Evaluation of the sludge blinding coefficient

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Virginia Polytechnic Institute and State University

The sludge blinding coefficient, β, was evaluated in this experimental study, to determine if β could be used as a useful characterization parameter for sludge filterability. Fresh activated sludge, activated sludge aged at room temperature, primary sludge, alum sludge, and a calcium carbonate slurry were filtered using a Buchner funnel apparatus and varying size filter media at various pressure differentials. Particle size measurements were also performed on the above mentioned sludges using an automated particle size analyzer to examine the impact of particle size and size distribution on β. Effects of conditioning, elutriation, supernatant removal, and replacement on β were also studied.

In general, β correlated well with the average specific resistance, indicating that it could be useful in predicting a sludge filtration pattern. β was found to increase as the mean particle size of a sludge decreased, or the particle size distribution of a sludge widened. Conditioning, elutriation, supernatant removal, and replacement were found to reduce β by improving the mean particle size of a sludge and narrowing a sludge particle size distribution. In addition, β was found to increase by the applied pressure differential and filter media pore sizes for a few sludges.