Comparison of single mechanism and multi mechanism‐based approaches for kinetics of sediment removal

Abstract

The process of cohesive particle sedimentation in aquatic environments is perceived as one of continuous formation of aggregates by coagulation and their separation from the water column by accumulation on the deposition bed. Over the temporal scales of practical interest for natural systems, many physical, chemical, and environmental factors govern the rate of sedimentation, hence a purely physics‐based description has not yet been developed. A new information‐based model that uses experimental information to derive governing parameters, while predicting removal through power law relationships, is proposed and tested. Analytical solutions derived for this model are shown to be applicable over large ranges of concentrations and to various fluid‐sediment environments. Comparisons with numerically derived and observed data show that the analytical model is a versatile tool that improves fundamental understanding of the physical processes involved in sedimentation. The inverse problem of identification and quantification of model parameter values from experimental results is discussed. Predictions based on average sediment kinetics are found to be in reasonable agreement with experimental observations in a variety of special cases examined.

Keywords:

• Aggregation
• kinetics
• cohesive sediments
• sedimentation
• collision mechanisms