AWWA ACE62959

Disinfection is often considered the most critical step in any drinking water treatment process (Trussel, 1999; LeChevallier, 1999). Secondary disinfection is the primary mitigation step used by utilities to control microbiological growth in distribution systems. Currently, the US Environmental Protection Agency (USEPA) requires that a residual of 0.2 mg/ L disinfectant residual be maintained at the entry point of a distribution system (Federal Register document #52 FR 42199). Research has shown that microorganisms can survive in distribution systems despite the continuing presence of disinfectants (e.g., Pryor et al., 2003; Chauret et al., 2001), therefore placing doubt on the ability of a disinfectant residual to ensure microbial protection from events such as breeches in distribution integrity. It has been shown that a residual of 0.2 mg/L limits the growth of heterotrophic bacteria in the distribution system; however there is limited data that can identify the appropriate amount of disinfectant required to inactivate known pathogens in distribution systems such as E. coli. The focus of this project was to investigate the anti-microbial resistance of E. coli in disinfected annular reactors (ARs) that were operated under conditions relevant to drinking water distribution systems. In addition, this work compared the potential synergies of ultraviolet (UV) treatment and disinfection on E. coli in distribution systems. For comparative purposes, both cast iron and polycarbonate ARs were used to compare disinfectant efficacy on different pipe material. Additionally, three disinfectants were examined during separate AR trials (Cl₂, ClO₂, and NH₂Cl). Includes 7 references.