Analysis of Colloid Transport and Colloidal Size Effect Using Filtration Theory

Abstract

The role of colloid particles in radionuclide transport leads us to investigate the factors affecting the colloid transport in groundwater. Predictive models that can be generalized, however, are not available as yet. In this paper the mechanisms that affect the colloid transport were investigated and to evaluate the extent of their effects, a modified filtration equation including gravitational settling was developed. This equation was solved as functions of colloidal size, grain diameter of porous media, groundwater velocity, distance and time. As another measure to estimate the effect of colloidal size on the transport mechanism, the concept of transport velocity was introduced. Finally, colloid transport was compared with solute transport under the same condtions. Numerical results indicate that a reduction in colloidal size enhances the colloid concentration. In particular, it is found that at long times the relative contribution of colloid to radionuclide transport is of growing importance. If solute concentration is determined realistically, this tendency will be more remarkable. The filtration equation improved in this paper has the feature of inclusion of colloidal size effects such as size distribution and gravitational settling and simplicity of application because it is not difficult to determine parameters used in this equation.