Biofilm Shearing under Dynamic Conditions

Abstract

Experimental data on biofilm shearing were collected for columns packed with granular activated carbon. The columns were operated under dynamic conditions, experiencing a wide range of biodegradation rates. Under conditions of rapidly changing biodegradation rate, biofilm shearing was much more closely related to the microbial growth rate than to the amount of attached biomass, as had been previously proposed. A two‐term model of biofilm shearing was proposed and described the data well. The first term is a proportionality between shearing and attached biomass, as used by others. The second term is a proportionality between shearing and microbial growth rate, exclusive of loss mechanisms. The two parameters in the model were evaluated by linear regression analysis of specific shearing rate versus specific growth rate. Parameter values were determined for the substrates, phenol and paranitrophenol. The value of the growth‐related shearing parameter appeared to have a significant substrate dependence. Substantial biofilm shearing occurred during periods of rapid biodegradation, demonstrating the importance of this process in attached growth reactors.