Disinfection By-products Research Articles

Regulated 1-2 Carbon Disinfection Byproducts do not Correlate with Cytotoxicity with Increasing Disinfectant Contact Time During Chlorination, Chlorination Followed by Chloramination or Granular Activated Carbon Followed by Chlorination.

Regulations typically use four trihalomethanes (THM4) and five haloacetic acids (HAA5) as metrics of consumer exposure to disinfection byproducts (DBPs) and their chronic health risks. Their use as exposure metrics assumes that their concentrations correlate with DBP-associated toxicity. For a chlorine-disinfected surface water, this study demonstrates that increasing chlorine contact time from 1 to 7 days was associated with a 62-76% increase in THM4 and HAA5 but a 40-47% decrease in total cytotoxicity. Thus, the use of THM4 and HAA5 may divert regulatory attention away from the low water age sections of distribution systems near treatment facilities that may feature the highest cytotoxicity but lowest THM4/HAA5 concentrations. Among common options to reduce THM4/HAA5, this study also shows that chlorine disinfection followed by chloramines for maintaining a distribution system residual did not substantially reduce cytotoxicity. Granular activated carbon followed by chlorine reduced cytotoxicity by 28-80%, even at the lowest water ages where cytotoxicity was maximized. These findings highlight the need to identify DBPs that better correlate with toxicity than THM4/HAA5 to serve as metrics of exposure. These metrics could help identify distribution system locations exhibiting higher consumer risk and develop modifications to disinfection systems that effectively reduce consumer risk.

Ethylhexyl triazone sunscreen and its disinfection byproducts obtained after chlorine treatment: Ecofriendliness or ecotoxicity?

In recent years, there has been a growing demand for high-quality sunscreens that combine high efficacy with ecological characteristics. This trend has led to an increased use of triazine compounds, which represent an emerging class of UV filters. While it is well-established that sunscreens can have significant environmental impacts, there is limited data on the degradation of triazine UV filters, despite available information on their environmental persistence, particularly in relation to disinfection processes. This study investigates the chemical fate of ethylhexyl triazone (EHT) under chlorination conditions, typical of swimming pools. Twelve disinfection byproducts (DBPs) were isolated and fully identified using nuclear magnetic resonance and mass spectrometry, with three of these byproducts being identified for the first time. DBP1–DBP12 were isolated at relative percentages of 1.26, 9.68, 1.05, 0.42, 0.84, 3.37, 3.58, 1.89, 0.84, 1.47, 0.42, and 0.63. Additionally, a mechanism for their formation was proposed. The ecotoxicological assessment of EHT and of byproducts (DBP1-DBP4) was conducted using acute, sub-chronic or chronic toxicity tests in producers and primary consumers of the freshwater trophic chain. The organisms included the alga Raphidocelis subcapitata, the rotifer Brachionus calyciflorus, the crustacean anostracan Thamnocephalus platyurus and the benthic ostracod Heterocypris incongruens. EHT caused a lethal median concentration in rotifers, with values in the range of tens of mg/L. EHT, DBP1, and DBP4 exhibited sub-chronic effects in ostracods at concentrations in the μg/L range, with EC50s of 210, 9, 20 μg/L, respectively. Rotifers were slightly affected by DBP3 with a chronic EC50 of 200 μg/L. Algae were not affected by either EHT or byproducts.

Estro-Androgenic Disrupting Effects of Halogenated Disinfection Byproducts: A Comprehensive Evaluation and Comparison.

Drinking water halogenated disinfection byproducts (DBPs) have become an increasing health concern. However, the endocrine-disrupting effects of DBPs have not been well evaluated, and the limited available data have inhibited a comprehensive understanding of their health risks. In this study, a total of 43 DBPs were evaluated for their estro-androgenic effects using two types of human breast cancer cells. Among the tested DBPs, 16 exhibited estrogenic/antiestrogenic/androgenic/antiandrogenic effects, and the effects could be observed even at concentrations typically detected in drinking water. Iodinated and polyhalogenated DBPs generally showed higher effects than other species. For a broader comparison, DBP endocrine-disrupting effect data from this study and previous studies were summarized. It was found that the endocrine disruption efficacy of DBPs followed the rank order of iodinated > brominated > chlorinated species, and halophenolic DBPs were potential endocrine-disrupting compounds. Moreover, molecular docking results demonstrated that the binding of DBPs to estro-androgenic receptors was dominated by hydrophobic bonding, hydrogen bonding, halogen bonding, and van der Waals forces. The force strength and molecular volume were related to the magnitude of the estro-androgenic effects. Iodinated DBPs and polyhalogenated DBPs tended to have larger binding forces than other analogues and thus exhibited stronger effects.

