Initial Assessment of Microbial Fuel Cells for the Treatment of Tofu Processing Waste

Abstract

Due to ever increasing industrial organic material wastewater regulations, there is growing interest in the food production industry for technologies to mitigate soluble waste discharges. Currently, food manufacturers in NYS with wastewaters that have high concentrations of soluble organic material, indicated by its chemical oxygen demand (COD), are charged substantial premiums by publicly owned treatment works (POTWs) to dispose of their high COD wastewaters. As a result, these producers are keen on pursuing more economical and sustainable alternatives. One novel option is a microbial fuel cell (MFC), a recently developed type of bioreactor that greatly reduces soluble COD by harnessing the electrochemical potential found in the chemical bonds of these organic materials through redox reactions under anaerobic conditions facilitated by exoelectrogenic microorganisms. MFC technology treating homogeneous substrates such as acetate at the laboratory scale has advanced to the point where COD removal efficiencies of over 90% are commonly achieved; however, efficiencies at treating less uniform, high COD level industrial scale food manufacturing wastewaters have only been investigated in a handful of studies. Since most real world wastewaters are non-uniform, MFC performance characterization of treating these actual discharges is crucial in determining their efficacy and cost effectiveness in large scale applications. To help fill this gap, this paper gives a relative efficacy comparison of five identical 3 L bench scale single chamber and three dual chamber MFC configurations (SCMFCs and DCMFCs, respectively) to a simulated POTW aeration process treating high COD whey effluent from a tofu manufacturing plant. Standard parametric EPA water quality tests of COD reduction were performed to assess the extent of the MFCs and POTW simulant effectiveness. COD levels in the MFC’s were reduced between 72% and 92%, while the POTW aeration process reduced levels 98%. This corroborates previously published studies showing that POTW systems are effective in reducing COD, but also that MFCs could be a more sustainable option due to their unique ability to directly produce, rather than consume, electric current. While these findings are promising, more studies are required to accurately determine the relative proportion of bioelectrochemical and methanogenic processes in the actual lowering of the COD levels.