Protecting California's Groundwater with Recycled Water
The Water Replenishment District (WRD) of Southern California is the regional groundwater management agency charged with protecting and preserving water supply for over 4 million residents in Los Angeles County. It manages the groundwater resources of the Central and West Coast Basins, and artificially replenishes each basin by spreading and injecting imported and treated recycled water back into the system via seawater intrusion barriers like the Alamitos and Dominguez Gap barriers, and mid-basin spreading grounds like the Montebello Forebay.
The district’s state-of-the-art Leo J. Vander Lans water treatment facility in Long Beach, California receives treated water from the Los Angeles County Sanitation Districts’ Long Beach water reclamation plant. The water is purified using advanced treatment technologies and is then injected into the Alamitos Barrier, protecting groundwater from seawater contamination and replenishing the local water supply aquifer. Originally commissioned to produce 3 million gallons per day (mgd) of purified water, the facility was expanded to 8 mgd in 2014 to provide the water needed to eliminate injection of imported potable water into the barrier. Due to limitations in local sewer capacity, the expansion needed to be achieved without increasing waste flows beyond those of the original facility.
“The Vander Lans facility was groundbreaking for its time and remains uniquely innovative,” says Greg Wetterau, CDM Smith discipline leader for membrane technologies and water reuse expert. “The facility’s water recovery rate is the highest of any plant in the industry."
Enhancing the Treatment Process
Innovative modifications to the facility helped support the Vander Lans facility’s expansion to 8 mgd:
- An expanded microfiltration (MF) system, with a backwash recovery process, produces 8.65 mgd of filtrate with a recovery exceeding 99%. Dissolved air flotation and secondary MF are used to recover backwash water from the primary MF system, with filtrate from both systems blended and sent to the downstream reverse osmosis (RO) system. This was the first facility in California to receive pathogens credits for a secondary MF system.
- A first-of-its-kind third stage brine recovery system was added to the RO process to increase recovery from 85% to 92.5%, cutting the resulting brine flow in half. Inter-stage booster pumps were added between each RO stage to improve flow balance, and a permeate flush system was added to prevent fouling during plant shut-downs. The improvements allowed the expanded plant to operate for an unprecedented two years without an RO cleaning, even in the aggressively operated brine recovery skids.
- An expanded ultraviolet disinfection system incorporates advanced oxidation to remove constituents of emerging concern (CECs). The system utilizes hydrogen peroxide for the advanced oxidation process (AOP), however, a first-of-its-kind full-scale test of free chlorine UV/AOP was conducted during start-up, confirming its improved efficiency compared with peroxide based UV/AOP.
The facility's water recovery rate is the highest of any plant in the industry.