Chlorination of Biopterin in Water: Deciphering the Kinetics, Disinfection Byproducts, and Toxicity.

Pterins, including biopterin prevalent during cyanobacterial blooms, are nitrogen-containing heterocyclic compounds ubiquitous in both natural and engineered environments. However, their roles and associated human risks in water treatment remain poorly understood. This study systematically investigated the kinetics, disinfection byproducts (DBPs), and toxicity of biopterin in chlorination. For deciphering the reaction kinetics, 1,3,5-trimethoxybenzene proved to be a more effective chlorine quencher than the commonly used reducing agents, as it preserved N-chlorinated intermediates without reversing them back to biopterin. The pH-dependent kinetics demonstrated that both chlorine and biopterin species had a significant influence on the reaction rates, with deprotonated biopterin exhibiting a markedly higher reactivity toward HClO/ClO-. Based on time-of-flight mass spectrometry, ten transformation products (TPs) including seven halogenated N-Cl ones, have been identified for the first time. These cyclic TPs were transformed into various aliphatic carbonaceous and nitrogenous DBPs during the subsequent chlorination process. Notably, theoretical predictions and the luminescent bacteria assay confirmed potential higher toxicities of these products than biopterin. These findings highlight the potential risks of pterins during water disinfection and provide a reference framework for accurately revealing the chlorination behavior of emerging nitrogenous chemicals.

Wane-and-wax mechanism of nitrogenous disinfection byproducts with constant Cl/N peak under UV/chlorine treatment: Implication for new drinking water disinfection strategy

Nitrogenous disinfection byproducts (N-DBPs) are notorious for their serious health risks, yet nitrate (NO3-) mediates N-DBPs generation during UV/chlorine treatment remains unexplored. This study investigated the interaction of chlorine and NO3- on N-DBPs formation and developed a specific fragment-based screening method using UPLC-QTOF-MS to explore the underlying mechanism. Results showed that the chlorine-to-nitrogen (Cl/NO3--N) molar ratio significantly affects dichloroacetonitrile (DCAN) and dichloroacetamide (DCAM) generation, with peak concentrations at a Cl/NO3--N molar ratio of around 15. NO3- promotes the production of HO•, which positively correlates with DCAN and DCAM concentrations, also peaking at this ratio. Utilizing our developed method, three key hydroxyl-substituted intermediates that circumvent the previously reported “limiting-steps” in DCAN formation were identified. This reaction proceeds via a stepwise mechanism involving hydroxylation and chlorine substitution to produce hydroxyl-phenylacetonitrile and hydroxyl-chlorine-phenylacetonitrile. The conversion rate of hydroxyl-chlorine-phenylacetonitrile to DCAN was 8.6 times higher at Cl/NO3--N molar ratio of 15 compared to conditions without NO3-, attributed to the weakened bond strength of the side chain, as supported by density functional theory calculations. This study provides novel insights into the mechanistic pathways of DCAN and DCAM formation, critical for developing more effective drinking water disinfection technologies to control N-DBPs.

Trihalomethane Formation Potential at the Barekese Water Treatment Plant and the Related Cancer Risk to Consumers in the Kumasi Metropolis of Ghana

