Disinfection By-products Research Articles

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.

Reduction of organic matter and disinfection by products formation at surface water treatment plants in Egypt

ABSTRACT Although the removal of colloidal particles continues to be an important reason for using coagulation, currently a newer approach, the removal of organic matter to reduce the formation of disinfection byproducts (DBPs) such as trihalomethanes (THMs) are suspected carcinogens. Inefficient removal of total organic carbon (TOC) leads to the formation of carcinogenic THMs. This motivates the research efforts to find a way to reduce them in potable water. The first objective of this research is monitoring the water quality (raw and produced) for selected three water treatment plants within Giza Governorate to reveal the most polluted site (high TOC in the raw water and THMs in the treated water) in the study areas. The second objective of this study is enhancing coagulation to reduce TOC and THMs from surface water treating. In this study, two different coagulants aluminum sulfate (alum), and ferric chloride were tested under different conditions of pH and coagulant concentration to determine their effectiveness for removal of TOC, THMs and turbidity. Optimum values for the mentioned conditions were used to achieve the maximum reduction for TOC and THMs in Al-Ayat drinking water treatment plant (DWTP) which recorded the highest concentration of TOC and THMs. Ferric chloride as a coagulant achieved the maximum removal percentage % of TOC, THMs and turbidity as 79%, 82% and 94%, respectively, at ferric chloride dose 100 mg/L, while alum as a coagulant recorded the maximum removal percentage % of TOC, THMs and turbidity as 46%, 52% and 91%, respectively, at alum dose 100 mg/L. The results indicated that ferric chloride as a coagulant has the highest efficiency reduction of TOC, THMs and turbidity if compared to alum with the same dose added.

Advanced reduction processes initiated by oxidative radicals for trichloroacetic acid degradation: Performance, radical generation, and mechanism

The degradation of haloacetic acids (HAAs) in aqueous environments poses a challenge due to their oxidative resistance. Given that HAAs are highly carcinogenic disinfection byproducts, it is imperative to develop effective degradation methods to reduce their potential health risk. In this study, we found that only 27.2% of 200 μM trichloroacetic acid (TCA) was removed in the UV-activated persulfate (PS) system after 2 h, while complete removal was achieved with the addition of 15 mM formic acid (FA). The main products of TCA degradation were dichloroacetic acid and monochloroacetic acid. Results from free radical quenching experiments and electron paramagnetic resonance spectroscopy analyses indicated that reductive carbon dioxide radical (CO2•−) was the main active species responsible for TCA reduction. Oxidative radicals (i.e., SO4•− and •OH) generated from PS activation reacted with FA to form CO2•−, efficiently degrading TCA. The effects of PS and FA concentrations, solution pH, anions (e.g., Cl−, SO42−, and HCO3−), and small organic molecules (e.g., methanol, ethanol, and acetic acid) on degradation efficiency were examined. Overall, this study proposes a simple and efficient method to improve the degradation efficiency of HAAs in the UV/PS system and provides new insights into the advanced reduction processes used for water treatments.

Impacts of iodoacetic acid on reproduction: current evidence, underlying mechanisms, and future research directions.

In light of the undeniable and alarming fact that human fertility is declining, the harmful factors affecting reproductive health are garnering more and more attention. Iodoacetic acid (IAA), an emerging unregulated drinking water disinfection byproduct, derives from chlorine disinfection and is frequently detected in the environment and biological samples. Humans are ubiquitously exposed to IAA daily mainly through drinking water, consuming food and beverages made from disinfected water, contacting swimming pools and bath water, etc. Mounting evidence has indicated that IAA could act as a reproductive toxicant and bring about multifarious adverse reproductive damage. For instance, it can interfere with gonadal development, weaken ovarian function, impair sperm motility, trigger DNA damage to germ cells, perturb steroidogenesis, etc. The underlying mechanisms predominantly include cytotoxic and genotoxic effects on germ cells, disturbance of the hypothalamic-pituitary-gonadal axis, oxidative stress, inhibition of steroidogenic proteins or enzymes, and dysbiosis of gut microbiota. Nevertheless, there are still some knowledge gaps and limitations in studying the potential impact of IAA on reproduction, which urgently need to be addressed in the future. We suppose that necessary population epidemiological studies, more sensitive detection methods for internal exposure, and mechanism-based in-depth exploration will contribute to a more comprehensive understanding of characteristics and biological effects of IAA, thus providing an important scientific basis for revising sanitary standards for drinking water quality.

