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As an emerging class of uncontrolled disinfection by-products, halobenzoquinones (HBQs) are 3 to 4 orders of magnitude more cytotoxic and genotoxic than regulated disinfection by-products. However, the formation of HBQs in different types of water sources is still unclear. In this study, 2,6-dichloro-1,4-benzoquinone (DCBQ) was selected as the representative species of HBQs to evaluate the formation characteristics during the chlorination of Yellow River diversion water, river water, south–north diversion water and mountain water. Principal component analysis and Pearson correlation analysis were carried out on the relationship between water quality characteristics and the formation of disinfection by-products in order to understand the formation potential of HBQs in each water source and the organic properties of disinfection by-product precursors such as HBQs. The results showed that different water sources have different capacities to form HBQs. The DCBQ formation potential (DCBQ-FP) of river water was the highest, followed by mountain water. The DCBQ-FP of Yellow River diversion water and south–north water diversion water was relatively the lowest. The DCBQ-FP was higher during the high temperature and high algal phase than during the low temperature and low turbidity phase. DCBQ precursors were mainly derived from algal-derived organic matter, low molecular neutrals (LMWN) during periods of high temperature and algal blooms. Aromatic compounds contribute significantly during the regular water quality period. The relationship with microbial metabolites (SMP) was high during periods of low temperature and low turbidity.

Perfluoroalkyl acids (PFAAs) have received considerable attention due to their potential risks to ecological safety and human health. This study detailed the characteristics, source apportionment and health risk assessment of PFAAs in surface drinking water of multiple sources in Shandong Province, eastern China, including the Eastern Route of South-to-North Water Diversion Project (ER-SNWDP) reservoirs, the Yellow River and the local reservoirs. The concentrations of ∑PFAAs in source water ranged from 1.0 to 107.0 ng·L−1, with perfluorooctanoic acid (PFOA) dominating. Correlation analysis and a principal component analysis-multiple linear regression model (PCA-MLR) collectively identified potential pollutant sources and quantified the contributions. In the wet season, fluoropolymer production, fabric and textile industries, and food packaging were the most polluted (99.07%), followed by the metal-plating industry and atmospheric deposition sources (0.93%); in the dry season, fluoropolymer production, fabric and textile industries, and food packaging were still the most polluted (47.96%), followed by atmospheric deposition (33.1%) and the metal-plating industry (18.94%). Cumulative health risk values for different age groups indicated negligible health risks through drinking water exposure, all <0.2. However, the mixture of PFAAs posed the highest hazard to children aged 3–6 years. Potential risks to human health may be present at some sampling sites in the ER-SNWDP since PFOA concentrations exceeded the United States Environmental Protection Agency (USEPA) lifetime health advisory level (70 ng L−1) and were calculated to obtain high risk quotient (RQ) values. The study findings had significant implications for decision-makers to monitor the main sources and reduce the pollution of PFAAs.

Total organic halogen (TOX) is widely used as a surrogate bulk parameter to measure the overall exposure of halogenated disinfection byproducts (DBPs) in drinking water. In this study, we surprisingly found that the level of TOX in chlorinated waters had been significantly underestimated under common analytical conditions. After the addition of quenching agent sodium thiosulfate, total organic chlorine and total organic bromine exhibited a two-phase decomposition pattern with increasing contact time, and a significant decomposition was observed for different types of quenching agents, quenching doses, and pH conditions. More importantly, the decomposed TOX closely correlated with the acute toxicity of quenched water against luminous bacteria, implying that the DBPs responsible for TOX decomposition could be of important toxicological significance. Based on nontarget analysis by using high-resolution mass spectrometry, molecular formulas for the decomposed TOX were determined. After re-examining the mass balance of TOX in the context of unintentional decomposition, it was found that both the level and percentage of unknown TOX in chlorinated waters were considerably higher than historically thought. Overall, this study brings new insights into the knowledge of TOX formed during chlorination, providing important clues on the identification of toxicity driver in drinking water.

Two SBBR systems, designated FSCSBBR (floating spherical carrier) and SCSBBR (multi-faceted polyethylene suspension carrier), were constructed for in-situ sludge reduction. The effects of the operating temperature (T), hydraulic retention time (HRT) and dissolved oxygen (DO) concentration on in-situ sludge reduction in the two SBBR systems were investigated, and the optimum carrier and operating parameters were determined. The results showed that an FSC carrier exhibited a better in-situ sludge reduction efficiency and contaminant removal efficiency than an SC carrier. The optimal operating parameters were a temperature of 25°C, HRT of 12 h and DO concentration of 4–5 mg/L, and the observed sludge yield was 0.21 ± 0.10 g MLSS/g COD. The analysis of biofilm samples showed that FSCSBBR biofilms were richer in microbial species and exhibited higher diversity than SCSBBR biofilms. Biofilm sludge hydrolysis and cytolysis promoted in-situ sludge reduction.

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.

The Yangtze River basin covers one-fifth of China’s land area and serves as a water source for one-third of China’s population. During long-distance water transport from upstream to downstream, various sources of dissolved organic matter (DOM) lead to considerable variation in DOM properties, significantly impacting water treatability and disinfection byproduct (DBP) formation after chlorination. Using size-exclusion chromatography and fluorescence spectroscopy, the spatial variation in DOM characteristics was comprehensively investigated on a basin scale. The formation of 36 DBPs and speciated total organic halogen in chlorinated samples was determined. Overall, the Yangtze River waters featured a high proportion of terrestrially derived humic substances that served as important precursors for trihalomethanes and haloacetic acids, which was responsible for the increase in total DBP formation along the Yangtze River. The downstream waters were characterized by high levels of microbially derived protein-like biopolymers, which significantly contributed to the formation of haloacetaldehydes and haloacetonitriles that dominated DBP-associated mammalian cell cytotoxicity. Moreover, the precursors of haloacetaldehydes and haloacetonitriles in downstream waters were highly hydrophilic, posing a challenge for water treatment. This study presents an extensive basin-scale study, providing insights into DOM variations along the Yangtze River, illustrating the impact of DOM properties on drinking water from a DBP perspective.