Abstract
Experimental data show that the breakthrough curves observed in filtration in the case of both surface-force-dominated deposition and flocculation-dominated deposition display a general similarity. Some theoretical observations on these extreme cases of deposition behavior are presented which focus on the prediction of the breakthrough curves that could be expected in each case. Solutions for breakthrough curves are given, and their relationship to the deposition mechanisms and the corresponding boundary conditions is examined. The accumulation-detachment model is based on the fact that filtration is a process of accumulation where partial but continuous pore clogging takes place. Both cases involve similar theoretical and mathematical formulations and similar solutions. The pore-clogging model uses four easily determinable parameters: filter capacity, hydraulic conductivity, and accumulation and detachment coefficients. These are physically meaningful parameters, determining the volume of water that can be treated, the rate of clogging, and the flocculation efficiency. For a given water and filter bed, the two filtration coefficients depend on flocculant types and filtration rate. The coefficients can be used to evaluate flocculant performance. The smaller the detachment coefficient, the better the removal efficiency; however, the head loss develops faster. These predictive models are applicable to various waters, filter beds, flocculants, and soil types. They have a practical value in the design of new filters as well as in the upgrading of existing filters. (Geiger-PTT)