Lotka–Volterra equation based modeling of aerobic granulation process in sequencing batch reactors

• A model based on Lotka–Volterra equation was established to simulate the aerobic granulation process in a SBR.
• The higher VS and μmax can accelerate the granulation process.
• The biomass growth is the other key process for the formation of aerobic granules.

Aerobic granulation is a special form of biofilm growth and is the process of microbial immobilization. Selection pressure resulted from sedimentation and discharge processes is a decisive factor of aerobic granulation. Thus, on the basis of the Lotka–Volterra competition equation and selection pressure, a mathematic model was established to simulate the aerobic granulation process in a sequencing batch reactor (SBR). The sensitivity of the mean diameter toward the minimum settling velocity (VS) and the maximum specific growth rate (μmax) is analyzed. The selection coefficient was predicted in the case of VS = 20 cm min−1 and VS = 40 cm min−1, respectively. The growth of biomass is calculated based on diffusion and reaction theory. The model is also able to predict variation rate and size distribution of bioparticle. The results indicated that VS can control the granulation process and the characteristics of granules. The model evaluation results demonstrate that the developed model is applicable to simulating the aerobic granulation process appropriately. These simulated results are helpful for designing and controlling of aerobic granulation process.