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Gravity-driven membrane (GDM) systems are increasingly recognized as sustainable and energy-efficient solutions for decentralized water treatment. However, membrane fouling, particularly by organic matter, remains a significant operational challenge, necessitating regular chemical cleaning to maintain performance. The present study was undertaken to investigate the cleaning efficiency of sodium dichloroisocyanurate (NaDCC) tablets, a novel solid-state alternative to conventional liquid cleaning agents such as sodium hypochlorite (NaOCl), sodium lauryl sulfate (SLS), acetic acid, and citric acid. NaDCC tablets, originally developed for drinking water disinfection, offer advantages in terms of transport, storage, and safety compared with conventional liquid formulations. A comparative evaluation of cleaning agents was conducted on hollow fiber membranes used in GDM systems, with the concentration and contact times optimized for each chemical. NaOCl demonstrated the highest permeability recovery, reaching 48.29% at 500 mg L−1 after 12 h, followed closely by NaDCC, with a recovery of 46.55% under similar conditions. Conversely, SLS, acetic acid, and citric acid presented significantly lower recovery rates, with maximum flux restorations of 14.57%, 14.90%, and 16.73%, respectively. These results highlight the comparable performance of NaDCC and NaOCl in addressing organic fouling while offering practical advantages such as greater stability and reduced chemical handling risks. This study highlights the efficacy of NaDCC as a viable detergent for GDM systems, and also provides a comprehensive comparative analysis of the water permeability performances of commercial detergents such as NaOCl, which cause various ecotoxicities, and suggests the feasibility of NaDCC as a chemical detergent in practical membrane processes. Our findings contribute to the development of more sustainable and cost-effective membrane-cleaning protocols that enhance long-term operational efficiency and minimize environmental impacts. [Display omitted] • Comprehensive comparison of NaDCC and commercial cleaning agents was conducted. • Organic fouling was identified as the main contributor to performance decline. • NaDCC achieves 46.55% permeability recovery, comparable to NaOCl's 48.29%. • NaDCC tablets offer a solid-state alternative to liquid membrane cleaning agents. • NaDCC tablets are easier to store, transport, and handle than liquid alternatives. [ABSTRACT FROM AUTHOR]

Global concern regarding transformation products (TPs) derived from contaminants, including pesticides, in the environment and during water treatment has been growing markedly. In the present study, we investigated the anti-acetylcholinesterase (AChE) activity of an aqueous solution of the organophosphorus insecticide disulfoton, a toxicological endpoint for determining the acceptable daily intake of disulfoton, both in the presence and the absence of metabolism during chlorination. Disulfoton rapidly reacted with free chlorine and completely disappeared within 0.25 h. Although the aqueous disulfoton solution did not induce anti-AChE activity before chlorination, the chlorinated samples did induce anti-AChE activity, both with (indirect toxicity) and without (direct toxicity) metabolism. These observations clearly indicated that disulfoton was converted into toxic TPs through reactions with free chlorine. Liquid chromatographic fractionation followed by an anti-AChE activity assay revealed that three TPs were responsible for the observed direct toxicity. Further mass spectrometric analyses showed that these TPs were disulfoton-oxon-sulfone, and mono- and dichloro-substituted derivatives of disulfoton-oxon-sulfoxide (O -(1-chloroethyl) S -[2-(ethanesulfinyl)ethyl] O -ethyl phosphorothioate and O -(1,2-dichloroethyl) S -[2-(ethanesulfinyl)ethyl] O -ethyl phosphorothioate, respectively), none of which were simply oxon. Results of the anti-AChE activity assay on the chemical standard of disulfoton-oxon-sulfone after metabolism and quantification of the disulfoton-oxon-sulfone in the chlorinated samples revealed that the observed indirect toxicity was solely induced by this TP. It is recommend that drinking water treatment plants that use free chlorine as a disinfectant monitor the concentrations of at least disulfoton-oxon-sulfone, which is commercially available, in finished water in addition to disulfoton itself, to ensure the safety of tap water. [Display omitted] • Chlorination caused aqueous disulfoton solution to induce anti-AChE activity. • Toxicity was not due to well-known simple oxon derivative. • Disulfoton-oxon-sulfone significantly contributed to the observed toxicity. • Chloro-substituted oxon-sulfoxides also similarly contributed to the toxicity. [ABSTRACT FROM AUTHOR]

In this study, we fabricated phosphorus-modified carbon felt electrode anodes for chloride oxidation in saline solutions to produce HClO via electrocatalysis, forming a compound fungicide saline applicable for debridement and disinfection. A low-cost phosphorus-modified carbon felt electrode (P@CF) with high chlorine evolution reaction activity was synthesized to address the reduced efficiency of CER and the solution's pH increase. Heteroatoms P and O were introduced into the carbon felt by phosphoric acid activation followed by heat treatment. The maximum active chlorine concentration on the P@CF electrode could reach 616.8 mg/L in 60 min under the optimal synthesis conditions of a phosphoric acid mass fraction of 30%, a phosphoric acid impregnation time of 3 h, and a heat treatment temperature of 300 °C. The active chlorine concentration was 1.8 times higher on the P@CF electrode compared to the original carbon felt electrode. The optimal reaction conditions for the generation of active chlorine were as follows: salt concentration of 9 g/L, voltage of 7 V, and electrode spacing of 2 cm as verified by response surfaces. This electrolysis reaction follows one-stage reaction kinetics. Subsequently, the disinfection efficacy of the produced disinfectants was examined. The prepared disinfectant was also compared to a commercially available hypochlorite disinfectant, showing similar disinfection effects on E. coli for both. [Display omitted] • Synthesis of phosphorous modified carbon felt electrode to enhance HClO yield. • Optimization of key parameters using response surface methodology. • Achieving disinfectant efficacy comparable to commercial products. [ABSTRACT FROM AUTHOR]

The presence of microplastics (MPs) in water may affect the efficacy of the disinfection process and induce toxicity changes to MPs themselves during disinfection. Therefore, this study evaluated the two-way effects of polyethylene microplastic (MP) particles in water and wastewater during sodium hypochlorite (NaClO) disinfection. On the one hand, it has been confirmed that the presence of MPs reduced the disinfection efficiency of NaClO. The required CT (concentration of the disinfection × contact time) for a 2–4-log inactivation of Escherichia coli (E. coli) in different water samples was in the order of deionized water < turbid water (1 NTU) < water with MPs (1 mg/L) < turbid water (10 NTU). On the other hand, although exposure to MPs did induce significant changes in the activities of superoxide dismutase and glutathione, compared to pristine MPs, the MPs treated by NaClO at current conditions (0.3 and 3.0 mg/L for 30 min) did not show significant changes in their toxicity on zebrafish, at an MP exposure concentration of 1 mg/L. There was no significant difference in the survival rate and weight growth rate, neither as in the activities of the oxidative stress-related enzymes (superoxide dismutase, catalase, glutathione, glutathione peroxidase, and glutathione s-transferase) in both gut and muscle tissues of the zebrafish, between exposure to the pristine and NaClO-treated MPs. It is indicated that NaClO disinfection commonly applied for water and wastewater treatment would not pose a serious concern to effluent safety in the presence of mild levels of MPs. [Display omitted] • Microplastics in water reduced NaClO disinfection efficiency. • NaClO treatment of MPs did not induce changes in survival and weight growth rate. • MPs treated by NaClO did not alter the activity of oxidative stress-related enzymes. [ABSTRACT FROM AUTHOR]

To optimize the ultraviolet (UV) water disinfection process, it is crucial to determine the ideal geometric dimensions of a corresponding model that enhance performance while minimizing the impact of uncertain photoreactor inputs. As water treatment directly affects people's lives, it is crucial to eliminate the risks associated with the non-ideal performance of disinfection photoreactors. Input uncertainties greatly affect photoreactor performance, making it essential to develop a robust optimization algorithm in advance to mitigate these effects and minimize the physical and financial resources required for constructing the photoreactors. In the suggested algorithm, a two-objective genetic algorithm is integrated with a non-intrusive polynomial chaos expansion (PCE) technique. Additionally, the Sobol sampling method is employed to select the necessary samples for understanding the system's behavior. An artificial neural network surrogate model is trained using sufficient data points derived from computational fluid dynamics (CFD) simulations. A novel type of UV photoreactors working based on exterior reflectors is chosen to optimize the process with three uncertain input parameters, including UV lamp power, UV transmittance of water, and diffusive fraction of the reflective surface. In addition, four geometrical design variables are considered to find the optimal configuration of the photoreactor. The standard deviation (SD) and the reciprocal of log reduction value (LRV) are set as the objective functions, calculated using PCE. The optimal design provides a LRV of 3.95 with SD of 0.2. The coefficient of variation (CoV) of the model significantly declines up to 7%, indicating the decreased sensitivity of the photoreactor to the input uncertainties. Additionally, it is discovered that the robust model exhibits minimal sensitivity to changes in reflectivity in various flow rates, and its output variability aligns with the SD obtained through robust optimization. [Display omitted] • A UV water disinfection reactor is optimized using a novel robust algorithm. • Robust optimization enhances LRV and reduces the uncertainties' impact. • A trained artificial neural network predicts LRV as the model's output. • The proposed method combines genetic algorithm with polynomial chaos expansion. • The model's coefficient of variation decreases, reducing sensitivity to uncertainties. [ABSTRACT FROM AUTHOR]

This research investigated the comparative efficacy of sulfamic acid (SA) and phytic acid (PA), both individually and in combination, for treating potential foodborne pathogens and pre-formed foulants. Pathogens studied included Listeria monocytogenes , E. coli DH5α, Salmonella typhimurium , Staphylococcus aureus , and vegetative Bacillus cereus , in suspended aqueous solutions, as well as Pseudomonas aeruginosa biofilm on quartz glass surfaces. Inactivation kinetics for Listeria monocytogenes revealed concentration-dependent rate constants (k) of 6.6(±0.2) × 10−6 M and 2.8(±0.1) × 10−8 M for single treatments of SA and PA, respectively, and ranged from 6.9(±0.3) to 50.7(±2.3) × 10−6 M for combined treatments with PA pre-treatment concentrations of 75–758 μM. Observable cellular abnormalities in Listeria monocytogenes , such as membrane vesiculation, chelation, cellular disruption, biomolecule leakage, and lipid peroxidation, were identified after exposure to PA or SA, either individually or in combination. The optimized combined treatment of PA and SA achieved significant removal (i.e., >3-log; 99.9%) of potential foodborne pathogens under simulated food-washing process conditions. Additionally, over 90% descaling efficacy was observed for pre-formed foulants such as CaCO 3 precipitates and Pseudomonas aeruginosa biofilm on quartz glass surfaces with the combined treatment. These findings provide novel insights into the versatile utility of PA and SA for optimizing combinational water disinfection systems and addressing (in)organic foulant scaling on surfaces in the food processing industry. [Display omitted] • Kinetics and mechanisms of Listeria monocytogenes inactivation were assessed. • Combined treatment with PA and SA exhibited higher rate constants (k). • Discernible abnormalities in physiological and biochemical parameters were observed with the treatment of PA and SA. • Five foodborne pathogens were removed under simulated fresh washing processes. • Surface scales of biofilms or calcium carbonate precipitates were mitigated. [ABSTRACT FROM AUTHOR]

