Effects of temperatures and organic loading rates on biomethanation of acidic petrochemical wastewater using an anaerobic upflow fixed-film reactor

The effect of temperature and organic loading rate on the rate of methane production from acidic petrochemical wastewater without neutralization was investigated by continuously feeding an anaerobic upflow fixed-film reactor. The temperatures selected for the studies were 25, 37, 45 and 55 °C. Organic loading rate (OLR) for each temperature was varied from 3.6 to 21.7 kg COD m−3 d−1. Best performance with respect to COD and BOD reduction, total gas production and methane yield was obtained with the reactor operating at 37 °C. OLR could be increased to a maximum of 21.7 kg COD m−3 d−1 with 90–95% COD and BOD reduction and methane yield of 0.450 m3 kg−1 COD d−1 added. The reactor operating at 55 °C gave the highest methane yield of 0.666 m3 kg−1 COD d−1 at an OLR of 6 kg COD m−3 d−1. This decreased to 0.110 m3 kg−1 COD d−1 when the OLR was increased to 18.1 kg COD m−3 d−1. The reactor operating at 45 °C gave a maximum methane yield of 0.416 m3 kg−1 COD d−1 added at an OLR of 6 kg COD m−3 d−1. On further increasing the OLR to 9 kg COD m−3 d−1, COD reduction was 89%, however, methane yield decreased to 0.333 m3 kg−1 COD d−1 added. The highest methane yield of 0.333 m3 kg−1 COD d−1 added at an OLR of 6 kg COD m−3 d−1 was obtained with reactors operating at 25 °C. These studies indicate potential rates of methane production from acidic petrochemical wastewater under different temperatures. This provides a guideline for various kinetic analyses and economic evaluation of the potential feasibility of fermenting acidic wastewater to methane.