Like thousands of cities throughout the United States, the City of DeSoto purchases treated water from a nearby wholesaler. In this case, the wholesaler is Dallas Water Utilities  or DWU.

DWU operates three surface water treatment plants and disinfects treated water with chloramines, which are less reactive than free chlorine and result in fewer disinfection byproducts (DBPs). Formed by reacting ammonia and chlorine, chloramines are a very effective disinfectant and typically have a high level of persistence in water systems with high water ages.

The challenge for DeSoto is managing complex water chemistry in a distribution system with over 200 miles of pipeline and millions of gallons of stored water, all while meeting increasingly stringent state and federal quality standards for drinking water. One downside of chloramines is that the disinfectant molecule can break down over time and liberate free ammonia, which can then become a food sources for nitrifying bacteria – leading to tank nitrification.

Operators at DeSoto were manually dosing chemicals into storage tanks in an attempt to boost residual levels. They were raising and lowering tank levels (a practice known as “deep cycling”) or they were flushing millions of gallons of water from the tanks to bring in fresher water with higher levels of residual disinfectant.

Learn how DeSoto went from this to flushing 90% less water while maintaining consistent disinfectant residual levels in compliance with water quality regulations.