DNR wants lower phosphorus levels in Roberts’ wastewater
Roberts Public Works Director John Bond is dedicated to running the wastewater treatment plant in such a way that the environment is protected. That’s one reason why the pilot microfiltration plant project he has been experimenting with is so important.
Simply put, the Wisconsin DNR Natural Resources Board adopted administrative rules aimed at cutting phosphorus coming from farms and industrial and municipal wastewater dischargers in June 2010.
Under the new rules, which are in effect, a handful of municipalities were hit with the strictest phosphorus limits the DNR could impose on a treatment plant. Roberts was one of them.
That may be because the plant’s wastewater is discharged into what is considered an “impaired” body of water -- Twin Lakes, Bond said.
By impaired, the DNR means bright green with algae, Bond said. He also said the amount of phosphorus in the discharged water is not nearly enough to cause the algae growth that is there.
“There’s no doubt that Roberts contributes to that,” Bond said. “That’s where our pipe goes. But what people don’t realize is that when East Twin Lake was dried up pre-1980, cattails grew tall there. It was more of a wetland.”
Bond said that cattails are extremely high in phosphorus content, and that when those plants died and decayed in the lake bed, they left behind a high phosphorus content, which contributes to the current algae growth.
“Our pipe going into the lake is a visible point source,” Bond said. “But what people can’t see are the non-point sources, like the cattails releasing phosphorus as they decay, or the runoff from lawns and fields. Our point source was an easy target.”
Phosphorus causes algae blooms in lakes, which can eventually take enough oxygen out of the water that fish will die from lack of it, especially in seasons with a lot of rain.
According to Bond, under the new limits, only 0.04 milligrams per liter of phosphorus in wastewater discharge is allowed. The current rate has been one milligram per liter of phosphorus in wastewater discharge with a mass limit of 880 pounds permitted a year. The Roberts plant produced 128 pounds of phosphorus in its discharge last year, well below the limit.
“Technology has not yet caught up with the levels that the DNR wants,” Bond said. “But the levels aren’t going away and we must get there eventually.”
Every five years a treatment plant has to submit an application to the state. The DNR looks at a list of criteria and comes up with rules for individual treatment plants to follow, Bond said.
The new limits of phosphorus must be met in four years, unless the plant files for a variance, Bond said. Roberts is in the middle of a permit cycle right now, so the new limits deadline would come after a new permit is issued.
Under the current limits of one milligram per liter, the microfiltration pilot plant Bond has been testing has been getting the levels down to anywhere from 0.2 to 0.4 or 0.5 milligrams per liter. The technology currently out there has not yet found a way to test if equipment can get to the 0.04 milligram per liter that the DNR wants, Bond said.
Bond got the chance to test a pilot plant free of charge thanks to connections he has with Energenics, a wastewater treatment plant equipment vendor, and the State Board of Directors for Wisconsin Wastewater Association. The pilot plant is a small version of a treatment plant with new technology to see what it can and cannot treat.
Bond must run the pilot plant on a daily basis by keeping the proper chemical levels full, collecting samples of water and data, and sending it to a lab for testing in Colfax every two weeks to see if the new pilot plant can get the levels down to meet the new limits.
Testing began in January and will go until at least May.
“I wanted to run it in cold weather, and I guess I got what I asked for,” Bond said. “We have been running it slowly to work out the bugs and we will begin running it faster once we know we can get to the needed levels consistently. We need to know how often we can get it there.”
The pilot plant runs on 10-minute cycles. Water is forced with a reverse osmosis membrane that creates a vacuum. The barrier collects phosphorus as it passes through the membrane. So far, everything seems to be running smoothly, Bond said.
The current treatment plant was built in August of 2006, Bond said.
“It’s frustrating because we didn’t think we would have to do modifications or build for another 20 years,” Bond said. “We worked with the DNR when building this so there were no surprises.”
While the DNR may not necessarily force Roberts to build or upgrade its current plant, and Bond is hoping this new pilot plant could be an answer, Bond estimates the cost to create a plant that can do what the DNR wants as far as phosphorus levels go, could be $5 million to $6 million.
“People already can’t afford the water and sewer expense,” Bond said. “You come up with a $6 million capital expense spread between 1,600 people and, well.”
All of this is pure speculation, Bond said. He said it’s sometimes challenging to go to the Village Board with information such as this, not because they’re not supportive, but because it’s hard to make people understand the DNR’s requirements and their ramifications.
“We will try to remove everything we can,” Bond said. “It’s part of my responsibility to protect the environment.”