Ecological Model Analysis of Predator-Prey Relationships in Anaerobic-Aerobic (Oxic) EBPR Activated Sludge Process

Abstract

Predator-prey relationships between bacteria and predators including protozoa and metazoa in the anaerobic-aerobic (oxic) enhanced biological phosphorus removal (EBPR) activated sludge process were analyzed using a mathematical model to clarify the roles of these micro-organisms. The analysis revealed that the growth rate of predators in the oxic phase, μ_pb, has a little effect on the ratio of MLSS of predator (P-SS) and total MLSS, and that the growth limit of predators as a ratio of MLSS of bacteria (B-SS) and P-SS in the oxic phase, GLR_pb, has large effect on the ratio of P-SS and total MLSS. In the steady state, B-SS increases rapidly with GLR_pb increases from one to eight, then increases gradually with GLR_pb increases to forty. P-SS decreases during GLR_pb increases from one to forty. Clarifying the relationships between predator and bacteria would contribute to waste sludge reduction.