CAREER: Detachment from Biofilms Under Dynamic Operating Conditions - Integrating Fundamental Research and Practical Biofilm Modeling Education

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0134104MorgenrothThe overall objective of this proposal is to determine the influence of dynamic variations of shear stress on biofilm detachment. Mechanisms of biofilm detachment are poorly understood and procedures for the design and operation of biofilm reactors are mainly empirical. In biofilm reactors, the process of detachment is necessary to balance bacterial growth and to prevent clogging. In addition, the overall rate and time dependent variation of detachment significantly influence bacterial selection within the biofilmcommunity. Specific objectives of this proposal are to determine the relationship between detachment rate, detached particle characteristics, and overall reactor performance under constant or dynamically fluctuating shear conditions. Based on experimental results, a dynamic mathematical biofilm model will be developed. The model will be used for experimental design, interpretation of research results and toteach students and practitioners the underlying principles governing the application of biofilms in biological treatment processes. Innovative tools for on-line monitoring of detachment will be developed. Laser backscattering and in-line video microscopy will be adapted to provide continuous information on the size and shape characteristics of detached particles. On-line techniques for measuring bacterial respiration rates within the biofilm reactor will be developed and used to correlate overall biofilm reactor performance with detachmentdynamics. Detached particles will also be characterized for strength, surface hydrophobicity, surface charge, and abundance of nitrifying bacteria. Laboratory scale biofilm systems will be developed that allow biofilms to grow under defined hydrodynamic conditions (annular reactor) or under conditions used in full-scale reactors (packed bed reactor, airlift reactor). A mathematical biofilm model will be developedthat will be applied both in research and in teaching. Inputs to the model will consist of wastewater composition, biofilm thickness distribution, and detached particle size distribution. The mathematical model will be tested in the laboratory and in full-scale biofilm reactors.