Control Of Disinfection By-products Research Articles

A group of emerging heterocyclic nitrogenous disinfection byproducts: Formation and cytotoxicity of halopyridinols in drinking water

Recently, a new group of halopyridinol disinfection byproducts (DBPs) was reported in drinking water. The in vivo developmental and acute toxicity assays have shown that they were more toxic than a few commonly known aliphatic DBPs such as bromoform and iodoacetic acid. However, many pyridinol DBPs with the same main structures but different halogen substitutions were still unknown due to complicated water quality conditions and various disinfection methods applied in drinking water treatment plants. Studies on their transformation mechanisms in drinking water disinfection were quite limited. In this study, comprehensive detection and identification of halopyridinols were conducted, and five new halopyridinols were first reported, including 2-chloro-3-pyridinol, 2,6-dichloro-3-pyridinol, 2-bromo-5-chloro-3-pyridinol, 2,4,6-trichloro-3-pyridinol and 2,5,6-trichloro-3-pyridinol. Formation conditions and mechanisms of the halopyridinols were explored, and results showed that chlorination promoted their formation compared with chloramination. Halopyridinols were intermediate DBPs that could undergo further transformation/degradation with increasing contact time, disinfectant dose, bromide concentration, and pH. The in vitro cytotoxicity of the halopyridinols was evaluated using human hepatocellular carcinoma cells. Results showed that the cytotoxicity of 3,5,6-trichloro-2-pyridinol was the highest (EC50 = 474.3 μM), which was 13.0 and 1.6 times higher than that of 2-bromo-3-pyridinol (EC50 = 6214.5 μM) and tribromomethane (EC50 = 753.6 μM), respectively.

Control of chlorination disinfection by-products in drinking water by combined nanofiltration process: A case study with trihalomethanes and haloacetic acids

Disinfection by-products (DBPs) are prevalent contaminants in drinking water and are primarily linked to issues regarding water quality. These contaminants have been associated with various adverse health effects. Among different treatment processes, nanofiltration (NF) has demonstrated superior performance in effectively reducing the levels of DBPs compared to conventional processes and ozone-biological activated carbon (O3-BAC) processes. In this experiment, we systematically investigated the performance of three advanced membrane filtration treatment schemes, namely "sand filter + nanofiltration" (SF + NF), "sand filter + ozone-biological activated carbon + nanofiltration" (SF + O3-BAC + NF), and "ultrafiltration + nanofiltration" (UF + NF), in terms of their ability to control disinfection by-product (DBP) formation in treated water, analyzed the source and fate of DBP precursors during chlorination, and elucidated the role of precursor molecular weight distribution during membrane filtration in relation to DBP formation potential (DBPFP). The results indicated that each treatment process reduced DBPFP, as measured by trihalomethane formation potential (THMFP) and haloacetic acid formation potential (HAAFP), with the SF + O3-BAC + NF process being the most effective (14.27 μg/L and 14.88 μg/L), followed by the SF + NF process (21.04 μg/L and 16.29 μg/L) and the UF + NF process (26.26 μg/L and 21.75 μg/L). Tyrosine, tryptophan, and soluble microbial products were identified as the major DBP precursors during chlorination, with their fluorescence intensity decreasing gradually as water treatment progressed. Additionally, while large molecular weight organics (60–100,000 KDa) played a minor role in DBPFP, small molecular weight organics (0.2–5 KDa) were highlighted as key contributors to DBPFP, and medium molecular weight organics (5–60 KDa) could adhere to the membrane surface and reduce DBPFP. Based on these findings, the combined NF process can be reasonably selected for controlling DBP formation, with potential long-term benefits for human health.

Formation potential of disinfection byproducts during chlorination of petroleum hydrocarbon-contaminated drinking water

Recent leaks of underground fuel storage tanks in the Pearl Harbor region have led to direct release of un-weathered petroleum hydrocarbons (PHCs) into drinking water sources, which then directly underwent chlorination disinfection treatment. Since the control of disinfection byproducts (DBPs) traditionally focuses natural organic matters (NOM) from source water and little is known about the interactions between free chlorine and un-weathered PHCs, laboratory chlorination experiments in batch reactors were conducted to determine the formation potential of DBPs during chlorination of PHC-contaminated drinking water. Quantitative analysis of regulated DBPs showed that significant quantities of THM4 (average 3,498 μg/L) and HAA5 (average 355.4 μg/L) compounds were formed as the result of chlorination of un-weathered PHCs. Amongst the regulated DBPs, THM4, which were comprised primarily of chloroform and bromodichloromethane, were more abundant than HAA5. Numerous unregulated DBPs and a large diversity of unidentified potentially halogenated organic compounds were also produced, with the most abundant being 1,1-dichloroacetone, 1,2-dibromo-3-chloropropane, chloropicrin, dichloroacetonitrile, and trichloracetonitrile. Together, the results demonstrated the DBP formation potential when PHC-contaminated water undergoes chlorination treatment. Further studies are needed to confirm the regulated DBP production and health risks under field relevant conditions.