The prevalence of disinfection by-products in drinking water supplies is a global concern due to their carcinogenicity. However, the monitoring of DBPs such as trihalomethanes (THMs) and haloacetic acids (HAAs) in drinking water supplies is non-existent in many developing Asian, South American, and African countries. The formation of THMs during disinfection arises from a reaction between the disinfectant and natural organic matter in the water, particularly, dissolved organic carbon (DOC). This reaction is hastened by increases in temperature, high levels of disinfectant doses or residual, elevated water pH, long disinfection contact times, and high DOC concentrations. However, the inclusion of a granular activated carbon adsorption process in the water treatment process is the most effective method for the removal of the main precursor (DOC) for the formation of THMs in treated water. The Barekese WTP, which disinfects with chlorine, has no adsorption process for DOC removal, and supplies over 80% of pipe-borne water to the city of Kumasi in Ghana, was assessed for the THM formation potential (THMFP). A THM predictive model was used to determine the potential THM concentration in the final water. The THMFP at the Barekese WTP ranged between 22.42 and 38.94 µg/L, which was below the 100 µg/L threshold set by the WHO. The lifetime average daily doses were 3.9494 × 10−4 µg/Kg/d and 3.9294 × 10−4 µg/Kg/d for male and female consumers, respectively. The lifetime integrative cancer risks associated with consumption of the water were 1.817 × 10−5 and 1.808 × 10−5 for males and females, respectively. The cancer risk posed was acceptably low. However, direct measurement of DBPs is required to corroborate these findings and verify the cancer risk posed to the consumers of treated water from the Barekese WTP to inform policies, regulations, public health interventions, and investment.

Cancer incidence associations with drinking water arsenic levels and disinfection methods in Maine, USA

ABSTRACT Maine is a largely rural state where nearly half of the population uses drinking water from private wells. Arsenic (As) is present in some groundwater in the state and has been linked to cancer, and a lack of testing and treatment may expose people with private wells to elevated As levels. Disinfection byproducts (DBPs) include known and suspected carcinogens that form when chlorine or chloramines are added to water. People served by public water systems may be exposed to elevated levels of regulated DBPs such as trihalomethanes and haloacetic acids associated with chlorine and/or unregulated nitrogenous DBPs, or N-DBPs, such as nitrite and N-nitrosodimethylamine associated with chloramines. Contrary to initial expectations, there were no significant associations between median town As in well water and bladder, lung, kidney, or skin cancer incidence. Furthermore, bladder, melanoma, and other skin cancer incidence rates were negatively correlated with the percent of the town population using private wells. Analysis of cancer incidence associated with chlorine and chloramine disinfection showed elevated melanoma, and other skin cancer with chloramine use and elevated bladder and non-melanoma skin cancer with chlorine use compared to the no disinfectant case. We recommend more research on the links between disinfectant use and cancer.

A convenient reduction method for the detection of low concentration free available chlorine——utilizing sodium sulfite as a quencher

Chlorine, serving as the mainstream disinfectant, can react with dissolved organic matter (DOM) to form undeserved disinfection by-products (DBPs). Free available chlorine (FAC) concentration is crucial to ensure effective disinfection while minimizing the formation of toxic DBPs. In this study, we propose a convenient method using sodium sulfite (Na2SO3) to reduce oxidized chlorine in FAC. The molar concentration of reduced chloride ion (Cl−) was quantified directly by ion chromatography to reflect FAC concentration. Compared with common FAC detection techniques including DPD colorimetry, iodometric, and UV methods, this novel reduction method exhibits a lower detection limit and is more resistant to interference. Common water matrices, such as DOM and anions did not affect the method accuracy (< 3.6%). Furthermore, carbonaceous DBPs (C-DBPs) like regulated trihalomethanes and halogenacetic acids, unregulated aromatic chlorophenols, did not interfere with the determination of FAC by using this reduction method. This lack of interference can be attributed to the low redox potential of Na2SO3, which does not readily react with these C-DBPs. However, nitrogenated DBPs (N-DBPs) like dichloroacetonitrile displayed slight interference (the effect of common dichloroacetonitrile concentration in water on FAC was less than 0.0007 μM). This suggests that this method is well-suited for determining FAC in chlorination processes where the C-DBPs predominated. Overall, the reduction method enables precise determination of FAC and proves valuable in assessing residual chlorine levels in both laboratory and real disinfected water samples dominated by C-DBPs.

