar breakthrough profiles of PFAS, indicating that the intraparticle diffusivity was independent of adsorbent diameter in the given conditions. Among the tested carbons, the positively charged adsorbents (F400, HPC, and CMR400) showed higher apparent adsorption capacities for hydrophilic (Log Dow at pH 7 < 0) and marginally hydrophobic PFAS (Log Dow at pH 7 between 0 and 1) than the negatively charged adsorbent (Carbsorb 40). In addition, activated carbons with higher micropore surface areas exhibited higher apparent adsorption capacities of hydrophilic and marginally hydrophobic PFAS among the positively-charged activated carbons, whereas the mesoporous carbon (HPC) exhibited an increasingly larger adsorption capacity for more hydrophobic PFAS compared to the microporous carbon (F400) at a later breakthrough possibly due to less pore blockage.
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•Apparent adsorption capacity of PFAS was proportional to their hydrophobicity.•Overshoot concentrations were observed for hydrophilic short-chain PFBA and PFPeA.•Similar breakthrough profiles were observed among the tested adsorbent sizes.•Micropore surface area was important to determine apparent adsorption capacity.•Mesopores played increasingly important roles for hydrophobic PFAS adsorption.
The insect repellent diethyltoluamide (DEET) is among the most frequently detected organic chemical contaminants in water across a wide range of geographies from around the world. These observations ...are raising critical questions and increasing concerns regarding potential environmental relevance, particularly when the emergence of severe neurological conditions attributed to the Zika virus has increased the use of insect repellents. After dermal application, DEET is washed from the skin when bathing and enters the municipal sewer system before discharge into the environment. Mainly measured by gas chromatography or liquid chromatography coupled to mass spectrometry (GC‐MS or LC-MS), more than 200 peer-reviewed publications have already reported concentrations of DEET ranging ng/L to mg/L in several water matrices from North America, Europe, Asia, Oceania, and more recently Africa and South America. While conventional wastewater treatment technology has limited capacity of removal, advanced technologies are capable of better attenuation and could lower the environmental discharge of organic contaminants, including DEET. For instance, adsorption on activated carbon, desalinating membrane processes (nanofiltration and reverse osmosis), ozonation, and advanced oxidation processes can achieve 50% to essentially 100% DEET attenuation. Despite the abundant literature on the topic, the ubiquity of DEET in the environment still raises questions due to the apparent lack of obvious spatio-temporal trends in concentrations measured in surface water, which does not fit the expected usage pattern of insect repellents. Moreover, two recent studies showed discrepancies between the concentrations obtained by GC‐MS and LC-MS analyses. While the occurrence of DEET in the environment is well established, the concentrations reported should be interpreted cautiously, considering the disparities in methodologies applied and occurrence patterns observed. Therefore, this manuscript provides a critical overview of the origin of DEET in the environment, the relevant analytical methods, the occurrence reported in peer-reviewed literature, and the attenuation efficacy of water treatment processes.
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•DEET is detected in Africa, America, Asia, Europe and Oceania.•DEET is detected in all types of water matrices, from landfill leachate to drinking water.•Frequent detection of DEET in blanks•Advanced wastewater treatment can improve the attenuation of DEET.•An analytical interference or the occurrence of a mimic are not excluded when measuring DEET.
In environmental engineering and science, fluorescent excitation-emission matrix (EEM) has increasingly been utilized to characterize chromophoric dissolved organic matter (CDOM). This study aims to ...delineate EEM data processing, including calculation of total fluorescence (TF) which is an emerging water quality parameter often used as a surrogate for micropollutant removal by advanced water treatment processes. In addition, sample handling procedures such as storage, use of preservatives, and oxidant quenching agents were evaluated. In this study, three antimicrobial preservatives were tested: sodium azide, sodium omadine, and thymol. All the tested preservatives altered optical properties of samples, and were therefore not suitable for the preservation of EEM samples. Without preservative, storage of samples at 4 °C maintained TF within 7.5% of its original value for 21 days, while TF of samples stored at the room temperature more drastically changed (up to 15%). The impacts of three oxidant quenching agents including ascorbic acid, sodium bisulfite, and sodium thiosulfate on EEM were also tested. Among the quenching agents, sodium bisulfite was found to be suitable since it little influenced optical properties of samples while the other two were not favorable due to interference. We also scrutinized the use of TF as surrogate to monitor micropollutant rejection by nanofiltration membrane.
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•Commonly applied biocides can negatively impact the fluorescence EEM surrogate.•Sodium bisulfite was determined to be the most appropriate oxidant quenching agent for EEM.•Recycled water samples were stable in terms of EEM when stored at 4 °C for 21-days.•Fluorescence is a powerful surrogate for monitoring nanofiltration processes.
