Change of genotoxicity for raw and finished water: Role of purification processes

In China, the safety of drinking water becomes a significant issue due to serious aquatic environmental pollution. The genotoxic levels of raw and finished water from seven typical waterworks located in the five basins in China were then evaluated using umu test. Effect of conventional treatment processes (coagulation, filtration and disinfection) on the genotoxicity and the fate of dissolved organic matter (DOM) was discussed. The results showed that most of the selected finished water presented genotoxicity at or lower than 300 mL water sample exposure dose. The genotoxic effects of finished water were significantly higher than those of raw water. It also exhibited that there existed higher correlation between genotoxic effect and Br− than the other water quality parameters. The brominated trihalomethanes played a more important role in finished water genotoxicity than brominated haloacetic acids. The treatment processes could increase the genotoxic effects of finished water, especially for the chlorination treatment. The fluorescence spectra and high performance size-exclusion chromatogram analysis of DOM characters indicated that the proportion of low molecular weight acids, nitrogen containing aromatics, proteinaceous and microbially derived organic matters (200–300 Da) increased during purification processes, which indicated probably the release or formation of drinking water genotoxins.

Research highlights
► Most of the selected finished water samples presented safety risk.
► Successive treatment processes could increase the genotoxic effects of finished water, especially chlorination treatment.
► Br− and brominated THMs played a more important role in finished water genotoxicity.
► The increase of low molecular weight organic matters (200–300 Da) after treatment might be presented by the formation of drinking water genotoxins.