Diatomite Filtration Equations for Various Septa

Previously developed diatomite filtration equations have been found to be invalid for use with cylindrical septa because they fail to describe the significant effect of the increasing filtering area associated with cylindrical filter cakes. Also, they do not describe the initial transitional period resulting from initial mixing of the influent with the clean water in the filter left over from the precoating operation (dilution effect). The initial dilution effect is less important and can probably be ignored for most practical applications. The increasing area effect, however, should not be ignored. Diatomite filtration equations were developed theoretically herein from the generally accepted filtration rate equation. The hypotheses assumed in the derivation of these equations are explicitly stated. These equations account for the effects of both initial dilution and increasing area. The equations were used to determine filter cake resistance, and to predict filter performance under different operating conditions.