Eastern Municipal Water District (EMWD) serves about 142,000 customers in Riverside County, California. The EMWD service area is one of the largest for any water district in arid southern California. On the drinking water side, EMWD manages two water treatment plants and over 15 reservoirs. With 70% of the district’s water coming from the Metropolitan Water District with chloramine disinfection, EMWD has become reliant on chloramine disinfection to manage long transmission lines and longer detention times due to on‐going water scarcity.

As is common in systems utilizing chloramines for secondary disinfection, EMWD experiences chronically low disinfection residuals at certain points in their distribution system – especially in warmer months. In 2016, UGSI Solutions partnered with EMWD to pilot the Monoclor® Residual control system at one of the two 5.5 million gallon Landmark reservoirs. The site has two 5.5 million gallon tanks with a common inlet and outlet. The site was ideal for performance comparison as one tank could act as a control to the other tank utilizing the trailer mounted Monoclor® residual control system.