Physicochemical Approach to Water and Wastewater Filtration

A conceptual model has been developed for the depth filtration of water and wastewater using granular beds considering the effect of gravity, interception, hydrodynamic forces, London attraction and Brownian diffusion for systems with negligible double layer forces. The ultimate capture of particles in a packed bed is determined not only by the transport mechanisms but also by the short-range surface forces which play a dominant role in their attachment to the media grains. The experimental data obtained for the filtration of secondary effluents using a polymer-coated sand bed were in good agreement with the predictive model for systems where the effluents were preconditioned using polymeric aids to reduce the double layer forces to a minimum.