Synergistic effects of anaerobic digestion from sewage sludge with lime mud

Abstract Waste reuse and renewable energy generation are encouraged in many countries. Anaerobic digestion of sewage sludge is usually limited by the slow hydrolysis rate of the sludge. To resolve the problem the lime mud was used in this biomethane production. Batch tests were performed at 55 °C with lime mud concentrations ranging from 1.25 to 5.00 g/L. The results showed that the highest methane yield per gram of volatile solid and volatile solid reduction were 146 ml and 42.4% at lime mud concentration of 2.50 g/L, which were 1.77 and 3.01 times higher than that of the control tests without lime mud, respectively. However, high levels of lime mud reduced the amount of available substrate and inhibited the anaerobes, thereby decreasing the methane production. The modified Gompertz model showed a better fit for the results than the first-order model. It was also found that the eco-friendly treatment of two types of solid waste had the potential to synergistically contribute to waste reuse and energy recovery.