AWWA WQTC71630

This paper discusses research at the Greater Cincinnati Water Works (GCWW) to determine cytotoxicity and genotoxicity associated with medium pressure and low pressure ultraviolet (UV) disinfection, and pre- and post-UV chlorination. The experimental approach used post-granular activated carbon (GAC) water from GCWW's full-scale treatment process for the pilot influent. The study used a 55 gpm pilot unit consisting of a single lamp medium pressure reactor (MP, model PMT ISO D1/3) and a 6-lamp low pressure reactor (LP, model ALT230) from Aquionics. There were two phases to the experiment. In the first phase, chlorine was added after the reactors. Samples were collected after the reactors and then dosed with chlorine bleach and sodium hydroxide to obtain a free chlorine residual of 1.5 mg/L and a pH of 8.6. The chemical dosing was completed in a manner to mimic normal plant operation. These samples were then held for three days in a constant water bath to simulate the distribution system. In the second phase, chlorine bleach was applied to the pilot unit prior to the reactors. Chlorinated samples were collected after the reactors and adjusted to a pH of 8.6 with sodium hydroxide. These samples were also held for three days in a constant water bath to simulate the distribution system. After the three days, all of the samples were extracted through XAD resin and concentrated. Includes 4 references, table, figures.