Modeling of biological wastewater treatment in sequencing batch reactors

Abstract

The Sequencing Batch Reactor (SBR) system is one of the biological methods used for the treatment of industrial and domestic wastewaters. Compared to the continuous flow activated sludge systems, the mathematical description of the SBR system is not fully developed yet. Therefore, for the improved understanding of the performance and design of the SBR, a mathematical model which takes into account fill, react and settle periods of the SBR was developed and tested against experimental data from the literature. The Monod equation was used to describe microbial growth kinetics. The developed model is capable of predicting microbial cell and substrate concentrations at various time horizon during SBR treatment of wastes. The resulting differential equations governing the SBR system, being nonlinear and transient, were solved numerically using 4th order Runge-kutta method. The model predictions compared well with experimental results reported in the literature. Simulation results have indicated that an extended fill period is beneficial to the treatment of toxic and high-strength wastes as it mitigates inhibition and organic overloading effects. An experimental work was also carried out to investigate the microorganisms responsible for phenol biodegradation. It was found that the microbial species known as Psuedomonas aeruginosa was the predominant one over other microbial populations for biological treatment of phenolic waste.