As global effects of water scarcity raise concerns and environmental regulations evolve, contemporary wastewater treatment plants (WWTPs) face the challenge of effectively removing a diverse range of contaminants of emerging concern (CECs) from municipal effluents. This study focuses on the assessment of advanced oxidation processes (AOPs), specifically UV-C/H 2 O 2 and UV-C/Chlorine, for the removal of 14 target CECs in municipal secondary effluent (MSE, spiked with 10 μg L−1 of each CEC) or in the subsequent MSE nanofiltration retentate (NF R , no spiking). Phototreatments were carried out in continuous mode operation, with a hydraulic retention time of 3.4 min, using a tube-in-tube membrane photoreactor. For both wastewater matrices, UV-C photolysis (3.3 kJ L−1) exhibited high efficacy in removing CECs susceptible to photolysis, although lower treatment performance was observed for NF R. In MSE, adding 10 mg L−1 of H 2 O 2 or Cl 2 enhanced treatment efficiency, with UV-C/H 2 O 2 outperforming UV-C/Chlorine. Both UV-C/AOPs eliminated the chronic toxicity of MSE toward Chlorella vulgaris. In the NF R , not only was the degradation of target CECs diminished, but chronic toxicity to C. vulgaris persisted after both UV-C/AOPs, with UV-C/Chlorine increasing toxicity due to potential toxic by-products. Nanofiltration permeate (NF P) exhibited low CECs and microbial content. A single chlorine addition effectively controlled Escherichia coli regrowth for 3 days, proving NF P potential for safe reuse in crop irrigation (<1 CFU/100 mL for E. coli ; <1 mg L−1 for free chlorine). These findings provide valuable insights into the applications and limitations of UV-C/H 2 O 2 and UV-C/Chlorine for distinct wastewater treatment scenarios. [Display omitted] • Photo-treatments applied to real municipal secondary effluent and its NF retentate. • UV-C/H 2 O 2 and UV-C/Chlorine were compared for the removal of CECs and ecotoxicity. • UV-C/H 2 O 2 removed 74% of average CECs and eliminated toxicity in secondary effluent. • UV-C/AOPs removed 40% of average CECs in NF retentate posing challenges to AOPs. • 1 mg L−1 of chlorine in NF permeate ensured E.coli <1 CFU/100 mL after 3-day storage. [ABSTRACT FROM AUTHOR]

Amino acids (AAs) account for about 15–35% of dissolved organic nitrogen (DON), and are known as the important precursors of nitrogenous disinfection by-products (N-DBPs). Determining the formation potential (FP) of AAs to DBPs is used to reveal the key precursors of DBPs for further control, while the ideal method for N-DBPs FP of AAs during chlorination is not revealed. In this study, the ideal FP test models for five classes of priority DBPs during chlorination of four representative AAs (accounted for about 35% of total AAs) were analyzed. For haloaldehydes (HALs), haloketones (HKs), haloacetonitriles (HANs), haloacetamides (HAMs), and halonitromethanes (HNMs), their FPs during chlorination of four AAs were 0.1–13.0, 0.01–1.1, 0.1–104, not detectable (nd)-173, and nd-0.4 μg/mg, respectively. The FPs of priority DBPs had significant deviations between different FP test models and different tested AAs. For HALs, the model, whose chlorine dosage was determined by 15 × molar concentration of AAs [Cl (mM) = 15 × M](named: model II), was the ideal model. For HKs, model II was also the ideal FP test model for AAs with ≤3 carbons, while for AAs with 4 carbons, the model, whose chlorine dosage was determined by keeping the residual chlorine at 1 ± 0.2 mg/L after 24 h of reaction (named: model 4), was the ideal model. For HANs and HNMs, model 4 was the ideal FP test model for most of the studied AAs. The performance of HAMs during chlorination of amino acids was totally different from other P-DBPs, and model 3 was recommended to be the ideal model, in which chlorine dosage was determined by 3 × mass concentration of AAs [Cl (mg/L) = X × DOC]. This study is a reference that helps researchers select an ideal model for N-DBPs FP study of AAs. [Display omitted] • The ideal FP test models for AAs during chlorination were analyzed. • For P-DBPs, their FPs for four AAs ranged from 0 to 173 μg/mg. • P-DBP FPs had significant deviations between different FP test models. • This study helps researchers to select a ideal model for FP study of AAs. [ABSTRACT FROM AUTHOR]

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. [Display omitted] • Regulated DBPs were produced when jet fuel petroleum hydrocarbons reacted with free chlorine. • Chloroform was the most abundant regulated THM compound, followed by bromodichloromethane and dibromochloromethane. • Monobromoacetic acid was the most abundant regulated HAA, followed by dibromoacetic acid and monochloroacetic acid. • A large diversity of unregulated DBPs, including a complex group of high-molecular-weight compounds, were also detected. Synopsis: Petroleum hydrocarbon leakage into drinking water aquifers is becoming more and more prevalent. This research investigates the formation of disinfection byproducts through chlorination of petroleum hydrocarbons in water. [ABSTRACT FROM AUTHOR]

Haloacetonitriles (HANs) are unregulated disinfection by-products that are more toxic than regulated species. Therefore, efficient decomposition of HAN precursors prior to disinfection is crucial for allaying the potential HAN-induced health risks. This study investigated the key roles of ultraviolet-activated persulfate (UV/PS) treatment in alleviating HAN formation. The effects of UV/PS treatment were evaluated by correlating with the characteristics of organic matter in surface water and comparing with conventional UV/H 2 O 2 treatment. Upon irradiating raw water samples and a Suwannee River humic acid solution spiked with 10 mM PS or H 2 O 2 with 254 nm UV light, UV/PS treatment was found to be more potent than UV/H 2 O 2 in mitigating the HAN production and degrading organic substances; moreover, UV/PS treatment effectively decreased the dissolved organic nitrogen (DON) content. In contrast, UV/H 2 O 2 treatment did not induce any noticeable reduction in DON level. Furthermore, both UV/PS and UV/H 2 O 2 treatments reduced the dichloroacetonitrile (DCAN) formation potential (FP), leading to strong correlations with the degradation of aromatic and humic-acid-like compounds. Notably, UV/PS treatment efficiently decreased the FP of bromochloroacetonitrile (BCAN) and dramatically reduced that of dibromoacetonitrile (DBAN) after a sharp increase; however, UV/H 2 O 2 treatment gradually increased the DBAN-FP. Bromide was activated by sulfate radicals during UV/PS treatment, negatively correlating with the BCAN-FP and DBAN-FP, indicating that the formation of reactive bromine species increased the DBAN-FP; however, excessive oxidation possibly led to the recovery of inorganic bromine for decreasing the BCAN-FP and DBAN-FP. Additionally, UV/PS treatment effectively suppressed toxicity owing to its high reduction rate for brominated HANs; in contrast, UV/H 2 O 2 treatment resulted in less significant BCAN and DBAN reductions, leading to minimal net reduction in toxicity. Overall, UV/PS treatment was remarkably effective at diminishing the toxicity of brominated HANs, underscoring its potential to mitigate drinking-water-related health risks. [Display omitted] • UV/persulfate (PS) allayed haloacetonitriles (HANs) more effectively than UV/H 2 O 2. • Both UV/PS and UV/H 2 O 2 effectively decreased the dichloroacetonitrile content. • Only UV/PS reduced the bromochloroacetonitrile and dibromoacetonitrile contents. • Toxicity assessment revealed the significant effects of UV/PS on HAN mitigation. [ABSTRACT FROM AUTHOR]

This paper highlights the potential to effectively inhibit nitrification and restore chloramine levels using a low copper concentration in a biofilm-affected (surface-to-volume ratio 16 m−1) continuous-flow laboratory-scale chloraminated system. High nitrite and low chloramine containing tanks are always recovered with chlorine "burn" by water utilities. The "burn" is not only costly and operationally complex, but also compromises the water quality, public health, and customer relations. A laboratory system comprising five reactors connected in series was operated. Each reactor simulated conditions typically encountered in full-scale systems. Low amount of copper (0.1–0.2 mg-Cu L−1) was dosed once per day into nitrified reactors. At any given time, only one reactor was dosed with copper. Not only inhibition of nitrification, chloramine decay associated with bulk water, biofilm and sediments also improved. However, the improvement was quicker and more significant when the influent to the reactor contained a high chloramine and a low nitrite concentration. Ammonia oxidising microbes exhibited resilience when exposed to low copper and chloramine concentrations for an extended period. Chloramine decay due to planktonic microbes and chemical reactions in bulk water decreased more rapidly than decay attributed to biofilm and sediments. The concept "biostable residual chlorine" explained how copper and chloramine can inhibit nitrification. Once nitrification was inhibited, the chloramine supplied from upstream effectively continued to suppress downstream nitrification, and this effect lasted more than 50 days even at 22 °C. The findings could be used to develop short-term copper dosing strategies and prevent negative impacts of nitrification and breakpoint chlorination. [Display omitted] • Copper inhibits nitrification at concentrations above 0.046 mg-Cu/L. • Key to chloramine recovery is adopting synergistic effect of copper and chloramine. • Biofilm and sediments were affected slower by copper than that of bulk water. • Once inhibited at the first nitrifying point, chloramine can penetrate downstream. • After the chloramine recovery, the effect can last longer without copper dosing. [ABSTRACT FROM AUTHOR]

