City begins effort of meeting new phosphorus guidelines for treatment plant

by Emmitt B. Feldner of The Review staff

PLYMOUTH – The city has to reduce the amount of phosphorus in the water it puts into the Mullet River from the wastewater treatment plant by 2022.

The City Council Tuesday approved a $45,000 contract with McMahon Engineers Architects of Neenah to develop a plan to meet the Department of Natural Resourcesordered limit of .075 milligrams per liter of phosphorus in the plant effluent.

“The phosphorus compliance was part of our wastewater treatment plant permit from the DNR in 2013 and we need to have a preliminary plan put together by the summer of 2016,” City Administrator Brian Yerges told the council’s Public Works and Utilities Committee, which recommended hiring McMahon to create the plan.

“Because levels in the Mullet River are above .075 (mg/L), the DNR has given you a compliance schedule with a significant tightening of that window,” Chad Olsen of McMahon told the committee.

Those levels have been measured at between .1 and .2 mg/L consistently in the river, Olsen said, “so you’re not that far off.

“By July, the DNR would like a preliminary assessment of where you are and what you plan to use,” to meet the new discharge level, Olsen continued. “Our goal is to help you determine the best plan for the city.”

Olsen noted that the city is already working with the Nature Conservancy and the Sheboygan County Planning and Resources Department to identify and address phosphorus sources in the Mullet River watershed, both upstream and downstream from the plant, as part of the effort to reduce levels in the river.

For the past several years, the phosphorus level in water discharged from the plant has been at or below .1 mg/L, according to the information presented by Olsen and his colleague, Nick Vande Hey, to the committee.

“Historically, we’ve added just enough chemicals to get (the phosphorus level) down to .1, but it’s expensive,” WWTP Superintendent Mike Penkwitz told the committee members. “I don’t think that can be done day after day.”

Olsen and Vande Hey said a threepronged attack would probably be the best solution, with treatments and equipment at the plant to further reduce phosphorus levels in the water combined with adaptive management techniques at the plant and water quality trading with other areas along the river.

“There is flexibility – you don’t have to meet the new phosphorus level right at the treatment plant outflow,” Olsen noted.

Yerges noted that the study should also include a look at the city’s storm water system and the contribution that makes to phosphorus levels at the wastewater treatment plant.

He noted that, should the city’s population grow to more than 10,000 in the future, there would be more stringent DNR regulations that the city would have to comply with regarding storm water management.

City Engineer/Director of Public Works Bill Immich noted that the city has been working on the phosphorus issue since the DNR issued the permit for the wastewater treatment plant in 2013, but that the DNR did not set the timeline for compliance until last year.

The first step is the report due in July which McMahon will prepare. A final compliance plan would be due a year later, with the hope substantial changes from the preliminary plan would not be needed.

“That sounds like that’s far away, but it really isn’t because of all that needs to be done,” Yerges said of the deadline for the report. “We need to try to hone in on what makes sense from an economic standpoint.

“No matter what we do, there will be an economic impact to our rate payers,” Yerges conceded. But he added that the cost of noncompliance would be far greater.

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