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The existence of natural organic matter (NOM) causes many problems in drinking water treatment processes. The degradation of different fractions of NOM in drinking water was studied using the ultraviolet/persulfate (UV/PS) process. The NOM was separated into hydrophobic (HPO), transition hydrophilic (TPI) and hydrophilic (HPI) fractions by reverse osmosis and XAD series resins. The effects of degradation were evaluated by dissolved organic carbon (DOC), UV 254 , three-dimensional fluorescence-parallel factor analysis (EEM-PARAFAC), and trihalomethane formation potential (THMFP). The results showed that UV/PS process could remove the three fractions of DOC, UV 254 , as well as the fluorescent components humic acid-like (C1 and C2) and protein-like (C3). The maximum removal rates of DOC of HPO, TPI, and HPI fractions were 34.6%, 38.4%, and 73.9%, respectively, and the maximum removal rates of UV 254 were 72.1%, 86.3%, and 86.8%, respectively. The removal rate of the three fluorescent components can reach 100%, and C3 is easier to remove than C1 and C2 under the low PS dosage conditions. The order of kinetic degradation rate constant of UV 254 first-order reaction is HPI > TPI > HPO. The optimum pH conditions for the degradation of HPO, TPI, and HPI fractions were acidic, basic, and neutral, respectively. The specific THMFP of HPO was higher than that of TPI and HPI. The specific THMFP of HPO and TPI fractions increased with the increase of radiation time, while the HPI fraction showed the opposite trend. THMFP has different degrees of correlation with DOC, UV 254 , C1, and C2. This study can provide a theoretical basis for the selection of the UV/PS process for drinking water sources containing NOM with different characteristics., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

This study examined the effectiveness for degradation of hydrophobic (HPO), transphilic (TPI) and hydrophilic (HPI) fractions of natural organic matter (NOM) during UV/H 2 O 2 , UV/TiO 2 and UV/K 2 S 2 O 8 (UV/PS) advanced oxidation processes (AOPs). The changing characteristics of NOM were evaluated by dissolved organic carbon (DOC), the specific UV absorbance (SUVA), trihalomethanes formation potential (THMFP), organic halogen adsorbable on activated carbon formation potential (AOXFP) and parallel factor analysis of excitation-emission matrices (PARAFAC-EEMs). In the three UV-based AOPs, HPI fraction with low molecular weight and aromaticity was more likely to degradate than HPO and TPI, and the removal efficiency of SUVA for HPO was much higher than TPI and HPI fraction. In terms of the specific THMFP of HPO, TPI and HPI, a reduction was achieved in the UV/H 2 O 2 process, and the higest removal rate even reached to 83%. UV/TiO 2 and UV/PS processes can only decrease the specific THMFP of HPI. The specific AOXFP of HPO, TPI and HPI fractions were all able to be degraded by the three UV-based AOPs, and HPO content is more susceptible to decompose than TPI and HPI content. UV/H 2 O 2 was found to be the most effective treatment for the removal of THMFP and AOXFP under given conditions. C1 (microbial or marine derived humic-like substances), C2 (terrestrially derived humic-like substances) and C3 (tryptophan-like proteins) fluorescent components of HPO fraction were fairly labile across the UV-based AOPs treatment. C3 of each fraction of NOM was the most resistant to degrade upon the UV-based AOPs. Results from this study may provide the prediction about the consequence of UV-based AOPs for the degradation of different fractions of NOM with varied characteristics., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this article., (Copyright © 2022. Published by Elsevier B.V.)