The key to 2,6-dichloro-1,4-benzoquinone reproductive toxicity and green tea detoxification: Covalent binding and competitive binding

Halobenzoquinones (HBQs) are ubiquitous disinfection by-products (DBPs) in chlorinated drinking water with various health risks including reproductive toxicity, while the potential mechanisms are still unclear. Although green tea exhibits common detoxifying properties, its ability to mitigate the toxicity of HBQs still needs to be further deepened and explored. This study attempted to investigate the possible mechanism of the most common HBQ, 2,6-dichloro-1,4-benzoquinone (2,6-DCBQ) induced reproductive toxicity and elucidate the protective effect of green tea using a series of liquid chromatography-tandem mass spectrometry (LC-MS) approaches. Firstly, in vivo experiments showed that 2,6-DCBQ could induce testicular damage in male rats via significantly decreasing sperm-associated Leydig cells and seminiferous tubules. Then, in vitro incubation of 2,6-DCBQ with amino acids suggested that 2,6-DCBQ could bind to proteins via residues of cysteine or lysine and provided five additional modification patterns. Following, proteomics analysis revealed that at least 42 proteins were modified by 2,6-DCBQ, which were mainly enriched in the reproductive system. These results highlighted the significance of covalent protein modification in 2,6-DCBQ reproductive toxicity. Fortunately, we found that catechins (a class of major components of green tea) could competitively bind to 2,6-DCBQ in vivo and in vitro, reducing the amount and type of 2,6-DCBQ-protein adducts, thereby attenuating the reproductive system damage caused by 2,6-DCBQ. This study provides new insights into 2,6-DCBQ-induced reproductive system damage and reveals a new mechanism of green tea detoxification. Moreover, these findings offer potential strategies for alleviating the harmful impacts of environmental toxicants on human health.

Optimizing natural organic matter removal at the Koka water treatment plant, Ethiopia, using soil–alum composite material

ABSTRACT Conventional water treatment methods often fail to remove natural organic matter (NOM), leading to the formation of harmful disinfection by-products in chlorinated water. This study aimed to develop a synergistic, local soil–aluminum sulfate (alum) composite material to enhance NOM removal from real water samples. Locally derived soil (Chalaltu) samples were collected from selected locations and subjected to thermal treatment at elevated temperatures. The thermally treated soil was then combined with alum at varying mixing percentages to create the composite material. The synthesized composite materials were thoroughly characterized using X-ray diffraction, X-ray fluorescence, scanning electron microscopy, Fourier transform infrared, and Brunauer–Emmett–Teller techniques. The alum-treated soil, obtained through thermal treatment at 500 °C with a mixing ratio of 50%, a dosage of 25 mg/L, and a settling time of 25 min, exhibited impressive removal efficiencies. The composite material increased removal efficiency by 1.5 times for both UV254 absorbance (91.1%) and dissolved organic carbon (90%), while reducing the alum dose by 58% compared to the existing Koka water treatment plant process. Reducing alum usage could lead to cost savings and alleviate concerns about its association with Alzheimer's disease. This technique is essential within the context of water treatment technology.

The Generation of ROS by Exposure to Trihalomethanes Promotes the IκBα/NF-κB/p65 Complex Dissociation in Human Lung Fibroblast.

Background: Disinfection by-products used to obtain drinking water, including halomethanes (HMs) such as CH2Cl2, CHCl3, and BrCHCl2, induce cytotoxicity and hyperproliferation in human lung fibroblasts (MRC-5). Enzymes such as superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) modulate these damages through their biotransformation processes, potentially generating toxic metabolites. However, the role of the oxidative stress response in cellular hyperproliferation, modulated by nuclear factor-kappa B (NF-κB), remains unclear. Methods: In this study, MRC-5 cells were treated with these compounds to evaluate reactive oxygen species (ROS) production, lipid peroxidation, phospho-NF-κB/p65 (Ser536) levels, and the activities of SOD, CAT, and GPx. Additionally, the interactions between HMs and ROS with the IκBα/NF-κB/p65 complex were analyzed using molecular docking. Results: Correlation analysis among biomarkers revealed positive relationships between pro-oxidant damage and antioxidant responses, particularly in cells treated with CH2Cl2 and BrCHCl2. Conversely, negative relationships were observed between ROS levels and NF-κB/p65 levels in cells treated with CH2Cl2 and CHCl3. The estimated relative free energy of binding using thermodynamic integration with the p65 subunit of NF-κB was -3.3 kcal/mol for BrCHCl2, -3.5 kcal/mol for both CHCl3 and O2•, and -3.6 kcal/mol for H2O2. Conclusions: Chloride and bromide atoms were found in close contact with IPT domain residues, particularly in the RHD region involved in DNA binding. Ser281 is located within this domain, facilitating the phosphorylation of this protein. Similarly, both ROS interacted with the IPT domain in the RHD region, with H2O2 forming a side-chain oxygen interaction with Leu280 adjacent to the phosphorylation site of p65. However, the negative correlation between ROS and phospho-NF-κB/p65 suggests that steric hindrance by ROS on the C-terminal domain of NF-κB/p65 may play a role in the antioxidant response.