Increasing chemical pollution of aquatic environments is a growing concern with global relevance. A large number of organic chemicals are termed as “micropollutants” due to their low concentrations, ...and long-term exposure to micropollutants may pose considerable risks to aquatic organisms and human health. In recent decades, numerous treatment methods and technologies have been proposed to remove micropollutants in water, and typically several micropollutants were chosen as target pollutants to evaluate removal efficiencies. However, it is often unclear whether their toxicity and occurrence levels and frequencies enable them to contribute significantly to the overall chemical pollution in global aquatic environments. This review intends to answer an important lingering question: Which micropollutants or class of micropollutants deserve more attention globally and should be removed with higher priority? Different risk-based prioritization approaches were used to address this question. The risk quotient (RQ) method was found to be a feasible approach to prioritize micropollutants in a large scale due to its relatively simple assessment procedure and extensive use. A total of 83 prioritization case studies using the RQ method in the past decade were compiled, and 473 compounds that were selected by screening 3466 compounds of three broad classes (pharmaceuticals and personal care products (PPCPs), pesticides, and industrial chemicals) were found to have risks (RQ > 0.01). To determine the micropollutants of global importance, we propose an overall risk surrogate, that is, the weighted average risk quotient (WARQ). The WARQ integrates the risk intensity and frequency of micropollutants in global aquatic environments to achieve a more comprehensive priority determination. Through metadata analysis, we recommend a ranked list of 53 micropollutants, including 36 PPCPs (e.g., sulfamethoxazole and ibuprofen), seven pesticides (e.g., heptachlor and diazinon), and 10 industrial chemicals (e.g., perfluorooctanesulfonic acid and 4-nonylphenol) for risk management and remediation efforts. One caveat is that the ranked list of global importance does not consider transformation products of micropollutants (including disinfection byproducts) and new forms of pollutants (including antibiotic resistance genes and microplastics), and this list of global importance may not be directly applicable to a specific region or country. Also, it needs mentioning that there might be no best answer toward this question, and hopefully this review can act as a small step toward a better answer.
This review summarizes major findings over the last decade related to N-Nitrosodimethylamine (NDMA) in water and wastewater. In particular, the review is focused on the removal of NDMA and of its ...precursors by conventional and advanced water and wastewater treatment processes. New information regarding formation mechanisms and precursors are discussed as well. NDMA precursors are generally of anthropogenic origin and their main source in water have been recognized to be wastewater discharges. Chloramination is the most common process that results in formation of NDMA during water and wastewater treatment. However, ozonation of wastewater or highly contaminated surface water can also generate significant levels of NDMA. Thus, NDMA formation control and remediation has become of increasing interest, particularly during treatment of wastewater-impacted water and during potable reuse application. NDMA formation has also been associated with the use of quaternary amine-based coagulants and anion exchange resins. UV photolysis with UV fluence far higher than typical disinfection doses is generally considered the most efficient technology for NDMA mitigation. However, recent studies on the optimization of biological processes offer a potentially lower-energy solution. Options for NDMA control include attenuation of precursor materials through physical removal, biological treatment, and/or deactivation by application of oxidants. Nevertheless, NDMA precursor identification and removal can be challenging and additional research and optimization is needed. As municipal wastewater becomes increasingly used as a source water for drinking, NDMA formation and mitigation strategies will become increasingly more important. The following review provides a summary of the most recent information available.
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•The primary source of NDMA precursors in surface water are municipal wastewater discharges.•Chloramination and ozonation are the most common source of occurrence of NDMA in water.•UV irradiation at doses above disinfection are most commonly employed for NDMA removal.•Optimized biological treatment processes are also efficient for reducing NDMA concentrations.•NDMA precursor attenuation remains challenging and requires additional research.
A fully automated online solid-phase extraction (SPE) with directly coupled liquid chromatography–tandem mass spectrometry (LC–MS/MS) method for analysis of 34 trace organic compounds in diverse ...water matrices has been developed. The current method offers several advantages over traditional offline SPE methods including low sample volume (1.7mL), decreased solvent use, higher throughput, and increased reproducibility. The method uses simultaneous positive and negative ESI for analysis of all compounds in one injection, which reduces cycle time (extraction+analysis) to <15min. Method optimization included testing different online SPE cartridges, mobile phase compositions, and flow rates. The method detection limits (MDLs) ranged from 0.1 to 13.1ng/L with 80% of the compounds having an MDL <5ng/L. Matrix spike recoveries in three different water qualities were evaluated and ranged from 61.2% to145.1% with 95% of the recoveries ranging between 70–130%. As part of the method validation studies, linearity (0.9911–0.9998), intra-day variability (1.0–10.4%), inter-day variability (1.0–11.9%), and matrix effects were also assessed. The use of 26 isotopically-labeled standards increased the reliability of the method while retention time locking and use of two transitions for most compounds increased the specificity. The applicability of the method was tested on samples across treatment points from two wastewater plants, a septic tank, surface water and groundwater.
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•A fully-automated online SPE LC-MS/MS method for analysis of 34 TOrCs has been developed.•Simultaneous ESI+ and − allows for analysis in 1 injection and reduced cycle time of <15min.•Method detection limits range from 0.1–13.1ng/L.
