Nitrogen from sewage-treatment plants, along with other nutrient sources, are known to trigger plankton blooms that lead to dangerous low-oxygen conditions in Puget Sound — a phenomenon that has been studied for years.
Map: Washington Department of Ecology
Now state environmental officials are working on a plan that could eventually limit the amount of nitrogen released in sewage effluent.
The approach being considered by the Washington Department of Ecology is a “general permit” that could apply to any treatment plant meeting specified conditions. The alternative to a general permit would be to add operational requirements onto existing “individual permits” issued under the National Pollutant Discharge Elimination System, or NPDES.
The general permit would involve about 70 sewage-treatment plants discharging into Puget Sound. Theoretically, an overall nitrogen limitation would be developed for a given region of the sound. Treatment plant owners could work together to meet that goal, with the owner of one plant paying another to reduce its share of the nutrient load.
