Water Resources Research Act Program

Details for Project ID 2014SD235B

Nutrient Removal from Agricultural Subsurface Drainage Using Denitrification Bioreactors and Phosphate Adsorbents

Institute: South Dakota
Year Established: 2014 Start Date: 2014-03-01 End Date: 2015-02-28
Total Federal Funds: $23,353 Total Non-Federal Funds: $48,489

Principal Investigators: Guanghui Hua, Christopher Hay, Jeppe Kjaersgaard, Christopher Schmit

Abstract: Agricultural subsurface drainage is widely used to remove excess water from the soil in the Midwestern United States and other areas. This practice enables timely field operations, contributes to improved yields, and minimizes soil compaction and salt buildup. However, excess plant nutrients in the soil combined with subsurface drainage can result in the export of nutrients (such as nitrate and, to a lesser degree, phosphate) from the field to surface waters. Elevated levels of nutrients in natural waters may have a number of adverse effects including toxic algal blooms, depletion of dissolved oxygen in the water, and population decline in aquatic life. High concentrations of nitrate in drinking water supplies is also a public health concern as it can cause adverse health effects in very young infants and susceptible adults. Therefore, it is critical to develop effective technologies to reduce the amount of nutrients reaching surface waters to protect natural water resources and public health. This research aims to develop a treatment system that combines biological denitrification and chemical adsorption to remove nutrients from subsurface drainage. Denitrifying woodchip bioreactors have been used to reduce the nitrate loads from agricultural drainage waters. However, denitrifying bioreactors are typically not effective in removing phosphate. Steel byproducts, such as steel wool and turnings have been used as adsorption media to remove phosphate from water. These readily available industrial byproducts are highly efficient adsorbents for phosphate removal. Thus, we propose a new woodchip bioreactor system that uses iron media as pre- and/or post-treatment to simultaneously remove nitrate and phosphate from agricultural subsurface drainage. We will use a laboratory-scale column reactor to evaluate the performance of combined woodchip and iron media for nitrate and phosphate removal. The experimental conditions of the reactors will simulate typical conditions of subsurface drainage in South Dakota such that the results of this study can be used to predict the performance of full-scale bioreactors. Our goal is to develop a cost-effective and low maintenance bioreactor system to remove nitrate and phosphate from subsurface drainage. This innovative treatment system has great potential to reduce the nutrient loads and protect the water resources of South Dakota and other areas.