Over the last few years considerable attention has been devoted to biological fluidized-bed technology which seems to be potentially more advantageous than both dispersed biomass processes and fixed bed systems. An obstacle to the spreading of this technology is the lack of rigorous criteria in designing reactors, due to the poor knowledge of interconnections of fluid-dynamic aspects with kinetic ones.

This paper reviews the rational basis for reactor design and reports on the experimental tests carried out in order to gain a better understanding in the areas of biofilm modelling and fluidization mechanics.

In particular a biofilm model, in the general case of the Michaelis and Menten equation, was developed and its validity was verified utilizing experimental data obtained in nitrifying batch tests. As to fluidization mechanics the experimental work confirms the Wen and Yu(1966) approach to correlate the bed porosity with the superficial liquid velocity.

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