Abstract
A mathematical model of bacteria and predators of bacteria including protozoa and metazoa in the anaerobic-aerobic (oxic) enhanced biological phosphorus removal (EBPR) activated sludge process is presented to clarify the roles of these microorganisms based on the colony forming counts (CFU) analysis of activated sludge bacteria. A laboratory-scale batch-type anaerobic-oxic activated sludge process was operated with mixed liquor withdrawal operation (MWO), which is normally used for pure culture cultivations. While MLSS concentration of the activated sludge in the anaerobic phase and in the oxic phase were almost the same in this operation, CFU of heterotrophic bacteria in the anaerobic phase was much larger than that in the oxic phase. The mathematical model analysis revealed that this difference could be attributed to the food chain of microorganisms in the activated sludge. When population of predators including protozoa and metazoa was expressed as population of a protozoa specie based on the yield coefficient obtained from literatures, the analysis results showed a small increase in predator population could cause much decrease of bacterial population in EBPR process.
