Sand Filtration of Particulate Matter

The penetration of particulate matter through sand filters can be eliminated entirely or greatly reduced by the application of a coagulating chemical supplied as a solution directly to the filter influent. At high densities of organism, the inability to remove all cells of Selenastoum and the diminishing rate of removal associated with increased coagulant dosages indicates the necessity of pretreatment. The modification of the pattern of coagulant deposit, the head loss increase pattern, and the inability to remove all algal cells at high densities seem to indicate the decided importance of the chemical nature of the floc in any filtration mechanism. The location of powered activated carbon deposited under plain filtration was shown to be logarithmic with depth. The location of deposited coagulant and activated carbon declined logarithmically with depth in the upper part of the uniform size filter media.