Wastewater Recycling: A means to increase water use efficiency in drought-stricken California

By Visting Poster, Nathan Chan

The current drought being experienced by the Western United States has brought water conversation to the forefront of the political conversation. Earlier this year California Governor, Jerry Brown, declared a state of emergency, and President Obama announced hundreds of millions of dollars in aid for the agricultural industry and affected communities in the West. Some fear that the drought that California is experiencing may become the new normal, bad news for a state that relies on agriculture as one of its main industries. Even if drought is not the norm for the West, it behooves California to improve its water-use efficiency, as growing population will continue to stress the state’s water resources.

Significantly decreased water levels at Lake Oroville, evidence of California's extreme drought. Justin Sullivan/Getty Images.

Significantly decreased water levels at Lake Oroville, evidence of California’s extreme drought. Justin Sullivan/Getty Images.

California lacks any significant policy response to the “state of emergency” Governor Brown announced in February. Neither the state government nor any significant number of local water agencies have called for mandatory restrictions of water use. In order to properly respond, the state of California will need to make significant changes in water-distribution infrastructure to ensure that man and the rest of nature have access to adequate resources.

The use of recycled wastewater plays a large role in supporting California’s population and economy, but has significant room to grow. The California Water Recycling Act passed in 1991 set goals of 700,000 acre-feet of recycled water in 2000 and over 1,000,000 acre-feet in 2010. Since the passage of the Water Recycling Act, many other bills, acts and policies have moved through the state government encouraging and creating incentives for the public to increase their usage of recycled water. Nationwide, the United States only reclaims about 7% of its municipal wastewater. In comparison, Israel reclaims more than 70% and Australia reclaims 8% with a national goal of 30% by the year.

In order for wastewater to be recycled back into use, it must be treated at a wastewater treatment plant. There are three treatment levels that recycled water can reach. Primary treatment consists of undertaking physical processes (filtering, sedimentation) to remove suspended soil and organic matter in the water. The secondary treatment level consists of treating the water with biological processes involving microorganisms, to reduce suspended solids and organic matter. The tertiary level requires the use of chemical, physical, and/or biological processes to remove suspended and dissolved material, and often requires chemical disinfection and filtration. In general a minimum level of un-disinfected secondary must be achieved for water to be recycled back into use, although minimum standards are dependent on specific use. After wastewater is processed by a certified treatment plant it can be recycled and used for the following purposes:

  • Agricultural Irrigation
  • Landscape Irrigation
  • Groundwater Recharge
  • Seawater Intrusion Barrier
  • Habitat Restoration
  • Industrial Use
  • Recreational Impoundment
  • Other/Mixed Use

Reclaimed wastewater can be used for agricultural irrigation directly, i.e. water is transported directly to farms, or indirectly, where reclaimed water is disposed of into rivers where it can be used by anyone with access. Different crop types require different levels of treatment according to the California Department of Public Health. Undisinifected secondary treated water can be used for orchards and vineyard crops so long as there is no contact with the edible crop, and for all non-food bearing trees and fodder or fiber crops. Food crops that have their edible portion above ground can use disinfected secondary treated water. Any crops that have an edible portion underground require disinfected tertiary treated water.

Pongamia orchard planting in Arizona, irrigated with recycled wastewater.

Pongamia orchard planting in Arizona, irrigated with recycled wastewater.

Due to the drought over 420,000 acres of cropland are our of production and the California agriculture industry is expecting to see a loss of $1.5 billion dollars due to reduced crop production and water pumping costs.

In 2009, over 669,000 acre-feet of recycled wastewater were used in California, well short of 1,000,000 acre-feet goal set forth in 1991. Approximately thirty-seven percent of that recycled water went to agricultural irrigation. According to a report co-authored by the National Resources Defense Council (NRDC) and the Pacific Institute, there is significant room for the use of recycled wastewater to expand, citing a number of an additional 1.2 to 1.8 million acre-feet (reference the report). Two-thirds of which would occur along the coast where treated wastewater is normally released into the ocean or streams. Urban re-usage would not go directly to agricultural re-use, but would instead be reused for urban uses such as landscape irrigation. An expansion of the use of recycled water in both urban and rural areas would provide a more reliable, local water-supply and reduce vulnerability to drought.

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