If the solids content of the filtrate = Wf (lb per gallon), then ZcWf represents the solids that pass through the cloth. If pc is the cake density, the following equation calculates the cake thickness as discharged (Lc, ft):
cake volume, ft3 c hr X drum area X drum speed, revolutions per hr cake mass rate per cake density hr X drum area X drum speed, revolutions per hr
A comparison of Equations 7.47(7) and (8) indicates that as the drum rotation speed increases, the solids rate also increases, but the filter cake becomes thinner. The pas sage of fine solids through the filter cloth is often unavoidable in continuous filtration and can require recycling the filtrate to the clarifier. Cake washing is of minor importance in waste treatment filters, but when it is required, batch filters are usually superior to continuous
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