Effect of hydraulic retention time on the performance of a novel tubular MFC fed with petroleum hydrocarbons

Pollution of groundwater by petroleum hydrocarbons is a serious threat to human health as the hydrocarbons are toxic, mutagenic and carcinogenic. Microbial fuel cells (MFCs) could be employed in the treatment of these recalcitrant pollutants with concomitant bioelectricity generation. For practical application the MFCs would have to be effective, efficient and robust. This study investigated the performance of a novel tubular MFC, operated in a continuous mode at different hydraulic retention times, HRT, in the range 2.5 to 10 days at room temperature. Bromate was employed as the catholyte and the inoculum was an adapted anaerobic microbial consortium. A mixture of benzene and phenanthrene was used as the substrate. Total chemical oxygen demand removal efficiencies and peak power densities decreased from 74 to 57% and 3.4 to 1.1mW/m2 respectively when HRT was decreased from 10 to 2.5 days.The removal efficiencies were higher than 90% for both phenanthrene and benzene.Bromate removal efficiencies increased from 52.5-78.6% as HRT was raised from 2.5-10d. The outcome of this study suggests the application of MFCs in the simultaneous removal of petroleum hydrocarbons and bromates (with concomitant power production) in anoxic environments, especially deep groundwater reservoir. MFC technology could possibly be a substitute for the more expensive conventional technologies such as permeable reactive barrier (PRB) and electroremediation which are currently employed in remediation of hydrocarbon pollutants in subsurface environments.