Reducing the burden of food processing washdown wastewaters using microbial fuel cells

A tubular Microbial Fuel Cell (MFC) reactor consisting of four modules (total reactor volume of 1 l) was fed with food processing washdown water as a chemical oxygen demand (COD) removal process to decrease effluent pollution levels and discharge costs. Two different operational modes were tested: (A) Under static electrical loads with substrate circulated to and from different storage vessels and (B) employing maximum peak power point tracking (MPPT) whilst re-circulating substrate through a single storage vessel. After 7 cycles through the reactor, notionally equivalent to 28 concatenated tubular MFC modules, 84% of the soluble COD (960 mg l⁻¹) was removed from the effluent in Mode A and 70% (800 mg l⁻¹) in Mode B with MPPT. In the study, acetic acid was consumed first and propionic acid increased initially before depletion after 7 cycles, showing that higher carbohydrates were degraded during the effluent polishing process.