Insights into water insecurity in Indigenous communities in Canada: assessing microbial risks and innovative solutions, a multifaceted review.

Canada is considered a freshwater-rich country, despite this, several Indigenous reserves struggle with household water insecurity. In fact, some of these communities have lacked access to safe water for almost 30 years. Water quality in Canadian Indigenous reserves is influenced by several factors including source water quality, drinking water treatments applied, water distribution systems, and water storage tanks when piped water is unavailable. The objective of this multifaceted review is to spot the challenges and consequences of inadequate drinking water systems (DWS) and the available technical and microbiological alternatives to address water sanitation coverage in Indigenous reserves of Canada, North America (also known as Turtle Island). A comprehensive literature review was conducted using national web portals from both federal and provincial governments, as well as academic databases to identify the following topics: The status of water insecurity in Indigenous communities across Canada; Microbiological, chemical, and natural causes contributing to water insecurity; Limitations of applying urban-style drinking water systems in Indigenous reserves in Canada and the management of DWS for Indigenous communities in other high-income countries; and the importance of determining the microbiome inhabiting drinking water systems along with the cutting-edge technology available for its analysis. A total of 169 scientific articles matched the inclusion criteria. The major themes discussed include: The status of water insecurity and water advisories in Canada; the risks of pathogenic microorganisms (i.e., Escherichia coli and total coliforms) and other chemicals (i.e., disinfection by-products) found in water storage tanks; the most common technologies available for water treatment including coagulation, high- and low-pressure membrane filtration procedures, ozone, ion exchange, and biological ion exchange and their limitations when applying them in remote Indigenous communities. Furthermore, we reviewed the benefits and drawbacks that high throughput tools such as metagenomics (the study of genomes of microbial communities), culturomics (a high-efficiency culture approach), and microfluidics devices (microminiaturized instruments) and what they could represent for water monitoring in Indigenous reserves. This multifaceted review demonstrates that water insecurity in Canada is a reflection of the institutional structures of marginalization that persist in the country and other parts of Turtle Island. DWS on Indigenous reserves are in urgent need of upgrades. Source water protection, and drinking water monitoring plus a comprehensive design of culturally adapted, and sustainable water services are required. Collaborative efforts between First Nations authorities and federal, provincial, and territorial governments are imperative to ensure equitable access to safe drinking water in Indigenous reserves.

Formation and estimated cytotoxicity of trihalomethanes and haloacetic acids during ozonation of nonylphenol in bromide-containing water after chlorination process: Impact of ozonation initial pH

The presence of nonylphenol (NP) in bromide-containing water contributed to the formation of regulated disinfection by-products (DBPs): trihalomethanes-4 (THM4) and haloacetic acids-5 (HAA5). This study investigates the effects of ozonation pH on the degradation of NP, DBP formation, and DBP-estimated cytotoxicity. The ozonation pH was varied to 5, 7, and 9 to determine the effect of acidic, neutral, and alkaline conditions. The increase of ozonation initial pH improved the NP degradation. Ozonation of all initial pH conditions could decrease TCM, BDCM, and BDCM formation but increase the TBM formation at alkaline conditions. The formation of mono-HAA5 on the other hand, increased at all ozonation initial pH. Ozonation at acidic and neutral initial conditions can reduce the estimated cytotoxicity of the total formation of THM4 and HAA5 by 74.34 % and 93.31 %, respectively. In contrast, DBP's estimated cytotoxicity was raised by 33.72 % upon ozonation at an initial pH of alkaline. According to the study's findings, lowering the cytotoxicity of DBPs in acidic or alkaline environments can be achieved without changing the ozonation's pH. Based on these findings, pH changes are not required to reduce DBP during ozonation of NP-bromide-containing water. Future research on the impact of natural organic matter is recommended to investigate ozonation's capacity to reduce DBP production during ozonation of NP-containing natural water.

