Combined Treatment of Nitrogen and Phosphorus from Subsurface Drainage Using Low-Cost Industrial By-Products and Woodchip Bioreactors.

Nutrient enrichment has substantially impaired the quality of many coastal and freshwater systems in the world. Increased loadings of nitrogen (N) and phosphorus (P) accelerate the eutrophication of surface waters. Of these nutrients, P often is a limiting factor in fresh water eutrophication and algae growth, even at rates that are considered low in an agronomic context. The development of subsurface (tile) drainage contributes to exports of N and P from agricultural fields into receiving water bodies. Edge-of-field woodchip bioreactors have proved to be effective in removing nitrate-N from drainage water. However, further nutrient management practices are needed to reduce P exports. Although best agricultural practices, such as improved management of manure and fertilizer, may lower P losses, they are often not effective enough to meet water quality goals. Using low-cost industrial by-products, we will install a P removal bed in-line adjacent to existing bioreactors in eastern South Dakota. We will collect and analyze water samples before and after moving through the bioreactor and P-removal bed media to evaluate the efficiency of the installed media in both N and P removal from drainage water. This study will benefit producers and policy makers by providing recommendations for conservation drainage practices as well as minimizing negative environmental impacts on water quality. 

Keywords: Eutrophication, nitrate, nutrient removal, phosphate, tile drainage, water quality