Development of an integrated ultrasonic biofilm detachment model for biofilm thickness control in membrane aerated bioreactors

Abstract

Controlling biofilm thickness in an aerated membrane biofilm reactor (MBfR) has been recognized as a key for MBfRs to achieve a long-term stable performance. In this context, acoustic cavitation is an effective strategy that can be used for controlling biofilm thickness. However, to maintain the biofilm thickness at an optimum value, it is necessary to understand the effect of acoustic parameters and cavitation bubble distribution on biofilm detachment and establish a link between biofilm detachment and regrowth. The purpose of this study is to provide an integrated mathematical model that describes biofilm development in an aerated membrane biofilm reactor using a nonlinear reaction-diffusion model and its response to mechanical stress generated from acoustic cavitation. The simulation results show that pressure, amplitude and frequency of transducer are two key factors that affect biofilm detachment. Moreover, uniform distribution of cavitation along the biofilm surface is critical to achieve an even biofilm thickness. Furthermore, periodic cavitation detachment with an appropriate resting time in between is important for maintaining the biofilm thickness at a desired value. Therefore, the purpose of this study is to present an integrated modeling approach to optimize acoustic cavitation parameters and methods to achieve effective biofilm thickness control in MBfRs.