REDUCING CANCER RISKS BY IMPROVING ORGANIC-CARBON REMOVAL

A computer simulation methodology is described that examines on a case -specific basis the effect of water quality on the formation of trihal omethanes (THMs) and their associated theoretical cancer risks. The st rategy of controlling organic carbon concentrations at the point of ch lorination was evaluated for its ability to reduce predicted cancer in cidence. In waters containing bromide, the absolute concentrations of the more brominated THMs can increase as organic carbon concentration is reduced at the point of chlorination; total theoretical cancer risk s induced by THMs, however, decreased for all water qualities consider ed. Reduction of THM-induced cancer risks by enhanced coagulation, gra nular activated carbon adsorption, and membrane filtration increased a s the source water bromide concentration increased. When risks induced by haloacetic acids are considered, these technologies may achieve si gnificantly greater levels of risk reduction than are estimated by con sidering THM risks only.