Application of Aquatic Vegetation As a Bio-Filter for Phosphorous Reduction.

            Phosphorous (P) loads from various anthropogenic sources including animal waste, fertilizer use, and wastewater increase eutrophication and reduce water quality, especially in freshwater aquatic systems where P is generally the limiting nutrient. This project will test the application of managing two floating aquatic vegetation (FAV) species - water hyacinth (Eichhornia crassipes) and water lettuce (Pistia stratiotes) to mechanically remove P from the water column of agricultural field ditches. We hypothesize that biological uptake of P by FAV can be used as a treatment technology to reduce P loads exiting agricultural fields in surface waters. This project will quantify the amount of P removed through mechanical management of FAV. This study will also examine how flow facilitated by hydraulic pumps situated at the inflow locations of the treatment ditches influences water quality and the distribution of sediment particles. A LS 13 320 Laser Diffraction Size Analyzer was used to determine sediment particle size. Significant differences (P<0.02) were observed in the median particle size between sediments collected in the inflow and outflow locations of the treatment ditches. Coarser textured particles (137±7 μm) were observed in the inflow locations and finer textured particles (86 ±10 μm) were observed in the outflow locations. Water circulation through the ditches could cause coarser particles to settle near the inflow and finer particles to settle near the outflow. Water and sediment are sampled from inflow and outflow locations of the field ditch to examine how the management of FAV and flow change their physical and chemical characteristics. A P fractionation experiment will be conducted to examine the forms of P present in ditch sediments and the role of particle size in P retention.