Efficacy of biofilms under toxic conditions

Response of biofilms to toxic compounds has been modeled using Monod-type inhibition kinetics. Biofilm inhibition due to substrate, secondary substrate, and product is considered. For biofilm inhibition due to substrate and secondary substrate with high inhibitory substances, the model predicted the biofilm effectiveness factor to be higher than unity. On the other hand, for slightly inhibitory substances, substrate limitations within the biofilm due to mass transfer resistance resulted in a reduction in biofilm effectiveness factor as its thickness increased. In case of product inhibition, the effectiveness factor of the biofilm was always lower than one due to accumulation of product leading to higher concentrations within the biofilm than in the bulk. The generalized models developed for effectiveness factors under various conditions of inhibition can be used as a predictive tool in design of wastewater treatment systems.