Vegetated Floating Mats Effectively Remediate Nutrients

As urbanization and concerns over deteriorating water quality increase, the importance of remediating nutrient rich runoff from agricultural and other non-point source contributors will increase.  Floating mat treatment systems are potential alternatives to constructed wetland systems for remediating nutrient rich water and can be established in existing drainage ditches and retention ponds.  This researched examined the remediation efficacy of floating mat systems at two treatment scales.  Agrostis sp., Canna flaccida, Eleocharis montana, and Juncus effusus were established in the large-scale pond system treatment, and a small-scale trough system treatment was established using C. flaccida and J. effusus.  We measured plant growth parameters (shoot and root height and branching) on a biweekly basis and monitored various water quality parameters (pH, conductivity, dissolved oxygen, temperature, and nutrient concentrations) weekly for five months.  At harvest, plant shoots and roots were harvested, dried, ground, and analyzed for mineral content.  Nitrogen and phosphorus effluent concentrations averaged 0.13 ± 0.03 mg/L N and 0.02 ± 0.003 mg/L P after treatment.  Of the plant species examined, Canna and Juncus nitrogen and phosphorus tissue concentrations were highest when normalized by total plant biomass.  When normalized on a per unit area basis, Juncus shoots and roots fixed the most phosphorus of any species examined, respectively fixing 184.0 and 110.3 mg P per m² area.  The floating mat systems were easy to install, maintain, and harvest.  These systems may prove most effective in low nutrient environments where “polishing” effluent water quality to very low phosphorus concentrations is necessary.