Regular articleReducing the burden of food processing washdown wastewaters using microbial fuel cells

•Tubular MFCs may usefully treat washdown wastewaters from food production.•Maximum power point tracking control strategy resulted in 70% COD removal.•Significant cost savings of 0.466 £UK m−3 treated were achieved.•Power production was associated with the availability of acetic- and propionic acid.

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.