Control of drinking water disinfection byproducts with a novel bromide-selective anion exchange resin: Design, mechanism, and performance

In regions where drinking water sources containing elevated bromide levels, the formation of brominated disinfection byproducts (Br-DBPs) is enhanced, which may increase risks of cancer and birth defects. Anion exchange resin (AER) adsorption is a promising approach for reducing precursors of Br-DBPs (e.g., bromide and natural organic matter) due to its strong electrostatic force for reversible ion exchange process. However, high bromide water sources typically have high salinities, and the presence of co-existing ions (e.g., sulfate, nitrate, chloride) can significantly diminish the efficiency of conventional AERs, which use polyacrylic or polystyrene skeletons with trimethyl-ammonium functional groups. This study designed a novel AER with the polystyrene skeleton and tripentyl-ammonium functional group for the selective bromide removal, which resisted interferences from co-existing ions based on ion dehydration and ion-pairing electrostatic interactions. Column experiments with continuous high-bromide water flows demonstrated that the novel AER exhibited up to three times the operating capacity of conventional AERs, achieving reductions of 71.2 %, 44.6 %, and 67.7 % in bromide, dissolved organic carbon, and specific UV absorbance, respectively. Competitive experiments showed that the novel AER's strong sulfate interference resistance enhanced its bromide selectivity. The electrostatic interactions between AER fragments and bromide or sulfate particles were quantitatively evaluated using density functional theory calculations. Treatment with the novel AER led to reductions in total organic bromine, aliphatic Br-DBPs, and cyclic Br-DBPs by 76.7 %, 62.5 %, and 90.5 %, respectively. Notably, cytotoxicity assays using Chinese hamster ovary cells indicated a 39.7 % decrease in overall cytotoxicity of chlorinated drinking water following treatment with the novel AER.

Occurrence, toxicity, and control of halogenated aliphatic and phenolic disinfection byproducts in the chlorinated and chloraminated desalinated water

Seawater desalination is widely used to overcome the freshwater shortage worldwide. However, even after three-stage reverse osmosis treatment, the desalinated water still contained 14.6 μg/L of aliphatic disinfection byproducts (DBPs), 384.2 ng/L of bromophenolic DBPs, 3.5 ng/L of iodophenolic DBPs, 1024.7 μg/L of Br-, 2.8 μg/L of I-, and 2.4 mg C/L of dissolved organic carbon (DOC). After the desalinated water was disinfected with chlor(am)ine, the concentrations of halogenated aliphatic and phenolic DBPs further increased, and bromophenolic DBPs were the toxicity forcing agents. When surface water was mixed with desalinated water and then chlorinated, the yield of aliphatic and phenolic DBPs significantly elevated. Separately chlorinating desalinated water and surface water before mixing could mitigate this adverse situation. Chloramine disinfection was more conducive to reducing the total calculated toxicity of disinfected desalinated waters and mixed waters compared to chlorine disinfection. The treatment of desalinated water with granular activated carbon could effectively remove DOC and UV254, leading to a reduction in the content of total organic halogen after chlor(am)ination. Although anion exchange resin could adsorb Br-, it also released the organic precursors of DBPs, ultimately increasing the yield of DBPs. The results of this study can provide a reference for the seawater desalination industry to improve seawater pre-treatment and desalination processes and thus minimize the DBPs.

Role of iron homeostasis in the mutagenicity of disinfection by-products in mammalian cells