Chlorinated organic compounds are widely used as solvents, but they are pollutants that can have adverse effects on the environment and human health. Dissimilatory iron-reducing bacteria (DIRB) such as Shewanella and Geobacter have been applied to treat a wide range of halogenated organic compounds due to their specific biological properties. Until now, there has been no systematic review on the mechanisms of direct or indirect degradation of halogenated organic compounds by DIRB. This work summarizes the discussion of DIRB's ability to enhance the dechlorination of reaction systems through different pathways, both biological and biochemical. For biological dechlorination, some DIRB have self-dechlorination capabilities that directly dechlorinate by hydrolysis. Adjustment of dechlorination genes through genetic engineering can improve the dechlorination capabilities of DIRB. DIRB can also adjust the capacity for the microbial community to dechlorinate and provide nutrients to enhance the expression of dechlorination genes in other bacteria. In biochemical dechlorination, DIRB bioconverts Fe(III) to Fe(II), which is capable of dichlorination. On this basis, the DIRB-driven Fenton reaction can efficiently degrade chlorinated organics by continuously maintaining anoxic conditions to generate Fe(II) and oxic conditions to generate H 2 O 2. DIRB can drive microbial fuel cells due to their electroactivity and have a good dechlorination capacity at low levels of energy consumption. The contribution of DIRB to the removal of pesticides, antibiotics and POPs is summarized. Then the DIRB electron transfer mechanism is discussed, which is core to their ability to dechlorinate. Finally, the prospect of future work on the removal of chlorine-containing organic pollutants by DIRB is presented, and the main challenges and further research directions are suggested. [Display omitted] • Dehalogenation of chlorinated organics by DIRB through biodegradation and biochemical systems. • Shewanella and Geobacter have functional differences in actual dechlorination. • This review discusses the mechanism by which DIRB is involved in dechlorination in different capacities. • Improvement methods and future research direction are suggested to enhance the dechlorination performance of DIRB. [ABSTRACT FROM AUTHOR]

Antibiotic residues and their chlorinated disinfection by-products (Cl-DBPs) have adverse effects on organisms in aquaculture water. Taking enrofloxacin (ENR) as target antibiotic, this study investigated the degradation and transformation of ENR Cl-DBPs in constructed wetlands (CWs). Results showed that, ENR and its Cl-DBPs affected the biodegradation of CWs at the preliminary stage, but did not affect the adsorption by plant roots, substrates, and biofilms. The piperazine group of ENR had great electronegativity, and was prone to electrophilic reactions. The carboxyl on quinolone group of ENR had strong nucleophilicity, and was prone to nucleophilic reactions. C atoms with significant negative charges on the aromatic structure of quinolone group were prone to halogenation. During the chlorination of ENR, one pathway was the reaction of quinolone group, in which nucleophilic substitution reaction by chlorine occurred at C26 atom on carboxyl group, then halogenation occurred under the action of Cl+ at C17 site on the aromatic ring; the other pathway was the reaction of piperazine group, in which N7 atom was firstly attacked by HOCl, resulting in piperazine ring cleavage, then followed by deacylation, dealkylation, and halogenation. During the biodegradation of ENR Cl-DBPs, the reactivity of piperazine structure was strong, especially at N6, N7, C13, and C14 sites, while the ring structure of quinolone group was quite stable, and only occurred decyclopropyl at N5 site. Overall, the biodegradation of ENR Cl-DBPs in CWs went through processes including piperazine ring cleavage, tertiary amine splitting, dealkylation, and aldehyde oxidation under the action of coenzymes, in which metabolites such as ketones, aldehydes, carboxylic acids, amides, primary amines, secondary amines, tertiary amines and acetaldehyde esters were produced. Most ENR Cl-DBPs had greater bioaccumulation potential and stronger toxicity than their parent compound, fortunately, CWs effectively reduced the environmental risk of ENR Cl-DBPs through the cooperation of adsorption and biodegradation. [Display omitted] • For the first time transformation pathway of ENR Cl-DBPs in CWs was proposed. • ENR and its Cl-DBPs affected the biodegradation of CWs rather than the adsorption. • Piperazine structure of ENR and its Cl-DBPs was easily prone to electrophilic reaction. • Six ENR Cl-DBPs and their twenty-three degradation products in CWs were identified. • Bioaccumulation potential of ENR Cl-DBPs effectively reduced via degradation by CWs. [ABSTRACT FROM AUTHOR]

Nitrate-contaminated groundwater is a pressing issue in rural areas, where up to 40 % of the population lacks access to safely managed drinking water services. The high costs and complexity of centralised treatment in these regions exacerbate this problem. To address this challenge, the present study proposes electro-bioremediation as a more accessible decentralised alternative. Specifically, the main focus of this study is developing and evaluating a compact reactor designed to accomplish simultaneous nitrate removal and groundwater disinfection. Significantly, this study has established a new benchmark for nitrate reduction rate within bioelectrochemical reactors, achieving the maximum reported rate of 5.0 ± 0.3 kg NO 3 − m−3 NCC d−1 at an HRT cat of 0.7 h. Furthermore, the in-situ generation of free chlorine was effective for water disinfection, resulting in a residual concentration of up to 4.4 ± 1.1 mg Cl 2 L−1 in the effluent at the same HRT cat of 0.7 h. These achievements enabled the treated water to meet the drinking water standards for nitrogen compounds (nitrate, nitrite, and nitrous oxide) as well as pathogens content (T. coliforms, E. coli , and Enterococcus). In conclusion, this study demonstrates the potential of the electro-bioremediation of nitrate-contaminated groundwater as a decentralised water treatment system in rural areas with a competitive operational cost of 1.05 ± 0.16 € m−3. [Display omitted] • Treated groundwater meets standards for nitrogen compounds and pathogens. • Highest reported nitrate reduction rate of 5.0 kg NO 3 − m−3 d−1 at HRT cat of 0.7 h. • Water disinfection ensured through in-situ electrochemical chlorine evolution. • Cost-effective treatment with an estimated competitive operational cost of 1.05 € m−3. [ABSTRACT FROM AUTHOR]

The formation of toxic disinfection by-products during water disinfection due to the presence of bromide and iodide is a major concern. Current treatment technologies such as membrane, adsorption and electrochemical processes have been known to have limitations such as high energy demand and excessive chemical use. In this study, the selectivity between bromide and iodide, and their removal in membrane capacitive deionisation (MCDI) was evaluated. The results showed that iodide was more selectively removed over bromide from several binary feed waters containing bromide and iodide under various initial concentrations and applied voltages. Even in the presence of significant background concentration of sodium chloride, definite selectivity of iodide over bromide was observed. The high partial-charge transfer coefficient of iodide compared to bromide could be a feasible explanation for high iodide selectivity since both bromide and iodide have similar ionic charge and hydrated radius. The result also shows that MCDI can be a potential alternative for the removal of bromide and iodide during water treatment. Image 1 • Bromide and iodide selectivity in MCDI were systematically assessed. • MCDI can significantly reduce bromide and iodide concentration in the water. • Iodide showed preferential adsorption compared to bromide. • Electronegativity of ions can also affect ion selectivity in MCDI. [ABSTRACT FROM AUTHOR]

Biochar (BC) is as an emerging and promising adsorbent for the removal of pollutants from aqueous solutions in water treatment given its porous structure, large surface area, and numerous O-functional groups. However, the effects of BC on the formation of disinfection byproducts (DBPs) during the disinfection process of water treatment remains largely unknown. This study investigated the influence of aqueous solution chemistry on DBP formation in the presence of BC during chlorination. BC samples prepared from different biomass precursors (wheat straw, peanut shells, and shaddock peel) with different pyrolysis temperatures were compared, and the effects of aqueous solution chemistry were systematically investigated. Results indicated that DBPs could be formed during disinfection with BC. Certain intermediate DBP products would undergo base catalysis to form trichloromethane (TCM) via hydrolysis as pH increased. This phenomenon would increase TCM content, as well as decrease chloral hydrate and 1,1-dichloro-2-propanone content. The increment in inorganic ion (NaCl) content showed negligible effects on DBP formation during BC chlorination. DBP formation was restrained in the presence of humic acid (HA) because the number of active sites on BC that participated in the reaction decreased when BC adsorbed HA. • Chlorination of biochar can form DBPs during the water treatment. • The pyrolysis temperature of biochar highly affects the DBP concentrations. • The release of organic precursors from biochar to produce DBPs is affected by pH. • Biochar could inhibit the DBPs formation during the chlorination of SRHA. [ABSTRACT FROM AUTHOR]

Transformation of endocrine active compounds (EACs) by either chlorination (Cl-D) or UV disinfection (UV-D) was studied by field sampling and bench-scale validation studies. Field testing assessed concentration of 13 EACs in effluent at two Chicago area 250 MGD wastewater reclamation plants (WRP) over two years. One WRP uses chlorination/dechlorination while the other employs UV disinfection. Target compounds included bupropion, carbamazepine, citalopram, duloxetine, estradiol, estrone, fluoxetine, nonylphenol, norfluoxetine, norsertraline, paroxetine, sertraline, and venlafaxine. Concentrations of 9/13 target compounds were partially reduced after disinfection (5–65% reduction). None of the target compounds were fully transformed by either chlorination or UV treatment at the WRP scale. In bench-scale experiments each compound was spiked into deionized water or effluent and treated in a process mimicking plant-scale disinfection to validate transformations. Correlation was observed between compounds that were transformed in bench-testing and those that decreased in concentration in post-disinfection WRP effluent (10/13 compounds). A survey of potential reaction products was made. Chlorination of some amine containing compounds produced chloramine by-products that reverted to the initial form after dechlorination. Transformation products produced upon simulated UV disinfection were more diverse. Laboratory UV-induced transformation was generally more effective under stirred conditions, suggesting that indirect photo-induced reactions may predominate over direct photolysis. • Representative contaminants were measured in wastewater pre- and post-disinfection. • Both UV and chlorination were studied at two Chicago treatment plants. • Bench-scale measurements mimicking the disinfection processes were conducted. • UV and chlorination both partially decrease the concentration of some compounds. • Neither process leads to elimination of the representative contaminants. [ABSTRACT FROM AUTHOR]

