TRAVERSE CITY — Two equipment malfunctions tipped off operators of Traverse City’s wastewater treatment plant to a bottleneck that must be replaced.
A proposed consent order between the city and the state Department of Environment, Great Lakes and Energy requires an estimated $150,000 fix to the plant this year and a $3 million replacement of the ultraviolet disinfection system by 2026.
Plant operating firm Jacobs reported two incidents in September 2016 when high water flows through the UV disinfection system channels knocked the system offline, plant Assistant Project Operator Mark Huggard said. Faulty sensors were to blame for both, he said.
State permits require water coming out of the plant to contain fewer than 200 fecal coliform bacteria per 100 milliliters. The plant’s membrane filtration system keeps limits below this, but the state requires disinfection regardless, he said.
Tests during both outages showed levels were well below the limit, Huggard said.
“However, the permit requirement of maintaining UV disinfection at all times was not being met,” he said.
The second outage led to findings that the ultraviolet disinfection system treating Traverse City Regional Wastewater Treatment Plant’s outflow can’t handle the plant’s maximum output of 17 million gallons a day, Huggard said. What’s more, its capacity falls as Boardman River levels rise.
Plant flows typically peak at five million gallons a day at current usage levels, Huggard said.
Commissioner Brian McGillivary referred to tables showing the UV disinfection system can flow seven million gallons a day, even when the Boardman River is at 100-year flood levels.
The city under the consent order would need to apply for a permit to make the first fix by Nov. 27, documents show. Those include removing the UV disinfection system’s electrical components from the wastewater channel and raising a discharge structure rim by at least 1.1 feet.
Then, the plant needs a new UV disinfection system by July 2026, documents show.
City Manager Marty Colburn said commissioners could vote June 17 to agree to the consent order.
Don Brady, an EGLE Water Resources Division environmental engineer, told commissioners the consent order’s not meant to be punitive.
The UV disinfection system replaced a previous one that used chlorine gas, Commissioner Richard Lewis said. He was city manager in 1995 when it was first installed, and said the state department has been a partner with the city all along.
“They could’ve brought a bigger hammer on us if they want to and they don’t,” he said. “They know we’re very serious, they know we want to do it right,” he said.