Disinfection by-products (DBPs) generated from water treatment have serious adverse effects on human health and natural ecosystems. However, research on the mutagenicity of DBPs with different chemical structures is still limited. In the present study, we compared the mutagenicity of 8 typical DBPs in human-hamster hybrid (AL) cells and clarified the mechanisms involved. Our data displayed that the rank order for mutagenicity was as follows: iodoacetamide (IAcAm) > iodoacetonitrile (IAN) > iodoacetic acid (IAA) > bromoacetamide (BAcAm) ≈ bromoacetonitrile (BAN) > bromoacetic acid (BAA), which was confirmed by DNA double strand breaks and oxidative DNA damage. In contrast, bromoform (TBM) and iodoform (TIM) had minimal mutagenicity. The mutation spectrum analysis further revealed that IAN, IAcAm, and IAA could induce multilocus deletions in mammalian cells. Interestingly, nitrogenous DBPs (N-DBPs) and IAA were found to cause varying degrees of iron overload and lipid peroxidation, which was mediated by the activation of the Nrf2/HO-1 signaling pathway. Moreover, the presence of deferoxamine (DFO), an iron ion inhibitor, effectively reduced γ-H2AX and 8-OHdG induced by N-DBPs and IAA. These results indicated that the variations in genotoxicity among DBPs with different structures were associated with their ability to disrupt iron homeostasis. This study provided new insights into the mechanisms underlying the structure-dependent toxicity of DBPs and established a foundation for a more comprehensive understanding and intervention of the health risks associated with DBPs.

Novel Catalyst-free Activation of Chlorine by Visible Light for Micropollutant Abatement

This study systematically investigated the direct activation of chlorine by visible light emitting diode (Vis-LED). Vis-LED could effectively activate chlorine to degrade micropollutants with degradation efficiency and pseudo-first-order degradation rate constant range of 64.3%-100% and 0.0340-0.195min-1, respectively. Quenching experiments and modeling results suggested that reactive chlorine species (RCS, including ClO•, Cl2•-, and Cl•) and hydroxyl radical (•OH) were involved in the degradation of atenolol (ATL). The contribution ratio of ClO•, free available chlorine, Cl•, Cl2•-, and •OH to ATL degradation were 58.7%, 17.4%, 15.6%, 1.8%, and 5.9%, respectively, in Vis-LED448/chlorine process. Moreover, the innate quantum yields of HClO and ClO- decreased from 0.229 and 0.0206 to 0.0489 and 0.0109mol·Einstein-1, respectively, as the wavelength increased from 448 to 513nm, leading to a decrease in ATL degradation, which was consistent with the model results. Experimental and modeling results have confirmed that ATL degradation decreased when pH increased from 4.0 to 9.0. Cl- had little effect on the degradation of ATL, while HA and HCO3- affected ATL degradation by scavenging reactive species and/or shielding effect. The concentration of disinfection by-products decreased with the increase of wavelength and pH. In summary, Vis-LED/chlorine is an efficient water treatment process even without a catalyst.

In-depth analysis of natural organic matter fractions in drinking water treatment performance: Fate and role of humic substances in trihalomethanes formation potential

In this study we investigate the compositional changes in dissolved organic matter (DOM) fractions across diverse water sources and treatment processes in three Drinking Water Treatment Plants (DWTPs). High-Performance Size Exclusion Chromatography coupled with Diode Array Detection and Organic Carbon Detection (HPSEC-DAD-OCD) was employed to characterize DOM fractions, offering insights into treatment optimization. We examine bulk water parameters, DOM distributions, and the efficiency of treatment trains in reducing DOM fractions. Results reveal distinct DOM composition profiles in river-sourced versus reservoir-sourced waters, with implications for treatment processes. Coagulation, Granular Activated Carbon (GAC) adsorption, Electrodialysis Reversal (EDR), and Ion Exchange (IEX) were evaluated for their efficacy in removing DOM fractions. The analysis highlights the effectiveness of coagulation in reducing high molecular weight (MW) fractions, while GAC filtration targets lower MW fractions. EDR shows significant removal of anions and aromatics, while IEX demonstrates high removal efficiencies for removing humic substances (HS) fractions. Spectroscopic analysis further elucidates changes HS sub-fractions and their role in disinfection by-products (DBP) formation. To quantitatively assess the relationship between HS sub-fractions and trihalomethane formation potentials (THMFP), Pearson correlation analysis were conducted, unveiling robust associations between HS sub-fractions and THM-FP that can be predicted by surrogate parameters such as A254.

