Abstract
The application of thermal pretreatment methods has aroused attention to enhance anaerobic digestion of sewage sludge. Three thermal pretreatment temperatures (50, 70 and 90 °C) were chosen for anaerobic pretreatment of sewage sludge (primary sludge, secondary sludge and mixed primary and secondary sludge). Effect of temperature on sludge characteristics, biogas production potential and energy balance was investigated. The pretreatment results in a higher solubilization of organic matters at higher temperature, especially for that in secondary sludge. The concentrations of soluble CODCr, carbohydrate and protein had increased by 10, 3.5, 74 times, respectively, comparing to those in the secondary sludge without thermal pretreatment. After thermal pretreatment, the methane production potential of primary sludge deteriorated, while that of secondary sludge increased. At 70 °C, the biogas production potential of secondary sludge increased by 15%, comparing to that without pretreatment. The energy balance of anaerobic digestion of sewage sludge shows that in the case of power generation, thermal pretreatment via cogeneration at 70 °C, 90 °C, the power self-sufficiency rate is 60.1, 62.7%, 64.5%, respectively.
