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'This isn’t a scene out of a sci-fi movie': FdL Wastewater Treatment Plant preps to meet phosphorus limit

Posted at 2:27 PM, Oct 04, 2023
and last updated 2023-10-04 15:27:03-04
  • Fond du Lac’s Wastewater Treatment Plant is preparing to meet a new limit from the DNR on the amount of phosphorus in the water that it’s pumping into Lake Winnebago, which can be challenging during months of heavy rainfall.
  • If the city doesn't meet the DNR's phosphorus limit, it can be fined. But the city can do things to earn "credits" to offset this fine.
  • The city is currently waiting on a new draft permit from the DNR. This will have a more specific timeline for the new limit to be implemented.

(The following is a transcription of the full broadcast story)
“You see a lot of algae blooms that occur in summertime, that's excess nutrients and sediment that really is preventing the sunlight from penetrating the water and getting to the native vegetation, getting the oxygen that's needed into the lake for the wildlife.”

Fond du Lac Wastewater Superintendent Cody Schoepke said they’re anticipating that the DNR’s new phosphorus concentration limit for the plant will be 60 percent lower than the current limit.

This limit could be hard to reach. On heavy days the water flow can reach 60 million gallons per day -- compared to 7 million gallons on an average day.

“The plant’s certainly not designed to see flow increases of that magnitude,” Schoepke said.

To meet this limit, the plant is refining their process… which has four main steps:

1. The facility removes inorganic material like trash and debris from the water.

“If you look here and see all the little holes, wastewater close to this channel, and anything larger than those holes, which are an eighth of an inch, is caught,” Schoepke said.

2. The water undergoes primary treatment, where organic solids and the water separate.

“Any of those solids, those organic solids that are heavier than water can settle in to the bottom,” Schoepke said.

3. The water is treated with bacteria to break down the phosphorus.

“These are known as aeration basins,” Schoepke said. “See the white bubbles that are down there? That's for areas added to provide oxygen to the bacteria.”

4. And no, this isn’t a scene out of a sci-fi movie (context: the water pictured here is glowing green)-- the water is disinfected with u-v light.

“It's high intensity light as the wastewater flows through a series of holes, that high-intensity light essentially de-activates the DNA of those organisms and bacteria, preventing them from doing anything downstream,” Schoepke said.

Then, the water flows back out to Lake Winnebago.