An Innovative Approach to Water Supply—The Groundwater Replenishment System

The Groundwater Replenishment (GWR) System, in Orange County, CA, is an indirect potable reuse project that is initially producing up to 265,000 cubic meters per day (m³/d) of highly treated recycled water with an ultimate capacity of 492,000 m³/d for groundwater recharge and direct injection to protect the groundwater basin from seawater intrusion. The project is jointly sponsored by the Orange County Water District (OCWD) and the Orange County Sanitation District (OCSD) and consists of three major components: 1) the Advanced Water Purification Facility (AWPF) and pumping stations, 2) a 14-mile pipeline connecting the treatment facilities to existing recharge basins, and 3) an expansion of the existing seawater intrusion barrier. The AWPF treats clarified secondary effluent, currently discharged into the ocean, using microfiltration (MF), reverse osmosis (RO) and ultraviolet light/advanced oxidation (UV/AOP). The product water is then lime stabilized and pumped into injection wells and recharge basins, where it naturally passes through the ground blending with Orange County's groundwater supplies. This new source of water, which is of near distilled water quality, provides enough water for 500,000 people and lessens the demand on imported water supplies. The project has been in operation since January 2008 and the AWPF treatment processes operated satisfactorily during the year, producing high-quality water in compliance with all permit requirements. Concentrations of inorganic constituents, such as arsenic and chromium, were either non-detectable or far below the permit limits. All potentially toxic organics, such as volatile organic compounds, pesticides and other synthetic organic compounds, were also non-detectable or far below permit limits. Analyses of AWPF recycled water for unregulated compounds indicated that concentrations of endocrine disrupting chemicals and pharmaceuticals were at non-detectable levels. For the various other unregulated constituents, test results indicate that the levels of these chemicals are not present in the recycled water. The focus of this paper will be on presenting the first year MF, RO and UV/AOP effluent quality including emerging contaminant removal by the overall treatment processes.