Groundwater Replenishment System (GRWS)

By January 1, 2017 October 2nd, 2017 Desalination

Orange County is a recognized national leader in purifying waste water for groundwater recharge. Orange County’s system is the largest of its kind in the world and has garnered international praise for its design and operation.

In 1997, the Orange County Sanitation District and the Orange County Water District collaborated to create a system that would preserve local groundwater resources and prevent seawater from infiltrating and contaminating the groundwater basin (a saltwater intrusion barrier).

The system diverts sewage from the Orange County Sanitation District, originally destined for the ocean, and pretreats the water by submerging membrane modules before it enters a Reverse Osmosis unit where it is then treated by ultraviolet light and hydrogen peroxide disinfectant. The result is water that satisfies federal drinking water standards and even requires the addition of minerals before it is discharged. Operational since 2008, GWRS generates enough purified water to serve 500,000 people.

Half of the purified water is diverted to recharge the Orange County basin aquifer and the remaining water is injected into the seawater intrusion barrier. In addition to protecting our groundwater supply, another advantage to this system is that it diverts sewage away from discharge into the natural environment, thereby reducing our impact on the sensitive marine environment. GWRS is an existing proven technology, which demands less energy and generates fewer greenhouse gas emissions than the unproven Poseidon desalination plant or importing water from northern California.

The Orange County Sanitation District and Orange County Water recently expanded the state-of-the-art GWRS to 100 MGD from 70 MGD and has approved another 30MGD expansion of the system. With projected population increases and an anticipated reduction in water diversion from northern California and the Colorado River, Orange County should be investing more towards recycling, stormwater capture, and conservation measures.

GWRS is the most practical option for our regional water supply problems and recognizes the expansion of existing infrastructure as the most cost-effective approach to reducing our dependence on imported fresh water. According to the Report Card for America’s Infrastructure, GWRS is between 35% and 75% less expensive than saltwater desalination and will consume half the energy.