Effect of propionate toxicity on methanogenesis of night soil at phychrophilic temperature

The effect of propionate concentrations on biodegradation of human waste (night soil) was studied at 10 °C. Propionate was toxic for the biomethanation at all the pH tested (6.0, 7.0 and 8.0). The maximum reduction in biogas production in presence of 200 mM propionate was observed at pH 7.0 followed by 8.0. The methane content in biogas also followed a similar trend and at pH 7.0 an 11.5% decrease was observed. Propionate caused the reduction of methanogenic count by an approximately 2 log value. Total volatile fatty acids increased with the increase in propionate concentration and particularly accumulation of propionate was observed. The results were also compared with the 30 °C fermentation.