Date of Award
Master of Science
Agricultural and Biosystems Engineering
Agricultural and Biosystems Engineering; Civil Engineering
Michelle L. Soupir
In early spring, there is a need to treat large volumes of cool tile water containing high nitrate concentrations. However, lower nitrate removal rates in denitrifying woodchip bioreactors have been observed when hydraulic retention time (HRT) and water temperature are low. One potential approach to improve woodchip bioreactor performance is to provide an alternative and readily available energy source to the denitrifying microorganisms through electrical stimulation. Previous work has demonstrated the capability of bio-electrochemical reactors (BER) to remove a variety of water contaminants, including nitrate, with the presence of a soluble carbon source. The objective of this study was to evaluate the denitrification rate of electrically augmented woodchip bioreactors and conduct a simple TEA to understand the possibilities and limitations for full-scale BER implementation for treatment of agricultural drainage. Three duplicated up-flow column woodchip bioreactors were studied: two controls (non-energized, and without electrodes), two electrically enhanced bioreactors using a 316 stainless steel anode coupled with graphite cathodes, and two electrically enhanced bioreactors using with graphite for both anode and cathodes. Both pairs of electrically enhanced bioreactors demonstrated higher denitrification rates than controls when 500 mA of current was applied. While this technology appeared promising from the perspective of denitrification rate, the techno-economic analysis revealed that higher N removal cost ($/kg N) is needed. With our current reactor design, opportunities to make this technology cost effective require denitrification efficiency of 85% at 100 mA. This work informs the design of electrically stimulated woodchip bioreactors with optimized performance to achieve lower capital and maintenance costs, and thus lower N removal cost.
Ji Yeow Law
Law, Ji Yeow, "Opportunities and challenges to use electrical stimulation for enhanced denitrification in woodchip bioreactors" (2017). Graduate Theses and Dissertations. 15557.