Puget Sound wastewater treatment plants to tackle nutrient pollution with new permit

Artwork fountain at the Edmonds Wastewater Treatment Plant

To stop the flow of nitrogen pollution and improve the health of Puget Sound, the Washington State Department of Ecology is requiring — starting Jan. 1 — that wastewater treatment plants — including those in Edmonds and Lynnwood — monitor discharges, optimize operations and plan for infrastructure investments.

Excess nitrogen is the main pollutant causing low, unhealthy oxygen levels in Puget Sound, and a cascade of problems for fish and other marine life, the Department of Ecology says. The new Puget Sound Nutrient General Permit puts 58 wastewater treatment plants on a multi-year path to control and significantly reduce nitrogen discharges. Most of these facilities do not currently have nutrient control technologies in place. This means the nitrogen in human waste is flowing from homes and businesses, through the facilities, directly into Puget Sound.

While Edmonds and Lynnwood have their own treatment plants, Mountlake Terrace sends its wastewater to the City of Edmonds for treatment. Brier’s wastewater, meanwhile, flows to King County Metro’s West Point treatment plant.

The permit works in five-year cycles, with the Department of Ecology updating and refining requirements every cycle based on what is learned from permit implementation and public feedback. Because of the large difference in the amount of nitrogen discharged from facilities, requirements are split into three categories: dominant (seven facilities), moderate (20 facilities), and small (31 facilities).

City of Lynnwood Wastewater Treatment Plant.

The seven dominant facilities are responsible for over 80% of the excess nitrogen going into Puget Sound. The moderate-sized facilities account for 19%, and the small facilities contribute less than 1%. Ecology developed these categories, and the related requirements, based on feedback from an advisory committee and two rounds of public comment held earlier this year. (Edmonds and Lynnwood are considered moderate-sized facilities.)

The first five years of the permit (2022-2026) focus on preventing the nutrient problem from getting worse while facilities identify long-term technology upgrades and other investments to better control nutrients. The Department of Ecology is requiring facilities to:

  • Monitor wastewater for nutrient reductions, and collect data to support potential water quality trading among facilities.
  • Optimize current treatment processes to remove as much nitrogen as possible.
  • Plan for future facility upgrades to control nutrients.

Optimizing performance during the first five years of the permit is the first step to reducing nutrients entering Puget Sound from these facilities. Ecology anticipates many plants can reduce nitrogen by 5-7% or more by optimizing existing treatment processes during this time. Optimization alone will prevent thousands of pounds of nitrogen per year from entering Puget Sound. Facilities are eligible for grants from Ecology to help cover the costs of optimization and planning.

The seven facilities in the dominant category have additional requirements. If they cannot maintain or reduce their nitrogen levels through optimization, they must find ways to reduce their nitrogen by 10% in the short-term while planning long-term investments.

Communities and their facilities have a range of options when it comes to how they reduce the amount of nitrogen they are discharging into Puget Sound. As part of the required planning, the Department of Ecology said it expects facilities to consider what is affordable for their community. Ecology anticipates nutrient control technologies will be online at most facilities in the next 15-20 years. This reflects the time and financial resources it takes to plan and build these major infrastructure improvements.

The new permit is effective in 30 days, starting Jan. 1, 2022. To view the permit and other related materials, visit ecology.wa.gov/NutrientPermit.

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