Chlorite and bromate alter the conjugative transfer of antibiotic resistance genes: Co-regulation of oxidative stress and energy supply

The widespread use of disinfectants during the global response to the 2019 coronavirus pandemic has increased the co-occurrence of disinfection byproducts (DBPs) and antibiotic resistance genes (ARGs). Although DBPs pose major threats to public health globally, there is limited knowledge regarding their biological effects on ARGs. This study aimed to investigate the effects of two inorganic DBPs (chlorite and bromate) on the conjugative transfer of RP4 plasmid among Escherichia coli strains at environmentally relevant concentrations. Interestingly, the frequency of conjugative transfer was initially inhibited when the exposure time to chlorite or bromate was less than 24 h. However, this inhibition transformed into promotion when the exposure time was extended to 36 h. Short exposures to chlorite or bromate were shown to impede the electron transport chain, resulting in an ATP shortage and subsequently inhibiting conjugative transfer. Consequently, this stimulates the overproduction of reactive oxygen species (ROS) and activation of the SOS response. Upon prolonged exposure, the resurgent energy supply promoted conjugative transfer. These findings offer novel and valuable insights into the effects of environmentally relevant concentrations of inorganic DBPs on the conjugative transfer of ARGs, thereby providing a theoretical basis for the management of DBPs.

Photothermal assisted space-confined chlorine activation for removal of pharmaceuticals and personal care products coupled with disinfection by-products control

The solar/chlorine process provides an energy-efficient technique for the abatement of some pharmaceuticals and personal care products (PPCPs) but it is inefficient in degrading PPCPs lacking electron-donating group and suffers high formation of disinfection byproducts (DBPs). In this study, a photothermal approach is developed to promote chlorine activation (photothermal/chlorine) under solar radiation to effectively remove a wide range of structurally diverse PPCPs and to control DBPs formation. To this end, a carbon black (CB) coated 3D porous melamine sponge (MS), namely CB@MS, is developed for the photothermal/chlorine application, achieving significantly enhanced PPCPs degradation with an ibuprofen (IBU) removal rate constant (0.22 min−1) 3.76 times that of the solar/chlorine process (0.058 min−1). Mechanistic investigations revealed that CB@MS confines the thermal energy within the 3D porous structure to achieve high localized heating for boosting PPCPs degradation in the confined space, which is equivalent to the thermal effect achieved by the solar/chlorine process at constant solution temperature of around 70 °C. Moreover, the photothermal/chlorine process reduces TOCl and DBPs formation by 77.6 % and 67.5 %, ascribed to adsorption by CB@MS, less chlorine exposure, and altered PPCPs degradation pathways. The broad applicability in various water matrices, and good reusability and stability of the photothermal/chlorine system also ensure its excellent practicality. This study offers in-depth mechanisms and practical insights into the development of a novel photothermal/chlorine process for PPCPs abatement and DBPs control.

Detection, Generation, and Control of Disinfection By-products of Reclaimed Water

At the time when water resources are in short supply,wastewater recycling is both an important environmental protection strategy and also a resource strategy. Disinfection is essential to ensure the biological safety of reclaimed wastewater by killing pathogens and preventing the spread of waterborne diseases. However,the disinfection process could inevitably produce toxic disinfection byproducts(DBPs)due to the reaction between the disinfectants and wastewater organic matters. Regarding wastewater DBPs,this study reviewed their identification methods,formation conditions(including precursors,the effect of water quality,disinfectants,and operational parameters on DBPs),and control methods(including source control,process control,and end control). In addition,future research trends of wastewater DBPs were discussed.

