New safeguards added to King County's South wastewater plant permit

BELLEVUE, WA, Sept. 30, 2009 -- The Washington Department of Ecology (Ecology) today issued a renewed discharge permit that includes some more-stringent requirements for Washington's second-largest municipal wastewater treatment plant (WWTP)...

BELLEVUE, WA, Sept. 30, 2009 -- The Washington Department of Ecology (Ecology) today issued a renewed discharge permit that includes some more-stringent requirements for Washington's second-largest municipal wastewater treatment plant (WWTP). The five-year discharge permit for King County's South wastewater treatment plant in Renton is a key tool to provide critical water-quality protection for Puget Sound.

"One of the foundations of water-quality protection is municipal wastewater treatment," said Kelly Susewind, who manages Ecology's water quality program. "Treatment plants operate under conditions set by permits, based on the standards and requirements in our clean water laws and regulations. The permit ensures that the sewage that comes into the plant goes out as treated water suitable for release to Puget Sound."

The South WWTP serves 25 cities and sewer districts in south and east King County. The facility treats an average of approximately 80 million gallons of incoming sewage per day. Treatment plant permits last for five years.

Ecology issued a similar permit in June 2009 for King County's larger West Point treatment plant in Seattle.

New or updated provisions in the renewed South Plant permit include:

• More restrictive dilution factors than in the previous permit.
• Requires increased monitoring of priority and toxic pollutants in the South Plant discharge.
• Requires King County to more extensively test for sediment toxicity in the vicinity of the South Plant outfall -- in Elliott Bay, off Duwamish Head in Seattle -- than the previous permit.
• Adds requirements to track the input of industrial chemicals into the sewer system.

The King County treatment-plant permit upgrades come as Ecology conducts several studies and plans to support long-range goals to restore and protect Puget Sound.

Under a special condition in the draft permit, if studies on low dissolved oxygen problems in southern Puget Sound waters point to South Plant as a significant contributor, the renewed permit would require King County to propose changes to further improve its discharge.

"The studies now under way for the Puget Sound Initiative will provide information that could lead to new or changed strategies," said Susewind. "If the findings show a need for changes at treatment plants before the next scheduled permit upgrade, Ecology can take steps to do so."

Puget Sound studies currently under way that could affect future permits for South Plant and other treatment plants include:

Controlling nutrient pollution to maintain dissolved oxygen levels:

1. South Sound Dissolved Oxygen Study. This research includes King County's wastewater treatment plants. It examines how various sources of nitrogen and phosphorus affect dissolved oxygen levels. These pollutants feed processes that use up oxygen that fish and other marine life need to live. Preliminary results are due in later this year, with a final report in 2010.
2. An economic and technology study will evaluate the costs and benefits of available technologies that can reduce nitrogen and phosphorus in treated wastewater.

Toxics and pharmaceuticals:

1. A study -- due later this year -- will assess the presence of pharmaceuticals and endocrine disruptors (which interfere with biological reproduction).
2. An evaluation -- due in about one year -- will report on the concentrations of toxic compounds released by treatment plants.

To learn more about protecting water quality protection in Puget Sound, please visit http://www.ecy.wa.gov/puget_sound/index.html.

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