Year Established: 2016 Start Date: 2016-03-01 End Date: 2017-02-28
Total Federal Funds: $26,676 Total Non-Federal Funds: $53,029
Principal Investigators: ChanLan Chun, Daniel Jones
Abstract: In Minnesota, elevated levels of sulfate in surface waters have drawn increasing attention due its adverse impacts on wild rice ecosystems and possible contributions on methylmercury production and eutrophication. Among the different sulfate treatment strategies, biological sulfate removal has potential to be cost effective and versatile in terms of applications. To effectively use biological process for sulfate remediation, a supply of defined growth substrates in treatment systems is required, but this may present technical challenges such as periodic reapplication or constant feeding. We propose to develop an alternative treatment approach in which low electrical potential is used to sustain biological sulfate reduction by continuously supplying electron donor substrates. We hypothesize that the application of electrolysis will stimulate and sustain biological sulfate reduction in anaerobic bioreactors, and simultaneously facilitate the subsequent removal of the reduced sulfur end product from the effluent. We predict that this can be used to maximize the removal of sulfate from mine water. The specific objectives of this project are 1) to determine the efficacy of electrolysis of water and/or iron to enhance microbial surface reduction and sulfur recovery from high sulfate waste streams; and 2) to determine how the microbial community responsible for the biological transformations (sulfate reduction, elemental sulfur production) responds to electrochemically-stimulated production of reductants and oxidants. In an experimental system, we will use electrode-integrated fixed-bed bioreactors in which cathodic hydrogen production is used to stimulate sulfate reduction near the influent, and anodic oxygen or reactive iron species production will facilitate sulfide precipitation near the effluent. Sulfur and iron species produced and consumed will be monitored during reactor operation to compare performance under different conditions, and changes in the anaerobic and microaerophilic microbial communities will be quantified by culture-independent methods. We anticipate that our proposed project will result in a proof-of-concept application of electrical potential to provide electron donor and acceptor substrates to biological sulfate treatment in a controlled manner. Our proposed application is flexible and could in theory be adopted for either conventional passive or active treatment systems. Demonstrable new concepts that improve the efficacy and sustainability of biological treatment systems will ultimately lead to more widespread adoption of these cost effective sulfate removal technologies. In the long run, this project represents a promising contaminant removal strategy to improve water quality. Alternative cost-effective treatment options like this will benefit both the industries that need to meet water quality standards (such as mining industries and municipal wastewater facilities), and the people that rely on clean water and healthy environments (such as the Ojibwe and other Minnesotans that depend on healthy wild rice ecosystems).