Minnesota Cities Magazine
More from Nov-Dec 2018 issue

Focus on Small Cities: Clean, Clear Water—St. Martin Builds Biological Water Treatment Plant

By Tad Simons

Every time Cara Olmscheid turns on the faucet in her home to fill a glass of water, a minor miracle happens: the water comes out clean and clear, and it doesn’t taste like metal shavings. In 2016, the city where Olmscheid lives and works—St. Martin, population 344—installed Minnesota’s first all-biological water-treatment facility, turning what was once a ritual of frustration and disgust into a pleasantly refreshing experience, one others might take for granted, but not the residents of St. Martin.

“It was awful,” says Olmscheid of the city’s former water quality. “If you filled the bathtub up, you couldn’t see to the bottom. You couldn’t wash anything white, because it would come out orange. And almost everyone drank bottled water, because the tap water was brown.”

Time to act

That’s the way it was for decades in St. Martin, until Mayor James Rothstein and Olmscheid, the city’s clerk and only fulltime employee, decided to do something about it. “We needed clean water,” says Rothstein. Getting it became one of his first priorities as mayor.

Rothstein grew up in St. Martin but spent most of his working life in New York. He returned to St. Martin to care for his aging parents, then got elected mayor in 2002 and also served as president of the Sauk River Watershed District. Residents had been complaining about the water quality for years, he knew, and various solutions had been proposed, but all were deemed too expensive.

To find a workable solution, Olmscheid spent eight years researching the city’s infrastructure, water tables, and usage. She didn’t mind doing it, she says, because she’s “interested in that kind of thing.”

In the process, Olmscheid and Rothstein learned more about an emerging technology that uses only natural bacteria and oxygen to filter water and remove contaminants. Most cities use a combination of chemicals and filtration membranes to treat their water, but biological filtration offered a solution that was both ecologically responsible and, as it turned out, less expensive than building a traditional water treatment facility.

“A mechanical plant would have been unaffordable,” Olmscheid says. “We knew some filters were going biological, and we didn’t care for all the chemicals. But no one in Minnesota had built a biological plant from the ground up, so we had to study it and come up with a plan.”

Working with the Minnesota Department of Health (MDH), the U. S. Department of Agriculture, Tonka Water of Plymouth, and WSB & Associates in St. Cloud, St. Martin developed a four-month pilot program to test the long-term viability of a biological water treatment facility. Not only did they need to prove that such a facility would work, they also had to model operations and maintenance costs, as well as the impact a new facility would have on water rates.

“We didn’t just take the advice of state engineers before we built this thing,” says Mayor Rothstein. “You have to do your homework. We talked to several hydrologists and engineers. We had a geologist from the University of Minnesota come out to determine what our ground is made of. There’s a lot more to it than just digging a well.”

Research and testing

And St. Martin has dug many wells. Before its new water-filtration system came online, the water in St. Martin was being pumped directly from the ground into people’s homes. Between 2006 and 2011, however, the city shut down two wells due to mechanical failures and proximity to an open creek. It then dug two deeper wells outside the city limits in order to access a different aquifer located beneath a granite shelf.

Those wells now flow into the new water-treatment facility, but before the wells were dug, the quality of the water coming from the new aquifer was unknown. Presumably it was cleaner because the well was deeper.

But testing revealed that, in addition to the expected iron and manganese, the water coming from the new aquifer also had high levels of ammonia. Testing of the new wells in this case was critical because St. Martin didn’t know it had an ammonia issue until the MDH told them.

“If we’d built this and didn’t address the ammonia problem, that would have been a big mistake,” says Olmscheid. Instead, engineers designed a filter to specifically target ammonia, along with the iron and manganese, thereby creating a system custom-designed to treat the water coming out of St. Martin’s aquifers.

According to Kim Larsen of the MDH, the biological water treatment option worked for St. Martin partly because the composition of St. Martin’s water matches up well with the strengths of the biological filtration process itself. Iron, manganese, and ammonia were St. Martin’s major contaminants, and those also happen to be contaminants that are effectively removed through biological filtration.

“Biological filtration is not a new technology. It’s actually an old technology that many people are looking at more closely and finding ways to optimize in order to remove different contaminants,” says Larsen. Some larger communities in Minnesota are currently exploring biological filtration as well, she says, and in general there is renewed interest in biological because it is considered a “greener” option.

Biological filters harness the chemical-neutralizing properties of naturally occurring bacteria to work their magic. To filter out ammonia, for instance, bacteria feeds on the ammonia and breaks it down into ammonia nitrate.

The St. Martin plant actually has three separate filters, or vessels, which facilitate different parts of the process. The first uses air and bacteria to oxidize iron and to convert ammonia into nitrite, then nitrate. The second filter completes the ammonia nitrification process, and the third uses anthracite and green sand to filter out oxidized manganese and any other particulate matter.

After the water is filtered, the city adds fluoride, chlorine, and a corrosion-control agent, and then it’s ready for distribution into the city’s water system. The plant produces 100 gallons of clean water per minute during regular operation, but has the capacity to produce twice that, if necessary.

Among the side benefits of biological filtration is that less money needs to be spent on chemicals, and the process itself doesn’t create any biologically hazardous byproducts. In St. Martin, iron sediment and excess nitrates are kept in a backwash pond, where bacteria continues to break down contaminants until they are biologically inert and can be disposed of through the regular sewer system.

Planning and cost

The St. Martin plant cost $3 million, 45 percent of which was financed by a U.S. Department of Agriculture (USDA) Rural Community Development Grant through Minnesota’s Water and Waste Disposal Loan and Grant Program, and the rest through a 40-year, fixed-rate loan at 1.875 percent. According to Brett Repulske, the USDA area specialist who arranged the deal, “Any community in Minnesota under 10,000 people can qualify for similar assistance for water, sewer, or stormwater infrastructure projects,” provided they meet the program’s eligibility criteria.

Indeed, one problem smaller communities often encounter— and St. Martin avoided—is a lack of up-to-date information on their current infrastructure. During the eight years that Olmscheid was researching St. Martin’s water issues, she compiled detailed maps of the city’s water and sewer systems, including the location, age, and condition of fire hydrants, meters, pipes, and valves, as well as the depth and location of old and new wells.

Not only is such information useful from a city planning standpoint, it also helps state agencies work with cities to provide appropriate solutions and develop detailed plans for ongoing infrastructure maintenance and replacement. “Everything we did was documented and recorded,” says Mayor Rothstein, and not just because the project demanded it. “We aren’t going to be here forever,” he says; the documentation is for both the current and future leaders of St. Martin. He also hopes that St. Martin’s success in building an all-biological water treatment system will encourage other communities in Minnesota to consider it as an option.

As for water rates in St. Martin, they have remained the same, on average, but residents have gone from paying a flat rate to a rate based on usage, so some bills have gone up, while others have gone down.

“People are very happy,” says Olmscheid.

Mayor Rothstein is one of them. “My bill went down $4,” he claims. More importantly, he will leave a legacy of clean water in St. Martin for generations to come.

Tad Simons is a freelance writer from St. Paul.

Read the Nov-Dec 2018 issue of Minnesota Cities magazine

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