The Safe Drinking Water Act at 50: Another Identity Crisis

Key TakeawaysThe Safe Drinking Water Act (SDWA) of 1974 (amended in 1986, 1996, and 2018) shows the tension between purity and safety, cost and benefits, and balancing risks, down to today's policy debates.Following the 1996 amendments, regulatory successes include arsenic, radionuclides, filter backwash recycling, total coliform, disinfectants and disinfection byproducts, and enhanced surface water treatment.With recent drinking water standards, such as the 2024 per‐ and polyfluoroalkyl substances rule, based on very low detection levels, the SDWA continues to generate intense public dialogue.

Ozone disinfection of waterborne pathogens: A review of mechanisms, applications, and challenges.

Water serves as a critical vector for the transmission of pathogenic microorganisms, playing a pivotal role in the emergence and propagation of numerous diseases. Ozone (O3) disinfection technology offers promising potential for mitigating the spread of these pathogens in aquatic environments. However, previous studies have only focused on the inactivated effect of O3 on a single pathogenic microorganism, lacking a comprehensive comparative analysis of various influencing factors and different types of pathogens, while the cost-effectiveness of O3 technology has not been mentioned. This review synthesized the migration characteristics of various pathogenic microorganisms in water bodies and examined the properties, mechanisms, and influencing factors of O3 inactivation. It evaluated the efficacy of O3 against diverse pathogens, namely bacteria, viruses, protozoa, and fungi, and provided a comparative analysis of their sensitivities to O3. The formation and impact of harmful disinfection by-products (DBPs) during the O3 inactivation process were assessed, alongside an analysis of the cost-effectiveness of this method. Additionally, potential synergistic treatment processes involving O3 were proposed. Based on these findings, recommendations were made for optimizing the utilization of O3 in water inactivation in order to formulate better inactivation strategies in the post-pandemic eras.

Probing the role of BrCl in benzotriazole transformation during seawater chlorination

A common understanding attributes the formation of brominated disinfection by-products (Br-DBPs) in seawater chlorination to the conversion of hypochlorous acid to hypobromous acid (HOBr) by bromide. In this study, we reveal that bromine chloride (BrCl), mediated by both chloride and bromide in seawater, plays a dominant role in the transformation of 1H-benzotriazole (BTA) and 5-methyl-1H-benzotriazole (MBTA) and in the formation of brominated DBPs. Using anisole as a reference compound, the second-order rate constant for the reaction of BrCl with BTA was determined to be (2.65 ± 0.13) × 105 L mol−1 s−1, which is over 30,000 times higher than that for the reaction between HOBr and BTA. Ten brominated products were identified and showed a successive bromination pattern. The bromination reaction mechanism was elucidated through theoretical calculations, and the pathways were proposed. The concentrations of brominated BTA and MBTA in seawater were 5.7 and 7.9 times higher than in bromide-only solutions, respectively. BrCl significantly promoted brominated product generation and increased the toxicity of blended DBPs. These results suggest that focusing solely on bromide's effect on brominated product generation may significantly underestimate the potential for DBP formation during seawater chlorination.

Aromatic Structures Govern the Formation of Chlorinated Byproducts in Dichlorine Radical Reactions.

Radical-induced disinfection byproduct (DBP) formation is drawing attention with increasing applications of advanced oxidation processes (AOPs). Cl2•- represents one of the extensively generated radicals in AOPs, whose behavior in DBP formation remains unknown. In this study, we found that aromatic structures serve as the main DBP precursors in Cl2•- reactions by employing diverse groups of model compounds. At a typical Cl2•- exposure of 1.2 × 10-9 M·s, the sum concentrations of 7 regulated aliphatic DBPs (e.g., trichloromethane, chloroacetic acids) are ∼0.10 to 0.48 μM for aromatic precursors and <0.05 μM for aliphatic ones. The DBP formation mechanisms from Cl2•- reactions involved the formation of chlorinated aromatics, radical-induced oxygen incorporation followed by ring cleavage, and the interactions of Cl2•- with ring-cleavage intermediates. In reacting with DOM, Cl2•- reactions produced much fewer aliphatic DBPs (5% of the total organochlorine vs 40% for chlorination) and chloroacetic acids dominated the aliphatic DBPs (usually trihalomethane for chlorination), which can be well interpreted by the precursors and mechanisms proposed. This work comprehensively reveals the precursors, formation patterns, and mechanisms of DBPs during the less-studied Cl2•- reactions, highlighting the importance of eliminating the aromatic structures of DOM before the AOPs.