The occurrence and removal efficiencies of organophosphorus flame retardants (OPFRs) by traditional treatment processes (pre-flocculation, sand filtration, and post-chlorination processes) and advanced treatment processes (i.e., ozone and granular activated carbon (GAC), ultraviolet/hydrogen peroxide (UV/H 2 O 2 ), GAC alone, ultrafiltration membrane, nanofiltration membrane) were examined in two municipal plants and a pilot plant in Jinan, China. The concentrations of six OPFRs in raw waters were at levels of 16.8-100.0 ng/L, and three OPFRs were below the detection limits. The traditional treatment processes could not effectively remove the OPFRs (the removal efficiency was - 12.0-15.4%). The advanced oxidation with ozone and GAC (the removal efficiency was 35.6-60.3%) or UV/H 2 O 2 and GAC processes (the removal efficiency was 68.0-86.7%) were more effective than the traditional water treatment processes. The removal efficiencies of ultrafiltration process for the OPFRs was 11.2-69.8% which were positively correlated with the logKow values of OPFRs. The nanofiltration membrane process with ultrafiltration membrane process as the pretreatment was the most effective process (the removal efficiencies were almost to 100%). These results imply that the combination of ultrafiltration membrane and nanofiltration membrane is an effective measure in the treatment of OPFRs in municipal drinking water plants., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Snow with large specific surface area and strong adsorption capacity can effectively adsorb atmospheric pollutants, which could/might lead to the increase of disinfection by-product (DBP) precursors in surface water. In this study, the contents and characteristics of dissolved organic matter (DOM) in meltwater were investigated, and DBP formation and the DBP-associated cytotoxicity index during chlorination of meltwater was first explored. Overall, meltwater exhibited high nitrogen contents. Meltwater-derived DOM was mainly composed of organics with low molecular weights, low aromaticity, and high unsaturated degrees. DBP formation potentials and cytotoxicity indexes in chlorinated meltwater were positively correlated with air quality index and were significantly impacted by snowfall stages. The trihalomethane and haloacetic acid yields from meltwater were relatively low, while yields of highly cytotoxic DBPs, especially halonitromethanes (6.3-10.8 μg-HNMs/mg-DOC), were significantly higher than those of surface water (1.7 μg-HNMs/mg-DOC). Notably, unsaturated nonaromatic organic nitrates in meltwater were important precursors of halonitromethanes. The actual monitoring results showed that snowfall significant increased the haloacetaldehydes and nitrogenous DBP formation levels of surface water. Considering increased DBP formation and DBP-associated toxicity, it was demonstrated that DOM derived from snowfall in atmosphere-polluted areas could deteriorate surface water quality and pose potential risks to drinking water.

2,6-dichloro-1,4-benzoquinone (DCBQ), a typical representative of Halobenzoquinones, is an emerging aromatic disinfection by-product (DBP) with high toxicity and carcinogenicity, generated commonly through the chlorination in the drinking water disinfection process while there is still a lack of research on its removal. In this study, the effects of ultraviolet-based advanced oxidation processes (UV-AOPs) on the degradation of DCBQ were evaluated. The results showed that UV-AOPs are effective in degrading DCBQ. The removal of DCBQ by UV/H 2 O 2 /O 3 was more significant than by UV/H 2 O 2 or UV/O 3, achieving a 96.7% removal rate at both the O 3 and H 2 O 2 doses of 1 mg/L. The results also indicated the alkaline and weakly acidic environments could facilitate the degradation of DCBQ, inorganic anions could inhibit DCBQ degradation and the degree of inhibition increased as the matrix concentration increased. The degradation of DCBQ was inhibited more by the CO 3 2- than the other matrix components, such as Cl - and NO 3 - . It was shown by the density functional theory simulations and the ultrahigh-performance liquid chromatography (UPLC) - Orbitrap mass spectra that the electrons in DCBQ are mainly on the chlorine atom connected to the carboatomic ring and that OH• can attack the chlorine atom to cause de-chlorination. The DCBQ degradation pathway may involve the oxidation of DCBQ to 3-hydroxy-2,6-DCBQ (HO-DCBQ) and 3,5-dichloro-1,2,4-pyrogallol, the further degradation of intermediate products by OH• to dechlorinated forms of HO-DCBQ and DCBQ., (Copyright © 2022. Published by Elsevier Ltd.)

Chlorine-resistant bacteria threaten drinking water safety in water distribution systems. In this study, a novel chlorine-resistant bacterium identified as Gordonia was isolated from the drinking water supply system of Jinan City for the first time. We examined the resistance and inactivation of the isolate by investigating cell survival, changes in cell morphology, and the permeability of cell membranes exposed to chlorine. After 240 min chlorine exposure, the chlorine residual was greater than 0.5 mg L -1 and the final inactivation was about 3 log reduction, which showed that the Gordonia strain had high chlorine tolerance. Flow-cytometric analysis indicated that, following sodium hypochlorite treatments with increasing membrane permeability, culturable cells enter a viable but nonculturable state and then die. We also investigated the inactivation kinetics of Gordonia following chlorine dioxide and ultraviolet radiation treatment. We found that these treatments can effectively inactivate Gordonia, which suggests that they may be used for the regulation of chlorine-resistant microorganisms.