Among numerous disinfection by-products (DBP) forming during aqueous chlorination nitrogen containing species are of special concern due to their toxicological properties. Nevertheless, corresponding reaction products of these natural and anthropogenic compounds are not sufficiently studied so far. An interesting reaction involves dealkylation of the substituted amine moiety. Here we present the results of the comparative study of one-electron oxidation and aqueous chlorination of several aliphatic and aromatic amines. The reaction products were reliably identified with gas chromatography – high resolution mass spectrometry (GC-HRMS), high pressure liquid chromatography – electrospray ionization high resolution mass spectrometry HPLC-ESI/HRMS), and electrochemistry - electrospray ionization high resolution mass spectrometry (EC-ESI/HRMS). Certain similarities dealing with the formation of the corresponding aldehydes and substitution of alkyl groups at the nitrogen atom for hydrogen were shown for the studied processes. The mechanism of the substituted amines' aqueous chlorination involving one-electron oxidation is proposed and confirmed by the array of the observed reaction products. Alternative reactions taking place in conditions of aqueous chlorination, i.e. aromatic electrophilic substitution, may successfully compete with dealkylation and produce major products. [Display omitted] • Aqueous chlorination of tertiary/secondary amines results in dealkylation process. • The dealkylation mechanism is similar to one-electron oxidation. • Arylamines undergo both dealkylation and electrophilic substitution. • Final DBPs of tertiary and secondary amines may be more toxic. [ABSTRACT FROM AUTHOR]

Amino acids are the main components of dissolved organic nitrogen in algal- and wastewater-impacted waters, which can react with chlorine to form toxic halogenated disinfection by-products (DBPs) in the disinfection process. In the presence of bromide, the reaction between amino acids and secondarily formed hypobromous acid can lead to the formation of brominated DBPs that are more toxic than chlorinated analogues. This study compares the formation of regulated and unregulated DBPs during chlorination and bromination of representative amino acids (AAs) (e.g., aspartic acid, asparagine, tryptophan, tyrosine, and histidine). In general, concentrations of brominated DBPs (trihalomethanes, haloacetonitriles, and haloacetamides, 24.9–5835.0 nM) during bromination were higher than their chlorinated analogues (9.3–3235.3 nM) during chlorination. This indicates the greater efficacy of bromine as a halogenating agent. However, the formation of chlorinated haloacetic acids during chlorination was higher than the corresponding brominated DBPs from bromination. It is likely that an oxidation pathway is required for the formation of haloacetic acids and chlorine is a stronger oxidant than bromine. Moreover, chlorine forms higher levels of haloacetaldehydes (74.4–1077.8 nM) from amino acids than bromine (1.0–480.2 nM) owing to the instability of brominated species. The DBP formation yields depend on the types of functional groups in the side chain of AAs. Eight intermediates resulting from chlorination/bromination of tyrosine were identified by triple quadrupole mass spectrometer, including N-chlorinated/brominated tyrosine, 3-chloro/bromo-tyrosine, and 3,5-dichloro/dibromo-tyrosine. These findings provided new insights into the DBP formation during the chlorination of algal- and wastewater-impacted waters with elevated bromide. [Display omitted] • Bromination forms higher levels of THMs, HANs and HAMs than chlorination. • Chlorination forms lower levels of HAAs and HALs than bromination. • Chlorine and bromine substitutions occur on the amino group and aromatic ring. [ABSTRACT FROM AUTHOR]

Permanganate is a common preoxidant applied in water treatment to remove organic pollutants and to reduce the formation of disinfection by-products. However, the effect of permanganate preoxidation on the transformation of dissolved effluent organic matter (dEfOM) and on the formation of unknown chlorinated disinfection by-products (Cl-DBPs) during chlorination remains unknown at molecular level. In this work, the molecular changes of dEfOM during permanganate preoxidation and subsequent chlorination were characterized using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Permanganate preoxidation was found to decrease the DBE (double bond equivalent) and AI mod (modified aromaticity index) of the dEfOM. The identity and fate of over 400 unknown Cl-DBPs during KMnO 4 -chlorine treatment were investigated. Most Cl-DBPs and the precursors were found to be highly unsaturated aliphatic and phenolic compounds. The Cl-DBPs precursors with lower H/C and lower O/C were preferentially removed by permanganate preoxidation. Additionally, permanganate preoxidation decreased the number of unknown Cl-DBPs by 30% and intensity of unknown Cl-DBPs by 25%. One-chlorine-containing DBPs were the major Cl-DBPs and had more CH 2 groups and higher DBE w than Cl-DBPs containing two and three chlorine atoms. 60% of the Cl-DBPs formation was attributed to substitution reactions (i.e., +Cl–H, +2Cl–2H, +3Cl–3H, +ClO–H, +Cl 2 O 3 –2H). This work provides detailed molecular level information on the efficacy of permanganate preoxidation on the control of overall Cl-DBPs formation during chlorination. [Display omitted] • Permanganate preoxidation led to the decrease of DBE w and AI mod,w in the dEfOM. • More than 400 unknown Cl-DBPs and their fate during KMnO 4 -chlorine treatment were characterized. • The Cl-DBPs and precursors molecular formulas featured with high unsaturation and aromaticity. • Permanganate preoxidation preferentially removed Cl-DBPs precursors with lower H/C and O/C. • 60% of the Cl-DBPs formation was attributed to substitution reactions. [ABSTRACT FROM AUTHOR]

Pharmaceutical active compounds (PhACs) are organic pollutants detected in wastewater and aquatic environments worldwide in concentrations ranging from ng L−1 to μg L−1. Wastewater effluents containing PhACs residues is discharged in municipal sewage and, subsequently collected in municipal wastewater treatment plants (WWTPs) where are not entirely removed. Thus, PhACs and its transformation products (TPs) are discharged into water bodies. In the current work, the transformation of PhACs under treatments used in municipal WWTPs such as biological, photolysis, chlorination, and ozonation processes was reviewed. Data set of the major transformation pathways were obtained of studies that performed the PhACs removal and TPs monitoring during batch-scale experiments using gas and liquid chromatography coupled with tandem mass spectrometry (GC/LC-MS/MS). Several transformation pathways as dealkylation, hydroxylation, oxidation, acetylation, aromatic ring opening, chlorination, dehalogenation, photo-substitution, and ozone attack reactions were identified during the transformation of PhACs. Especially, hydroxylation reaction was identified as transformation pathway in all the processes. During the elucidation of hydroxylated TPs several isobaric compounds as monohydroxylated and dihydroxylated were identified. However, hydroxylated TPs monitoring in wastewater and aquatic environments is a topic scarcely studied due to that has no environmental significance, lack of available analytic standars of hydroxylated TPs and lack of analytic methods for their identification. Thus, screening strategy for environmental monitoring of hydroxylated TPs was proposed through target and suspect screening using GC/LC-MS/MS systems. In the next years, more studies on the hydroxylated TPs monitoring are necessary for its detection in WWTPs effluents as well as studies on their environmental effects in aquatic environments. [Display omitted] • PhACs and its TPs are not efficiently removed in municipal WWTPs. • TPs of PhACs are scarcely monitored in WWTPs effluents and aquatic environments. • Transformation of PhACs in WWTPs include to hydroxylation reaction as key pathway. • Monohydroxylated and dihydroxylated TPs are generated during the PhACs removal. • Identification strategy for hydroxylated TPs include target and suspect screening. [ABSTRACT FROM AUTHOR]

Fungi and substrates undergoing fungal decomposition were collected from forests in northern and southern Sweden and analyzed for chlorinated dimethoxybenzenes (DMBs). Specimens were fungi fruiting bodies, rotting wood, forest litter and underlying humus. Targeted compounds were DAME (1,2,4,5-tetrachloro-3,6-DMB) and related fungal secondary metabolites. A screening procedure was developed which involved soaking the specimens in ethyl acetate followed by analysis by capillary gas chromatography – mass spectrometry with mass selective detection (GC-MSD). DAME was the most frequently found (62% of 47 specimens) and often the most abundant target compound, with range and mean ± SD concentrations of <0.0017–3.81 and 0.21 ± 0.63 mg kg−1 ww. Based on log-log correlations of partition coefficients of hydrophobic compounds between fungal biomass/water (K D) and octanol/water (K OW), five species of fungi are suggested to produce DAME de novo versus bioaccumulation from forest runoff water. Full-scan mass spectra of some high-concentration specimens indicated the presence of a Cl 2 DMB and a Cl 3 DMB, which could not be identified further due to lack of standards, and drosophilin A (DA = 2,3,5,6-tetrachloro-4-methoxyphenol), the precursor to DAME. Tetrachloroveratrole (TeCV = 1,2,3,4-tetrachloro-5,6-DMB) was found in only a few specimens. This study supports our hypothesis of fungi as a source of DAME in terrestrial runoff and indicates that other chlorinated secondary metabolites are present. DAME is widely distributed globally, and it would be good to have a better understanding of its sources and pathways as a marker of terrestrial organochlorines and their availability for bioaccumulation. [Display omitted] • A screening method was developed for chlorinated fungal metabolites. • Drosophilin A methyl ether (DAME) was identified in in fungi and forest litter. • Five fungal species were suggested to produce DAME de novo. • Other chlorinated dimethoxybenzenes were found in some specimens. [ABSTRACT FROM AUTHOR]

Monitoring and prevention of the formation of disinfection by-products (DBPs) is paramount in drinking water treatment plants (DWTP) to ensure human health safety. This review provides an overview of how fluorescence techniques are developed to predict DBP formation and to evaluate the reduction of fluorescence components and DBPs following individual DWTP processes. Evidence has shown that common DBPs, nitrogenous DBPs and specific emerging DBPs exhibit positive linear relationships with terrestrial, anthropogenic, tryptophan-like, and eutrophic humic-like fluorescence. Due to the interrelationships of both regulated and emerging DBP types with fluorescence components, the limitations arise when attempting to predict emerging DBPs solely through linear relationships. Monitoring the reduction of DBP precursors after each treatment process can be achieved by studying the relationship between fluorescence components and DBPs. During the coagulation process, highest reduction rates are observed for terrestrial humic-like fluorescence. Advanced treatments such as granular, powdered, silver-impregnated activated carbon, magnetic ion exchange resins, and reverse osmosis, have revealed a significant reduction of fluorescent DBP precursors, ranging from 53% to 100%. During chlorination, the reduction rate follows the order: terrestrial humic-like > microbial humic-like > protein/tryptophan-like fluorescence. This review provides insights into the reduction of fluorescence signatures following individual DWTP processes, which offers information regarding DBP formation. These insights could assist in optimizing the treatment process to more effectively manage DBP formation. For the identification of emerging DBP generation, the utilization of advanced models is imperative to precisely predict emerging DBPs and to more accurately trace DBP precursors within DWTPs. [Display omitted] • Review of methods for predicting DBP precursors using fluorescence techniques. • Comparison of reduction in fluorescence components across treatment processes. • Detail report on reduction behaviors of DBP precursors in water treatment processes. • Identification and discussion of challenges in using fluorescence to monitor DBPs. [ABSTRACT FROM AUTHOR]

