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Protecting California's Groundwater with Recycled Water

water replenishment district of southern california long beach, california, usa
In a joint effort with CDM Smith, the Water Replenishment District of Southern California has expanded its Leo J. Vander Lans advanced water treatment facility to protect groundwater without using imported potable 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 Bruce Chalmers, CDM Smith vice president and potable reuse expert. “The facility’s water recovery rate is the highest of any plant in the industry."

mgd of purified recycled water produced
%
overall recovery rate
months without chemical cleaning on the RO

Enhancing the Treatment Process

Even before its expansion, Vander Lans had been a pioneer for the California model of indirect potable reuse (IPR): a multi-step treatment train that includes micro­fil­tra­tion, reverse osmosis and ultraviolet light disin­fec­tion. This supplies a flow of highly-purified recycled water back to the Alamitos Barrier, assisting the WRD in lessening the area’s dependence on imported water. The plant expansion was the first facility to receive regulatory approval under California’s finalized Groundwater Recharge Reuse regulations, setting the precedent for pathogen removal credits used at subsequent facilities throughout California and the United States. 

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.
bruce chalmers, potable reuse expert
By creating a reliable and cost-effective potable water source for the future, the district was able to move closer toward its goal of becoming 100% independent from imported water. Vander Lans is now operating with the lowest waste flows of any advanced treatment potable reuse facility in the world, producing reliable, high quality water to replenish the highly-stressed water supply aquifer in southern Los Angeles County. 
 
“Using recycled water to replenish the Alamitos Barrier was a critical step forward in preserving California’s precious water resources,” says Bruce Chalmers. “Not only has a strong Alamitos Barrier prevented seawater intrusion, but we are now able to conserve the potable water we once used to strengthen that barrier.”

Securing A Region's Future
The project is part of the Water Inde­pen­dence Now (WIN) program that focuses on an inde­pen­dence from imported water and a move toward self-sufficient and self-sustaining groundwater basins. 

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