Groundwater Recharge with Recycled Water Frequently Asked Questions

Groundwater Recharge with Recycled Water

1) What is recycled water?

Recycled water is wastewater from homes, businesses, and industry that, as a result of advanced treatment, has been made reusable again for various types of uses.

groundwater recharge with recycled water

2) Why do we have to use recycled water?

As the population increases, more demands are placed on water supplies. Traditional sources for the WRD service area have been local groundwater and imported surface water through the Metropolitan Water District of Southern California from the Colorado River and State Water Project. To meet the demand for new water, water recycling is one nontraditional way to help stretch the available supplies and result in improved reliability of supply for everyone in Southern California in the long run. Other strategies include water conservation, water transfers, and desalinated water from the ocean.

3) How is recycled water made?

Various treatment processes are utilized. The amount of treatment depends upon the end use for the recycled water. For the WRD service area, the Los Angeles County Sanitation Districts utilizes physical, biological and chemical processes to create the recycled water that is used for both landscape irrigation in various communities and for groundwater replenishment. These processes replicate and accelerate nature?s purification process.

For recycled water that is percolated into the local groundwater basins, the soil itself acts as additional treatment to purify the water. This is often known as ?Soil Aquifer Treatment? and has been studied extensively, and shown to be safe, effective and sustainable.

In special applications where recycled water is used for seawater barriers, recycled water is treated further before it is blended with water in the local groundwater basins. In addition to the 3 treatment processes already mentioned, it is further treated with microfiltration, reverse osmosis and ultraviolet light. These processes virtually remove any remaining constituents that might be harmful in the water.

4) How safe is recycled water? How does recycled water compare to drinking water?

The regulatory agencies responsible for issuing permits for the use of recycled water impose many conditions and requirements to ensure that it is safe to use. One of them is that recycled water must meet drinking water standards before it can be used for groundwater recharge. These are the same standards that are required for drinking water being served in our local communities. However, the recycled water is NOT used directly for drinking. It is blended with other water and also must be retained in the ground for additional purification and as a safeguard before the blend becomes a water supply source.

There are also additional water quality criteria that must be met. Most critical, of course, is that the water must be adequately disinfected against microorganisms that can cause diseases. Treatment is continuously monitored to ensure that the water meets these criteria before it leaves the treatment plant.

Recently, pharmaceuticals and other chemicals have been found at very low levels (parts per trillion) in recycled water, about 1 million times less than normal doses taken for therapeutic effects. One part in a trillion is equivalent to a few drops in a water-filled stadium like the Rose Bowl or the Coliseum. At these extremely low levels, there is no evidence of any significant impacts on human health. It is a subject of continued research. Some studies have shown that the soil is very effective in removing many pharmaceuticals and other chemicals.

5) Who regulates recycled water? What laws and regulations have to be met?

In California, the permits for the use of recycled water are granted by the State Water Resources Control Board and its nine Regional Water Quality Control Boards (RWQCB). The California Department of Public Health (CDPH) reviews and establishes water recycling criteria and regulations. For each water recycling project, CDPH makes recommendations to the RWQCB. These regulations are among the most stringent in the world. The permits incorporate these recommendations and also other conditions for the safe use of recycled water.

Water is continuously monitored before and after treatment. If treatment is not performing properly, then investigations are conducted. If necessary, recycled water deliveries are suspended until the causes are identified and resolved There are also wells located between the point of percolation/ injection and production wells that are monitored regularly. Monitoring of these wells serve as an early warning system. Water drawn from these wells are tested for many chemicals and if the results show that drinking water standards are exceeded or if any other chemicals of concern are detected, it would trigger additional investigations.

6) Where has recycled water been used for groundwater recharge?

The Orange County Water District (OCWD) has been recharging with Santa Ana River water since it was formed in 1933. As the watershed became more populated, more of the river flow was comprised of treated wastewater. This river continues to be a source of replenishment for groundwater basins.

In the early 1960?s, the WRD and the Los Angeles County Sanitation Districts formed a partnership and began using recycled water in the Montebello Forebay area of Southern Los Angeles County. Treated wastewater is used for recharge in the Whittier Narrows area of Los Angeles County.

In 1976 the OCWD began treating recycled water with reverse osmosis and then blending it with other water and injecting it into the Talbert Gap to stop the flow of seawater into the local basins. It was the first time recycled water was used for such an application. Many studies have been conducted, and results show that this project is safe and effective.

Since 1985, 10 million gallons per day of recycled water has been used to recharge the Hueco Bolson groundwater basin in El Paso, Texas. Advanced treatment, which includes activated carbon and ozone, is used to treat the recycled water to a very high level of quality before injection into the aquifer.

In Arizona, recycled water is used for groundwater recharge in Tucson, Mesa, and Phoenix. All of these sites began using recycled water in the early to mid 1990?s. In 1995, the West Basin Municipal Water District began delivering recycled water to the West Coast Basin Seawater Barrier. In 2006, a permit was granted to increase the amount of recycled water for this use.

In 2005, the WRD began producing recycled water from the Leo J. Vander Lans Advanced Water Treatment Facility using microfiltration, reverse osmosis and ultraviolet light. The high quality recycled water is blended with imported water and then delivered to the Alamitos Seawater Barrier.

In 2006, the City of Los Angeles Department of Water and Power began delivering recycled water from the Terminal Island Advanced Treatment Facility to the Dominguez Seawater Gap.

Most recently, in January 2008, the OCWD began operation of the Groundwater Replenishment System, which utilizes microfiltration, reverse osmosis, ultraviolet light to produce recycled water that is used for percolation in ponds and for seawater barrier protection.

7) Where can I get more information on recycled water?