AWWA JAW56603

Haloacetic acids (HAAs) are a group of disinfection byproducts (DBPs) resulting from chlorination of natural organic matter in drinking water. Concerns over the carcinogenic effects of HAAs prompted the US Environmental Protection Agency to regulate them through the Stage 1 Disinfectants/DBP Rule. The stability of HAAs in distribution systems and during sample storage is not well understood, but their control in finished water is important to water utilities. The objectives of this study were to investigate the stability and biodegradation of HAAs in the presence of suspended bacteria or biologically active carbon (BAC) in water and evaluate the carbon adsorption capacities of HAAs through experiments. HAAs were not found to be stable in the presence of biological activity, BAC effectively removed milligram-per-litre, level HAAs spiked in dechlorinated drinking water. The degradation of HAAs coincided with an increase in heterotrophic bacteria growth, indicating that a certain portion of common heterotrophic bacteria in treated water was able to degrade HAAs. Granulated activated carbon (GAC) also removed HAAs, through a combination of carbon adsorption and biodegradation. Zhou and Xie suggest that the carbon adsorption of HAAs could supplement biological HAA removal - when new GAC filter media are installed in water treatment systems, carbon adsorption could remove HAAs before bioactivity is fully developed. By the time the carbon adsorption capacity is exhausted, biodegradation will be dominant in removing HAAs. This study provides water professionals with a better understanding of the stability of HAAs in the distribution system and the importance of sample preservation during HAA monitoring and analysis. Includes 19 references, table, figures.