(418j) Anoxic Regions In Gas-Liquid-Solid Fluidized Bed Bioreactor

Fluidized bed bioreactors can be used for wastewater treatment.  Fan and Wen (1982) patented a process with the region near the distributor plate fluidized and a region near the top of the bed that is fixed bed. A restraining sieve plate is used to achieve the fixed bed at the top.  Tand and Fan (1987) discuss use of fludizied bed bioreactors for fermentation and wastewater treatment processes.  Fluidized bed biofilm reactor has been demostrated to outperform other reactor configurations used in wastewater treatment such as activated sludge system and trickling filter bioreactor.  Causative factors identified for better performance are; (i) better capacity to handle higher biomass concentration due to immobilization of cells onto the solid particles; (ii) relaxation of limit on operational liquid flow rates on account on CSTR limiations on operational flow rates; (iii) intimate contact achievable between the liquid phase and solid phase achievable and; (iv) higher microbial activity achievable by use of support particles.  Mathematical mode is developed in order to describe the simultaneous diffusion and reaction of oxygen. Michaelis and Meten kinetics is assumed to be obeyed. The anoxic regions are identified in the asymptotic limit of zeroth order and maximum reaction rate at steady state.  The turbulence in the fluidized bed has been noted as a causative factor in poorer solids capture. More solids can be captured when the fluidization conditions such as particle size and flow regimes are identified.  Transient concentration profile of oxygen, organics, microbes and nutirents are modeled using: (i) Fick's law of diffusion; (ii) Damped Wave Diffusion and Relaxation (Sharma, 2005). Penetration distances and inertial lag times are calculated.  When to use Monod kinetics and when to use Michaelis and Menten kinetics are shown clearly (Levenspiel, 1999).   Efforts are underway to find the muliplicity even at steady state when Haldane equation that is nonlinear need be used.