New permit could address excess-nitrogen threat to Puget Sound

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.

Nitrogen sources used to predict future water-quality in the Salish Sea Model
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.

The idea of a general permit is open for comments and discussion through Oct. 21. Comments may be made online through a link on the website of the Puget Sound Nutrient Source Reduction Project, which contains documents and slide shows presented during meetings that began in July 2017. A fact sheet on the proposal (PDF 223 kb) also is available.

The nutrient problem in Puget Sound was examined in a package of stories I wrote last year for the Encyclopedia of Puget Sound. See “Does Puget Sound need a diet? Concerns grow over nutrients.”

Since then, a group led by Ecology, called the Puget Sound Nutrient Forum, has been discussing the best way to get excess nitrogen under control. In a meeting earlier this month, Ecology’s Rachel McCrea explained the differences between an individual and a general permit. Check out her slide show (PDF 743 kb) from the meeting.

Numerous cities and counties that operate sewage treatment plants around Puget Sound have been following the process, and they seem to acknowledge the problem with excess nitrogen. Many would, however, like the final solution to involve other sources of nitrogen — including agricultural runoff and septic systems from individual homesites. In total, these other sources are said to make up roughly half of the problem.

Other waterways in the U.S. with low-oxygen problems have adopted a general permit to reduce nutrient loading. For Chesapeake Bay on the East Coast, Virginia has adopted a general permit that sets limits on discharges. See the official factsheet on the program (PDF 4 mb).

“We know nutrient controls are not a simple matter of flipping a switch at a facility,” Ecology spokeswoman Colleen Keltz told me in an email. “If we move forward with the general permit, we envision a step-wise process that will recognize the infrastructure investments many facilities will need to make …

“During the first five-year permit, facilities would likely focus on what they can do now, with their current technologies,” she continued. “We would look at near-term actions, such as optimization, planning, and data collection. Optimization refers to near-term efforts to maximize nutrient reduction at the wastewater treatment plants based on existing infrastructure. We haven’t yet determined how to express optimization requirements in a general permit.”

Colleen explained that eventually the general permit would include a numerical limit for the amount of nitrogen that can be safely released into an area of Puget Sound. That determination would come from testing at the treatment plants and monitoring of conditions in Puget Sound, along with simulations from the Salish Sea Model. The model can predict plankton blooms and low-oxygen conditions based on nitrogen loads and constantly evolving weather and sea conditions in Puget Sound.

Because sewage-treatment plants are already contributing to the problem, Ecology has a regulatory responsibility to curb additional nutrient loading, she said, perhaps through a near-term cap on the amount of discharge from sewage facilities.

Nina Bell, executive director of Northwest Environmental Advocates, said a cap on nutrient loading cannot come soon enough. She worries that the first and maybe the second five-year general permit will have no limits on the amount of nitrogen going into Puget Sound. That would mean that 10 years could pass before limits are imposed, with another five years for facilities to come into compliance.

“I don’t think there is anything inherently wrong with using a general permit for the purpose of controlling nitrogen discharges to Puget Sound…,” she wrote in an email. “The problem is that, regardless of whether a permit applies to all sources or applies to individual sources…, it is not legal for Ecology to issue a permit that allows a source to cause or contribute to violations of water quality standards, which is precisely what Ecology is proposing here.”

Northwest Environmental Advocates is suing the state of Washington for failing to require that all sewage-treatment plants install advanced systems, known as tertiary treatment. State law requires “All Known, Available and Reasonable Treatment” technologies to be used, and NWEA contends that nothing less than tertiary treatment will meet that AKART standard.

Ecology’s position is that requiring tertiary treatment is not a “reasonable” approach, for it is neither affordable nor necessary for all treatment plants.

I outlined NWEA’s case and Ecology’s response in a blog post in January (Water Ways, Jan. 31, 2019). A hearing on the matter is scheduled for next January in Thurston County Superior Court.

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