Using floating plants in a constructed wetland for phosphorus removal from tile drain runoff

Phosphorus runoff to inland lakes can occur from a number of sources, including tile drain from farm fields. A project currently underway is testing the effectiveness of using a combination of floating vegetation mats and a filtration bed for capturing water from tile drain and then removing nutrients by directing the water to two connected wetlands. Water samples are collected every 48 hours using automatic sampler and drainage control structures to measure water flow and concentrations of phosphorus (P) and nitrogen. Video cameras set up around the wetlands allow for continuous visual inspection of the site. Currently, four plant species [common bulrush (Scirpus atrovirens), fox sedge (Carex vulpinoidea), hispid buttercup (Ranunculus hispidus), and common rush (Juncus effusus)] planted on floating mats and grown hydroponically are being analyzed for changes in biomass, nutrient concentration and temperature hardiness. Average wet weight gain after year one, ranged from a low of 32g for buttercup to a high of 176g for bulrush. Concentrations of phosphorus and nitrogen are currently being measured for both roots and shoots in the four species.

Presented by Lois Wolfson and Jeremiah Asher, Michigan State University, during the 2020 Michigan Inland Lakes Convention