Orange County, California, USA
#00175
Case study of
#00185 Potable reuse of treated wastewater behind multi-barrier treatment and long acceptance-building
Implementer
Orange County Water District and Orange County Sanitation District
Timeline
Since Jan 1, 2008
Location
Description
The Groundwater Replenishment System (GWRS) in Orange County purifies secondary-treated wastewater through a multi-barrier train (microfiltration, reverse osmosis, UV/AOP) and injects it into the local groundwater basin for indirect potable reuse. Operated jointly by Orange County Water District and Orange County Sanitation District, it launched in 2008 at 70 MGD and expanded to 130 MGD (~492,000 m³/day) after a 2023 expansion, serving ~2.5 million people. Total capital exceeds $900M, assembled through layered federal and state financing plus district funds. The district invested more than 10 years in public outreach before and during rollout. Aquifer injection served as both an environmental buffer and a regulatory/psychological acceptance mechanism. Production cost is below the cost of imported water, and the project halted active seawater intrusion into the aquifer.
Metrics
2Funding
Lessons learned
- Using an aquifer as an environmental buffer functions as a political tool: recharging groundwater rather than piping directly to taps reduced regulatory barriers and public aversion significantly.
- More than a decade of sustained, structured public outreach preceded and accompanied construction; acceptance held throughout the build and operation phases.
- At 130 MGD scale, potable reuse production cost undercuts imported water cost, making the economics replicable in regions dependent on expensive water imports.
Documented Jul 24, 2026