Adaptation of water treatment processes for controlling disinfection byproducts in supply waters to compensate the effects of climate change

The water treatment processes (WTPs) need adaptation to climate change. Safe water supply is being challenged by the deteriorating trend of water quality, which can increase disinfection byproducts and impose cancer/non-cancer risks to humans. In this study, implications of climate change and water quality deterioration on the formation of trihalomethanes' (THMs), and risks from 2020 to 2050 were predicted. In 2020, averages of temperature, dissolved organic carbon (DOC) and pH in source waters from Newfoundland (Canada) were 7.92 °C, 6.40 mg/L and 6.53 respectively, which were predicted to be 9.95 °C, 8.56 mg/L and 7.65, respectively in 2050. Three scenarios of free chlorine and bromide ions [(2.0 mg/L, 10 μg/L), (3.5 mg/L, 25 μg/L) and (5.0 mg/L, 50 μg/L)] were simulated. Two models (Model-1 and Model-2) were applied for predicting THMs, risks and allowable DOC for target risks. For Model-1, DOC in 2030, 2040 and 2050 were predicted to be in the ranges of 4.53–4.92, 3.32–3.84 and 2.49–3.06 mg/L respectively to impose similar risks as of 2020. For Model-2, DOC ranges were 5.02–5.95, 3.92–4.99 and 3.60–4.80 mg/L respectively. The lower ranges of DOC in future years were due to increased effects of pH and temperature. To maintain the risks of 2050 to the levels of 2020, WTPs need to reduce DOC by 64.3–70.9 % (Model-1) and 43.8–57.9 % (Model-2). The granular activated carbon filtration is widely used for reducing DOC, which can be further assessed for extensive applications in the WTPs.

Disinfection by-products control in wastewater effluents treated with ozone and biological activated carbon followed by UV/Chlor(am)ine processes

Sequential utilization of ozone (O3) and biological activated carbon (BAC) followed by UV/chlor(am)ine advanced oxidation process (AOP) has drawn attention in water reuse. However, the formation of disinfection by-products (DBPs) in this process is less evaluated. This study investigated the DBP formation and the relevant toxicity during the O3-BAC-UV/chlor(am)ine treatment of sand-filtered municipal secondary effluent. DBP formation in UV/chlorine and UV/dichloramine (NHCl2) processes were compared, where the impact of key operational parameters (e.g., UV wavelength, pH) on DBP formation were comprehensively evaluated. O3-BAC significantly reduced DBP formation potential (DBPFP) (58.2 %). Compared to UV/chlorine AOP, UV/NHCl2 AOP reduced DBP formation by 29.7 % in short-time treatment, while insignificantly impacting on DBPFP (p > 0.05). UV/NHCl2 AOP also led to lower calculated cytotoxicity (67.7 %) and genotoxicity (55.9 %) of DBPs compared to UV/chlorine AOP. Compared to 254 nm UV light, the utilization of 285 nm UV light decreased the formation of DBPs in wastewater treated with the UV/chlorine AOP and UV/NHCl2 AOP by 31.3 % and 19.2 %, respectively. However, the cytotoxicity and genotoxicity in UV/NHCl2 AOP using 285 nm UV light increased by 83.4 % and 58.5 %, respectively, compared to 254 nm. The concentration of DBPs formed in the UV/NHCl2 AOP at pH 8 was 54.3 % lower than that at pH 7, suggesting a better control of DBPs at alkaline condition. In the presence of bromide, UV/NHCl2 AOP tended to generate more brominated DBPs than UV/chlorine AOP. Overall, UV/NHCl2 AOP resulted in lower concentration and toxicity of DBPs compared to UV/chlorine AOP.

Formation and control of disinfection by-products during the trichloroisocyanuric acid disinfection in swimming pool water

The increasing demand for trichloroisocyanuric acid (TCCA) in swimming pool disinfection highlights the need to evaluate its applicability in terms of disinfection by-product (DBP) formation. Nevertheless, there is limited understanding of DBP formation and control during TCCA disinfection, particularly concerning the effects of various management parameters. This study aimed to fill this knowledge gap by comprehensively investigating DBP formation during TCCA chlorination, with a particular focus on assessing the contribution and interaction of influencing factors using Box-Behnken Design and response surface methodology. Results indicated that the concentrations of trichloroacetaldehyde, chloroform, dichloroacetic acid, trichloroacetic acid, and dichloroacetonitrile produced by TCCA disinfectant were 42.5%, 74.0%, 48.1%, 94.7% and 42.6% of those by the conventional sodium hypochlorite disinfectant, respectively. Temperature exhibited the most significant impact on chloroform formation (49%), while pH played a major role in trichloroacetaldehyde formation (44%). pH2 emerged as the primary contributor to dichloroacetic acid (90%) and trichloroacetic acid (93%) formation. The optimum water quality conditions were determined based on the minimum total DBPs (pH = 7.32, Temperature = 23.7 °C, [Cl−] = 437 mg/L). Chlorine dosage and contact time exhibited greater influence than precursor concentration on chloroform, dichloroacetonitrile, trichloroacetaldehyde, trichloroacetic acid, and total DBPs. Although the interaction between water quality parameters was weak, the interaction between disinfection operating parameters demonstrated substantial effects on DBP formation (8.56–19.06%). Furthermore, the DBP predictive models during TCCA disinfection were provided for the first time, which provides valuable insights for DBP control and early warning programs.

