Upflow biological filter: Modeling and simulation of filtration

One of the most important operating parameters for the operation and the de sign of biofilters is the headless due to clogging of the system leading to a semi-continuous operation with filtration cycles and backwashes. Some ba sic aspects of the filtration operation have been studied. The work consist s in understanding and modelling the clogging phenomena due to the suspende d solids retention, and validating the simulation results by calibration wi th experimental and full-scale results. Tracer experiments allowed us to simplify the hydrodynamics within the Biof ilters into a plug-flow reactor with axial diffusion. Mass balances for the suspended solids have been therefore written accordingly, including solids retention represented as a mass transfer from the liquid to the solid phas e. This affects the porosity of the system, leading on one hand to a modifi cation of the filtration coefficient (responsible for the transfer of SS fr om liquid to "solid" phase) and on the other hand to an increased clogging measured by the headless in the system. The Kozeny-Carman equation could successfully be used and a linear relation ship between the filter coefficient and the water porosity could be validat ed. Experimental work has been conducted to calibrate the model and in this paper validations from pilot scale unit to full-scale plant are shown. (C) 1999 IAWQ Published by Elsevier Science Ltd. All rights reserved.