Wastewater Utility Prepared for New Phosphorus Limits

DNR Takes Steps to Address Water Quality

Marshfield, WI (OnFocus) Phosphorus in Wisconsin’s lakes and rivers have left a quarter of the state’s 700 waterbodies below water quality, according to the DNR.

To combat harmful algae growth and address the issue, the Wisconsin DNR limited phosphorus output to 1.0 parts per million (1 milligram per liter) starting in 1992, one of the first states to do so, with further revisions to water quality standards in 2010. That year, phosphorus was also banned from lawn fertilizer.

Aiming to lower limits scientifically using EPA guidelines, the DNR has set TMDL (Total Maximum Daily Load) standards for the Wisconsin River. TMDL determines how much of a pollutant a body of water can receive and still meet water quality standards.

The DNR will impose newly lowered phosphorus limits in the next few years for wastewater plants and factories. Marshfield Wastewater Utility will be tasked with reducing their phosphorus output in October 2023 from the current 1.0 limit to an anticipated 0.3 — but luckily, they’re already there.

“Right now for the last 12 months our average has been 0.18, so we’re actually half the limit,” said Sam Warp, Wastewater Superintendent. “The lower we go, the better it helps Petenwell and Castle Rock [lakes].”

Marshfield Wastewater Utility is one of only a handful of wastewater facilities in the nation which treats its phosphorus through a biological, rather than chemical, process.

“We remove all the phosphorus by growing the right bugs, the bacteria that eat it up and take it out,” said Warp.

Formerly the plant used chemicals to bring phosphorus down to the 1.0 limit, and now the process is made far easier and more effective through the biological process.

“The only hiccups are if we get high rain or if somebody dumps something down the drain that kills the bacteria. Then we start over,” he said.

The facility made the switch in 2016 and will be making further upgrades in the next five years to improve the biological phosphorus process, starting with two section hauler tanks for high strength industrial waste.

The bid for the $1,000,500 project was awarded to Staab Construction Corp. Funding comes from the city’s 2019 budget at $685,000 with the remaining cost covered through reserves that had been set aside for phosphorus compliance.

The upgrades planned over the next five years will help Marshfield Wastewater Utility complete phosphorus removal more efficiently.

“The problem is we get the majority of our food for those bugs during the day, then at night very little food that comes in,” said Warp. “We think it can run better if we put in these tanks and then the excess food that comes in during the day, we’ll have that pumped back in at night.”

The system will give the bacteria an even source of food both day and night.

“If we can keep the food going, we should keep more healthy bacteria,” he said. “Even though we’re below our limit, we have good days and bad. It depends on temperature and rainfall and what people send us. The whole goal is to ride through some of those rough times a bit better.”

Part of future upgrades will be to replace the aerators, which typically have a 20-year lifespan which is now up.

“The aerators that we have are not very efficient. They were the best there was when they were designed back in the late 1990s, but motors and gear boxes and aerators are much more efficient nowadays,” said Warp. “We’d like to put more newer energy efficient equipment, which will help lower costs.”

The projected $5 million improvements will occur over the next 5 years at a price far less than a full upgrade, which would have cost upwards of $27 million or more to complete according to estimates completed in 2016.

“Now we’re doing these projects each years with the money we have and we’re not borrowing a single penny to do it,” Warp said. “You really save money when you’re not paying interest.”

As wastewater plants tackle their phosphorus output, the EPA is also expected to set a limit for nitrogen in Wisconsin in the next decade. The limit would address nitrogen pollution in the Mississippi River, pollution which contributes to drinking water contamination and the hypoxic zone in the northern Gulf of Mexico, an oxygen-poor area hostile to marine life.

“That’ll be the next hurdle,” said Warp.

Marshfield Wastewater Utility treats nitrogen with bacteria which convert it to nitrogen gas, a natural part of breathable air.

“We monitor the nitrogen now and we are much better at taking it out than we were even five years ago,” he said. “Who knows what the new limits will be?”

A major source of pollution comes from farm field runoff, an issue being addressed with legislation that aims to provide a third-party clearinghouse funded by wastewater plants and factories to help farmers afford equipment upgrades that would keep more nutrients in the soil and out of the water.

The bill passed the state Senate unanimously and now moves onto the Assembly with passage expected this fall. Farm groups have supported the bill.

“It’s better in the long run,” said Warp. “Change is difficult and change is slow, but we’ll get there someday. I’m confident.”

Found OnFocus: Sam Warp, Wastewater Utility

About Wastewater Treatment in Marshfield

Kaylin S
Author: Kaylin S

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