Relationship of gravel filtration to exhibited sediment charge

Abstract

This research concerns a study of the nature of the process of removal of suspended sediment by filtration of turbid water through 1aged" pea size gravel. A hypothesis is formulated that the removal process occurs as the result of adsorption of the suspended sediment to the schmutzdecke coating the gravel rather than by the classic concept of straining, sedimentation and to a small degree, adsorption. The method of indicating the validity of this contention is to show the relationship between the electrokinetic potential of the suspended sediment and the efficiency with which this material is removed during filtration, and to determine if, during filtration, there is any fractionation as to particle size. Values of influent and effluent turbidity and specific surface area of suspended material, along with the electrophoretic mobility of the clay particles were determined during the process of filtration. An analysis of the data showed that there was an excellent correlation between an increase in removal efficiency and an increase in particle electroktnetic potential, and that there is essentially no fractionation as to particle size. The results were interpreted to mean that the removal process is, by nature, one of adsorption.