Characteristics of Deposit in Filter Using Model Materials for Slender Type Diatoms and Effective Parameters to Clogging of Rapid Sand Filter

Abstract

Most of algae which affect the filter clogging are slender type diatoms like Synedra, Fragilaria and Asterionella. In this study, model materials for diatoms and sand are used. A deposited amount of diatoms on a grain of a filter, a deposit distribution in the filter and the penetration depth of diatoms in the filter are discussed based on filtration experiments.
The amount of 95 per cent of total deposit is captured within the layer as thick as 30 times of the diameter of a filter grain under the condition of size of a filter grain from 2 to 6 times of diatom length. The ratio of deposited amount on a grain to filter depth is a main factor to estimate the degree of lean of amount of unlateral deposit at the surface layer part of filter layer and it decreases with the diameter of a filter grain. The result in this study shows useful points to design the thickness of filter for protection of filter clogging.