Abstract Disinfection byproducts (DBPs) are produced during the disinfection of drinking water and pose a hazard to human health. As a typical type of DBPs, iodoacetic acid (IAA) exhibits prominent cytotoxicity in mammalian cell systems which links with oxidative stress. However, little is known about the relationship of catalase (CAT) with the cytotoxicity of IAA and the adverse effects of IAA to CAT. This study investigated the effects of IAA on the cell viability and CAT activity in the mouse primary hepatocytes. It was shown that IAA exposure induced the loss of cell viability and the increase of intracellular CAT activity. Intracellular CAT activity significantly increased due to the stimulation of CAT production under IAA exposure. The molecular CAT activity was inhibited due to the direct interaction of IAA with HIS 74 and TYR 357 around the active sites of CAT. IAA binds to CAT with (4.05 ± 1.98) sites via van der Waals and hydrogen bonding interactions, resulting in the loosening of protein skeletons and the change of protein size. Highlights • The work offers a combined cellular and molecular toxicity evaluation method. • CAT activity increased due to the stimulation of CAT production in the hepatocytes. • IAA triggered conformational changes in CAT and inhibit CAT activity. • IAA binds to CAT with (4.05 ± 1.98) sites mainly via van der Waals and hydrogen bonds. • IAA preferentially binds to the interface of CAT rather than its active site. [ABSTRACT FROM AUTHOR]

Waterborne pathogens, especially bacteria and viruses, pose significant health risks to the public, calling for the development of a sustainable, efficient, and robust disinfection strategy with reduced energy footprint and minimized byproduct formation. Here, we developed a sustainable photocatalytic composite for antimicrobial applications by integrating visible-light-responsive graphitic carbon nitride (g-C 3 N 4 ) with low-density porous expanded perlite (EP) mineral, and g-C 3 N 4 /EP-520 showed a high specific surface area of 45.3 m 2 /g and optimum performance for disinfection. g-C 3 N 4 /EP-520 achieved 8-log inactivation of E. coli and MS2 under 180 and 240 min visible-light irradiation without stirring, respectively. Water quality parameters were found to influence the disinfection performance of g-C 3 N 4 /EP-520: MS2 inactivation was promoted with the increase of dissolved oxygen (DO), proton concentration, salinity (NaCl), and hardness (Ca 2+ ). Importantly, g-C 3 N 4 /EP-520 could fully inactivate MS2 in a real source water sample with prolonged light irradiation, and negligible activity loss was observed in recycle use, demonstrating its viability and robustness for waterborne pathogen removal. Antimicrobial mechanisms of g-C 3 N 4 /EP-520 were systemically evaluated by radical scavenger addition, and revealed that the inactivation behavior was dependent on the type of microorganisms. Microscopic analyses confirmed that the destruction of bacterial cells and viral particles, leading to the inactivation of microorganisms. [ABSTRACT FROM AUTHOR]

Pillararene polymers have been widely used as excellent adsorbents for water treatment, but pillararene polymers with ultra-high specific surface area and versatility are still rarely reported. Herein, a quaternary ammonium salt modified pillar [5] arene polymer, QPBP [5], with specific surface area of 1844 m2 g−1 was successfully synthesized. Since QPBP [5] has abundant different adsorption sites, it exhibits excellent performance for the simultaneously removal of organic pollutants with different charges from water. The selected three model pollutants, Rhodamine B (RhB, positively charged), Sulfamethazine (SMT, electrically neutral) and Fulvic acid (FA, negatively charged), could be rapidly and efficiently removed from water by QPBP [5] within 10 min, which are much faster than them by most of the reported adsorbents. RhB and SMT are mainly adsorbed through hydrophobic interactions with the QPBP [5] surface, while FA is mainly removed through ion exchange. In addition, QPBP [5] also showed excellent reusability and adsorption performance for the environmentally relevant concentration of pollutants. Furthermore, the quaternary ammonium groups on QPBP [5] makes it a solid disinfectant with excellent antibacterial properties. In conclusion, QPBP [5] is a promising multifunctional adsorbent for the treatment of complex pollutants in water. [Display omitted] • Quaternary ammonium salt modified pillar [5] arene polymer was synthesized. • The polymer has a specific surface area up to 1844 m2 g−1. • The polymer can efficiently remove contaminants of different charge types. • The polymer showed excellent disinfection properties. [ABSTRACT FROM AUTHOR]

Trihalomethanes (THMs) are classified as volatile organic compounds, considered to be a disinfection by-product during water disinfection process. THMs have been shown to be cytotoxic, genotoxic and mutagenic, with a risk of cancer when they contact with people directly. To protect public health and monitor water quality, it is important to monitor and measure THMs in drinking water. Therefore, it is crucial to develop fast, accurate, highly sensitivity and green analysis methods of THMs in various complicated matrices. Here, this review presents an overall summary of the current state of the pretreatment and detection methods for THMs in various sample matrices since 2005. In addition to the traditionally used pretreatment methods for THMs (such as headspace extraction, microwave-assisted extraction, liquid-liquid extraction), the new-developed methods, including solid-phase extraction, QuEChERS and different microextraction methods, have been summarized. The detection methods include gas chromatography-based methods, sensors and several other approaches. Additionally, benefits and limitations of different techniques were also discussed and compared. This study is anticipated to offer fruitful insights into the further advancement and widespread applications of pretreatment and detection technologies for THMs as well as for related substances. [Display omitted] • Advances in pretreatment and detection methods of THMs in water samples are reviewed. • The future trends of state-of-the-art techniques are thoroughly discussed. • Simple, fast, green microextraction techniques are raising substantial interest. • A comparison of various GC-based detection methods is presented. [ABSTRACT FROM AUTHOR]

Triclocarban (TCC) is an antimicrobial agent commonly used in many household and personal care products, and has been found persistent in the aquatic environment. Here we elucidate the kinetics and mechanism of TCC degradation during chlorination process by density functional theory (DFT) calculation and experimental verification. Results showed that hypochlorous acid (HOCl)/hypochlorite (OCl−) reacted with TCC via Cl-substitution, OH-substitution and C–N bond cleavage pathways. The reactivity of OCl− (2.80 × 10−7 M−1 s−1) with TCC was extremely low and HOCl (1.96 M−1 s−1) played the dominant role in TCC chlorination process. The N site of TCC was the most reactive site for chlorination. The second-order rate constants, which are determined using density functional theory (DFT) (k T C C − c h l o r i n e C , 1.96 M−1 s−1), can be separated into reaction rate constants related to the reactions of HOCl and OCl− with different isomers of TCC (TCC2 and TCC6). The obtained k T C C − c h l o r i n e C was consistent with the experimental determined second-order rate constant (k T C C − c h l o r i n e E , 3.70 M−1 s−1) in chlorination process. Eight transformation products (TP348, TP382, TP127, TP161, TP195, TP330, TP204, and TP296) were experimentally detected for chlorination of TCC, which could also be predicted by DFT calculation. Explicit water molecules participated in the chlorination reaction by transmitting the proton and connecting with TCC, HOCl/OCl− and other H 2 O molecules, and obviously reduced the energy barrier of chlorination. [Display omitted] • Chlorination of antimicrobial triclocarban (TCC) was investigated. • The major reaction pathways were Cl-substitution, OH-substitution and C–N bond cleavage. • HClO played the major role in chlorination process to degrade TCC. • Explicit water molecules reduced the energy barrier of TCC chlorination. • Eight products calculated by DFT were confirmed by experimental identification. [ABSTRACT FROM AUTHOR]

Aquifer clogging plays a critical role in the efficiency of reclaimed water recharge. While chlorine disinfection is commonly used for reclaimed water, its impact on clogging has seldom been discussed. Thus, this study aimed to investigate the mechanism of chlorine disinfection on clogging by establishing a lab-scale reclaimed water recharge system that utilized chlorine-treated secondary effluent as feed water. The findings indicated that increasing the chlorine concentration led to a surge in the total amount of suspended particles, and the median particle size increased from 2.65 μm to 10.58 μm. Furthermore, the fluorescence intensity of dissolved organic matter decreased by 20%, with 80% of these compounds, including humic acid, becoming entrapped within the porous media. Additionally, the formation of biofilms was also found to be promoted. Microbial community structure analysis unveiled a consistent dominance of Proteobacteria consistently exceeded 50% in relative abundance. Moreover, the relative abundance of Firmicutes increased from 0.19% to 26.28%, thereby verifying their strong tolerance to chlorine disinfection. These results showed that higher chlorine concentrations could stimulate microorganisms to secrete an increased quantity of extracellular polymeric substance (EPS) and form a coexistence system with the trapped particles and natural organic matter (NOM) within the porous media. Consequently, this supported the formation of biofilms, thereby potentially elevating the risk of aquifer clogging. [Display omitted] • Physical and biological clogging during reclaimed water recharge were evaluated. • High chlorine concentration increased the median particle size of suspended particles. • High chlorine concentration promoted the formation of biofilms. • Pseudomonas, Mycobacterium, and Legionella were the dominant chlorine-resistant bacteria. [ABSTRACT FROM AUTHOR]

