Comparison methane production potential between granular and suspended sludge at varying ammonia concentration

Abstract

Anaerobic digestion of Thermally Hydrolyzed Wasted Sludge (THWS) with high strength ammonia was evaluated through batch and two-phase Upflow Anaerobic Sludge Blanket (UASB) reactors with two kinds of anaerobic microbial types (suspended and granular). In the batch test, biogas yield and gas production rate increased as microbial concentration increased for the wastewaters with a high ammonia concentration of 0.8 g FA/L. Also, the lag time and finishing time of gas production could be shortened by applying higher microbial concentrations. The granular sludge presented a higher biogas yield, shorter lag time and shorter finishing time of gas production when compared with suspended sludge. The comparative reactor operation using suspended sludge and granular sludge demonstrated that the granular sludge had more competitive advantages for the biogas production from THWS at a high ammonia concentration of 9.2 g NH4+/L. Therefore, the application of granular sludge could be more appropriate for the anaerobic treatment of wastewater containing high strength ammonia since the granular sludge can have a higher resistance to toxicity and maintain a higher microbial concentration.