By Wendy Wert
On September 13, 2007 the Orange County Water District and the Orange County Sanitation District hosted LABS and SARBS participants on their annual joint facility tour. This year attendees were given the opportunity to visit the Groundwater Replenishment (GWR) System, which is the largest water purification project of its kind in the world. When completed the system will have the capacity to produce 70 million gallons per day of finished water or enough the meet the needs of 144,000 families.
For decades imported water from Colorado River and State Water Project has been relied upon. In recent years there has been a reduction in imported water supplies due to recurring droughts. Reduced supply has been coupled with population expansion, which leads to the need to secure new water sources.
The Orange County Water District and the Orange County Sanitation District worked together to meet this challenge through the construction of the new GWR System. The GWR System takes highly treated sewer water and purifies it using a state-of-the-art three-step process.
The advanced treatment system includes: microfiltration, reverse osmosis, and ultraviolet light with hydrogen peroxide disinfection. Microfiltration is a low-pressure membrane process that removes suspended particles, protozoa, bacteria and some viruses. Reverse osmosis is a high-pressure membrane process that forces water through the molecular structure of a thin membrane that filters out minerals and contaminants, including salts, viruses, pesticides and other materials. During disinfection, water is exposed to ultraviolet light and hydrogen peroxide. Due to the advanced treatment level, some alkalinity must be replaced in order to stabilize the pH. Lime is added to the finished water for this purpose.
Roughly half of the water from the GWR System will be injected into Orange County’s seawater barrier. The seawater barrier is an underground pressure ridge of water formed by injection wells along the coast of Orange County. The remaining water will be piped to recharge lakes in Anaheim, where the water will filter through clay, sand and rock to the groundwater basin. A mix of federal, state and local funding is being applied to this project, estimated at $487 million.
One of the most interesting features of this project is the unique partnership between the Orange County Water District (OCWD) and the Orange County Sanitation District (OCSD). California’s water supply from the Colorado River will be reduced by 2016. A five-year drought has negatively impacted the Santa Ana and Colorado Rivers. The future supply is complicated by the fact that Orange County’s population is expected to increase by 300,000 to 500,000 people by 2020, Southern California’s by seven million and the state’s by some 15 million.
After evaluating many alternatives the OCWD and the OCSD chose to form a joint authorities agreement partnership for the GWR project. This project benefits both agencies and the constituency in general, in that it helps to meet the long-term plan developed by the Metropolitan Water District of Southern California to maintain and improve the reliability of Southern California’s water supply. It also protects against future droughts, produces high quality water to replenish the groundwater basin, protects the environment by reusing a vital resource. In addition there are energy advantages to the project. The facility will use approximately one-half the amount of energy that is required to transport water from Northern California to Southern California and it provides “water diversity” in an arid region.
Water reuse projects are subject to scrutiny with respect to health and safety concerns. The GWR System must be reviewed, approved and permitted by the California Department of Health Services and the California Regional Water Quality Control Board, Santa Ana River Basin, to ensure public health, water quality and environmental compliance before the system is brought on-line. The OCWD and the OCSD took a proactive approach to these concerns and initiated a 7-year study to evaluate the water quality of potential raw water sources. Sources include the State Water Project (SWP), Colorado River Allocations (CRA), the Santa Ana River (SAR) and finished product water from the GWR System. Results of the study show the quality of the GWR System source with respect to total dissolved solids and total organic compounds.
The award winning GWR System has received the following: 2004 Flex Your Power energy efficiency award, 2002 EPA’s Environmental Achievement Award, 1998 WateReuse Association’s Planned Project of the Year and the 2008 Stockholm Water Prize, one of the highest honors in the industry.
For more information visit: www.gwrsystem.com.