The addition of Fe 3+ to TiO 2 is one of the effective methods to inhibit the recombination of photogenerated electrons and holes and thus improve the photocatalytic activity of TiO 2 . The effect of PVDF-PVP-TiO 2 -FeCl 3 (PPTFe) membrane filtration-photocatalytic system on the removal of trace concentration of sulfadiazine (SD) in water was evaluated. A two-factor four-level experiment was established to optimize 16 self-made modified membranes. The optimal membrane was then characterized in seven tests (SEM, EDS, membrane pure water flux, contact angle, porosity, mean pore size, ATR-FTIR), resulting in the optimal ratio (PPTFe membrane with 1.2 wt%TiO 2 and 0.8 wt%FeCl 3 ). Compared with the original membrane, the pore number, pore size, permeability, and hydrophilicity of the PPTFe membrane were all enhanced. The removal efficiency (92.63%) of SD by PPTFe membrane filtration-photocatalysis system was investigated. The reaction rate (0.0214 min -1 ) of the removal SD of the system was determined according to the pseudo-first-order kinetic model. The removal performance of membrane type, pH, and water quality parameters (Cl - , SO 4 2- , NO 3 - , HA) on PPTFe membrane filtration-photocatalytic system were also made a deep inquiry. The results reflected that acidic conditions (pH = 3) were beneficial to SD removal, the presence of Cl - , SO 4 2- , and HA could inhibit SD removal, while the existence of NO 3 - was unaffected. Furthermore, the removal rate of SD in the actual water body was displayed well in this system. Finally, the possible photocatalytic degradation mechanism was proposed.Graphical abstract.

This study investigated the prevalence of ten odorous compounds (2-methylisoborneol, trans-1,10-dimethyl-trans-9-decalol, isophorone, 2,4,6-trichloroanisole, 2,3,6-trichloroanisole, 2,3,4-trichloroanisole, β-cyclocitral, β-ionone, 2-isobutyl-3-methyoxypyrazine, and 2-isopropyl-3-methoxypyrazine) in raw drinking water, as well as their removal by traditional processes, advanced oxidation processes, ultrafiltration, and nanofiltration processes, with the use of an ultrahigh-resolution Orbitrap. The most abundant odorous compounds referred to 2-methylisoborneol and trans-1,10-dimethyl-trans-9-decalol with maximal concentrations of 1.6 ng/L and 0.09 ng/L after treatment by traditional processes respectively, and their maximal concentration was 2.05 ng/L and lower than the detection limit after treatment by advanced oxidation processes, while the raw drinking water of the mentioned two processes was different. The high concentration of isophorone in water treated by traditional process, advanced oxidation process, and membrane process was also ascertained. On the whole, the removal rate of membrane process is the maximal for all odorous compounds except for 2,3,6-trichloroanisole, followed by the advanced oxidation process as well as the traditional process. Eight odorous compounds identified in raw water were preserved after traditional treatment, while five compounds were preserved after the advanced oxidation treatment. The combined ultrafiltration and nanofiltration with pre-flocculation was more effective than either the advanced oxidation process or the traditional treating process in removing odorous compounds, and over 90% of all the odorous compounds were removed. Further investigation is required to facilitate the removal of odorous compounds from drinking water by the incorporation of ultrafiltration and nanofiltration units based on current drinking water treatments.

Trihalomethanes (THMs) and adsorbable organic halides (AOX) were generated in chlorinated water. The purpose of the study was to provide a comprehensive picture of concentration distribution, the seasonal and different water source variability of THMs and AOX. Data for THMs, AOX, and other physico-chemical parameters were from 538 samples of 16 drinking water work through a 3-year sampling program which was conducted in Shandong province with typical temperate and monsoonal climate. Selected samples were considered with the influence of factors such as season, water source, and disinfectant. The THMs and AOX concentration of the samples disinfected with chlorine ranged from 2.1-105 μg/L and 11-238 μg/L, respectively. The THMs and AOX concentration of the samples disinfected chlorine dioxide ranged from N.D.-47.6 μg/L and N.D.-102 μg/L, respectively. The median concentration of THMs and AOX of samples disinfected with chlorine were 35 μg/L and 61 μg/L, much higher than chlorine dioxide, respectively. Ninety-two percent of the samples disinfected with chlorine and all samples disinfected with chlorine dioxide met Chinese drinking water standard for THMs. The ratio of tribromethane (TBM) to THMs of samples disinfected with chlorine was 19%, lower than chlorine dioxide 42%. Bromine substitution factor (BSF) of THMs and initial concentration of bromide showed weak correlation, and the Spearman correlation coefficient was 0.38. THMs and AOX concentrations showed noticeable seasonal variations with the highest median concentrations in spring. The levels of THMs and AOX in drinking water varied with different water sources and followed the order local reservoir > Yellow River reservoir > ground water. The survey results complement the database of THMs and AOX occurrence in drinking water in China, and offer a significant reference data for setting disinfections by-products occurrence in countries or regions with similar climate around the world.

