Remediation of BTEX and Cr(VI) contamination in soil using bioelectrochemical system-an eco-friendly approach

Soil contamination with benzene, toluene, ethylbenzene and xylene isomers (BTEX) has raised increasing concern because of its high solubility in water and toxicity to biotic communities. This study aims at investigating the process and prospects of deploying bioelectrochemical system (BES) for the removal of BTEX from artificially contaminated soil using Pseudomonas putida YNS1, alongside the reduction of hexavalent chromium (Cr(VI)). The BES was setup with desired operating conditions: initial concentration of BTEX (50-400 mg/L in 100 mL of sterilized water), pH (4-10) and applied potential voltage (0.6-1.2 V) with 10 μL log-phase culture along with the addition of Cr(VI) (10 mg/L). Samples were collected at regular intervals and analysed for BTEX degradation using gas chromatography and Cr(VI) reduction using UV-Vis spectrophotometer. Under optimized conditions (initial BTEX concentration, 200 mg/L; pH 7; and applied voltage 0.8 V with Cr(VI) of 10 mg/L), 92% of BTEX was degraded and 90% Cr(VI) was reduced from the contaminated soil. The intermediates produced during degradation were analysed through gas chromatography-flame ionization detector (GC-FID), and the possible degradation pathway was elucidated. The results indicated that BES could be effective for simultaneous degradation of BTEX along with Cr(VI) reduction.