Characteristics of aerobic granular sludge membrane bioreactor for domestic wastewater treatment

Domestic wastewater was used to cultivate aerobic granular sludge in SBR system. The controlling factors for cultivation of aerobic granular sludge were hydraulic shear stress and hydraulic retention time. Matured granular sludge was then inoculated into MBR reactor to establish aerobic granular sludge membrane bioreactor(AGSMBR). The main focus of this study was (a) to investigate the effect of hydraulic retention time and hydraulic shear stress on cultivation of aerobic granular sludge, (b) to compare AGSMBR with MBR by investigating the removal effeciency of COD, NH₃-N and TN, (c) to investigate the characteristics of membrane fouling in AGSMBR by analyzing transmembrane pressure (TMP) and membrane flux variation. The results showed that aerobic granular sludge can be successfully cultivated by controlling hydraulic retention time and hydraulic shear stress in SBR reactor. There are three stages i.e. the granular sludge growth-start-up stage, adaptation stage and formation stage. The first two phases require a lower sludge loading and longer aeration time, while the third phase requires a shorter settling time and more aeration. The study of pollutants removal show that the difference of COD, NH₃-N removal efficiency in AGSMBR and MBR was very small, both were more than 80%. However, the difference of TN removal efficiency was significant i.e. more than 80% in AGSMBR and only 35%~40% in MBR system. The analysis of membrane fouling characteristics show that the colloidal particles and dissolved organic matter attached to the membrane surface were the major reasons for membrane flux declining and TMP increase.