Laser-induced graphene (LIG) has gained popularity for electrochemical water disinfection due to its efficient antimicrobial activity when activated with low voltages. However, the antimicrobial mechanism of LIG electrodes is not yet fully understood. This study demonstrated an array of mechanisms working synergistically to inactivate bacteria during electrochemical treatment using LIG electrodes, including the generation of oxidants, changes in pH—specifically high alkalinity associated with the cathode, and electro-adsorption on the electrodes. All these mechanisms may contribute to the disinfection process when bacteria are close to the surface of the electrodes where inactivation was independent of the reactive chlorine species (RCS); however, RCS was likely responsible for the predominant cause of antibacterial effects in the bulk solution (i.e., ≥100 mL in our study). Furthermore, the concentration and diffusion kinetics of RCS in solution was voltage-dependent. At 6 V, RCS achieved a high concentration in water, while at 3 V, RCS was highly localized on the LIG surface but not measurable in water. Despite this, the LIG electrodes activated by 3 V achieved a 5.5-log reduction in Escherichia coli (E.coli) after 120-min electrolysis without detectable chlorine, chlorate, or perchlorate in the water, suggesting a promising system for efficient, energy-saving, and safe electro-disinfection. [Display omitted] • An array of mechanisms works synergistically to inactivate bacteria close to LIG electrodes. • The RCS was likely responsible for the predominant cause of antibacterial effects in the bulk solution. • At a low applied voltage (3 V), highly localized RCS on the LIG surface contributed to efficient disinfection. • LIG with low voltages inactivated bacteria without high levels of oxidants, suggesting a safe electro-disinfection. [ABSTRACT FROM AUTHOR]

Degradation of Chlorine-containing disinfection by-products(Cl-DBPs) on surface by electrocatalytic hydrodechlorination (EHDC) is considered a promising advanced water treatment method. Cl-DBPs have ecological toxicity and health risks so that it is urgent to degrade DBPs. We designed and verified the degradation performance of the EHDC of 18 kinds of DBPs (TAAs, TANs, TALs, TNMs, TAcAms, THMs) with different substituents led by the Ti 3 C 2 X 2 (X = O/OH) system by the first-principles. On the surface of Ti 3 C 2 (OH) 2 , DBPs react with atomic hydrogen (*H) by a direct-indirect continuous reduction mechanism to eliminate the Cl atom in turn. Dissociative adsorption of DBPs on the surface of Ti 3 C 2 (OH) 2 simultaneously realizes the first electron transfer step and forms H vacancy, which makes its electrocatalytic activity superior to that of Ti 3 C 2 O 2. Removing the six types of DBPs only needs to add −0.1 V of applied potential. In addition, we investigated the impact of substituents and chlorination degree on the reactivity of DBPs removal. The strong electron-withdrawing group is more conducive to the dechlorination reaction. Dehalogenation is much favorable in thermodynamics as the increase in chlorination degree. This study provides important insights and efficient catalysts for the degradation of DBPs and shows the potential of MXenes in eliminating chloride in water. [Display omitted] • The degradation performance of Ti 3 C 2 (OH) 2 is superior to Ti 3 C 2 O 2. • Cl atom was removed in Ti 3 C 2 (OH) 2 by direct-indirect continuous reaction. • The high activity results from H vacancy formation and synchronous first electron transfer. • Substituents effect and chlorination degree affect the reaction activity. [ABSTRACT FROM AUTHOR]

Free chlorine is a commonly used disinfectant in drinking water treatment. However, disinfection by-products (DBPs) are formed during water disinfection. Haloacetic acids (HAAs) and trihalomethanes (THMs) are two major groups of DBPs. Iodo-HAAs and iodo-THMs (I-HAAs and I-THMs) are formed during the disinfection of the water containing high levels of iodide and are much more toxic than their chlorinated and brominated analogs. Peracetic acid (PAA) is a strong antimicrobial disinfectant that is expected to reduce the formation of HAAs and THMs during disinfection. In this study, the formations of thirteen HAAs and ten THMs, including the iodinated forms, have been investigated during PAA disinfection and chlorination as the comparison. The DBP formations under different iodide concentrations, pHs, and contact times were systematically investigated. Two types of commercial PAAs containing different concentrations of PAA and hydrogen peroxide (H 2 O 2 ) were studied. A solid-phase microextraction gas chromatography-mass spectrometry method was upgraded for THM analysis including I-THMs. HAAs were analyzed by following a recently developed high performance ion chromatography-tandem mass spectrometry method. Results show that the ratio of PAA and H 2 O 2 concentration significantly affect the formation of I-THMs and I-HAAs. During PAA disinfection with lower PAA than H 2 O 2 , no detectable levels of THMs and HAAs were observed. During PAA disinfection with higher PAA than H 2 O 2 , low levels of monoiodoacetic acid, diiodoacetic acid, and iodoform were formed, and these levels were enhanced with the increase of iodide concentration. No significant quantities of chloro- or bromo-THMs and HAAs were formed during PAA disinfection treatment. [ABSTRACT FROM AUTHOR]

Ozonation of the return activated sludge (AS) flow is an emerging option for excess-sludge reduction. This study aimed to evaluate the potential changes suffered by some kinetic parameters of the activated sludge models (ASMs) in the combined ozone-AS process. The heterotrophic maximum specific growth rate (μ Hmax ) was determined by respirometry in three model-sludges (S1 to S3) treated in batch with different O 3 doses. S1 was a fresh synthetic biosolid composed by only two particulate fractions. S2 was a digestate of S1 almost made by the endogenous residues. S3 was from a municipal wastewater treatment plant. μ Hmax increased significantly from 3.5 d −1 originally, to more than 10 d −1 in the ozonated sludges. Ozonation promoted the selection of fast-growing bacteria in the activated sludges, after transitory inactivation and long lag times. Some microorganisms survived to 3 months of digestion and subsequent ozonation, and then regrow faster than before, once fed again with acetate. The research is of interest from the point of view of the application of the ASM models to the ozone-AS process, but also for wastewater disinfection in general. [ABSTRACT FROM AUTHOR]

The reductions of dissolved organic matter (DOM) and disinfection byproduct precursors in four full-scale wastewater treatment plants (WWTPs) (Liaoning Province, China) where different biological treatment processes were employed in winter were investigated. The total removal efficiencies of dissolved organic carbon (DOC), ultraviolet light at 254 nm (UV-254), trihalomethane formation potential (THMFP), and haloacetic acid formation potential (HAAFP) were in the range of 70.3–76.0%, 49.6–57.3%, 54.4–65.0%, and 53.7–63.8% in the four WWTPs, respectively. The biological treatment was the predominant process responsible for the removal of DOC, THMFP, and HAAFP in WWTPs. Differences in the reduction of UV-254 were not significant ( p > 0.05) among biochemical reaction pool, secondary sedimentation tank, and disinfection tank. Biological aerated filter and suspended carrier activated sludge processes achieved higher DOM removal than the conventional active sludge and anaerobic–anoxic–oxic processes. Hydrophobic neutral and hydrophilic fraction were removed to a higher degree through biological treatment than the other three DOM fractions. HAAFP removal was more efficient than THMFP reduction during biological treatment. During primary treatment, fluorescent materials in secondary sedimentation tanks were preferentially removed, as compared to the bulk DOM. Humic-like fluorescent compounds were not readily eliminated during biological treatment. The fluorescent materials were more susceptible to chlorine than nonfluorescent compounds. [ABSTRACT FROM AUTHOR]

Carbonyl compounds can occur alpha-hydrogens or beta-diketones substitution reactions with disinfectants contributed to halogenated by-products formation. The objective of this research was to study the occurrence and fate of carbonyl compounds as ozonation by-products at two full-scale drinking water treatment plants (DWTPs) using different disinfectants for one year. The quality of the raw water used in both plants was varied according to the season. The higher carbonyl compounds concentrations were found in raw water in spring. Up to 15 (as the sum of both DWTPs) of the 24 carbonyl compounds selected for this work were found after disinfection. The dominant carbonyl compounds were formaldehyde, glyoxal, methyl-glyoxal, fumaric, benzoic, protocatechuic and 3-hydroxybenzoic acid at both DWTPs. In the following steps in each treatment plant, the concentration patterns of these carbonyl compounds differed depending on the type of disinfectant applied. Benzaldehyde was the only aromatic aldehyde detected after oxidation with ozone in spring. As compared with DWTP 1, five new carbonyl compounds were formed (crotonaldehyde, benzaldehyde, formic, oxalic and malonic acid) disinfection by ozone, and the levels of the carbonyl compounds increased. In addition, pre-ozonation (PO) and main ozonation (OZ) increased the levels of carbonyl compounds, however coagulation/flocculation (CF), sand filtration (SF) and granular activated carbon filtration (GAC) decreased the levels of carbonyl compounds. [ABSTRACT FROM AUTHOR]

The relationship between the disinfection by-products (DBPs) formed with chlorination and chloramination techniques and the water chemistry of Haihe River was compared. Samples were collected at 28 different points within the mainstream and tributaries of the river. The DBPs investigated include trihalomethanes (THMs), haloacetic acids (HAAs), haloacetonitriles (HANs), haloketones (HKs), and trichloronitromethane. THMs formed when the samples were chlorinated mostly exceeded 100 and 600 μg/L in the mainstream and tributaries and in the estuary, respectively. A similar trend was obtained for HAAs whose concentrations exceeded 150 μg/L in almost all samples. The amounts of DBPs formed when the samples were chloraminated were much lower than when chlorination was used. The concentrations and species of THMs and HAAs in samples collected from sites near the estuary were different from those in samples collected from the mainstream, which may be due to high concentrations of Cl − and Br − . Although natural organic matter is the major cause of DBP formation during water disinfection, this study shows that other water chemistry factors such as salt composition and concentrations may also considerably affect the formation of DBPs in natural aquatic systems. [ABSTRACT FROM AUTHOR]

The risk of eukaryotic microorganisms in drinking water treatment has not received sufficient attention. As the final step in ensuring drinking water quality, the effectiveness of disinfection in inactivating eukaryotic microorganisms remains to be qualitatively and quantitatively demonstrated. In this study, we conducted a meta-analysis using a mixed effects model and bootstrapping analysis to assess the effects of the disinfection process on eukaryotic microorganisms. The results revealed significant reduction of eukaryotic microorganisms in drinking water associated with the disinfection process. The estimated logarithmic reduction rates for chlorination, ozone, and UV disinfection were 1.74, 1.82 and 2.15 log, respectively, for all eukaryotic microorganisms. Analysis of relative abundance variation of eukaryotic microorganisms also indicated certain phyla and classes exhibited tolerance and competitive advantage during disinfection. This study provides qualitatively and quantitatively analysis on the influence of drinking water disinfection processes on eukaryotic microorganisms, and highlights the persistent risk of eukaryotic microbial contamination in drinking water even after disinfection, calling for further optimization of current conventional disinfection methods. [Display omitted] • The reduction was significantly associated with disinfection. • Ultraviolet disinfection is superior to chlorination and ozone. • Some classes of eukaryotes are more tolerant of disinfection. • There is still a risk of eukaryotic microbial contamination in the pipeline network. [ABSTRACT FROM AUTHOR]

