Halogenated disinfection byproducts (DBPs) are inevitably formed during chlorine disinfection of drinking water and they may threaten human health. Numerous efforts have been put in investigating the formation and toxicity of natural organic matter (NOM)-derived halogenated DBPs in the past decades. Recently, pharmaceuticals have been considered as a major group of emerging micropollutants in source waters, but their roles in DBP formation and toxicity during chlorine disinfection remain largely unclear. In this study, the contributions of NOM and pharmaceuticals (a mixture of ten selected pharmaceuticals) to the overall DBP formation and toxicity during drinking water chlorination were investigated. By comparing the total organic halogen (TOX) levels in “NOM only” and “Phar only” samples with “NOM + Phar” sample, NOM and pharmaceuticals were found to play additive roles on the halogenated DBP formation. In bromide-free samples with chlorine contact times of 0.5–2.0 h, NOM (2 mg/L as C) and pharmaceuticals (0.3 mg/L as C in total) contributed 79–83% and 17–22% of the total organic chlorine (TOCl), respectively. In bromide-containing samples, NOM (2 mg/L as C) and pharmaceuticals (0.3 mg/L in total) contributed 82–84% and 16–18% of the TOX, respectively. Using the obtained experimental data together with the quantum chemical calculations, a kinetic model involving chlorine reactions with pharmaceuticals and NOM was established to quantitatively predict the contributions of NOM and pharmaceuticals to the TOX formation in chlorination of source waters. Developmental toxicity results demonstrated that pharmaceutical-derived DBPs might contribute significantly to the overall toxicity. More interestingly, pharmaceutical-derived DBPs and NOM-derived DBPs showed an antagonistic effect on the developmental toxicity. A toxicity model was developed based on the concentration addition concept, which allows predicting the toxicity of DBP mixtures as a function of the concentrations of NOM and pharmaceuticals.

Pharmaceuticals might contribute to the formation and toxicity of DBP mixtures in chlorine disinfection

ACS Fall 2021

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