wastewater cleaning

Plant operator Toney Roy sprays accumulated sludge off sheets of fabric on an 18-foot-tall rack, one of 144 at the wastewater treatment facility.

The City of Driggs is in the midst of a major cleaning operation on its wastewater treatment plant, and is pioneering the process as it goes.

It’s the first time that such a plant, which uses a multi-stage activated biological process to treat wastewater, has ever been deep-cleaned, so the plant designers, Aquarius Technologies out of Wisconsin, visited to observe the process.

The plant was installed in 2013-14, and Aquarius recommended a complete basin clean every seven to ten years as part of ongoing maintenance, explained Driggs public works director Jay Mazalewski. Last month the city hired Depatco to clean one of the plant’s two basins, at a cost not to exceed $50,000. The process took longer than expected due to weather and experimentation, so the city approved a budget increase to $80,000 on April 20. The cleaning of the second basin will likely happen in the fall or next spring, when inflow is low and the public works crew has time to devote to the effort.

“The first week was rough, the second week went better, the third week we’re getting even faster,” Mazalewski said during a facility tour last week.

A crane operator lifts one 18-foot-tall rack at a time from the cell. The racks are draped with sheets of synthetic fabric, home to the organisms in charge of “eating” the plant’s biological influent. Depatco workers and city staff have hosed off approximately two tons of sludge from each rack; the sludge was then pumped into the adjacent storage lagoons with the city’s vacuum truck.

The plant has long been plagued with ammonia troubles and is required by the Department of Environmental Quality and Environmental Protection Agency to drastically lower the amount of ammonia it discharges into a tributary of the Teton River.

Mazalewski is optimistic that the deep clean will at least temporarily return the treatment plant to compliance by improving the environment of the basin to the optimal condition for the plant’s biology. (He expects, however, that the respite will come to an end once temperatures drop around Christmas.)

“We’re doing everything we can, and they can see that,” he said. “I just wrote DEQ and EPA a three-page letter detailing the cleaning process.”