ABSTRACT
This chapter presents insights into the diffusion behaviors of substrate and oxygen in aerobic granules, in view of the importance of substrate and oxygen in microbial culture. A plot of the specific growth rate against the specific substrate utilization rate further reveals that the slow substrate utilization by large-sized aerobic granules results in a low specific growth rate. Mature aerobic granules have an equilibrium or stable size when growth and detachment forces are balanced. The effectiveness factor decreases quickly with the further increase of radius of the aerobic granules, which indicates that the mass transfer limitation begins to play an important role in the overall reaction of aerobic granules. Smaller aerobic granules exhibited higher metabolic activity in terms of the substrate removal rate, while in an sequencing batch reactors dominated by aerobic granules with a size larger than 0.5 mm, the dissolved oxygen is the bottleneck that limits the substrate utilization.
