Water Recycling Funding Program (WRFP)
MUNICIPAL WASTEWATER RECYCLING SURVEY
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The State Water Resources Control Board, in collaboration with the Department of Water Resources, is releasing the final 2009 Municipal Wastewater Recycling Survey results (Table 1). The table updates the initial version of the results, released in the spring of 2011. The final version includes corrections to the data.
The recycling of municipal wastewater has become an integral part of California’s water supply. The survey was conducted to assess how much wastewater is being recycled in the state. The survey identified over 669,000 acre-feet1 of recycled municipal wastewater, an increase of approximately 144,000 acre-feet since 2001 (Figure 1). The 2009 survey categorized municipal wastewater recycling into to the following beneficial uses:
Agencies were also asked about surface water augmentation (the addition of recycled municipal wastewater to surface water reservoirs) and direct potable reuse (direct addition of recycled municipal wastewater to potable water supply lines), but neither use is currently occurring in California. However, surface water augmentation is being planned and piloted, so it may be an active beneficial use when the next survey is conducted.
The survey was conducted by contacting water and wastewater agencies by email and direct phone calls. Responders provided their information by completing data forms through an online database, by phone, or by email. Information was collected about where recycled water was obtained, where it was distributed, and its uses. In cases where a recycled water system involved multiple agencies in the treatment, wholesale and retail distribution of recycled water to an end user, every effort was made to avoid duplication. Additionally in-plant use, such as for washing tanks in a wastewater treatment plant, was considered part of treatment plant operations and was not included as recycled water. Only treated municipal wastewater originating in whole or in part from a domestic source and directly used in a beneficial manner was accounted for.
An important distinction made during collection of the survey data was disposal versus reuse. Every wastewater facility in the State of California disposes of its wastewater after it has been treated to the requirements established by each facility’s permits. If the recycled water was used to irrigate a crop, park, or rangeland upon which cattle grazed, then it was considered to be beneficially used and was included in the survey data. If the recycled water is put into disposal ponds that are not permitted for groundwater recharge, released into an adjacent river, or dispersed on a spray field without any crop harvest or pasturing, then the recycled water was considered to be disposed and was not included in the survey data.
This survey focused only on intentional reuse - where recycled water was delivered directly to customers for non-potable reuse, for seawater intrusion barriers, or to groundwater recharge basins for indirect potable reuse. An exception is when there is a contracted relationship between a producer and user of recycled water to use a natural watercourse as the method of conveyance to a downstream customer. There can often be post-disposal benefits resulting from release of recycled water into the environment. In some cases, agencies indicated that downstream users reused their water, or the groundwater basin was recharged by the stream or disposal ponds. Because these beneficial uses were incidental after the discharge or disposal of the effluent, they were not included in the survey, although it is acknowledged that they may be indirect benefits.
It is important to remember that Title 222 of the California regulations, which contains recycled water standards and uses, identifies multiple levels of wastewater treatment and appropriate uses for each level. For each beneficial use category in the survey, all levels of Title 22 recycled water were included but not differentiated. For example, agricultural irrigation can occur with un-disinfected secondary recycled water for certain types of crops (fodder crops, non food-bearing trees, sod farms, etc.), disinfected secondary3 (crops where the edible portion is above ground and does not contact the recycled water, pasture for animals producing milk), or tertiary level recycled water (food crops where the recycled water comes into contact with the edible portion of a food crop eaten raw). Each of these recycled water treatment levels and uses were grouped together as “agricultural irrigation.”
The results of the survey are summarized in Table 1. Because of the complexity in how recycled water is produced and distributed in California, it was not always straightforward to list one agency for each connected system. Recycled water systems often involve more than one agency serving different roles of treatment, distribution, retail sales, or geographic service areas. For example, in many instances, a wastewater agency will produce the recycled water, but a water agency will distribute and retail the water. In other cases, a wastewater agency will produce the recycled water then provide that it to a wholesaler, which in turn provides that recycled water to one or more retail agencies, which distributes and sells the recycled water to its customers. Finally, in other cases, multiple agencies jointly participate in the treatment and/or distribution of recycled water. The retail agency that distributes the recycled water is generally listed in Table 1, except in the Los Angeles area4 , where the relationships were too complex to provide that level of detail. In each case, where multiple agencies are involved, the table attempts to show participating agencies in the footnotes.
The distribution of recycled water use by county is shown in Figure 4. As the figure indicates, almost all counties in the state are recycling water to some degree.
For additional details, please refer to the article titled Results, Challenges, and Future Approaches to California’s Municipal Wastewater Recycling Survey.
The first comprehensive statewide survey of recycled municipal wastewater was conducted in 1970. Major updates were conducted in 1977, 1987, and 2001, with some interim or partial revisions between the major updates. Some noted observations or trends in recycled water use over time include:
- An increase in recycled water use in the Santa Ana, Los Angeles, and San Diego regions as a percentage of the overall state recycled use (see Figure 1).
- An increase in the diversity of recycled water beneficial uses. Prior to the 2001 survey, agricultural irrigation accounted for over 60 percent of the recycled water use. In the 2009 survey, it was 37 percent. The overall volume of agricultural irrigation has more than doubled since 1970, but other beneficial uses have diversified and increased to a greater extent. The primary changes include increases in landscape irrigation, groundwater recharge, and seawater intrusion barriers (see Figure 5 and Table 3)
- The distribution of beneficial uses of recycled water varies throughout the state. The Central Valley’s primary beneficial use of recycled water is agricultural irrigation. Urban regions of the state have a greater diversity of beneficial uses with their regions.
- An increase in complexity of recycled water interagency relationships.
- Cooperative solutions to access and distribute recycled water to areas of higher demand.
- Figure 1 - Historic trends of total recycled water use in California, by State Water Board regions.
- Figure 2 - Beneficial uses of recycled water in 2009.
- Figure 3 - Regional variation of recycled water volume and beneficial uses within each State Water Board region.
- Figure 4 - Total 2009 recycled water use, by county.
- Figure 5 - Historic trend in statewide recycled water beneficial use.
- Table 1 - 2009 survey results, by agency and beneficial use.
- Table 2 - Beneficial use data, by State Water Board regions.
- Table 3 - Historic trends in statewide beneficial uses.
- Recycled Water by Type of Use
- 2009 Survey Results by Regional Board/Type of Use
- 2001 Survey Results by Regional Board/Type of Use
- Trends in Recycled Water Use by Regional Board
- Targets and Trends in Recycled Water Use
Questions or Comments?
For Survey Related Inquiries, please contact:
Daman Badyal, P.E.
For General Program Related Inquiries, please contact:
Dan Newton, P.E.
Water Recycling Funding Program
State Water Resources Control Board
P.O. Box 944212
Sacramento, CA 94244-2120