Impact of Actual Domestic Sewage and Simulated Wastewater on an Aerobic Granular Sludge System

Abstract

Sludge returned from the secondary sedimentation tank of a sewage treatment plant is inoculated into two sequencing batch reactors (SBR):R1 and R2. Simulated wastewater and actual domestic sewage are used as the influents of R1 and R2, respectively, in order to study the impact of the influent water quality on the formation at normal temperature (20-30℃) and the stable operation of the system when the temperature changes. The results show that both R1 and R2 start successfully with 25 d and 42 d, respectively. The average size of the aerobic granular sludge in R1 and R2 is 1200 μm and 750 μm when the sludge granules stabilize. The average concentrations of COD, TP, and TN in the R1 and R2 effluent are 22.53, 0.48, and 7.70 mg·L-1 and 49.73, 0.49, and 14.55 mg·L-1, respectively, with average removal rates of 90.60%, 90.34%, and 87.85% and 79.74%, 88.59%, and 79.25%. When the temperature drops to 5-16℃, the granular sludge in R1 disintegrates, the removal rates of COD and TP are basically unchanged, the average concentration of TN in the effluent increases to 29.03 mg·L-1, the average removal rate decreases to 48.81%, and the denitrification performance is suppressed. The granular sludge in R2 remains stable; the average concentrations of COD, TP, and TN in the effluent are 14.31, 0.50, and 12.24 mg·L-1, and the average removal rates are 92.42%, 93.37%, and 86.28% respectively. The effluent reaches the IA standard of the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant". Both the simulated wastewater and actual domestic sewage can cultivate aerobic granular sludge successfully, but the aerobic granular sludge in the domestic sewage is more compact in structure, effectively suppresses the expansion of filamentous bacteria when the temperature drops to 5-16℃, and is more resistant to changes.