Ultraviolet/dielectric barrier discharge enhanced ultrafiltration for treating natural water: Performance, mechanism and iodinated disinfection by-product fate

This study employed ultraviolet (UV)/ dielectric barrier discharge (DBD) pre-treatment to mitigate ultrafiltration membrane fouling and enhance the purification efficiency of natural surface water. Moreover, as an emerging contaminant, the iodinated disinfection by-products’ fate and degradation performance were discussed. The investigation revealed that the generation of numerous active species (⋅OH, ⋅O2−, 1O2, etc) under high input voltage and low pH conditions were advantageous for augmenting membrane flux, with sodium sulfate electrolyte playing a role in promoting the formation of selective sulfate radicals. Fluorescence excitation-emission matrix spectroscopy indicated that the UV/DBD system at 5.5 kV can effectively degrade proteins and humic substances in surface water, leading to an enhancement in water quality. With the assistance of UV radiation, macromolecular organic matter underwent extensive decomposition into smaller molecules, thus creating an ideal environment for controlling membrane fouling in the UV/DBD system. Additionally, it was identified the intermediate products and degradation pathways during iopamidol degradation by UV/DBD. It also affirmed the minimal risk of disinfection by-product generation with this strategy. The study provides a viable and efficient pre-treatment approach for mitigating membrane fouling and purifying water.

Making waves: Intelligent phage cocktail design, a pathway to precise microbial control in water systems

Current practices in water and wastewater treatment to control unwanted microbes have led to new problems, including health effects from disinfection byproducts, growth of opportunistic pathogens resistant to residual disinfectants (e.g., chlorine), and antibiotic resistance. These challenges are spurring interest in rethinking our practices of microbial control. Simultaneously, advances in molecular biology and computation power are driving renewed interest in using phages (viruses that infect bacteria) to precisely control microbial growth (aka, phage biocontrol). In this Making Waves article, I begin by reviewing the current state of research into phage cocktail design, emphasizing our limited understanding of the features of successful phage cocktails (combinations of multiple types of phages). I describe the state of modeling phage-bacteria interactions and underscore the need for increasing research efforts to predict phage cocktail success, a key gap slowing the application of phage biocontrol. I also detail how research must also focus on techniques for engineering more effective phages to offer a more rapid alternative to phage discovery from natural environments. In this way, phage cocktails comprised of phages with complementary infection strategies may be designed. The final area for increased research effort that I highlight is the need for phage cocktail design to account for possible unintended environmental effects, a risk that is increasingly acknowledged in phage ecology studies but mostly ignored by those developing phage biocontrol technologies. By focusing more research effort towards the areas necessary for intelligent phage cocktail design, we can accelerate the development of phage-based biocontrol in water systems and improve public health.

Evaluation of the Safe Water Optimization Tool to Provide Evidence-Based Chlorination Targets in Surface Waters: Lessons from a Refugee Setting in Uganda.

The Safe Water Optimization Tool (SWOT) generates evidence-based point-of-distribution free residual chlorine (FRC) targets to adjust chlorine dosing by operators and ensure water quality at point-of-consumption. To investigate SWOT effectiveness in surface waters, we conducted two before-and-after mixed-method evaluations in a Uganda refugee settlement served by piped and trucked surface water systems. We surveyed 888 users on water knowledge, attitudes, and practices; collected 2768 water samples to evaluate FRC,Escherichia coli, and disinfection by-products (DBPs) concentrations; and conducted nine key-informant interviews with system operators about SWOT implementation. After baseline data collection, SWOT chlorination targets were generated, increasing point-of-distribution FRC targets from 0.2 to 0.7-0.8 mg/L and from 0.3 to 0.9 mg/L for piped and trucked systems, respectively. At endline, household point-of-consumption FRC ≥ 0.2 mg/L increased from 23 to 35% and from 8 to 42% in the two systems. With these increases, we did not observe increased chlorinated water rejection or DBPs concentrations exceeding international guidelines. Informants reported that SWOT implementation increased knowledge and capacity and improved operations. Overall, SWOT-generated chlorination targets increased chlorine dosage, which improved household water quality in surface waters although less than previously documented with groundwater sources. Additional operator support on prechlorination water treatment processes is needed to ensure maximally effective SWOT implementation for surface water sources.