Expansion of Granular Water Filters During Backwash (original) (raw)

In this study a mathematical model has been developed for graded filter media, which has a substantial size range, to predict the expansions at different flow rates. The model is applicable both for spherical and irregular media. Angularity greatly influences the whole behavior of fluidization during backwashing. To express sphericity, physical properties and hydrodynamic parameters of filter materials are used in the model. Filter media was divided into unisized portions for expanded length calculations. Backwashing experiments were also performed in the laboratory with sand and coal materials to check the validity of the derived model. Experiments cover the diffused layer for coal at the uppermost portion of the filter.