USE OF A LABORATORY-SCALE VERTICAL SLUDGE PRESS TO OPTIMIZE POLYMER-ENHANCED DEWATERING OF PULP-MILL WASTE-ACTIVATED SLUDGE

Installation of high-rate activated sludge effluent treatment systems has dramatically increased the amount of waste sludge produced by the Canadian pulp and paper industry. This material is approximately two t hirds fibrous waste from primary clarifiers and one third waste-activa ted sludge (WAS) from the secondary clarifiers. Most of this sludge is mechanically dewatered and either incinerated or landfilled. The econ omics of either disposal method are improved by efficient dewatering o f the sludges, an operation which is usually enhanced by a two-stage a ddition of coagulating and flocculating chemicals. The cost of these c hemicals can be significant. It is therefore a worthwhile exercise to optimize their addition. This paper describes the use of a vertical sl udge press which can be used to predict quickly and accurately the imp act of varied polymer types and doses on dewatering of pulp mill sludg es. Use of the laboratory sludge press indicated that sludge dewaterin g increased as a function of pressure exerted primary sludge fraction, and coagulant and flocculant type and dose. The laboratory-scale pres s was able to predict the impact of various polymer formulations on th e performance of full-scale sludge presses.