Axler and his colleagues are examining constructed wetlands, among other alternatives, as a way to treat wastewater in areas where traditional systems are inadequate. Our research focuses on how constructed wetlands remove organic matter, pathogens, and nutrients like nitrogen and phosphorous from residential septic tank effluent. 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. 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. 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.