By Lori Anne Dolqueist
Recycled water is former wastewater that is treated to remove solids and impurities. The treatment of recycled water depends on its source and how it will be used once treated. It can be used for a variety of purposes, including irrigating landscape, recharging groundwater aquifers, meeting commercial and industrial water needs, and even for drinking.
Since it is reused instead of discharged, recycled water furthers the goals of sustainability and conservation. It can be used to reduce the need for additional potable water supplies and to diminish the severity of water rationing during periods of drought.
This summer, California municipalities in particular are feeling the pressure. On April 1, Governor Jerry Brown ordered a statewide 25-percent reduction in potable urban water usage (as compared to 2013 usage levels). The established reduction levels vary by community and range from as low as 4 percent to as high as 32 percent. In California, many municipalities are turning to recycled water to meet mandated conservation goals. For others, recycled water projects are part of creating a more resilient water supply.
Although recent drought conditions throughout the west have thrust recycled water into the spotlight, its use is not new. As early as the 1920s and 30s, the cities of Los Angeles and San Francisco used reclaimed water for landscape irrigation in parks. As the cost of potable water increases and the availability of once-abundant water supplies decreases, more municipalities across the country are looking to include recycled water as part of their water portfolios.
Perhaps the most obvious use for recycled water -- and the most widely accepted -- is landscape irrigation. In times of scarcity, it is difficult to justify the use of potable water for decorative purposes in parks, medians and other large landscaped areas. Although such use may not be considered "essential," this type of landscaping is important: it impacts property values, quality of life, and public use and enjoyment of such spaces.
Recycled water used for landscape irrigation is treated but not to a "potable" level; it can be safely used to irrigate turf and most plants. Indeed, recycled water often contains higher levels of nutrients such as nitrogen and phosphorus that help meet the fertilizer needs of the landscape. But, recycled water often has higher levels of dissolved salts as well, so it is important to develop strategies to address this issue in order to avoid harm to the landscape.
Golf courses -- which consume large amounts of water -- have begun embracing the use of recycled water, particularly in the arid west and southwest. With their lush, rolling greens, golf courses can be easy targets for "drought shaming," so switching over to recycled water can help avoid negative public perception. Additionally, as the cost of potable water increases, it simply may not be financially feasible to continue to use it for golf course irrigation.
Another use for recycled water is to recharge groundwater basins, a use that dates back to the early 20th century in the United States. As with the use of recycled water for irrigation, however, water supply constraints are making groundwater recharge and storage an increasingly attractive option as it allows water providers to meet water needs in the face of increased demand and diminished (or prohibitively expensive) supply.
Wastewater slated for groundwater recharge is first treated at water reclamation plants and the resulting product typically meets the standards for drinking water. This treated water is placed into the ground via recharge ponds or injection wells, where it may receive additional geopurification treatment. As the recycled water moves through the aquifers, it mixes with other groundwater and goes through a natural purification process. It can then be pumped out of production wells and used to serve customers.