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

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
• Types of planned potable reuse approved for use in Washington
• Water reuse treatment category/type
• Potable reuse 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, potable water reuse potable water reuse The use of highly treated recycled water for drinking water purposes. This reuse application includes both indirect potable reuse through introduction of recycled water into an environmental buffer such as a surface reservoir or groundwater aquifer, and direct potable reuse through introduction of recycled water into a drinking water system. applications include direct potable reuse and indirect potable reuse (surface water augmentation, groundwater recharge and aquifer storage and recovery). 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 wastewater with a domestic wastewater component. The 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

Potable water in the United States must meet all applicable Safe Drinking Water Act (SDWA) requirements, including its implementing regulations (40 C.F.R. § 141) for chemical and microbial contaminants and pollutant discharges from a point source for surface water augmentation require a federal National Pollutant Discharge Elimination Systems (NPDES) permit (40 C.F.R. § 122). Additionally, all microbial and chemical contaminants must meet Washington State drinking water standards (Wash. Admin. Code § 246-290-310). In Washington, no reclaimed water may be distributed or used without a state-issued reclaimed water permit (Wash. Admin. Code § 219-070, Wash. Rev. Code § 90-46). In Washington, reclaimed water permits for surface water discharges are issued as combined NPDES/Reclaimed Water permits (40 C.F.R. § 122). Additionally, Washington IPR regulations require certain treatment requirements, which vary by class of recycled water. The technical basis for the removal of microbial and chemical contaminants is not explicitly specified.

Types of planned potable reuse approved for use in Washington

Wash. Admin. Code § 173-219 defines the following approved planned potable uses:

• Indirect Potable Reuse
  • Surface water augmentation (Class A or B) – the intentional use of reclaimed water for rivers and streams of the state or other surface water bodies, for the purpose of increasing volumes.
  • Groundwater recharge – introduction of reclaimed water to groundwater aquifers including:
    • Indirect (Class A or B) - reclaimed water is introduced to groundwater through surface or subsurface infiltration or percolation, where the introduced water travels through an unsaturated vadose zone and the commingling with groundwater of the state is not immediate.
    • Direct (Class A) – reclaimed water is released directly and immediately into groundwater of the state through direct injection or other means.
  • Aquifer storage and recovery (Class A) – Recovery of reclaimed water stored in an aquifer.
• Direct Potable Reuse (Class A+) – introduction of reclaimed water into an existing water distribution, storage or treatment system without an environmental buffer.

Water reuse treatment category/type

In Washington, reclaimed water is defined as “water derived in any part from wastewater with a domestic wastewater component that has been adequately and reliably treated, so that it can be used for beneficial purposes” (Wash. Rev. Code § 90-46). The various classes of water (Class B, Class A, Class A+) are defined by their respective wastewater treatment requirements and applicable performance standards. The respective treatment requirements are briefly summarized for potable reuse applications:

• Class A treatment must meet Class B requirements (secondary treatment including biological oxidation and disinfection) and one of the following treatment process train requirements:
  • 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. 
• Class A+ reclaimed water requirements are “established on a case-by-case basis by health” and must have approval of the state board of health before it can be beneficially used for direct potable reuse. No facilities currently produce Class A+ reclaimed water in Washington. 

Potable reuse specifications

Summary of Washington's Potable Reuse Specifications

Source = Wash. Admin. Code § 173-219

^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 potable reuse regulations were noted for Washington.

References:

EPA-Administered Permit Programs: The National Pollutant Discharge Elimination System, 40 C.F.R. § 122.

Maximum Contaminant Levels (MCLs) and Maximum Residual Disinfectant Levels (MRDLs), Wash. Admin. Code § 246-290-310.

National Primary Drinking Water Regulations, 40 C.F.R. § 141.

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

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

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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.