Pretreatment Program

The City’s Wastewater Treatment Plant is designed to treat wastewater generated by domestic sources, such as residential homes. It is not equipped to treat wastewater containing elevated levels of sludge, heavy metals, acids or bases, oil and grease, medical waste, or other hazardous materials typically associated with commercial and industrial (non-domestic) discharges.

The City established a Pretreatment Program in 1984 to protect the wastewater treatment system and prevent pollutants from entering the Spokane River. Under this program, commercial and industrial users are required to reduce pollutant concentrations in their discharges to levels that can be effectively treated by the City’s wastewater treatment facilities.

Residential facilities, including duplexes and apartment buildings, are classified as domestic dischargers. These facilities are not regulated under the City’s Pretreatment Program and are not required to obtain permits from the Wastewater Department.

All non-domestic users shall comply with City Code 13.20, the City’s Sewer Use Ordinance. Commercial and industrial users that generate process wastewater may be required to install pretreatment systems to reduce pollutant loading to levels comparable to typical residential discharge. Such pretreatment measures may include, but are not limited to, grease interceptors for food service establishments; oil-water separators for automotive repair facilities, car wash operations, industrial facilities, and parking garages; and pH adjustment and solids removal systems for industries such as breweries.

No Significant Industrial User (SIU) or Categorical Industrial User (CIU) may discharge wastewater into the City’s system without first obtaining a wastewater discharge permit from the Wastewater Department.

A facility is classified as a Significant Industrial User (SIU) if it meets any of the following criteria:

It is subject to federal categorical pretreatment standards; or

It meets one or more of the following conditions:

Discharges an average of twenty-five thousand (25,000) gpd or more of process wastewater to the POTW (excluding sanitary, noncontact cooling, and boiler blowdown wastewater); or

Contributes a process waste stream which makes up five percent (5%) or more of the average dry weather hydraulic or organic capacity of the POTW treatment plant; or

Is designated as such by the city on the basis that it has a reasonable potential for adversely affecting the POTW's operation or for violating any pretreatment standard or requirement.

A facility is classified as a Categorical Industrial User (CIU) if it is subject to federal categorical pretreatment standards established by the Environmental Protection Agency (EPA), as outlined in 40 CFR Chapter I, Subchapter N, Parts 405–471.

Facilities classified as SIUs or CIUs must complete, sign, and submit the SIU/CIU Wastewater Service Application at least 90 days prior to the anticipated connection date to the City’s sanitary sewer system.                                                                                                              

For additional information regarding the Pretreatment Program or assistance with completing application forms, please contact the Pretreatment Office at (208) 769-2276.