Improved Biogas Generation from Biomethanated Distillery Wastewater by Pretreatment with Catalytic Wet Air Oxidation

Abstract

Catalytic wet air oxidation (CWAO) is a prospective method for the treatment of distillery effluents. In this work, the biodegradability of biomethanated distillery spent wash (BOD5=8100 and COD=40000 mg/L) was improved by oxidation over ferrous sulfate catalyst. The homogeneous CWAO process was optimized by investigating the effects of reaction variables such as temperature (150-225 0C), oxygen partial pressure (0.69-2.07 MPa) and catalyst loading (16-48 mg/L). After oxidation at T=175 0C for 1 h, adsorption over activated carbon (loading 5%) was performed at ambient temperature. As a result, 73% reduction in COD and substantial rise (from 0.2 to 0.45) in the BOD5/COD ratio was observed. This ratio further rose to 0.52, when anaerobic digestion was performed using 1% acclimatized biomass. For every m3 of wastewater, 1.1 Nm3 of biogas was formed (methane 69%). After a final polishing step by aerobic treatment, BOD5/COD was 0.58 and 91% COD was destroyed. Clearly, this work has provided a useful solution t...