Summary of Washington's Water Reuse Guideline or Regulation for Agriculture

This page is part of the EPA’s REUSExplorer tool, which summarizes the different state level regulations or guidelines for water reuse for a variety of sources and end-uses.
The source water for this summary is Treated Municipal Wastewater.

On this page:

• Technical basis
• Water reuse for agriculture approved for use in Washington
• Water reuse treatment category for agriculture
• Additional context and definitions
• Water reuse for agriculture specifications (table)
• Upcoming state law or policy
• References
• Disclaimer

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This page is a summary of the state’s water reuse law or policy and is provided for informational purposes only. Please always refer to the state for the most accurate and updated information. 

In Washington, water reuse for agriculture water reuse for agricultureThe use of recycled water to land to assist in the production of both commercially and non-commercially processed food crops consumed by humans or livestock and non-food crops. Includes pasture for milking and non-milking animals, fodder, fiber, and seed crops, vineyards, orchards, ornamental nursery stock, Christmas trees, and silviculture. Excludes consumption by livestock, onsite non-potable reuse, and landscaping. includes irrigation of food crops, trees, fiber or seed crops in pastures accessed or not accessed by milking animals, nonfood crops, orchards and vineyards and process food crops; and frost protection of orchard crops. The source of water (treated municipal wastewater) treated municipal wastewater Treated wastewater effluent discharged from a centralized wastewater treatment plant of any size. Other terms referring to this source of water include domestic wastewater, treated wastewater effluent, reclaimed water, and treated sewage. is specified by the state as municipal wastewater. This write-up uses state terms when discussing sources or uses of water that may differ from the Regulations and End-Use Specifications Explorer's (REUSExplorer's) terms.

Technical basis

Washington approves the reuse of reclaimed water for agricultural irrigation including irrigation of food, nonfood and process crops, irrigation of orchards and vineyards and irrigation of trees, fodder, fiber or seed crops in pastures both accessible and non-accessible to milking animals (Wash. Admin. Code § 173-219). All applicable provisions of the Clean Water Act (CWA) (33 U.S.C. §§ 1251 et seq.), including its implementing regulations, must be met in addition to any relevant rule requirements under the Food Safety Modernization Act (FSMA) (124 Stat. 3885). In Washington, no reclaimed water may be distributed or used without a state-issued reclaimed water permit (Wash. Admin. Code § 173-219; Wash. Rev. Code § 90-46). Treatment requirements and performance standards are applied for the removal of microbial contaminants, chemicals and other relevant indicators related to agriculture and are summarized in the table. The technical basis for developing the specifications and/or removals of microbial contaminants, chemicals and other relevant indicators is not explicitly specified.

Water reuse for agriculture approved for use in Washington

Wash. Admin. Code § 173-219 defines the following approved water reuse for agriculture:

• Irrigation of food crops (unless otherwise specified) (Class A)
• Irrigation of trees, fodder, fiber or seed crops in pastures accessed by milking animals (Class A)
• Irrigation of nonfood crops (Class B)
• Irrigation of orchards and vineyards (Class B)
• Irrigation of process food crops (Class B)
• Irrigation of trees, fodder, fiber or seed crops in pastures not accessed by milking animals (Class B)
• Frost protection of orchard crops (Class B)

Water reuse treatment category for agriculture

The various classes of reclaimed water treatment are defined by their respective treatment requirements and applicable performance standards. The respective treatment requirements are briefly summarized regarding water reuse for agriculture: 

• Class A treatment must meet Class B requirements (secondary treatment including biological oxidation and disinfection). Disinfection methods include chlorine, UV or other disinfection methods that are in accordance with the most recent Criteria for Sewage Works Design (WA Ecology, 2022). Additionally, one of the following treatment process train requirements must be met:
  • Biological oxidation, followed by coagulation, filtration and disinfection, demonstrating at least a 4-log virus removal or inactivation.
  • Biological oxidation, followed by membrane filtration and disinfection, demonstrating at least a 4-log virus removal or inactivation.
  • Combination of biological oxidation and membrane filtration via a membrane bioreactor, followed by disinfection, demonstrating at least a 4-log virus removal or inactivation.
  • An alternative treatment method, that demonstrates to the satisfaction of the lead agency that it provides for equivalent treatment and reliability. 
• For Class B water, the treatment requirements are secondary treatment, including biological oxidation, followed by disinfection. Disinfection methods include chlorine, UV or other disinfection methods that are in accordance with the most recent Criteria for Sewage Works Design (WADOE, 2019).

Additional context and definitions

Washington defines reclaimed water as “water derived in any part from a wastewater with a domestic wastewater component that has been adequately and reliably treated to meet the requirements of this chapter, so that it can be used for beneficial purposes” (Wash. Admin. Code § 173-219).

Washington defines agricultural water use as “the use of water for irrigation and other uses related to the production of agricultural products. These uses include, but are not limited to, construction, operation, and maintenance of agricultural facilities and livestock operations at farms, ranches, dairies, and nurseries. Examples of these uses include, but are not limited to, dust control, temperature control, and fire control” (Wash. Admin. Code § 173-219). Some of these reuse applications are described on a separate webpage focused on other centralized non-potable reuse.

Class A and B municipal reclaimed water piping, valves, outlets, storage facilities and other appurtenances must be color-coded purple and the pipes must be at least 200 feet away from potable water intakes, including well-heads, springs, surface water or designated groundwater (Wash. Admin. Code § 173-219). The reclaimed water generator must notify the public and employees at the site of the reclaimed water (for all use areas) by posting advisory signs or distributing advisory notices. The signage must be purple-colored and read “Reclaimed Water – Do Not Drink.” 

Water reuse for agriculture specifications

Summary of Washington's Water Reuse for Agriculture Specifications

Source= Wash. Admin. Code § 173-219

* Information about sampling and monitoring requirements such as frequency, site and quantification methods not specifically listed in the table was not explicitly specified in the State-specific regulations.

^a Listed as 23 MPN/mL or CFU/mL in Wash. Admin. Code § 173-219.

^b Additional log reductions occur during drinking water treatment.

^c If chlorine was used as the disinfectant.

Upcoming state law or policy

No upcoming regulations pertaining to water reuse for agriculture were found for Washington.

References

Clean Water Act, 33 U.S.C. §§ 1251 et seq.

Food Safety Modernization Act (FSMA), 124 Stat. 3885.

Reclaimed Water, Wash. Admin. Code § 173-219.

Reclaimed Water Use, Wash. Rev. Code § 90-46.

State of Washington Department of Ecology (WA Ecology). 2022. Criteria for Sewage Works Design (Orange Book).

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Disclaimers

Please contact us at waterreuse@epa.gov if the information on this page needs updating or if this state is updating or planning to update its laws and policies and we have not included that information on the news page.