BTEX removal with bioelectrochemical systems

Benzene, toluene, ethylbenzene and xylenes (BTEX) are hazardous contaminants that can accidentally impact groundwater. Biological strategies can be used to remove BTEX compounds usually by adding oxygen to sustain the aerobic degradation. However, this approach can be expensive and technically difficult. The use of bioelectrochemical systems (BES) has been suggested as an alternative strategy. Anaerobic single chamber BES reactors (120 mL) have been set up using volcanic pumice as support material for the microbial growth and refinery wastewater as microbial inoculum. Graphite electrodes were connected to a power supply (external voltages of 0.8 V, 1.0 V and 1.2 V were applied over 160 days). A BTEX mixture was supplied as carbon source. Abiotic and open circuit controls were set up. Current production and sulphate reduction were associated to hydrocarbons degradation at all the potentials. The highest current output were observed at 0.8 V. The first order kinetic constants calculated for toluene, m-xylene and p-xylene were respectively 0.4 ± 0.1 days-1, 0.34 ± 0.09 days-1, 0.16 ± 0.02 days-1 at 0.8 V. Next generation sequencing of the 16S rRNA gene showed that the family Desulfobulbaceae was the most enriched in the anodic biofilms highlighting the importance of the sulphur cycle.