Sequential substrate utilization and effectiveness factor in fixed biofilms

A mathematical model describing the change in effectiveness factor or effective diffusivity for the intermediate substrate in sequential substrate removal reactions in fixed biofilms is developed. Typical results from the numerical solution of the resulting equation are presented. The production of intermediate substrate in the biofilm increases the conversion of primary substrate to ultimate product in all cases, but the increase is not always significant. Using typical data applying to laboratory anaerobic fermentation studies, it is demonstrated that a small but significant change in reaction kinetics and the effectiveness factor exists.