The formation and control of disinfection by-products by two-step chlorination for sewage effluent: Role of organic chloramine decomposition among molecular weight fractions

With the increasing discharge of wastewater effluent to natural waters, there is an urgent need to achieve both pathogenic microorganism inactivation and the mitigation of disinfection by-products (DBPs) during disinfection. Studies have shown that two-step chlorination, which injected chlorine disinfectant by splitting into two portions, was more effective in inactivating Escherichia coli than one-step chlorination under same total chlorine consumption and contact time. In this study, we observed a substantial reduction in the formation of five classes of CX3R-type DBPs, especially highly toxic haloacetonitriles (HANs), during two-step chlorination of secondary effluent when the mass ratio of chlorine-to-nitrogen exceeded 2. The shift of different chlorine species (free chlorine, monochloramine and organic chloramine) verified the decomposition of organic chloramines into monochloramine during second chlorination stage. Notably, the organic chloramines generated from the low molecular weight (< 1 kDa) fraction of dissolved organic nitrogen in effluent organic matter tended to decompose during the second step chlorination leading to the mitigation of HAN formation. Furthermore, the microbiological analysis showed that two-step chlorinated effluent had a slightly lower ecological impact on surface water compared to one-step chlorination. This work provided more information about the two-step chlorination for secondary effluent, especially in terms of organic chloramine transformation and HAN control.

Synergistic disinfection effects and reduction of disinfection by-products in water treatment using magnetic quaternized cyclodextrin polymer combined with chorine disinfection process

Disinfection is vital in ensuring water safety. However, the traditional chlorine disinfection process is prone to producing toxic and harmful disinfection by-products (DBPs). The combination of quaternary ammonium polymer and the chlorine disinfection process can solve this shortcoming. Currently, research on the control of DBPs through the combined process is not systematic and the control effect between reducing the dosage of disinfectants and DBPs remains to be studied. Quaternized cyclodextrin polymers have attracted increasing attention due to their excellent adsorption and antibacterial properties, but their synergistic effect with chlorine disinfection is still unclear. In this study, a magnetic quaternized cyclodextrin polymer (MQCDP) is synthesized in an ionic liquid green system, and a combined process of MQCDP treatment and chlorine disinfection is established. The disinfection performance of the combined process on the actual water body along with its reducing effect on the amount of chlorine disinfectant as well as the trihalomethanes (THMs) and haloacetic acids (HAAs) DBPs are explored. MQCDP has a porous structure with a specific surface area of 825 m2 g−1 and is easily magnetically separated. MQCDP can remove most of the natural organic matter (UV254 absorbance decreased by 97 %) in the water at the dosage of 1 g L−1 and kill bacteria with a sterilization rate of 85 %. Compared with disinfection using chlorine alone, the combined process has higher disinfection efficiency and significantly reduces the amount of disinfectant used. A concentration of 5 mg/L of NaClO was needed to meet the standard by chlorine disinfectant alone, while only 2 mg/L of NaClO can meet the standard for the combined process, indicating 60 % of the chlorine demand was reduced. More importantly, the combined process can significantly reduce the generation potential of DBPs. When 10 mg/L of NaClO is added, the THMs and HAAs generated by the combined process decreased by 65 % and 34 %, respectively, compared with the levels produced by single chlorine disinfection. The combined process can reduce the dosage of chlorine disinfectant and MQCDP can adsorb humic acid DBP precursors in raw water, thus lowering the generation of DBPs during disinfection. In summary, MQCDP has excellent separation and antibacterial ability, and its synergistic effects combined with the chlorine disinfection process are of great significance for controlling the amount of disinfectant and the formation potential of DBPs, which has potential applications in actual water treatment.

