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Water Treatment Plant General Permit

Water treatment plants produce water for drinking and industrial businesses. The Washington State Department of Health assures drinking water is safe and reliable. Our role ensures that the water treatment byproducts released from these plants do not harm the environment.

Treatment can involve:

  • Filtering and settling out sediment and disease-causing organisms.
  • Using chemicals to kill organisms or remove excess minerals and other contaminants.
  • Disinfection and chemical adjustment to reduce scaling or corrosion within the delivery system.

The current permit went into effect Sept. 1, 2014 and expires on Aug. 31, 2019.

We have developed the Water Treatment Plant General Permit (WTPGP) to help treatment facilities comply with state laws and the federal Water Pollution Control Act. This permit contains specific requirements and conditions for permittees to protect rivers and other waterbodies that receive wastewater discharges.

Water treatment plant general permit


Current permit

Does my facility need this permit?

You need a general permit if the water treatment plant discharges backwash to surface waters and:

  • Produces 35,000 gallons per day or more (monthly total divided by the number of days in the month) of finished drinking and industrial water.
  • Treatment and distribution of potable or industrial water is the facility's primary function.
  • Produces wastewater by filtration processes.
  • Is not a part of a larger permitted facility.

Operations not covered by this permit include discharge of wastewater that is:

  1. Produced by one of the following processes:
    • Ion exchange
    • Reverse osmosis
    • Slow sand filtration
  2. Sent to a publicly-owned treatment works.
  3. Release to land where runoff or overflow is impossible.

If any of these are the case, you may need an individual permit.

Previous permit



Richard Marcley
Permit Manager

Eastern Northwest Southwest