Contributions of Pharmaceuticals to DBP Formation and Developmental Toxicity in Chlorination of NOM-containing Source Water

Thisstudy uses both experimental and modeling approachesto reveal the important contributions of emerging pharmaceuticalsto DBP formation and toxicity during drinking water chlorination. Pharmaceuticals have been considereda priority group of emergingmicropollutants in source waters in recent years, while their rolein the formation and toxicity of disinfection byproducts (DBPs) duringchlorine disinfection remains largely unclear. In this study, thecontributions of natural organic matter (NOM) and pharmaceuticals(a mixture of ten representative pharmaceuticals) to the overall DBPformation and toxicity during drinking water chlorination were investigated.By innovatively normalizing chlorine exposure andconstructing a kinetic model, we were able to differentiate and evaluatethe contributions of NOM and pharmaceuticals to the total organichalogen (TOX) formation for source waters that contained differentlevels of pharmaceuticals. It was found that at a chlorine contacttime of 1.0 h, NOM (2 mg/L as C) and pharmaceuticals(total 0.0062-0.31 mg/L as C) contributed79.8-99.5% and 0.5-20.2%, respectively, of TOX. Thetoxicity test results showed that the chlorination remarkably increasedthe toxicity of the pharmaceutical mixture by converting the parentcompounds into more toxic pharmaceutical-derived DBPs, and these DBPsmight contribute significantly to the overall developmental toxicityof chlorinated waters. This study highlights the non-negligible roleof pharmaceuticals in the formation and toxicity of overall DBPs inchlorinated drinking water.

Automated summary

This study uses experimental and modeling approaches to investigate the contributions of emerging pharmaceuticals to the formation and toxicity of disinfection byproducts (DBPs) during drinking water chlorination. It was found that pharmaceuticals and natural organic matter (NOM) contribute to the formation of total organic halogens (TOX) in varying degrees. The toxicity test results show that chlorination increases the toxicity of pharmaceuticals by converting them into more toxic DBPs, which can significantly contribute to the overall developmental toxicity of chlorinated waters.