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5 ideas that could make water cleaner

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There is no shortage of scientists, environmentalists, entrepreneurs and regular citizens working to solve problems related to water quality in Minnesota. Researchers sample pollutants flowing down the Minnesota and Mississippi Rivers to determine their origins. Farmers install conservation measures to try to slow the water leaving their land. Lakeshore residents install rain gardens and barrels and nurture wetlands in order to protect their favorite swimming holes.

Along the way, people are discovering innovative solutions. Some are already in use and others remain on the drawing board.

Peat filter
Alternative septic systems, like this peat filter installed as part of an experiment near Duluth, can do a better job in some cases than more common types
Photo courtesy the Natural Resources Research Institute, U of M-Duluth

ALTERNATIVE SEPTIC SYSTEMS

In Minnesota, there are an estimated 500,000 septic systems, many of them poorly maintained and even leaking. Since they can be a source of nutrients like phosphorus and nitrogen, which in excess are harmful to lakes and rivers, it's important that they work properly. Yet not all types are suited for all situations.

The typical system here employs a tank and leach field, in part because they are cheap and well understood. But, according to University of Minnesota Duluth researcher Rich Axler, there are other types that could work as well or even better, depending on the setting.

"I would like to see people have options," Axler said. "But perhaps more important, I would like to see comprehensive watershed planning and zoning that takes into consideration the status and sensitivity of the groundwater and surface waters that receive the wastewater."

Several years ago, Axler conducted research at a correctional facility near Duluth, where he was able to funnel waste through a handful of experimental systems, including "constructed wetlands" and various configurations of peat, sand and textile filters. He found that, "They all had advantages and disadvantages depending on the setting, the specific site and the desires of the homeowner."

"Peat filters were especially good at removing solids, biodegrading organic matter, and filtering bacteria and viruses, even in winter," Axler said, but they had to be installed just right.

"Controlled wetlands were easier to operate and maintain, and if designed for it, had the potential to remove nitrogen and look nice, but performance declined markedly in winter and freezing could be a problem."

Floating islands
Islands made from recycled plastic bottles clean lakes and rivers of phosphorus and suspended particles.
Courtesy of Midwest Floating Island

POLLUTION-REMOVING PLASTIC ISLANDS

One of the most interesting uses yet for recycled plastic bottles comes in the form of floating islands that collect suspended particles and nutrients, thus helping to clean up a lake or river. Invented by Montana-based Floating Island International, they've been installed in various locations around the globe, including New Zealand, China, California and, as of August, tiny Spring Lake in Minneapolis.

The islands, which are planted with low maintenance perennials, act like concentrated wetlands only they are in some ways better because they can be moved. They are designed to withstand winter and simply freeze into the ice.

The seven, 90-square-foot islands recently launched in Spring Lake are designed not only to filter phosphorus, but also to serve as bird habitat. "Spring Lake used to be a bird sanctuary," said Arlys Freeman, who runs St. Paul-based Midwest Floating Island, which manufactured the local installation.

"We have this jewel in the middle of this area and we hope we can restore it."

"We expect greater use in Minnesota," she said. "We are working on proposals right now for a variety of applications."

LiDAR
Topographic images, made by shooting lasers from above, help scientists map where water flows and measure erosion over time.
Courtesy Sean Vaughn, Minnesota Department of Natural Resources

LIDAR MAPPING TECHNOLOGY

A precise form of laser mapping, used by NASA, is now being applied to farms and stream banks in Minnesota in order to track small changes in topography. Called LiDAR or "Light Detection and Ranging," images are made with lasers shot from airplanes or helicopters.

When a piece of land is mapped over time, the images can be compared to see where water flows or doesn't flow, where erosion is occurring and even the source of that erosion. A farmer might use the information to better understand the soils in a field and the effects of water movement.

"With LiDAR, you know where your worst ravines and stream banks are," said Kris Sigford, Water Quality Program Director for the Minnesota Center for Environmental Advocacy. "You can look at hydrological flow and know when there is too much agricultural drainage. You can know where it's coming from and what you have to fix."

"LiDAR is going to be a very useful tool for targeting where best management practices could go," Sigford said. "It's terrific."

Field of corn
Seed engineers are working to develop a strain of corn that grows with less nitrogen, which could increase yields and also help water quality.
MPR Photo/Nikki Tundel

SUPER CORN

Most of the big seed companies — from Monsanto to DuPont to Syngenta — are trying to develop a corn hybrid that will provide good yields with less nitrogen, a nutrient in fertilizer that's increasingly expensive for farmers and contributes to excessive algae growth and oxygen depletion in lakes and rivers.

Dubbed "super corn" or "clean corn," a successful seed is still as many as 10 years away, said Jeff Coulter, a corn crop researcher at the University of Minnesota, who recently visited several demonstration plots, including one near Northfield.

"It's got good potential," he said.

There are two benefits to more efficient corn,

"First, farmers can get by with less nitrogen and get the same yield," said Coulter. "Second, they can maintain the same nitrogen rates and get a higher yield." The second approach, of course, offers fewer benefits for water quality.

In one breakthrough, a test strain did well in nitrogen-deprived soil, but did poorly in soil with adequate nitrogen. To be successful, said Coulter, a seed will have to "perform well under nitrogen limiting and non-limiting conditions. In Minnesota, levels are quite variable from year to year." He adds, "If a farmer had a hybrid that could perform well under both conditions, it would be like an insurance policy."

Alfalfa hay bales
Linda Meschke of Rural Advantage has a plan to convert bales of native grasses like these, harvested near Fairmont, into gas.
Courtesy of Rural Advantage

PERENNIALS TO GAS

A few years ago, Linda Meschke, a water quality advocate who runs a non-profit in Fairmont called  Rural Advantage, decided that improvements in water quality in the state weren't happening fast enough. "I got to thinking," she said, "we need to go to a higher model of best management practices."

Meschke came up with the idea to build a system that would convert perennial crops to gas, thus creating a market for alfalfa and wheat straw and short rotation willow and encouraging farmers to grow those crops rather than corn and soybeans. She would build the plant — owned by a co-op called Prairie Skies Biomass — near a local meat processing outfit, who she said would use most of the energy.

"We've got 15 members in the co-op so far," she said. "It's a good solid core of people who are interested in this type of bio-energy, perennial-based bio-energy. They are all farmers."

Unlike more familiar ethanol, "which is an additive to gasoline, our project is to produce straight gas and diesel," Meschke said.

 "We're going from raw perennial biomass to gasoline. Raw biomass is just young coal or young petroleum." 

The process involves three stages. The first would convert plant matter into a coal-like substance through "torrefaction," an intense, high-pressure heating process. The second would gasify the torrefied material. The third would refine the gas.

Meschke is just now submitting a grant proposal for a feasibility study, which will help determine how many shares she needs to sell and at what price in order to draw loans from banks or others. The cost to build the first stage is estimated at $22 million.

"We could have real gains from this project," she said. "It's about sustainability, economic and social and environmental. We're looking to enhance all those areas as we move forward. We're on our way to doing it."

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