Effect of Combined Pretreatment of Waste Activated Sludge for Anaerobic Digestion Process

Alkaline and low-temperature thermal pretreatment has been used to the subsequent anaerobic digestion of waste activated sludge (WAS) respectively. Different combinations of these two methods were investigated and biochemical methane potential (BMP) test was used to assess the anaerobic digestibility of pretreated WAS. In this study, an optimal reaction condition was obtained by combined pretreatment and BMP test. The combination was after alkalized for 24 h, adding 0.05 g NaOH/g TS with 9 hours at 70°C. Under this condition the removal of SS was achieved 21% and soluble chemical oxygen demand (SCOD) was more than 200 times of control group. The ratio of soluble carbohydrate/total carbohydrate can reach 72.8%. For BMP test, it's nearly 6 times higher biogas production was obtained than the control and the average value of methane content of biogas production is 64%. Thus, combined (alkaline + low-temperature thermal) pretreatment was efficiency for solubilization and biogas production.