Water Reuse

Orange County, California

In January 2008, the Orange County Groundwater Replenishment System (GWR) opened.  It cost $480 million to build, will cost $29 million a year to run, and took more than a decade to get off the ground.  The decision to spend the time and money to build this system, which is the largest of its type in the world, was made for a variety of reasons.  The population was growing requiring a second sewage pipe to be built if the county stayed with its conventional configuration, saltwater from the Pacific Ocean was entering the county's water supply drawn in by overpumping from the groundwater basin, the area was in a near chronic drought, and the cost of importing water from the Colorado River and from Northern California was rising.

The GWR system takes effluent from a secondary treatment plant and purifies it using a state-of-the-art three-step process.  The first step, microfiltration, removes anything larger than 0.2 microns such as bacteria, protozoa, and suspended solids.  The second step is reverse osmosis which removes almost all nonwater molecules such as salts, viruses, and pharmaceuticals.  The final step of ultraviolet light with hydrogen peroxide disinfection takes care of any leftover living critters.  The purified water exceeds all state and federal drinking water standards and has a water quality similar to, or better than, bottled water.

Initially operational at 70 million gallons per day, the GWR system generates enough pure water to meet the needs of 500,000 people.  Roughly half of the water is piped to spreading basins in Anaheim, CA, where the water takes the natural path of rainwater as it filters through clay, sand, and rock to the deep aquifers of the groundwater basin.  The rest of the water is injected into Orange County's seawater barrier to help prevent saltwater intrusion from the ocean.

Orange County Groundwater Replenishment System

Source:
Royte, E. A Tall, Cool Drink of ... Sewage? The New York Times. August 10, 2008.