Some Chemical Aspects of Rapid Sand Filtration

Abstract

This article considers past efforts and present knowledge concerning the filtration process, with particular emphasis on particle removal mechanisms, and presents the results of research demonstrating chemical effects in the filtration of ferric floc suspensions. The results of this research provide experimental evidence that the surface properties of ferric floc particles markedly affect their filtrability, and that these properties depend on the chemical composition of the aqueous phase. These chemical effects in the filtration process are considered to result from interactions between the surfaces of the filter medium and the suspended floc particles; this conclusion lends strong experimental support to adsorption as a predominant removal mechanism in rapid sand filters. The data presented in this article indicate to the authors that rapid sand filtration can be chemically controlled through the influence of selected chemicals on the adsorption of suspended particles to the filter media.