Chapter 5 Factors affecting aerobic granulation

Abstract

This chapter discusses the factors that affect aerobic granulation. Aerobic granulation can be regarded as the gathering together of cells through cell-to-cell immobilization to form a stable, contiguous, multicellular association. These aggregated granules have a compact structure as compared with suspended sludge flocs. Studies show that aerobic granulation is a gradual process from seed sludge to compact aggregates, further to granular sludge and finally to mature granules. For cells in a culture to aggregate, a number of factors could affect this process. Aerobic granules can grow on a wide variety of organic substrates in sequencing batch reactor (SBR), including glucose, acetate, ethanol, phenol, particulate organic matter-rich wastewater, soybean-processing wastewater, and both simulated and real municipal wastewater. Aerobic granules is a process independent of or insensitive to the characteristics of feed wastewater, while evidence shows that the microbial structure and diversity of mature aerobic granules are closely related to the type of substrates used. Aerobic granulation in SBR is substrate concentration-independent, but the kinetics behavior of aerobic granules is related to the applied substrate loading. Similar to the formation of a biofilm, aerobic granules can form at different levels of hydrodynamic shear forces. As a result, hydrodynamic shear force is not a primary inducer of aerobic granulation in SBR.