Filtration of Treated Sewage Effluent

Effluent used in this investigation was obtained from a pilot scale activated sludge treatment plant, operated at a solids retention time of ten days. Particulate matter in the effluent was characterized by measurement of suspended solids, particle size and distribution, and particle charge and charge distribution. Although a number of removal mechanisms are operative, straining was found to be the principal mechanism responsible for the removal of particulate matter. The size and distribution of the influent particles, their floc strength, the size of the medium, the filtration rate, and amount of material arrested within the filter must be considered in the development of equations which can be used to describe the time-space removal of particulate matter within a granular filter. Equations were developed to predict filter performance as a function of these variables for the conditions studied. These equations can also be generalized for cases where straining is not the principal removal mechanism.