State-level regulation of disinfection byproducts in the United States

ABSTRACT Disinfection byproducts (DBPs), residual compounds formed from the chemical disinfection of drinking water, can cause a host of damaging public health and environmental impacts. This study evaluates the landscape of regulations designed to reduce the occurrence and/or impact of DBPs, focusing on regulations issued by the US states. Drawing on a systematic search of state administrative codes and agency websites, we first identify the presence, absence, and layering of DBP-related regulations. We then evaluate the number and types of policy tools – the specific approaches required by each regulation, such as monitoring requirements, economic incentives, and required treatment technologies – to identify how DBPs are being managed and how states cluster with relatively more and less robust regulatory frameworks. Finally, we evaluate the relationship between the regulatory approach and the frequency of drinking water quality violations for DBP compounds. While most states have at least one DBP-specific regulation, these vary substantially in their comprehensiveness. The most-used policy tools (monitoring, compliance schedules, and reporting) directly reflect federal regulations; few states have adopted innovative tools such as collaboration or financial incentives. We observe no relationship between regulatory efforts and water quality violations, suggesting that current policy implementation may not adequately address the complex risk of DBPs.

Ecotoxicity of bromate and human health risks resulting from wastewater treatment units' effluents associated with some key physicochemical parameters in two hotspots connected to the Egyptian Mediterranean Sea

This study is the first of its kind in terms of focusing on the seasonal monitoring of bromine species (bromide− and bromate) and some of the main physicochemical parameters in the surface water of stations inside and in front of the El Noubareya and El-Umum drains that flow directly or indirectly to the Egyptian Mediterranean coast at A (El Noubareya Drain) and B (El-Mex Bay) sites. Among the bromine species, bromate (BrO3−) is a disinfection byproduct considered by many international agencies to have a potential carcinogenic effect in humans and is also known to be ecologically toxic to aquatic organisms. Drain water samples collected from the studied sites A and B had a bromide/chlorinity ratio (3.85E-03 - 6.25E-03 and 3.27E-03 - 6.97E-03, respectively) significantly higher than the typical value for open seawater (3.50E-03), showing significant dilution with wastewater at drain stations in the investigated sites. The source and origin of bromine species and the major ions studied associated with the wastewater units were identified and tracked by calculating the ion/chlorinity ratio and multivariate analysis. The total hazard quotient (THQ) for bromate intake and dermal exposure in children, females, and males demonstrates negligible harm to human health. The toxic unit (TU) and the sum of toxic units (STU) values of the three trophic levels in the surface water for the two sites under investigation yielded approximately comparable values for risk quotient (RQ) and mixture risk characterization ratios (RCRmix(MEC/PNEC)), indicating that invertebrates are more sensitive to bromate dangers than fish and algae. The study highlights the importance of conducting large-scale laboratory tests on the effluents resulting from wastewater treatment units, including bromide levels, to prevent the formation of dangerous side compounds such as bromate, which may have negative effects on populations and may lead to the toxicity of trophic levels in ecosystems.

Reactivity, Pathways, and Iodinated Disinfection Byproduct Formation during Chlorination of Iodotyrosines Derived from Edible Seaweed.

Iodine derived from edible seaweed significantly enhances the formation of iodinated disinfection byproducts (I-DBPs) during household cooking. Reactions of chlorine with monoiodotyrosine (MIT) and diiodotyrosine (DIT) derived from seaweed were investigated. Species-specific second-order rate constants (25 °C) for the reaction of hypochlorous acid with neutral and anionic MIT were calculated to be 23.87 ± 5.01 and 634.65 ± 75.70 M-1 s-1, respectively, while the corresponding rate constants for that with neutral and anionic DIT were determined to be 12.51 ± 19.67 and 199.12 ± 8.64 M-1 s-1, respectively. Increasing temperature facilitated the reaction of chlorine with MIT and DIT. Based on the identification of 59 transformation products/DBPs from iodotyrosines by HPLC/Q-Orbitrap HRMS, three dominant reaction pathways were proposed. Thermodynamic results of computational modeling using density functional theory revealed that halogen exchange reaction follows a stepwise addition-elimination pathway. Among these DBPs, 3,5-diiodo-4-hydroxy-benzaldehyde and 3,5-diiodo-4-hydroxy-benzacetonitrle exhibited high toxic risk. During chlorination of MIT and DIT, iodinated trihalomethanes and haloacetic acids became dominant species at common cooking temperature (80 °C). These results provide insight into the mechanisms of halogen exchange reaction and imply important implications for the toxic risk associated with the exposure of I-DBPs from household cooking with iodine-containing food.