The addition of Fe3+ to TiO2 is one of the effective methods to inhibit the recombination of photogenerated electrons and holes and thus improve the photocatalytic activity of TiO2. The effect of PVDF-PVP-TiO2-FeCl3 (PPTFe) membrane filtration-photocatalytic system on the removal of trace concentration of sulfadiazine (SD) in water was evaluated. A two-factor four-level experiment was established to optimize 16 self-made modified membranes. The optimal membrane was then characterized in seven tests (SEM, EDS, membrane pure water flux, contact angle, porosity, mean pore size, ATR-FTIR), resulting in the optimal ratio (PPTFe membrane with 1.2 wt%TiO2 and 0.8 wt%FeCl3). Compared with the original membrane, the pore number, pore size, permeability, and hydrophilicity of the PPTFe membrane were all enhanced. The removal efficiency (92.63%) of SD by PPTFe membrane filtration-photocatalysis system was investigated. The reaction rate (0.0214 min−1) of the removal SD of the system was determined according to the pseudo-first-order kinetic model. The removal performance of membrane type, pH, and water quality parameters (Cl−, SO42−, NO3−, HA) on PPTFe membrane filtration-photocatalytic system were also made a deep inquiry. The results reflected that acidic conditions (pH = 3) were beneficial to SD removal, the presence of Cl−, SO42−, and HA could inhibit SD removal, while the existence of NO3− was unaffected. Furthermore, the removal rate of SD in the actual water body was displayed well in this system. Finally, the possible photocatalytic degradation mechanism was proposed. Graphical abstract [ABSTRACT FROM AUTHOR]

Humic acid (HA) in water is the main precursor of disinfection by-products in the chlorination process of drinking water. In this study, an ultraviolet/persulfate (UV/PS) process, in a laboratory-scale system, is successful in the degradation of HA. The results showed that HA was significantly degraded (UV254 removal rate of ~ 89%) and partially mineralized (~ 62.5%) by UV/PS treatment at a PS dose of 0.4 mM, pH of 7.12, and UV irradiation time of 160 min. The trihalomethane formation potential (THMFP) was also significantly reduced (THMFP reduction of ~ 85.4%). A strong linear relationship was observed between UV254 and dissolved organic carbon. The removal rate of HA at low pH was better than that at high pH conditions, and the inhibition by Cl− slowed down after an initial increase, and the inhibition was weaker than HCO3−. By analyzing the fluorescence spectrum of two humic-like substances, the fluorescent compounds C1 and C2 in HA were significantly degraded, and the change in C1 and C2 concentration was correlated with the decrease of THMFP. The degradation of different fractions of natural organic matter in real-world water samples indicated that UV/PS has significant potential to decrease HA in water. [ABSTRACT FROM AUTHOR]

• Younger and smaller carbons were associated with higher DOM removal rates. • Actinobacteria and Legionella were main microorganisms for BAC to degrade H 2 O 2. • Potential pathogenic microorganisms proportion in UV/H 2 O 2 -BAC effluent is smaller. • UV/H 2 O 2 -BAC process can be used as an alternative to the O 3 -BAC process. An UV/H 2 O 2 -BAC combination process was developed and the effects of activated carbon columns with carbon of different ages and particle sizes were compared and inspected under long-term operation conditions. In addition, differences in the microbial community structure of the biological membrane on the surface of the activated carbons was explored by scanning electron microscopy (SEM) and high-throughput sequencing. Furthermore, the removal efficiency of organic matter and the microbial community structure were compared between UV/H 2 O 2 -BAC and O 3 -BAC processes under the same treatment conditions. The results showed that younger carbon age and smaller particle size were associated with higher organic matter removal rates. Additionally, Actinobacteria and Legionella were the main microorganisms for BAC to degrade hydrogen peroxide, and the microbial species of the four activated carbons were basically the same, differing only in abundance. When compared with the O 3 -BAC process, the UV/H 2 O 2 -BAC process had higher removal efficiency for organic matter and higher effluent safety. Overall, the results indicate the UV/H 2 O 2 -BAC process can be used as an alternative to the O 3 -BAC process for control of bromate. [ABSTRACT FROM AUTHOR]