This study applied a method for estimating chlorine decay constant (k) in urban water distribution systems using fluorescence excitation–emission matrix spectroscopy-parallel factor analysis (FEEM-PARAFAC), considering that it accounts for the influence of organic matter in the target area. The simultaneous impacts of seasonal variations on chlorine consumption and dissolved organic matter (DOM) composition were investigated for a year in three full-scale water distribution systems in I city (areas S, K, and G). Bulk decay constants (kb) were obtained through bottle tests, and the kb value was observed to differ by season and significantly affected by temperature. It exhibited its highest value, 0.794 d−1, in summer at area G. As a result of analyses through F-EEM-PARAFAC, it was determined that the components of the target raw water were humic-like and tryptophan-like. The quantitative analysis of organic substances through PARAFAC revealed that area G had the highest score (C1+C2) than other areas. 11.568, 10.578, and 11.771 in summer at areas S, K, and G, respectively. The model equations were derived such that the significant (R2 = 0.85–0.95) correlation between the C1 and C2 model scores and total chlorine decay constants (kt) verified via PARAFAC analysis of the target raw water was considered. Furthermore, a method for obtaining the wall decay constants at a target point based on the correlation equation was investigated. [Display omitted] • To model the chlorine decay in a water distribution network, the reaction rates of chlorine with the water and pipe wall demands must be considered. • The proposed method of estimating the reaction constant with FEEM-PARAFAC is a practical tool to maintain the residual chlorine in urban water distribution system. [ABSTRACT FROM AUTHOR]

India faces high incidents of waterborne disease outbreaks owing to their limited access to safe drinking water. In many ways, the effort to improve the quality of drinking water is performed, and it has been keenly monitored. Among those, the disinfection of drinking water is considered a necessary and important step as it controls the microbial population. Chlorination is the most practiced (greater than 80%) disinfection process in India, and it is known to generate various disinfection byproducts (DBPs). Although the toxicity and trend of DBPs are regularly monitored and investigated in most countries, still in India, the research is at the toddler level. This review summarizes i) the status of drinking water disinfection in India, ii) types of disinfection processes in centralized water treatment plants, iii) concentrations and occurrence patterns of DBPs in a different region of India, iv) a literature survey on the toxicity of DBPs, and v) removal methodologies or alternative technologies to mitigate the DBPs formation. Overall, this review may act as a roadmap to understand the trend of disinfection practices in India and their impacts on securing the goal of safe drinking water for all. [Display omitted] • Chlorination is a widely used disinfection treatment in India. • Proper optimization of chlorine dosage is lacking in many water treatment plants (WTPs). • The governmental program acts as a forum to identify hotspots of microbial contamination. • In drinking water, trihalomethanes are the only regulated DBPs. • Halo acetic acids and nitrogen-based DBPs are emerging DBPs in Indian WTPs. [ABSTRACT FROM AUTHOR]

The coaxial electrospinning method for preparation of g-C 3 N 4 /polyacrylonitrile (PAN)/polyaniline (PANI)@LaFeO 3 cable fiber membrane (PC@PL) was designed for adsorption-filtration-photodegradation of pollutants. A series of characterization results show that LaFeO 3 and g-C 3 N 4 nanoparticles (NPs) are respectively loaded in the inner and outer layers of PAN/PANI composite fibers to construct the site-specific Z-type heterojunction system with spatially separated morphologies. The PANI in cable not only possesses abundant exposed amino/imino functional groups for adsorption of contaminant molecules but also due to the excellent electrical conductivity works as a redox medium for collecting and consuming the electrons and holes from LaFeO 3 and g-C 3 N 4 , which can efficiently promote photo-generated charge carriers separation and improve the catalytic performance. Further investigations demonstrate that as a photo-Fenton catalyst LaFeO 3 in PC@PL catalyzes/activates the H 2 O 2 generated in situ by LaFeO 3 /g-C 3 N 4 , further enhancing the decontamination efficiency of the PC@PL. The porous, hydrophilic, antifouling, flexible and reusable properties of the PC@PL membrane significantly enhance the mass transfer efficiency of reactants by filtration effect and increase the amount of dissolved oxygen, thus producing massive •OH for degradation of pollutants, which maintains the water flux (1184 L m−2. h−1 (LMH)) and the rejection rate (98.5%). Profiting from its unique synergistic effect of adsorption, photo-Fenton and filtration, PC@PL exhibits wonderful self-cleaning performance and distinguished removal rate for methylene blue (97.0%), methyl violet (94.3%), ciprofloxacin (87.6%) and acetamiprid (88.9%) within 75 min, disinfection (100% Escherichia coli (E. coli) and 80% Staphylococcus aureus (S.aureus) inactivation)) and excellent cycle stability. [Display omitted] • Porous coxial PC@PL membrane was prepared coaxial electrospinning stragey. • The membrane has flexible, superhydrophilic and tensile strength characteristics. • Site-specific Z-scheme with redox mediator promotes the carriers separation. • Exposed sorptive functional groups on membrane facilitate pollution adsorption. • Synergism of adsorption, filtration, and photocatalysis result in self-cleaning. [ABSTRACT FROM AUTHOR]

Monoiodoacetic acid (MIAA) is one of the highly toxic halogenated disinfection by-products, which is formed during water disinfection processes. Catalytic hydrogenation with supported noble metal catalyst is a green and effective technique for the transformation of halogenated pollutant, but its activity still needs to be identified. In this study, Pt nanoparticles were supported on CeO 2 modified γ-Al 2 O 3 (Pt/CeO 2 –Al 2 O 3) by chemical deposition method and the synergistic effect of Al 2 O 3 and CeO 2 on catalytic hydrodeiodination (HDI) of MIAA was systematically studied. Characterizations revealed that Pt dispersion could be improved by the introduced CeO 2 through the formation of Ce–O–Pt bond and MIAA adsorption could be facilitated by high Zeta potential of Al 2 O 3 component. Furthermore, optimal Ptn+/Pt0 could be obtained by adjusting CeO 2 deposition amount on Al 2 O 3 , which could effectively facilitate the activation of C–I bond. Therefore, Pt/CeO 2 –Al 2 O 3 exhibited remarkable catalytic activities and TOF values compared with those of Pt/CeO 2 and Pt/Al 2 O 3. Through detailed kinetic experiments and characterization, the extraordinary catalytic performance of Pt/CeO 2 –Al 2 O 3 can be attributed to the abundant Pt sites as well as the synergistic effect between CeO 2 and Al 2 O 3. [Display omitted] • A series of Pt/CeO2–Al2O3 catalysts were prepared by a chemical deposition method. • Catalytic hydrodeiodination of monoiodoacetic acid was firstly investigated over Pt/CeO2–Al2O3 catalysts. • The significant synergistic effect on catalytic hydrodeiodination of monoiodoacetic acid was identified between CeO2 and Al2O3, and Pt/CeO2(20)-Al2O3 exhibited the highest catalytic activity and TOF value. [ABSTRACT FROM AUTHOR]

In early January 2020, the causal agent of unspecified pneumonia cases detected in China and elsewhere was identified as a novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and was the major cause of the COVID-19 outbreak. Later, the World Health Organization (WHO) proclaimed the COVID-19 pandemic a worldwide public health emergency on January 30, 2020. Since then, many studies have been published on this topic. In the present study, bibliometric analysis has been performed to analyze the research hotspots of the coronavirus. Coronavirus transmission, detection methods, potential risks of infection, and effective management practices have been discussed in the present review. Identification and quantification of SARS-CoV-2 viral loads in various water matrices have been reviewed. It was observed that the viral shedding through urine and feces of COVID-19-infected patients might be a primary mode of SARS-CoV-2 transmission in water and wastewater. In this context, the present review highlights wastewater-based epidemiology (WBE)/sewage surveillance, which can be utilized as an effective tool for tracking the transmission of COVID-19. This review also emphasizes the role of different disinfection techniques, such as chlorination, ultraviolet irradiation, and ozonation, for the inactivation of coronavirus. In addition, the application of computational modeling methods has been discussed for the effective management of COVID-19. [Display omitted] • High concentrations of SARS-CoV-2 in wastewater have been reported globally. • Viral shedding via stool and urine are the primary route for SARS-CoV-2 in water. • WBE is an effective tool for early detection and assessment of COVID-19. • Inactivation of SARS-CoV-2 by disinfection is found to be effective. • Computational-based models are useful for the effective management of COVID-19. [ABSTRACT FROM AUTHOR]

Disinfection by-products (DBPs) remain an ongoing issue because of their widespread occurrence and toxicity. Boiling is the most popular household water treatment method and can effectively remove some DBPs. However, the transformation behavior of DBPs during boiling is still unclear, and the key contributors to toxicity have not been identified. In this study, the changes in the concentrations of DBPs in the single-DBP systems and the multi-DBP systems during boiling were monitored, and in-depth discussions on the removal and transformation of DBPs in both systems were carried out. The results showed that boiling was effective in removing volatile DBPs (over 90% for TCAL, TCAN, and DCAN, and over 60% for TCM), but ineffective for non-volatile DBPs (around 20% for TCAA and below 10% for DCAA and MCAA). By hydrolysis and decarboxylation, the transformation occurred among DBPs, i.e., 55% TCAL to TCM, followed by 23% DCAN to DCAA, 22% TCAN to TCAA, and 10% TCAA to TCM. The transformations were found to be significantly influenced by other co-existing DBPs. In multi-DBP systems, the transformations of DCAN to DCAA and TCAN to TCAA were both promoted, while the transformation of TCAN to TCAA was inhibited. Transformation and volatilization are the two processes responsible for DBP removal. Toxicity estimates indicated that boiling was effective in reducing the toxicity of DBPs and improving the safety of the water, despite the interconversion of DBPs in drinking water during boiling. This study emphasized the importance of studying the interconversion behaviors of DBPs in drinking water during boiling and provided practical information for end-use drinking water safety. [Display omitted] • Boiling is effective for the removal of volatile DBPs. • TCAL and TCAA transformed into TCM during boiling. • HANs transformed into HAAs during boiling. • TCAL is most susceptible to be conversed during boiling. • DCAN was identified as the critical DBP for the toxicity by the orthogonal experiments. [ABSTRACT FROM AUTHOR]

