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Article
Electrical stimulation for enhanced denitrification in woodchip bioreactors: Opportunities and challenges
Ecological Engineering
  • J. Y. Law, Iowa State University
  • Michelle L. Soupir, Iowa State University
  • D. Raj Raman, Iowa State University
  • T. B. Moorman, United States Department of Agriculture
  • Say K. Ong, Iowa State University
Document Type
Article
Publication Version
Published Version
Publication Date
1-1-2018
DOI
10.1016/j.ecoleng.2017.10.002
Abstract
Woodchip bioreactors are being implemented for the removal of nitrates in groundwater and tile water drainage. However, low nitrate removals in denitrifying woodchip bioreactors have been observed for short hydraulic retention time (HRT) and low water temperature (°C). One potential approach to improve woodchip bioreactor performance is to provide an alternative and readily available electron 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, in the presence of a soluble carbon source. The objective of this study was to evaluate the denitrification efficiency of electrically augmented woodchip bioreactors and conduct a simple techno-economic analysis (TEA) to understand the possibilities and limitations for full-scale BER implementation for treatment of agricultural drainage. Up-flow column woodchip bioreactors were studied included two controls (non-energized, and without electrodes), two electrically enhanced bioreactors, each using a single 316 stainless steel anode coupled with graphite cathodes, and two electrically enhanced bioreactors, each with graphite for both anode and cathodes. Both pairs of electrically enhanced bioreactors demonstrated higher denitrification efficiencies than controls when 500 mA of current was applied. While this technology appeared promising, the techno-economic analysis showed that the normalized N removal cost ($/kg N) for BERs was 2–10 times higher than the base cost with no electrical stimulation. With our current reactor design, opportunities to make this technology cost effective require denitrification efficiency of 85% at 100 mA. This work informs the process and design of electrically stimulated woodchip bioreactors with optimized performance to achieve lower capital and maintenance costs, and thus lower N removal cost.
Comments

This article is published as Law, J. Y., M. L. Soupir, D. R. Raman, T. B. Moorman, and S. K. Ong. "Electrical stimulation for enhanced denitrification in woodchip bioreactors: Opportunities and challenges." Ecological Engineering 110 (2018): 38-47. doi: 10.1016/j.ecoleng.2017.10.002. Posted with permission.

Rights
Works produced by employees of the U.S. Government as part of their official duties are not copyrighted within the U.S. The content of this document is not copyrighted.
Language
en
File Format
application/pdf
Citation Information
J. Y. Law, Michelle L. Soupir, D. Raj Raman, T. B. Moorman, et al.. "Electrical stimulation for enhanced denitrification in woodchip bioreactors: Opportunities and challenges" Ecological Engineering Vol. 110 (2018) p. 38 - 47
Available at: http://works.bepress.com/raj_raman/63/