Feasibility Study on Freeze/Thaw Conditioning of Pulp Mill Waste Activated Sludge

Abstract

A preliminary investigation has been performed to determine the feasibility of conditioning a sulfite pulp mill waste activated sludge (WAS) by freezing and thawing. A series of experiments quantifying dewaterability was performed on the frozen and thawed sludge (“conditioned”) and compared to sludge that had not been treated by freezing (“unconditioned”). These experiments consisted of quantifying the change in settling rates, filterability, and maximum attainable solids content, and were performed at −5°C, −10°C, and −25°C. As a result of freeze/thaw treatment, dewaterability improved dramatically for the conditioned sludges, with the greatest improvement noted for samples frozen at higher temperatures.