Wastewater Pretreatment Program


The Environmental Protection Agency (EPA) mandates the implementation of the General Pretreatment Regulations, 40 CFR 403, to all businesses that may affect the City’s POTW by the use of a Wastewater Pretreatment Program. The Washington State Department of Ecology (DOE) administers the regulations through the National Pollutant Discharge Elimination System (NPDES) Permit issued to the POTW.

The objective of the Wastewater Pretreatment Program is to protect the community and our POTW from pollutants discharged by certain businesses into the sanitary sewer. These pollutants can cause equipment damage, cause interference with plant processes, or may not be removed effectively by the POTW before being released into the aquifer. The program is implemented by DOE, and they will issue wastewater discharge permits to businesses. Taking samples of industrial wastewater and testing them for several pollutants will ensure that each business discharging to the City’s POTW remains in compliance with Federal, State, and local standards.


The goal of the Wastewater Pretreatment Program is to protect the public, the processes and equipment of the City’s Publicly Owned Treatment Works (POTW), and ultimately the waters of the State. This will help maintain a cleaner environment and extend the life and capacity of the POTW to serve the City’s future growth.

Who is Affected

Non-residential (non-domestic) customers are regulated by the Wastewater Pretreatment Program. Businesses may be classified as Significant Industrial Users (SIUs) or Minor Industrial Users (MIUs) based on the type of business and the characteristics and volume of wastewater being discharged.

Typical businesses covered under this program include manufacturing facilities, processing plants, automotive repair shops, detailing shops, and car/truck washes. Other businesses monitored by the program include, restaurants, espresso stands, cafeterias, bars, hotels, bakeries, or other establishments that prepare or serve food and wash dishes. Many Wastewater Pretreatment Programs monitor for heavy metals at businesses such as automotive repair shops, doctor and dental clinics, metal fabricators, and printing facilities.

If identified as an SIU or MIU, the City of Airway Heights Municipal Code (AWHMC), Chapter 13.06, requires users to obtain and comply with a wastewater discharge permit. The permit facilitates compliance with wastewater discharge limits. The limits are based on local conditions and are set by an analytical method approved by DOE. The Wastewater Pretreatment Program explains wastewater discharge requirements, and monitors business as needed to assure compliance.

One pollutant of great concern is fats, oils, and grease (FOG). FOG causes tremendous problems for the City’s POTW. Heavy concentrations of FOG have the potential to cause back-ups within sewer collection pipes, leading to flooding of wastewater into homes or businesses. Not only is this an extremely expensive and unpleasant situation, it is a health hazard.


The City’s Wastewater Pretreatment Program will be initiating a FOG program. The program will focus on educating managers and staff at food service establishments about proper FOG disposal. Establishments that serve or prepare food may introduce FOG into the sewer collection system. Most of these establishments are required to have grease interceptors to prevent the discharge of FOG. The program monitors businesses to ensure grease interceptors are being maintained and cleaned on a regular basis.


The City’s Wastewater Pretreatment Program will evaluate if a grease interceptor is required for a particular establishment per the AWHMC. The City’s Building Inspector will refer to the Uniform Plumbing Code to determine if the establishment has properly installed the right size grease interceptor.


Business owners and managers are responsible for maintaining grease interceptors, and documenting the cleaning schedule. Documentation must be available at the time of inspections by the Wastewater Pretreatment Program staff. Cleaning can be done by a contractor or by the business. If the City has to clean a sewer main blocked by FOG originating from a commercial establishment, the commercial establishment shall reimburse the City for those costs, in accordance with AWHMC 13.06.


The installation of a grease interceptor by itself does not assure compliance with the FOG limit. The volume and type of discharge, any pre-wash cleaning procedures, and frequency of grease interceptor cleaning are important factors that affect FOG levels and compliance.


Other businesses monitored by the Pretreatment Program for FOG include, but are not limited to, automotive repair shops, detailing shops, and car/truck washes. These businesses may be required to run their wastewater through an oil/water separator prior to discharging to the City’s POTW.

Other kinds of pollutants are regulated or prohibited from being discharged into the POTW. For example, potentially flammable wastes, acids, or other harmful chemicals are prohibited because they could harm City staff or equipment. The DOE regulates the allowable concentrations of heavy metals to be discharged by the City’s POTW to the aquifer or potentially, the City of Spokane Wastewater Plant. Concentrations of heavy metals and sediments are limited, but not prohibited. At certain businesses, petroleum products are monitored to prevent interference with the city’s POTW and pass-through into the aquifer.


For more information about the City of Airway Heights Wastewater Pretreatment Program, please call (509) 244-5429, or e-mail jwalruff@cawh.org, or refer to Chapter 13.06 of the Airway Heights Municipal Code.