Water Resources Research Act Program

Details for Project ID 2020SD260B

Improvement of Denitrification Bioreactor Performance Using Weathered Woodchips and Wet-Dry Cycle Control (Year 2)

Institute: South Dakota
Year Established: 2020 Start Date: 2020-03-01 End Date: 2021-02-28
Total Federal Funds: $22,636 Total Non-Federal Funds: $45,484

Principal Investigators: Guanghui Hua

Project Summary: Agricultural subsurface drainage uses a network of underground perforated pipes to remove excess water from the soil profile to improve crop production. Subsurface drainage has been widely used in the Midwestern United States and many other areas for agricultural water management. The use of subsurface drainage systems allows cultivation of agricultural fields with poor natural drainage. However, subsurface drainage systems can transport nutrients from agricultural fields to surrounding natural water. Elevated nutrient levels in surface waters can lead to negative impacts on water quality. It is important to develop technologies to reduce the loss of nutrients through subsurface drainage to protect natural water resources. The presence of nitrate in subsurface drainage has been a serious water quality concern. Denitrifying bioreactors are an edge-of-field best management practice that has been developed to remove nitrate in subsurface drainage. These bioreactors typically utilize an organic carbon medium to support the growth of denitrifying bacteria which reduce nitrate to nitrogen gas. Woodchips are by far the most widely used material in denitrification bioreactors. Many studies have evaluated the impact of reactor size, nitrate concentrations, hydraulic retention times and other environmental factors on the performance of woodchip bioreactors. Little is known about the effect of woodchip quality on denitrification efficiency. Several studies suggest that woodchip weathering before bioreactor installation and wet-dry cycle control after bioreactor installation may be able to improve the quality of organic substrates for denitrification. The objective of this study is to evaluate the use of weathered woodchips and a wet-dry bioreactor control strategy to improve the performance of denitrification bioreactors. The results of this study can lead to the optimization of woodchip bioreactors for nitrate removal from subsurface drainage.