Comparative effectiveness of sequential and synergistic (VUV/)UV and chlorine disinfection on DBPs and humic acid reduction

The widespread use of chlorine during disinfection has led to the problems of disinfection by-products (DBPs). Recently, the combination of ultraviolet (UV, 254 nm) and vacuum ultraviolet (VUV, 185 nm) with chlorine has been considered a promising strategy to mitigate the formation of DBPs. This study systematically evaluated the efficacy of six different disinfection methods in abating humic acid (HA), a common precursor of DBPs (UV-Chlorine, VUV/UV-Chlorine, Chlorine-UV, Chlorine-VUV/UV, UV/Chlorine, and VUV/UV/Chlorine). Under 40 mJ/cm2 UV fluence and 3 mg/L chlorine dose, the synergistic processes yielded DBP levels below 20 μg/L, whereas sequential disinfection resulted in DBP levels exceeding 100 μg/L. Additionally, there was no significant difference in the formation of DBPs between the two methods of chlorination followed by irradiation. However, for irradiation followed by chlorination, the addition of VUV led to an increase of 50 μg/L in trihalomethanes (THMs). As the irradiation time increased, the inclusion of VUV demonstrated enhanced control of DBP levels in the sequential disinfection process. Moreover, compared to UV/Chlorine, at 13 mg/L chlorine dose in VUV/UV/Chlorine process, the inclusion of VUV expedited the appearance of peak DBPs by two minutes and reduced the peak value by 25.6 %, but the DBP yield was 12.9 times higher than that at a chlorine dose of 3 mg/L. This study, comparing six combination disinfection methods, will provide deeper insights into precursor abatement and DBP control during drinking water disinfection.

Chemical-free vacuum ultraviolet irradiation as ultrafiltration membrane pretreatment technique: Performance, mechanisms and DBPs formation

Membrane fouling induced by natural organic matter (NOM) has seriously affected the further extensive application of ultrafiltration (UF). Herein, a simple, green and robust vacuum ultraviolet (VUV) technology was adopted as pretreatment before UF and ultraviolet (UV) technology was used for comparison. The results showed that control effect of VUV pretreatment on membrane fouling was better than that of UV pretreatment, as evidenced by the increase of normalized flux from 0.27 to 0.38 and 0.73 after 30 min UV or VUV pretreatment, respectively. This is related to the fact that VUV pretreatment exhibited stronger NOM degradation ability than UV pretreatment owing to the formation of HO•. The steady-state concentration of HO• was calculated as 3.04 × 10−13 M and the cumulative exposure of HO• reached 5.52 × 10−10 M s after 30 min of VUV irradiation. And the second-order rate constant between NOM and HO• was determined as 1.36 × 104 L mg−1 s−1. Furthermore, fluorescence EEM could be applied to predict membrane fouling induced by humic-enriched water. Standard blocking and cake filtration were major fouling mechanisms. Moreover, extension of UV pretreatment time increased the disinfection by-products (DBPs) formation, the DBPs concentration was enhanced from 322.36 to 1187.80 μg/L after 210 min pretreatment. However, VUV pretreatment for 150 min reduced DBPs content to 282.57 μg/L, and DBPs content continued to decrease with the extension of pretreatment time, revealing that VUV pretreatment achieved effective control of DBPs. The variation trend of cytotoxicity and health risk of DBPs was similar to that of DBPs concentration. In summary, VUV pretreatment exhibited excellent effect on membrane fouling alleviation, NOM degradation and DBPs control under a certain pretreatment time.

DOM and DON transformation in full-scale wastewater treatment plants: Comparison of autotrophic and heterotrophic nitrogen removal units