The presence of pharmaceuticals, hormones, pesticides and industrial contaminants collectively termed as trace organic compounds (TOrCs) in wastewater has been well-documented in USA, Europe, China ...and other regions. However, data from India, the second most populous country in the world is severely lacking. This study investigated the occurrence and concentrations of twenty-two indicator TOrCs at three wastewater treatment plants (WWTPs) in South India serving diverse communities across three sampling campaigns. Samples were collected after each WWTP treatment unit and removal efficiencies for TOrCs were determined. Eleven TOrCs were detected in every sample from every location at all sites, while only five TOrCs were detected consistently in effluent samples. Caffeine was present at greatest concentration in the influent of all three plants with average concentrations ranging between 56 and 65μg/L. In contrast, the x-ray contrast media pharmaceutical, iohexol, was the highest detected compound on average in the effluent at all three WWTPs (2.1–8.7μg/L). TOrCs were not completely removed in the WWTPs with removal efficiencies being compound specific and most of the attenuation being attributed to the biological treatment processes. Caffeine and triclocarban were well removed (>80%), while other compounds were poorly removed (acesulfame, sucralose, iohexol) or maybe even formed (carbamazepine) within the WWTPs. The effluent composition of the 22 TOrCs were similar within the three WWTPs but quite different to those seen in the US, indicating the importance of region-specific monitoring. Diurnal trends indicated that variability is compound specific but trended within certain classes of compounds (artificial sweeteners, and pharmaceuticals). The data collected on TOrCs from this study can be used as a baseline to identify potential remediation and regulatory strategies in this understudied region of India.
•Elevated levels of pharmaceuticals, artificial sweeteners and TOrCs measured in 3 WWTPs in Chennai, India•Iodinated x-ray contrast media reprepsent the highest contribution of wastewater indicators in the effulent•Different trends in TOrC concentrations compared to USA, Europe and other places around the globe•Artificial sweeteners showed clear diurnal changes in concentration•Iohexol was present in all there WWTP effluents ranging from 2 to 9µg/L
•Landfill leachates were analyzed to pollutants commonly associated with wastewater effluents.•Concentration of pollutants ranged several orders of magnitude (ngmgL−1).•Preliminary mass balance ...completed to estimate contribution of leachate to WWTPs.•Landfill leachate maybe an significant source of environmental pollution.
Landfill leachate samples (n=11) were collected from five USA municipal solid waste (MSW) landfills and analyzed for ten trace organic pollutants that are commonly detected in surface and municipal wastewater effluents (viz., carbamazepine, DEET, fluoxetine, gemfibrozil, PFOA, PFOS, primidone, sucralose, sulfamethoxazole and trimethoprim). Carbamazepine, DEET, PFOA and primidone were detected in all leachate samples analyzed and gemfibrozil was detected in samples from four of the five-landfill sites. The contaminants found in the highest concentrations were DEET (6900–143000ngL−1) and sucralose (<10–621000ngL−1). Several compounds were not detected (fluoxetine) or detected infrequently (sulfamethoxazole, trimethoprim and PFOS). Using the average mass of DEET in leachate amongst the five landfills and scaling the mass release from the five test landfills to the USA population of landfills, an order of magnitude estimate is that over 10000kg DEETyr−1 may be released in leachate. Some pharmaceuticals have similar annual mean discharges to one another, with the estimated annual discharge of carbamazepine, gemfibrozil, primidone equating to 53, 151 and 128kgyear−1. To the authors knowledge, this is the first time that primidone has been included in a landfill leachate study. While the estimates developed in this study are order of magnitude, the values do suggest the need for further research to better quantify the amount of chemicals sent to wastewater treatment facilities with landfill leachate, potential impacts on treatment processes and the significance of landfill leachate as a source of surface water contamination.
Conventional water resources in many regions are insufficient to meet the water needs of growing populations, thus reuse is gaining acceptance as a method of water supply augmentation. Recent ...advancements in membrane technology have allowed for the reclamation of municipal wastewater for the production of drinking water, i.e., potable reuse. Although public perception can be a challenge, potable reuse is often the least energy-intensive method of providing additional drinking water to water stressed regions. A variety of membranes have been developed that can remove water contaminants ranging from particles and pathogens to dissolved organic compounds and salts. Typically, potable reuse treatment plants use polymeric membranes for microfiltration or ultrafiltration in conjunction with reverse osmosis and, in some cases, nanofiltration. Membrane properties, including pore size, wettability, surface charge, roughness, thermal resistance, chemical stability, permeability, thickness and mechanical strength, vary between membranes and applications. Advancements in membrane technology including new membrane materials, coatings, and manufacturing methods, as well as emerging membrane processes such as membrane bioreactors, electrodialysis, and forward osmosis have been developed to improve selectivity, energy consumption, fouling resistance, and/or capital cost. The purpose of this review is to provide a comprehensive summary of the role of polymeric membranes and process components in the treatment of wastewater to potable water quality and to highlight recent advancements and needs in separation processes. Beyond membranes themselves, this review covers the background and history of potable reuse, and commonly used potable reuse process chains, pretreatment steps, and advanced oxidation processes. Key trends in membrane technology include novel configurations, materials, and fouling prevention techniques. Challenges still facing membrane-based potable reuse applications, including chemical and biological contaminant removal, membrane fouling, and public perception, are highlighted as areas in need of further research and development.
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