You are here:
Understanding Disinfection Residuals
Citation:
Pressman, J. AND D. Wahman. Understanding Disinfection Residuals. U.S. EPA’s Office of Research and Development and Region 6 2019 Small Drinking Water Systems Meeting, Dallas, Texas, May 21 - 22, 2019.
Impact/Purpose:
This study evaluated the meaning of minimum disinfection residuals, the effects of where water utilities monitor for disinfection residuals and how many samples are taken and evaluated EPA six year review data for chlorine residuals and corresponding total coliform positive samples. The results demonstrated that higher residuals result in less coliform positives. The results also showed that where and how often a water utility monitors chlorine residuals can have significant impact on understanding chlorine residuals throughout the distribution system. This has important implications on the management of chlorine and chloramines and the operation of water distribution systems. This research will be of high interest to water utilities and practitioners in the field of drinking water.
Description:
For public drinking water systems in the U.S. using surface water and/or groundwater under the influence of surface water sources, EPA and state regulations require residual disinfectants to be maintained throughout the water distribution system. However, minimum residual concentrations, number of samples, and locations for monitoring vary widely. This presentation reviewed the history of distribution system chlorine monitoring siting, overview the diversity in state regulations/guidance, and presented a case study demonstrating an evaluation of chlorine monitoring locations in a distribution system. Finally, residual disinfectant concentration vs. coliform/E. coli data were presented from the Agency’s recently released third Six-Year Review supporting the relationship between disinfectant residual and microbial stability reported in the scientific literature.