The haloacetic acid leap in effluent of a biologically active carbon filter experiencing a disinfectant switch

Water utilities must disinfect their water despite the formation of carcinogenic disinfection byproducts (DBPs) such as haloacetic acids (HAAs) upon chlorination. Although employment of a biologically active carbon (BAC) filtration process is able to reduce the HAA level preventively by removing the HAA precursors and correctively by removing the already-formed HAAs, this research reported an HAA leap in a bench-scale BAC filter effluent upon a disinfectant switch from chlorine to chloramine, posing a pressure of meeting the stringent HAA regulations. The HAA6 (sum of six HAAs) tripled from a 5 μg/L base level to a maximum of 17 μg/L during progressive switches with 3 chloramine doses at 5, 25, and 50 mg/L. Dichloroacetic acid (DCAA) accounted for the majority of the leap, which also influenced the bromine substitution factor during the HAA formation. Filtration of distilled water using heat-deactivated media evidenced slight HAA desorption and suggested potential roles of soluble microbial products from biofilms as new HAA precursors for a real BAC filter experiencing a disinfectant switch.