There is limited knowledge regarding the differences and relationships in molecular composition between dissolved organic matters (DOM) and dissolved organic nitrogen (DON) in autotrophic and heterotrophic nitrogen removal processes. In this study, the composition of DOM and DON during two full-scale wastewater treatment plants (WWTPs), an autotrophic nitrogen removal with partial nitrification-anammox process (PN/A) and a heterotrophic nitrogen removal with anaerobic/anoxic/oxic process (A2O), were systematically investigated by using ultraviolet–visible spectroscopy, Excitation-Emission Matrix (EEM) and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The results indicated that both PN/A and A2O resulted a decrease in molecular diversity and bio-availability of DOM. However, there were distinct variations in DON between the two processes. In PN/A, transformation of DOM and DON was found to be coupled, while there was a lack of correlation observed between DOM and DON in A2O. Pearson correlation analysis revealed that transformation of DOM and DON in WWTPs was associated with microbial roles. During biotreatment, PN/A exhibited a higher metabolic capacity for degrading high bio-available and high aromatic compounds compared to A2O. The autotrophic nitrogen removal unit in PN/A resulted in an increase in molecular weight (MW) of DON, as well as a decrease in bio-availability and unsaturation degree of DON. Therefore, autotrophic nitrogen removal unit may have a positive influence on control of eutrophication and disinfection by-products (DBPs) formation. This study improved the understanding of molecular composition and relationship between DOM and DON, as well as microbial roles on DON transformation within autotrophic and heterotrophic nitrogen removal processes.

Synergistic effects of trace sulfadiazine and corrosion scales on disinfection by-product formation in bulk water of cast iron pipe

The effects of trace sulfadiazine (SDZ) and cast-iron corrosion scales on the disinfection by-product (DBP) formation in drinking water distribution systems (DWDSs) were investigated. The results show that under the synergistic effect of trace SDZ (10 μg/L) and magnetite (Fe3O4), higher DBP concentration occurred in the bulk water with the transmission and distribution of the drinking water. Microbial metabolism-related substances, one of the important DBP precursors, increased under the SDZ/Fe3O4 condition. It was found that Fe3O4 induced a faster microbial extracellular electron transport (EET) pathway, resulting in a higher microbial regrowth activity. On the other hand, the rate of chlorine consumption was quite high, and the enhanced microbial EET based on Fe3O4 eliminated the need for microorganisms to secrete excessive extracellular polymeric substances (EPS). More importantly, EPS could be continuously secreted due to the higher microbial activity. Finally, high reactivity between EPS and chlorine disinfectant resulted in the continuous formation of DBPs, higher chlorine consumption, and lower EPS content. Therefore, more attention should be paid to the trace antibiotics polluted water sources and cast-iron corrosion scale composition in the future. This study reveals the synergistic effects of trace antibiotics and corrosion scales on the DBP formation in DWDSs, which has important theoretical significance for the DBP control of tap water.

A multi-analytical approach to investigate DOM dynamics and alum dose control in enhanced coagulation process using wide-ranging surface waters

In this study, enhanced coagulation (EnC) − as a recommended water treatment process for disinfection by-product control − was investigated using jar testing, multi-analytical techniques, and a wide range of surface water sources. In addition to commonly used dissolved organic matter (DOM) concentration indices, DOM characteristics using UV–Vis spectroscopy, fluorescence EEM (fEEM) data, high-performance size exclusion chromatography (HPSEC), as well as turbidity, zeta potential and chlorophyll-a were studied. The results showed similar removal trends for the DOC, A254 and fluorescent DOM (fDOMs) signals with increasing alum dosing. Absorbance at ∼230 nm and fEEM data near Peak C in raw waters showed the highest correlations with enhanced dose. A decrease in weight-average apparent molecular weight following EnC, and a higher coagulability of DOM fractions with higher molecular weight, was noticed. The optimum zeta potential window was found to be −13 to +4 mV for EnC. Charge neutralization is suggested as the dominant mechanism for the EnC process. In addition to providing comprehensive information on the DOM dynamics during the EnC process, this study helps assess the potential of different water quality analysis techniques for EnC process monitoring and alum dose control, particularly using a field-deployable fDOM probe, offering potential for online, real-time applications.

Chloro- and bromo-benzoquinone formation and transformation mechanisms in a drinking water-distribution system

Halogenated benzoquinones (HBQs) are frequently detected in tap water. HBQ levels are correlated with water age. As the water–transmission distance (water age) increases, the levels of bromo-benzoquinones (Br-BQs) decreased and those of chloro-benzoquinones (Cl-BQs) remained relatively stable in drinking water–distribution system in the presence of residual chlorine. 2,3,5,6-Tetrachloro-1,4-benzoquinone (TCBQ) and 2,6-dibromo-1,4-benzoquinone (DBBQ) were the most abundant Cl-BQ and Br-BQ, with maximum concentrations of 60.2 and 181.4 ng/L, respectively. TCBQ and DBBQ were chosen as representatives of HBQs to investigate their reactions with chlorine, including kinetics, pathways, and changes in toxicity. The hydrolysis and chlorination rates of HBQs were significantly pH-dependent, and the kinetic rates of DBBQ were faster than TCBQ in the pH range of 5–10. Chlorination converted highly toxic TCBQ and DBBQ to less-toxic chlorinated/brominated aliphatic disinfection by-products (DBPs), thereby reducing the overall toxicity of water bodies. This study provides comprehensive insights into the distinct life cycles of TCBQ and DBBQ in drinking water, covering formation, transformation, and toxicity. These findings provide a nuanced understanding of the risks posed by HBQs at various locations within the drinking water distribution system, offering valuable guidance for improving the control of DBPs in drinking water.

