INFLUENCE OF DESIGN AND OPERATION PARAMETERS ON THE FLOW PATTERN OF SUBMERGED FILTERS

The influence of design parameters (height and bed porosity) and opera tion parameters (liquid and gas superficial velocities) on the flow pa ttern of an up-flow biological aerated filter has been studied. A lith ium chloride pulse input was used for obtaining residence time distrib ution curves. Bed height was not found to influence the flow pattern b ut did increase retention time because of diffusion. Porosity was the controlling factor of the diffusional phenomena and, consequently, als o controlled the hydrodynamic performance of the reactor. Thus, the fl ow pattern approximated more to plug-flow and retention was greater in lower porosity filters (puzzolana bed) than in higher porosity units (sepiolite bed). The liquid velocity effect was more important than th e gas velocity effect.