Conventional wastewater treatment systems are not designed to remove pharmaceutical compounds from wastewater. These compounds can be degraded into many other transformation products which are hardly, if at all, studied. In this context, we studied the occurrence and degradation of furosemide, a very frequently detected diuretic, along with its known degradation products in several types of wastewater. Influent and effluent from the Seine-Centre Wastewater Treatment Plant (WWTP) (Paris, France) as well as outlet of residential care homes (Dordogne, France) were analyzed by Ultra-Performance Liquid Chromatography-tandem Mass Spectrometry (UPLC-MS/MS) to quantify furosemide and its known degradation products, saluamine and pyridinium of furosemide. Oxidation experiments (chlorination, ozonation and UV photolysis with hydrogen peroxide) were then performed on furosemide solutions and on water from residential care facilities to study the degradation of furosemide by potential advanced processes, and also to identify unknown oxidation products by high-resolution mass spectrometry. Furosemide was well degraded in Seine-Centre WWTP (>75%) but did not increase the concentrations of its main degradation products. Saluamine and pyridinium of furosemide were already present at similar concentrations to furosemide in the raw wastewater (∼2.5–3.5 μg.L−1), and their removal in the WWTPs were very high (>80%). Despite their removal, the three compounds remained present in treated wastewater effluents at concentrations of hundreds of nanograms per liter. Chlorination degraded furosemide without pyridinium production unlike the other two processes. Chlorination and ozonation were also effective for the removal of furosemide and pyridinium in residential care home water, but they resulted in the production of saluamine. To our knowledge this is the first evidence of saluamine and pyridinium of furosemide in real water samples in either the particulate or dissolved phase. [Display omitted] • Pyridinium of furosemide and saluamine were quantified for the first time in wastewater samples. • Seine-Centre WWTP shows a good removal of furosemide and its degradation products. • Ozonation and chlorination completely degrade furosemide but may produce saluamine. • New chlorination and UV/H 2 O 2 degradation products of furosemide were identified. [ABSTRACT FROM AUTHOR]

Peracetic acid (PAA) is a desirable disinfectant for municipal wastewater because of its potent disinfection performance and limited toxic by-products. This study explored the efficiency and mechanism of Escherichia coli inactivation by PAA combined with ultrasound simultaneously (ultrasound + PAA) or (ultrasound → PAA) sequentially. The result showed that 60 kHz ultrasound combined with PAA sequentially (60 kHz → PAA) had excellent inactivation performance on E. coli , up to 4.69-log 10. The result also showed that the increase of pH and humic acid concentration in solution significantly reduced the inactivation efficiency of 60 kHz → PAA treatment. We also observed that the increase of temperature was beneficial to the disinfection, while anions ( C l − ; H C O 3 −) had little effect. With 60 kHz → PAA, the PAA and the synergism between PAA and ultrasound played major contribution to the inactivation, which we assumed might be due to both the diffusion of PAA into the cells and the damage to the cytomembrane by ultrasound, as evidenced through the laser confocal microscopy (LSCM), scanning electron microscope (SEM) and transmission electron microscope (TEM). The inactivation mechanism involved the destruction of cell membrane and loss of intracellular material. Empirically, 60 kHz → PAA was found to be effective for the inactivation of E. coli in actual wastewater, and the regrowth potential of E. coli treated by 60 kHz → PAA was significantly lower than that treated only by PAA. [Display omitted] • The inactivation efficiency of 60 kHz.→ PAA treatment is highest (4.69-log) among all treatments. • PAA and 60 kHz ultrasound play excellent synergistic role in bacteria inactivation. • Inactivation mechanism involved damage of the cytomembrane and loss of cell contents in the 60 kHz.→ PAA treatment. • 60 kHz.→ PAA was effective for the inactivation of E. coli in real wastewater. [ABSTRACT FROM AUTHOR]

Aromatic amines (AAs), a characteristic pollutant with electron-donating groups in textile industry, having high reactivity with reactive chlorine free radicals, is probably the precursor of chlorinated aromatic products in advanced oxidation treatment. In this study, Fe2+/peroxydisulfate (PDS)/Cl- and Fe2+/H2O2/Cl-systems were used to treat four kinds of AAs (5-Nitro-o-toluidine (NT), 4-Aminoazobenzol (AAB), O-Aminoazotoluene (OAAT), 4,4′-Methylene-bis(2-chloroaniline) (MBCA)) in simulated wastewater, and the selectivity of various reactive species to AAs, the oxidation law and pathway of AAs were explored. The results showed that dichloride anion radical (Cl2·-) could effectively oxidize four AAs, and chlorine radical (·Cl) was strongly reactive to AAB and MBCA, especially MBCA. The largest f – (Fukui function) of MBCA is 0.0822, which is the lowest of the four AAs, so ·Cl might be more sensitive to electrophilic point than hydroxyl radical (·OH). The oxidation pathway of NT and MBCA showed that ·Cl mainly played the role of electron transfer to AAs instead of generating chlorinated products, but the addition of ·OH to –NH2 generated aromatic nitro compounds with higher toxicity than NT and MBCA. Therefore, the electron transfer of ·Cl and Cl2·- could not only improve the removal of AAs but also reduce the generation of toxic products. This study found that the reactivity of reactive chlorine free radicals was not necessarily related to chlorination, which provided a theoretical basis for the further studies into the formation mechanism of chlorination products. [Display omitted] • The oxidation of MBCA was obvious in the presence of a large amount of ·Cl. • ·Cl may be more sensitive to the low-activity electrophilic point than ·OH. • ·Cl or Cl 2 ·- has high reactivity with AAs and does not generate chlorinated products. • Reducing toxic products in the process of AAs degradation by electron transfer. [ABSTRACT FROM AUTHOR]

The simultaneous use of UVA light irradiation coupled with low energy cold plasma generated by a dielectric barrier discharge prototype, results in significant enhancement of efficiency of the integrated process with respect to the sole plasma treatment. This effect has been demonstrated both on microbial inactivation of a food-borne pathogen, i.e. Listeria monocytogenes, and on the degradation of a compound of biological origin such as phenylalanine. In the latter case, the analysis of its reaction intermediates and the spectroscopic identification and quantification of peroxynitrites, allowed to propose mechanistic hypotheses on the nature of the observed synergistic effects. Moreover, it has been demonstrated that the process does not affect the quality of trout fillets, indicating its suitability as a chlorine-free, green, and sustainable tool for the decontamination of fish processing water. [Display omitted] • Cold plasma is a chlorine-free technique for water decontamination and disinfection. • Coupling cold plasma with UVA irradiation leads to process intensification. • Synergy explained by the presence of photoactive species in plasma-activated water. • The treatment does not affect the quality of the food. [ABSTRACT FROM AUTHOR]

This review discusses disinfection by-products' (DBPs) potential precursors, formation, and toxicity, alongside available research on the treatment of DBPs in Southeast Asian countries' water sources. Although natural organic matter (NOM) in the form of humic and fulvic acids is the major precursor of DBPs formation, the presence of anthropogenic organic matter (AOM) also plays essential roles during disinfection using chlorine. NOM has been observed in water sources in Southeast Asian countries, with a relatively high concentration in peat-influenced water sources and a relatively low concentration in non-peat-influenced water sources. Similarly, AOMs, such as microplastics, pharmaceuticals, pesticides, and endocrine-disrupting chemicals (EDCs), have also been detected in water sources in Southeast Asian countries. Although studies regarding DBPs in Southeast Asian countries are available, they focus on regulated DBPs. Here, the formation potential of unregulated DBPs is also discussed. In addition, the toxicity associated with extreme DBPs' formation potential, as well as the effectiveness of treatments such as conventional coagulation, filtration, adsorption, and ozonation in reducing DBPs' formation potential in Southeast Asian sources of water, is also analyzed. [Display omitted] • DBPs formation of Southeast Asian water sources was presented. • The presence of NOM and AOM as potential precursors of DBPs were discussed. • Cytotoxicity and Genotoxicity of formed DBPs have been calculated and reviewed. • Research on DBPs control methods in Southeasts Asia has been summarized. • Prospects and challenges for controlling DBPs in Southeast Asia were proposed. [ABSTRACT FROM AUTHOR]

This article describes the assessment of a numerical procedure used to determine the UV lamp configuration and surface roughness effects on an open channel water disinfection UV reactor. The performance of the open channel water disinfection UV reactor was numerically analyzed on the basis of the performance indictor reduction equivalent dose (RED). The RED values were calculated as a function of the Reynolds number to monitor the performance. The flow through the open channel UV reactor was modelled using a k-ε model with scalable wall function, a discrete ordinate (DO) model for fluence rate calculation, a volume of fluid (VOF) model to locate the unknown free surface, a discrete phase model (DPM) to track the pathogen transport, and a modified law of the wall to incorporate the reactor wall roughness effects. The performance analysis was carried out using commercial CFD software (ANSYS Fluent 15.0). Four case studies were analyzed based on open channel UV reactor type (horizontal and vertical) and lamp configuration (parallel and staggered). The results show that lamp configuration can play an important role in the performance of an open channel water disinfection UV reactor. The effects of the reactor wall roughness were Reynolds number dependent. The proposed methodology is useful for performance optimization of an open channel water disinfection UV reactor. [ABSTRACT FROM AUTHOR]

UV reactors are an emerging choice as a big barrier against the pathogens present in drinking water. However, the precise role of reactor's wall roughness for cross flow ultraviolet (CF-UV) and axial flow ultraviolet (AF-UV) water disinfection reactors are unknown. In this paper, the influences of reactor's wall roughness were investigated with a view to identify their role on the performance factors namely dose distribution and reduction equivalent dose (RED). Herein, the relative effects of reactor's wall roughness on the performance of CF-UV and AF-UV reactors were also highlighted. This numerical study is a first step towards the comprehensive analysis of the effects of reactor's wall roughness for UV reactor. A numerical analysis was performed using ANSYS Fluent 15 academic version. The reactor's wall roughness has a significant effect on the RED. We found that the increase in RED is Reynolds number dependent (at lower value of turbulent Reynolds number the effects are remarkable). The effects of reactor's roughness were more pronounced for AF-UV reactor. The simulation results suggest that the study of reactor's wall roughness provides valuable insight to fully understand the effects of reactor's wall roughness and its impact on the flow behavior and other features of CF-UV and AF-UV water disinfection reactors. [ABSTRACT FROM AUTHOR]