Anaerobic biodegradation of benzene-laden wastewater under mesophilic environment and simultaneous recovery of methane-rich biogas

The present investigation emphasizes on the anaerobic biological treatment of benzene containing wastewater under mesophilic temperature towards elimination of chemical oxygen demand (COD) and simultaneous recovery of methane-enriched biogas. The anaerobic degradation of benzene has been examined over the influence of different co-substrates in an anaerobic bioreactor of 100 mL volume. Acetate and glucose are added as co-substrates with a concentration of 1 gL(-1) to monitor and compare the methanogenesis during anaerobic digestion. During the experiment, COD removal efficiency of 85% was achieved. Methane (CH4) and carbon dioxide (CO2) production has been observed to be higher in glucose (1 gL(-1)) fed anaerobic reactor with the highest amount of CH4 (306 mu L) and CO2 (248 mu L) produced under mesophilic condition (35 +/- 1 degrees C), pH of 6.82, conductivity of 0.073 mu S cm(-1) and at a concentration of 200 mgL(-1) of benzene analysed using gas chromatography coupled with thermal conductivity detector (TCD). Scanning electron microscopy (SEM) analysis demonstrated the high porous structure of anaerobic sludge with uniform channels confirming better mass transfer and high benzene removal. Energy dispersive x-ray (EDX) showed various constituent elements present in the microbial sludge including carbon, oxygen, magnesium, silicon, aluminium, and zinc. The specific methanogenic activity was found to be 1.8mM CH4 gVS(-1) day(-1) using acetate as a source of energy. The study reveals that the anaerobic reactor has made possible biogas production and COD removal through efficient degradation of complex substrate like benzene in wastewater.