Effect of extracellular polymers on freeze-thaw conditioning of activated sludge

In this study, the effects of extracellular polymers on freeze-thaw conditioning of activated sludge are investigated. Various physical and chemical extraction methods including centrifugation, blending, heat, EDTA, EGTA, and NaOH extraction were used to remove extracellular material from sludge matrix. The improvements in freeze-thaw conditioning were evaluated by commonly used measures of sludge dewaterability. The results of this study indicate that removal of extracellular polymers using relatively gentle extraction methods before freeze-thaw conditioning improves the sludge dewaterability after the freeze-thaw. In addition to extracellular polymers, cations also play an important role in determining the freeze-thaw effectiveness on activated sludge. Best dewaterability is achieved when both extracellular polymers and cations are removed from activated sludge before freeze-thaw conditioning.