Surface Water Treatment Rule Targets Microbials

Abstract

The goal of the Surface Water Treatment Rule (SWTR) is to ensure that harmful microbes are either removed or inactivated. This article discusses regulatory requirements, focusing on removal by filtration. Rather than performing difficult tests to monitor for microorganisms, water systems must accumulate a certain number of credits or points by achieving certain treatment goals. A table summarizes filtration credits, which are based on turbidity after filtration. Details on filtration credits and turbidity standards are given for conventional treatment with direct filtration, slow sand filtration, and diatomaceous earth filtration. Finally, some suggestions for improving filtration are given. This is one in a series of five articles about the Surface Water Treatment Rule. Other articles discuss “SWTR Disinfection Standards for Filtered Systems” (June 1993); “SWTR – C x T Values Indicate Disinfection Applied” (July 1993); “Configuration, Operation of System Affects C x T Values” (August 1993); and “SWTR Conditions to Avoid Filtration Are Demanding (September 1993).