AWWA WQTC64090

The objectives of this slide presentation were to: evaluate impacts of UV/Cl₂ on the formation of seven classes of disinfection byproducts (DBPs) including THMs, HAAs, HANs, CP, TCP, Haloacetamides, and TOX; Greater Cincinnati Water Works (GCWW) water from three locations; influent to carbon contactors (GACI); effluent from carbon contactors (CSW); effluent from the oldest carbon contactor (CN7); LPHO and MP UV were used @ 40, 105, and 140 mJ/cm². The testing protocol included: all samples at all doses were tested at conditions simulating GCWW's operations; 30º C, pH 8.6, 3-days retention time to simulate summer conditions; one set of testing was conducted at 10 and 20ºC using MP-UV (at 140 mJ/cm²) to simulate winter conditions; all samples were shipped to Duke University, where UV exposure, and 3- day plant simulation conditions were maintained; and, at the end of the simulation conditions, samples were dechlorinated. Samples were then shipped to UMASS where all the DBP analyses were performed. Conclusions were that: UV treatment did not substantially change water samples' tendency to form THMs, HAAs, haloacetonitriles, and the closely associated haloacetamides, or TOX under the conditions tested; no difference between LP and MP lamps for these DBPs was observed; and, the higher concentrations of DCA at 30ºC were likely due to the higher rate of DCAN degradation, therefore higher rate of formation; LP UV did not cause an increase in CP formation under all test conditions; CP increased as a result of MP UV treatment by about 0.9 µg/L under worst conditions (30ºC and 140 mJ/cm²) for carbon contacted water; the only drinking water standard for CP is in the State of California; an action level of 50 µg/L (37 µg/L T&O threshold) was included in a March 1986 list of DHS action; this was revised to 56 µg/L in 2002 and now referred to as historic archived advisory level. There is also a NIOSH standard of 100 ppb, based on its action as an eye irritant. It is very likely that impact of CP will be insignificant for drinking water disinfection doses. Finally, at normal disinfection doses of UV, chlorine, and pH there doesn't seem to be much increase in the DBPs studied.