Comparative performance of biofilm reactor types.

Development of a unified model of biofilm-reactor kinetics is based on substrate-utilization kinetics, mass transport, biofilm growth, and reactor analysis. The model is applied to steady-state conditions for complete-mix, fixed-bed, and fluidized-bed reactors with and without recycle. The results of modeling experiments demonstrate that simple loading factors and kinetic relationships are insufficient to describe the performance of a variety of biofilm processes. Instead, the interactions among utilization kinetics, biofilm growth, and reactor configuration determine the performance. For example, fluidized-bed reactors can achieve superior performance to complete-mix and fixed-bed reactors because the biofilm is evenly distributed throughout the reactor while the liquid regime has plug-flow characteristics. When it is possible, experimental results which demonstrate key concepts are presented.