Conditioning, Filtering, and Expressing Waste Activated Sludge

In this study, the applied liquid pressure was used to characterize the rate and extent of activated sludge dewatering in the expression phase. By characterizing the liquid pressure, three important features of expression phase dewatering were determined. First, as the depth of sludge cake increased, the ability to express water from the sludge cake was greatly reduced. Second, iron and lime were found to be superior to polymer, especially as the applied pressure increased. Third, for either type of conditioner, increased pressure resulted in a decreased rate of expression. This was probably due to the highly compressible nature of activated sludge, which responds to pressure by becoming less porous.