THE USE OF PULPED NEWSPRINT AS A CONDITIONING AID IN THE VACUUM FILTRATION OF A MUNICIPAL SLUDGE

Abstract The use of polymer plus newsprint pulp as a method of conditioning sludge for vacuum filtration was evaluated as a potential alternative to the addition of ferric chloride and lime. Bench scale experiments established basic relationships between various polymer/pulp/sludge mixtures and the dewaterability of the conditioned sample. Pilot and full scale vacuum filters were operated to determine scale-up relationships, to evaluate the importance of operating variables, and to document operating problems. Further dewatering of the filter cake to a moisture content which would allow autogenous combustion was attempted using a mechanical press, but was not a reliable operation with the equipment tested. Vacuum filtration of the polymer/pulp/sludge mixture resulted in higher yields, equivalent cake solids, and lower filtrate suspended solids compared to a ferric chloride and lime conditioned sludge. The results obtained in the bench scale tests gave a slightly over-optimistic prediction of performance to that actually achieved on the pilot and full scale equipment. The calorific content of polymer and pulp conditioned sludge was approximately 60% higher than that of the ferric chloride and lime conditioned sludge. Gas consumption during incineration of the polymer and pulp conditioned sludge was significantly reduced. Cost estimates indicated that the capital investment required for a polymer and pulp conditioning system at the test site, would be recovered in approximately two years by savings in operation and maintenance costs (primarily energy savings at a newsprint cost of $38.50/tonne).