The National Pollutant Discharge Elimination System (NPDES) and the Clean Water Act have regulated water quality since the early 1970s. This federal program identifies and regulates water pollution from point sources (such as the sewage treatment plant and outfall pipes) and non-point sources (stormwater runoff from streets).
The City of Portland has NPDES permits for its two sewage treatment facilities, the Columbia Boulevard Wastewater Treatment Plant and the Tryon Creek Wastewater Treatment Plant. The permits require the city to manage discharges to the treatment plants. In 1982, Portland began permitting industrial users and requiring them to pretreat wastewater discharged to the sewer system.
Pretreatment reduces the amount of pollutants and neutralizes wastewater to meet discharge requirements. Types of pretreatment include pH neutralization, solids separation, metals removal and oil/water separation. Many industries have installed pretreatment systems and control mechanisms to reduce pollutants in their discharge to meet the standards.