Recycled water is wastewater that has been purified through a series of treatment processes. Recycled water can provide a sustainable supply of water for agricultural and many other uses. Most treatment systems utilize three treatment processes in the production of recycled water:
According to the California Water Recycling Criteria, tertiary-treated recycled water is safe for all human contact except drinking. In the Napa area, recycled water is produced by the Napa Sanitation District at the Soscol Water Recycling Facility, located along the Napa River just south of the Highway 29 bridge. After entering the plant, wastewater from homes and businesses undergoes the primary, secondary, and tertiary treatment process. Throughout the process, samples are taken and tested in a state-of-the-art laboratory to ensure high-quality water.
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The California Department of Public Health (DPH) establishes and enforces the standards for recycled water. The DPH has established water quality standards and treatment reliability criteria for recycled water. These regulations guide the production, distribution, and use of recycled water.
Both the District and the customers using the water for irrigation must meet State requirements for recycled water. The District’s Recycled Water Program has been approved by the DPH, and any expanded program will be too. In addition, the California Regional Water Quality Control Boards issues water recycling permits based on the established DPH regulations.
In addition to meeting standards to protect human health, Napa Sanitation District’s recycled water is also analyzed to ensure it meets “agronomic standards.” This means that the water must be tested for parameters and constituents that are relevant to growing crops, such as total salinity, sodium, calcium, magnesium, nitrogen, and phosphorus. This information is provided to recycled water users so that they can adjust fertilization and irrigation practices to most successfully use recycled water.
The California Water Recycling Criteria (encoded in Title 22 of the California Code of Administration) allow 43 specified uses of recycled water, including irrigation of all types of food crops, parks and schools, golf courses, and landscaping. These criteria include different water quality requirements for different types of irrigation. The District’s recycled water meets the highest quality standard, “Unrestricted Use.”
In addition to crops and landscaping, the criteria also outline recycled water use for industrial applications such as cooling towers and toilet flushing. In specific instances recycled water can also be used for groundwater recharge. California’s regulations are among the most stringent in the world and have been used as a model for many other countries’ guidelines and water reuse regulations.
In the Napa Valley, recycled water is used to irrigate golf courses, vineyards, landscaping, pastureland, parks, playing fields, and a cemetery. Using recycled water for irrigation in place of potable or groundwater helps conserve water resources.
Recycled water is almost as pure as drinking water. It has been carefully treated and has been disinfected to kill microorganisms, making recycled water safe to use for irrigation. Recycled water has been used in agriculture since the 1880s and in California municipalities beginning in 1929. There has never been a documented disease or incidence of other adverse public health effect in the United States related to the use of recycled water that meets established standards.
Even if your child or pet swallowed recycled water, it should not cause illness. However, it still contains very small concentrations of some constituents and salts that prevent it from meeting California’s strict drinking water standards. Special precautions are taken to keep recycled water separate from drinking water.
To protect public safety, regulations require that recycled water facilities be completely separate from drinking water systems. Guidelines set by the California Department of Health Services require recycled water facilities to be clearly distinguishable from potable water facilities to avoid mixing the two supplies. Pipes and other hardware for recycled water systems are colored purple and labeled with words "Recycled Water, Do Not Drink."In addition, the District requires “cross-connection” monitoring for its recycled water users. This monitoring insures that recycled water does not become connected to a potable water pipeline when new plumbing is added to a property where recycled water is used. Likewise, backflow protection devices may be required to prevent any contamination from a customer from flowing back into the recycled water supply.
Using recycled water for irrigation helps to conserve drinking water supplies and provides a drought-resistant water supply to the Napa area for agricultural and landscaping irrigation. It can also protect the groundwater table when recycled water is used in place of groundwater pumping. Use of recycled water can also protect community and private investments in parks and landscaping during times of drought. Utilizing recycled water is also environmentally beneficial because it allows reuse of this valuable resource in place of discharge of treated wastewater into the Napa River.
Recycled water can also conserve energy when it is used in place of imported water sources that require significant amounts of energy for pumping. This conserved energy translates into a reduction in the carbon footprint when recycled water is used for irrigation. Recycled water also provides a significant portion of the nutrients needed by crops and landscaping, including nitrogen, phosphorus, and micronutrients, which can reduce the need for synthetic fertilizers.
The current price of recycled water is $0.94 per thousand gallons; this price is adjusted each year in January according to a formula based on the Consumer Price Index. In 2011, the District completed a recycled water rate study to determine the best way to pay for system improvements to increase production of recycled water, and this resulted in a new methodology (PDF) for setting recycled water rates, which went into effect in 2016. In addition, new users of recycled water may have to pay for construction of the pipeline to bring the recycled water to their property. See a table of past and future recycled water rates.
Although total wastewater flows may be reduced slightly, recycled water supplies are virtually 100% reliable during drought events. This is because wastewater flows are primarily generated by indoor water uses which are not reduced significantly during drought conditions compared to outdoor uses. In addition, in cases where the recycled water use is replacing the use of potable water, this increases the reliability of potable supplies.
Currently, the Napa Sanitation District provides recycled water along two main pipelines (PDF) to the southeast and north of the Soscol Water Recycling Facility. Customers include Gateway Park, Eagle Vines, Chardonnay Golf Clubs, and some District-owned properties in the southeast area. The service area north of the treatment plant includes Napa Valley Corporate Park, Kennedy Park, Napa Valley Memorial Park, Napa Municipal Golf Course, and Napa Valley College.
The District’s recent expansion efforts include constructing a recycled water pipeline through Napa State Hospital (NSH) to Skyline Park. This will reduce potable demand for landscaping irrigation at NSH by 200 acre-feet per year once their irrigation system is connected.
Napa County has also asked the District to oversee the design of a pipeline that could carry recycled water from Skyline Park to the water-deficient Milliken-Sarco-Tulocay (MST) area. If constructed, the MST pipeline could potentially be paid for by prospective recycled water users in the area, primarily vineyards and a golf course. Additional potential future expansion includes delivering recycled water to the Carneros area and Stanly Ranch.
Recycled water is available during the dry season, from May 1 to October 31. During the wet season, from November 1 through April 30, when water is typically not needed for irrigation, treated wastewater is discharged into the Napa River. River discharge is carried out under a permit from the State Water Resources Control Board. Water quality of the discharge and the river is monitored constantly and must meet standards that protect human health and aquatic life. Recycled water can be made available from November 1 to April 30 by working with Napa Sanitation Department to schedule delivery.
An effort is underway to bring recycled water to the water-short Coombsville / Milliken-Sarco-Tulocay (MST) area. Landowners who wish to receive recycled water (both commercial and residential) have joined a Community Facilities District and will be assessed fees to provide funding for pipeline construction. Participation in the recycled water project is voluntary. For more information, visit the County of Napa’s MST website.