Ozone pretreatment of biomethanated distillery wastewater in a semi batch reactor: mapping pretreatment efficiency in terms of COD, color, toxicity and biohydrogen generation

The present study reports the feasibility of ozone oxidation as a pretreatment option for biohydrogen production from complex biomethanated distillery wastewater with complications of low biodegradability index (biochemical oxygen demand (BOD)/chemical oxygen demand (COD) ratio < 0.2), high color, COD and toxicity. Ozone pretreatment of biomethanated distillery wastewater resulted in biodegradability index enhancement (0.17-0.6), color, COD and toxicity reduction. Ozone pretreated wastewater with enhanced biodegradability index on anaerobic digestion resulted in favorable biohydrogen production with hydrogen content up to 63% along with further COD reduction of 52.5%. A modified Gompertz equation illustrates the overall rate and hydrogen yield was higher for ozone pretreated effluent compared to the control. The ozone pretreated wastewater has shown a positive effect on seed germination (up to 35%), indicating toxicity reduction of wastewater post ozone pretreatment. Fourier transform infrared spectroscopy (FTIR) analysis also shows the cleavage of recalcitrant organic compounds and degradation of biomethanated distillery wastewater during ozonation pretreatment.