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Spotlight Hits Unsavory Subject

It’s in the news. A subject commonly left in the gutter has become a dinner-time topic and the point of innovative research. It’s now okay to discuss septic systems and new options for addressing this messy issue.

Around the nation homeowners are being held accountable for the water that swirls down their drains. In Minnesota, the 1994 Individual Sewage Treatment System Act increased pressure to replace failing or out-dated wastewater systems. St. Louis County, which encompasses Duluth and some of the more populous areas of the North Shore of Lake Superior, recently proposed an ordinance that would require homes to have adequate wastewater treatment prior to their sale. Systems where wastewater forms an above-ground pond (failing systems) would need to be replaced within two years. Systems lacking adequate soil or space (non-compliant systems) would need to be replaced within five years.

Example of constructed wetland.

This constructed wetland at Grand Lake, MN, filters human wastewaster and removes nutrients. Photo by the Natural Resources Research Institute

Although most people agree that under- and untreated sewage endangers public and environmental health, many city planners, property developers, and homeowners along the shores of Lake Superior don’t have the resources or technology to deal with wastewater. A study conducted by the Western Lake Superior Sanitary District in 1994 indicated that over 50 percent of the trench and mound systems along the North Shore are failing.

“The North Shore of Lake Superior and shorelines of numerous inland lakes within the Superior Basin provide a particularly difficult situation with regard to wastewater treatment because of the prevalence of shallow bedrock and high-clay soils,” said Sea Grant researcher Rich Axler, senior research associate with the University of Minnesota’s Natural Resources Research Institute (NRRI). Axler and his colleagues are examining constructed wetlands, among other alternatives, as a way to treat wastewater in areas where traditional systems are inadequate.

“In nature, wetlands are important traps for sediments, nutrients, and contaminants,” said Axler. “Our research focuses on how constructed wetlands remove organic matter, pathogens, and nutrients like nitrogen and phosphorous from residential septic tank effluent.”

Axler and co-principal investigators Barbara McCarthy, research fellow at NRRI, Randy Hicks, professor of biology at the University of Minnesota Duluth, and their staff are examining two constructed wetlands: one that serves ten homes abutting Grand Lake (near Duluth) and a site where a variety of alternative systems treat wastewater from a septic tank serving 125 inmates at the Northeast Regional Correction Center, also near Duluth.

illustration of a constructed wetland.

“The project has shown that even in the severe winters that typify northern Minnesota, constructed wetlands are a viable option in terms of cost and performance where the soil is adequate,” said Axler. “At Grand Lake, the constructed wetland provides treatment where little existed and has removed the nutrient input and potential health hazards from the lake.”

The constructed wetland research is a component of a larger multi-agency collaboration with industry. McCarthy spearheads the research with Axler and collaborators Jeff Crosby (St. Louis County Environmental Health Department), the Western Lake Superior Sanitary District, and Jim Anderson, professor of soil, water, and climate at the University of Minnesota. The test systems include constructed wetlands, single-pass peat and sand filters, drip irrigation, aerobic treatment units, recirculating peat and textile filters, and conventional trenches. Results suggest that constructed wetlands can remove more nitrogen than most systems. Their disinfecting capacity is satisfactory but lower than that of sand and peat filters. Like the other alternative technologies, constructed wetlands require more maintenance and exhibit more seasonal variability than traditional systems.

In a continuing effort to make science accessible, Minnesota Sea Grant participated in a satellite conference highlighting alternatives to traditional septic systems. The Next Generation of On-Site Sewage Treatment: Flushing in the New Millennium, included a discussion about the constructed wetland on Grand Lake and a segment on composting tanks that can even process paper towels and bacon grease. Barb Liukkonen, Minnesota Sea Grant water resources education coordinator, helped script commentary for the live conference she co-hosted with McCarthy and University of Minnesota Extension Service staff Dave Gustafson and Ken Olson.

People from 45 locations in Minnesota and 35 sites in 15 other states linked to the national satellite conference. Over 30 people attended in Duluth at the site co-sponsored by Minnesota Sea Grant and the St. Louis County Extension Service.

Ways to Save Your Septic System

  • Conserve water
  • Use products that promote water conservation
  • Repair leaky faucets
  • Spread water usage throughout the day and week
  • Minimize use of harsh cleaners, bleach, soaps, and detergents
  • Use low-phosphate detergents
  • Keep chemicals, paints, oils, and medications out of the drain
  • Keep grease, lint, food, and plastic products out of the septic system
  • Install an effluent filter on your septic tank
  • Inspect your septic tank yearly
  • Pump your septic tank every 2-3 years

By Sharon Moen
June 2000

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