The Eastern Municipal Water District (EMWD) serves nearly 1 million people within 558 sq. miles in Riverside County, California. As the state’s sixth-largest retail water agency, its mission is to provide, “safe, reliable, economical and environmentally sustainable water, wastewater and recycled water services.”
“We strive at all times to produce the highest quality water possible,” says Matthew Melendrez, P.E., assistant general manager, Operations and Maintenance, “and to do that as economically as possible for our customers to help keep their costs down.”
But a growing population and an expanding service area have put increased demands on the district. Its four reclamation plants treat about 48 million gallons of wastewater a day removing impurities.
“The two main things we're trying to remove are organics and ammonia,” Melendrez says. “If we don't clean those up, they have a large impact on the environment.”
Leaders at the EMWD knew they needed to improve efficiency and optimize aeration basin performance, conserve energy, reduce chemical use and cut operational costs.
Energy-Intensive Process to Control
Aeration is a key step in wastewater treatment, and one of the most energy intensive. The EMWD plants spend nearly half of its electric bills on dissolved oxygen used to biodegrade waste.
“The industry has struggled for a long time with aeration control and finding better ways to operate the basins,” Melendrez explains. “Process parameters change practically every minute of the day as flow rates and volumes of ammonia and organics fluctuate quickly, making it difficult to program a typical PID setpoint to hit its dissolved oxygen (DO) targets.”
