Nutrient removal in a woodchip bioreactor bed receiving silage bunker runoff at the UVM Miller Research Farm

Stormwater runoff from agricultural production areas contributes to the pollution and degradation of downstream water bodies. This runoff carries sediments, pathogens and nutrients; specifically, nitrogen and phosphorus. Many dairy farms store livestock feed in silage bunkers, where anaerobic fermentation preserves the quality of the plant material. Liquid silage leachate is a natural biproduct of this process and is characterized as a very potent wastewater due excessive nutrient content, high biochemical oxygen demand and low pH. Leachate production and runoff during storm events from these areas can be difficult to accurately predict and control. Therefore, there is a need to support farmers by providing low maintenance management practices to improve runoff quality before it leaves the farm. Woodchip bioreactors are a promising edge-of-field treatment technology designed to create an anaerobic environment and provide a carbon source for nitrate removal through heterotopic denitrification. In 2017, operation of a woodchip bioreactor bed began at the University of Vermont Paul R. Miller Research Complex. The system contains a series of three pre-treatment tanks for particle settling and aeration before the water is directed into the woodchip bed. This research evaluates the performance of this runoff treatment system for its effectiveness in the removal of nitrogen and phosphorus from silage runoff during storm events. Throughout the summer and fall of 2018, water samples were taken at four locations along the runoff flow path. These samples were analyzed for total phosphorus (TP), soluble reactive phosphorus (SRP), total nitrogen (TN), nitrate (NOx--N) and ammonium (NH4-N). Further monitoring of the system in 2019 will the evaluate proposed design modifications to improve performance. This presentation will discuss the system’s design, research questions, methods and preliminary results from the 2018 season