Modeling of sequencing batch reactors treating inhibitory and noninhibitory wastewaters

A mathematical model for sequencing batch reactors (SBR) that takes into account fill and react periods was developed and tested against experimental data from the literature. The Monod equation was used to describe microbial growth kinetics. The proposed model predicts the time dependent microbial cell and substrate concentrations during SBR treatment of wastes. A numerical method was used to solve the governing model equation which comprised nonlinear unsteady-state ordinary differential equations. Model simulations highlighted the importance of feed rate as a major operating parameter. For biodegradable wastes and low strength inhibitory wastes, an instantaneous fill is optimum whereas high strength inhibitory waste treatment is only possible with long fill times. The model predictions compared well with experimental results reported in the literature. This model is useful for further understanding of biological wastewater treatment kinetics by batch processes and may serve as a valuable design aid for practicing engineers.