EVALUATION OF MUNICIPAL SLUDGE DRYING AND DEWATERING WITH RESPECT TO SLUDGE VOLUME REDUCTION

A number of parameters that influence sludge dewatering behaviour have been identified, but there is a lack of consensus which of these are of the greatest concern in sludge treatment strategies. Moisture retention characteristics were obtained from vacuum drying of centrifuged sludge samples to subdivide moisture into immobilised, physically and chemically bound fractions. Physically bound moisture is responsible for unsatisfactory dewatering by centrifugation. Polyelectrolyte releases some of the immobilised water, but simultaneoulsy increases the physically bound moisture content which gives rise to large energy inputs during mechanical dewatering.