The City of San Luis Obispo’s Pretreatment Program was established in 1983 to provide protection to the Water Resource Recovery Facility (WRRF) and the sewer collection system by controlling the discharge of non-domestic wastes into the City’s sewer system.  The program is mandated by the Environmental Protection Agency and the State Water Resources Control Board.

The function of the program is to protect the WRRF from discharges that could upset or inhibit the plant’s processes, or pass through the process untreated and then be discharged into San Luis Creek. An illicit discharge to the WRRF can also result in a reduction of waste treatment, possibly contaminating biosolids or recycled water, resulting in expensive handling and disposal costs or degradation of the creek’s environment.

Significant Industrial User (SIU)

 A significant industrial user is any industrial user that meets one of the conditions below:

1. All Industrial Users who are subject to Categorical Pretreatment Standards under 40 CFR 403.6 and 40 CFR chapter I, subchapter N; 
2. Discharges ten thousand gallons per day or more of process wastewater;
3. Contributes five percent or more of the average dry weather hydraulic capacity of the treatment plant;
4. Discharges either continuously or intermittently to the POTW, process wastewaters containing priority pollutants as determined through analytical procedures or reasonable technical judgement; or
5. Has reasonable potential, in the opinion of the director, to adversely affect the POTW's operation or for violating any pretreatment standard or requirement.

Class I Industrial User

A Class I Industrial User is a business that has materials and/or wastes on site that if discharged to the sewer may impact the POTW in a negative manner.  These materials and wastes include, but are not limited to, any and all prohibited discharges described in Section 13.08.040 of the San Luis Obispo Municipal Code.

Class II Industrial User

Any industrial user that may discharge conventional pollutants to the POTW which may cause interference or pass-through.  These wastes include but are not limited to laundry discharges, nonhazardous solids and oil and grease of animal or vegetable origin.

 For more information check out the Fats, Oil, Grease (FOG) page.

Dentists

As of July 14, 2020 all dentists who place or remove dental amalgam are required to install, operate, and maintain an amalgam separator.