Novel Algae Bioreactor for Nutrient Removal from Subsurface Drainage Water

University of Minnesota/Dr. Satoshi Ishii

Many corn growers in Minnesota install subsurface (tile) drainage to remove excess water from their fam1land. While this practice greatly enhances agricultural productivity, it can also cause leaching of excess inorganic nutrients, especially nit rate, from soil to surrounding water environments. Nutrient pollution is of concern for human health and aquatic ecosystem function. Several approaches, such as constructed wetlands and woodchip bioreactors, have been used to remove nutrients from subsurface drain water.

However, the application of these technologies is disadvantaged by fluctuations in effluent quality, limitations in phosphorus removal, and frequent requirement of a large ecological footprint. New inventions are necessary to treat subsurface drainage water without sacrifice of agricultural productivity.

The proposed research will test a novel scientific approach to efficiently and cost-effectively remove inorganic nutrients from subsurface drainage water. Specifically, we will develop a novel bioreactor by combining algae-based water treatment and granular sludge technology. In this bioreactor, algae and bacteria form aggregates (i.e., granules), in which denitrifying bacteria reduce nitrate to nitrogen gas by using carbon substrate provided from algae. Algae and bacteria can also assimilate nitrogen and phosphorus into their bio mass, thereby removing these nutrients from water. This is a self-sustaining system, which requires low cost and low maintenance to operate. Results obtained in this project will be used as preliminary data to acquire further funding to complete this research.