Abiotic transport in a membrane aerated bioreactor

Abiotic transport characteristics of a nitrifying membrane-aerated bioreactor were empirically analyzed and a model was developed. The orientation of the membranes in the bioprocessor is novel and the membrane/reactor length ratio is much larger than similar reactors for enhanced mass conversion. While mass conversion may be improved due to increases in total specific surface area, abiotic transport was characterized to ensure transport properties were similar to other membrane aeration bioprocessors. The developed model indicated that oxygen mass transfer and nutrient convection may limit bioreactor performance. Peclet numbers indicated that the bioreactor could be modeled as a complete-mix reactor for an initial approximation, but further research should be conducted to characterize non-ideal hydraulic behavior. The random “coiled” orientation of the membranes provided enhanced surface area for microbial attachment, but may have caused flow misdistribution issues. In contrast to abiotic modeling, experiments with nitrifying biofilm indicated sufficient electron acceptor and nutrient transport for the operational conditions tested. It was concluded that the complex nature of the silicon membrane geometry and assumption of parameter interdependency caused the under prediction of bioreactor transport. This model is intended to establish a platform for future models attempting to predict transport conditions in developing robust bioprocessors under stringent size, mass and energy restrictions. The random coiled geometry of the membranes is a viable option for long-lifetime bioprocessors requiring high specific surface area.