Characterization of phthalate esters (PAEs) in urban water supply system: PAE-degrading bacteria existed in the pipeline biofilm.

The water supply system is a crucial infrastructure related to the people's livelihood. To enhance the performance of pipelines, additives are commonly added to the plastic pipes. Among these, phthalate esters (PAEs), a type of emerging contaminants, have been proven to be released from plastic pipes to water. In this study, we investigated the occurrence of PAEs in drinking water supply systems, isolated PAE-degrading bacteria and explored their characteristics. Firstly, a total of six PAEs were detected throughout the process from raw water to tap water, and the concentrations of ΣPAEs in tap water at three sampling sites were all higher than those in the finished water. Secondly, using PAEs as the sole carbon source, four strains of PAE-degrading bacteria were isolated from the simulated pipeline biofilm. Within 12 h, the degradation rates of these four strains towards ΣPAEs (initial concentration: 1 mg/L) were 34.83 % - 56.54 %. Thirdly, considering the presence of multiple carbon sources, residual chlorine, and other bacteria, the behavior of the isolated PAE-degrading bacteria in the actual pipeline environment was examined. It showed that PAE-degrading bacteria preferentially used other carbon sources in tap water rather than PAEs, and the residual chlorine inhibited the bacteria's ability to degrade PAEs. Moreover, despite the presence of other bacteria from the biofilm, the PAE-degrading bacteria still became the dominant bacteria. Consequently, this study demonstrated the feasibility of PAE degradation by bacteria isolated from the pipeline biofilm, which was helpful for understanding the biochemical degradation process of PAEs in drinking water supply systems.