Orange County, California, USA – World’s largest operating groundwater replenishment system supplying 23 cities
A pioneering collaboration between the Orange County Water District and the Orange County Sanitation District, the Groundwater Replenishment System (GWRS) stands as a global leader in advanced water purification systems for indirect potable reuse.
Since its operational debut in January 2008, the Groundwater Replenishment System has continually purified highly treated wastewater into high quality water through a meticulous three step process — low-pressure membrane filtration, reverse osmosis, and ultraviolet light with hydrogen peroxide. The result is water that meets and exceeds all state and federal drinking water standards.
The GWRS was preceded by Water Factory 21, which operated from 1976 until 2004 and produced recycled water for injection into a seawater intrusion barrier. The original Water Factory 21 treatment train was comprised of lime clarification, ammonia stripping, recarbonation, filtration, either granular activated carbon (GAC) or reverse osmosis operated in parallel, chlorination, and blending with local potable water or deep groundwater. Water Factory 21 was the first project in the world to employ reverse osmosis on wastewater that was injected into a potable aquifer.
In 2004, Water Factory 21 was shut down to make way for construction of the Groundwater Replenishment System and an interim project was built to maintain the seawater barrier. This interim project, Interim Water Factory 21 (IWF-21), operated from 2004 to 2006 and served as a training facility to allow operations staff to gain experience with the three-step treatment process later used in the Groundwater Replenishment System. Water Factory 21 and Interim Water Factory 21 were pioneering water reuse projects that paved the way for projects like the Groundwater Replenishment System.
With a daily production capacity of 130 million gallons (492,000 million litres), the Groundwater Replenishment System is a vital component of the region’s water infrastructure, providing an annual supply sufficient to meet the needs of approximately 1 million people. This achievement is complemented by the facility’s ability to recycle 100% of local reclaimable wastewater flows, marking a significant milestone in water recycling efforts within the community.
In support of environmental sustainability, the Groundwater Replenishment System typically sends 20-30 (75-113 million litres) per day into a seawater intrusion barrier comprised of coastal injection wells to protect the Groundwater Basin. Simultaneously, 5 to 10 million gallons (18-37 million litres) per day are separately injected into the central portion of the basin to provide replenishment to a heavily pumped area of the aquifer. The balance of Groundwater Replenishment System water produced, up to an additional 100 million gallons (375 million litres) per day, are directed to Orange County Water District’s surface recharge basins. Here, the water undergoes a natural filtration process, percolating through sand and gravel to recharge the deep aquifers of the groundwater basin, thereby enhancing the local drinking water supply.
The completion of the final expansion in early 2023 further solidifies the GWRS’s commitment to maximising water recycling efforts in the region. This expansion, bringing the daily production capacity to 130 million gallons (492 million litres), represents a significant stride towards sustainable water management.
For those interested in witnessing this ground-breaking system in action, tours of the GWRS can be scheduled through https://www.ocwd.com/contact-us/book-a-tour/ .
To explore more about OCWD and OC San’s ongoing efforts in water management, please visit www.ocwd.com and www.ocsan.gov.
