Efficient methane production from petrochemical wastewater in a single membrane-less microbial electrolysis cell: the effect of the operational parameters in batch and continuous mode on bioenergy recovery

Abstract

The main objective of this study is to evaluate the treatment and simultaneous production of methane from low-strength petrochemical wastewater by single membrane-less microbial electrolysis cells. To achieve this objective, the influence of variables such as applied voltage, operation mode, and hydraulic retention time (HRT) on the performance of the MEC system was investigated over a period of 110days. According to the obtained results, the maximum COD removal efficiency in the batch mode was higher than which in the continuous mode (i.e. 85.9 vs 75.3). However, the maximum methane production in the continuous mode was almost 1.6 times higher than which in the batch mode. The results show, COD removal, methane content, and methane production in both operation modes, were enhanced as applied voltage increased from 0.6 to 0.8-1V. The proportion of methane, methane production rate, and COD removal were increased as HRT decreased from 72 to 48h, while these values were decreased as the HRT decreased from 48 to 12h. In continues mode, the energy efficiency had a range of 94.7 to 97.9 with an average of 96.6 in phase III, which almost recovered all of the electrical energy input into the system. These results suggest that single membrane-less microbial electrolysis cell is a promising process in order to the treatment of low-strength wastewater and methane production.