Bacteria! The “Clear” Winner for New Water Treatment Plant

“They can drink it; they can finally take baths in it.”

Josh True, Onamia Water Operator

For years many people living in the town of Onamia, MN took it as a tradeoff for living along beautiful Lake Onamia that their water was not something to be used for cooking or drinking. 

The name “Onamia” comes from the Ojibwe word meaning, “red ochre” which is a color of clay in the area, but not the color that you want your water to be when it comes out of the tap. The area geology and water chemistry gave the drinking  water a dark color, so although it was technically safe to drink, it was off-putting. Josh True is the water operator in the town and for years he struggled with talking about water quality with his neighbors and friends. 

“When you tell somebody [that the water is drinkable], and they're holding a brown bottle towards you, it's hard to say it with a straight face… It was literally like you were drinking a swamp,” says True.

While the town’s water passed bacteria tests and met maximum contaminant levels required by the federal Safe Drinking Water Act (SDWA), most of the people living in town purchased bottled water for consumption up until September of 2025. That’s when a new water treatment plant officially went online, creating the first clear water the city had seen in its history. This water treatment plant is unique compared with many in the area; it uses bacteria as the solution to the city’s water woes.

What was the problem?

Collin Fetters is a district engineer for the area.  According to Fetters, testing for the water system before the new plant began functioning frequently showed ammonia at more than seven mg/L – which is roughly equivalent to a grain of sand in a bathtub. Small in scope, but a big roadblock when it came to building public trust in the community water system. 
This project also added an additional well, (Well #5) that is located near the facility.

In 2014 while MDH was conducting a study to find out why the city was having difficulty maintaining residual chlorine levels in the distribution system, it found extremely high levels of ammonia. The town is served by three wells that are built over the top of a large ammonia bed underground. While ammonia is not a contaminant that is regulated by the SDWA, it can lead to nitrification, which is a microbial process in drinking water systems where ammonia is oxidized to nitrite and then to nitrate. Nitrate has a maximum contaminant level of 10 mg/L, and while nitrate levels were always low during sampling, it was noted as a potential area for concern. The city’s drinking water also has high levels of iron and manganese, resulting in water with poor aesthetic quality. When the ammonia nitrified in the system, it led to the orange-colored water from one well, and greenish-black colored water from higher iron and manganese concentrations in well #4.

Engineering firm SEH, a company using a new kind of biological filtration treatment, contacted the city after the research study. The filtration process suggested by SEH uses biologically active media before the filters and can greatly improve the aesthetic quality of drinking water while helping meet treatment goals. 

“This process purposefully lets the naturally occurring bacteria treat the water first,” says Jeff Ledin, overall project manager with SEH. “The bacteria remove iron and manganese and convert the ammonia into low nitrate levels.” 

The firm, working with Minnesota Department of Health and the city, secured funding for the project and began to incorporate the new biological filtration method into their drinking water system. Kim Larsen was a district engineer during the first biological filtration study in 2014. Today she supervises the unit at MDH that works with community water systems. When that study was conducted, she realized that this new method of treatment could be a game changer for drinking water. 

According to Larsen, "They've always used biological treatment for wastewater. The realization came that if we don't have to add chlorine on the front end and we have [biological] activity that removes contaminants we don't want, that's a better result for drinking water as well.”

The Process: Biology (and Chemistry!) Matters

“You put water in, you add oxygen, and the bacteria does its job. It's in the water naturally. All you're doing is you're giving it a home.”

Josh True, Onamia Water Operator

True makes it all sound easy, but behind his words lies an enormous amount of sweat equity and hard work that he has personally put into making the plant run efficiently. Throughout the project True worked closely with SEH, MDH, and the contractor (Rice Lake) to get the plant operating at optimum levels. 

The process involves three basic steps:

1. Aerating the water to build up the oxygen. 
2. Injecting more oxygen into the water.
3. Finishing the water. 

Because the bacteria thrive on oxygen, they eat the ammonia and iron that occur naturally in the water. The ratio of oxygen to water varies based on conditions specific to a water system, so True had to do a lot of on-the-job research to determine exactly how much oxygen was needed to get the process moving. When he turned the plant on for the first time in August 2025, the bacteria removed the iron immediately, but it took about a month for the bacteria to start consuming the ammonia , and in the process the nitrate continued to climb. 

“It kind of gets stuck in a nitrite cycle… there were a couple times where the nitrite would be like really close [to the nitrate maximum contaminant level], so I'd do a lot of testing just to make sure that it wouldn’t climb above 10 mg/l. But eventually what happened is it was basically like night and day. One day it was doing one thing, the next day, all the ammonia was gone.”

With the bacteria taking care of the excess ammonia and resulting nitrates, the final step to ensure the water is ready to drink involves finishing the water. The Onamia plant uses a Granulated Activated Carbon (GAC) filter to remove disinfection byproducts and manganese from the water before it is distributed to customers.

Working together

A project like this doesn’t just happen overnight.  Like the water we all drink, this work requires the coordination of funders, planners, contractors, and most importantly, people who want to make a positive change in the drinking water for the community where they live, work, and play.

“You have to have a water operator who is willing to push it, and a city council who is willing to push it, and the hospital in town was interested in having better water. It took a long time to get it over the hump,” says Larsen.

One major barrier the city faced was the price tag. 

“There's been a lot of times when we talked about not keeping on with this because it's very expensive,” recalls True. “We can't afford it… but it's not really an option... I just kind of kept that in the council's mind that it's not really an option not to do something. We'll have to do something to the water to improve the quality.”

The total project cost was $9,751,000. The City worked with SEH to apply for federal funding from the US Department of Agriculture (USDA). They also applied for and received about $4 million from state funding. Despite the high price tag, the community welcomed the change.

"We, as the general contractor, are the last ones to join the team, but we felt welcomed from day one by everyone involved and the community. We brought in a bunch of equipment, dug a big hole, and started pouring concrete, and we didn't hear a single complaint. We take a lot of pride in helping communities improve their infrastructure and solve real problems. At the end of the day, we walk away, and the community is much better off."

To help offset funding the project, the City secured a loan portion of $772,000. Consequently, ratepayers saw an increase on their water bills, but many residents tell True the increased bill is well worth it.

“I mean, people in the town love the water now, says Josh. “It’s nice. I mean, I can't tell you how many times I get stopped and they tell me that it's great… And I guess the hospital maintenance guy, he tells us that the toilets are self-cleaning now.”

UPDATE: In recognition for his outstanding service to his community, the American Water Works Association of Minnesota awarded Josh Tre the "Meritorious Operator" award for 2026. The Meritorious Operator Award is presented annually by the Minnesota Section AWWA to an Operator who has brought a higher degree of excellence, learning, initiative and resourcefulness to bear in the operation of a public water supply system.

A complete list of feature stories can be found on the Waterline Articles and Feature Stories webpage.

Return to Waterline: Fall 2026.

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