Bibliometric analysis of disinfection by-product research trends in Türkiye

The goal of this study is to reveal the time dynamics of studies systematically and comprehensively on drinking water treatment and disinfection, as well as the situation in the literature, by using the bibliometric analysis method to examine scientific publications in the field of "Disinfection By-Products" between 2001 and 2022. The data gathered from the investigated articles is shown using the visual mapping approach. In this regard, the research provides for an evaluation of the disinfection by-products literature. The study's database contained 115 scientific papers retrieved from Web of Science. Istanbul Technical University is the most productive university with 23 published articles on Disinfection By-products, followed by Suleyman Demirel University with 18 published articles. Trihalomethanes, haloacetic acids are the most studied types of carbonaceous disinfection by-products in published articles, and N-nitrosodimethylamine is one of the most widely published nitrogenous disinfection by-products. The precursors of disinfection by-products or the removal of disinfection by-products are the two main focuses of the purpose of all studies. Coagulation, advanced oxidation processes and membrane processes constitute the methods used in the control of disinfection by-products. Brominated, and nitrogenous DBPs have attracted much attention due to their high toxicity. Future studies on disinfection by-products should focus on water quality standards, precursor controls, toxicity, and health effects. The necessity of bibliometric analysis of disinfection by-products is a necessity to fill the existing knowledge gaps in global and regional studies.

Nano-techniques: a tool to prevent disinfection by-product formation in drinking water

Water, a vital component required by all living things, becomes more and more polluted as a result of globalisation and industrialisation. Currently, pathogenic microbes, emerging pollutants, industrial chemicals and waste are polluting all-natural water resources and transportation systems. Therefore, before usage, drinking water has to be treated. When water disinfectants react with the organic natural components found in source waters, they may unintentionally produce disinfection by-products (DBPs), which have a negative impact on the biological system. There is a need for the development of innovative water-treatment solutions since traditional drinking water treatment (DWT) does not reduce emerging contaminants. The main objective of this study is to give an overview of disinfection techniques, DBP generation, health consequences and environmental repercussions. Additionally, there are advancements in nanotechnology that have been made in drinking water system treatment for the prevention of DBP and contaminant removal. Further review describes the analysis of advanced DWT processes that can be employed for the removal and control of precursors and DBPs.

Optimizing Ozone Disinfection in Water Reuse: Controlling Bromate Formation and Enhancing Trace Organic Contaminant Oxidation.

The use of ozone/biofiltration advanced treatment has become more prevalent in recent years, with many utilities seeking an alternative to membrane/RO based treatment for water reuse. Ensuring efficient pathogen reduction while controlling disinfection byproducts and maximizing oxidation of trace organic contaminants remains a major barrier to implementing ozone in reuse applications. Navigating these challenges is imperative in order to allow for the more widespread application of ozonation. Here, we demonstrate the effectiveness of ozone for virus, coliform bacteria, and spore forming bacteria inactivation in unfiltered secondary effluent, all the while controlling the disinfection byproduct bromate. A greater than 6-log reduction of both male specific and somatic coliphages was seen at specific ozone doses as low as 0.75 O3:TOC. This study compared monochloramine and hydrogen peroxide as chemical bromate control measures in high bromide water (Br- = 0.35 ± 0.07 mg/L). On average, monochloramine and hydrogen peroxide resulted in an 80% and 36% decrease of bromate formation, respectively. Neither bromate control method had any appreciable impact on virus or coliform bacteria disinfection by ozone; however, the use of hydrogen peroxide would require a non-Ct disinfection framework. Maintaining ozone residual was shown to be critical for achieving disinfection of more resilient microorganisms, such as spore forming bacteria. While extremely effective at controlling bromate, monochloramine was shown to inhibit TrOC oxidation, whereas hydrogen peroxide enhanced TrOC oxidation.