WERF Phase 1: Factors affecting conditioning during dewatering: Sludge and Polymer Characteristics

A study was performed to investigate the factors which impact polymer demand during conditioning such as biocolloid concentration, polymer characteristics and shear. The central hypothesis of the research was that biocolloids were directly related to polymer demand, and factors affecting biocolloid concentration and their charge neutralization would impact polymer demand. This is the first paper in the two-paper series which examines the role of biocolloids and polymer characteristics on polymer demand. Biocolloids are defined as small particles that are detached from the larger flocs, and are primarily protein and polysaccharide produced by microbes. In addition the role of polymer characteristics was investigated. The results showed a very good linear correlation (r2=0.83) between biocolloid concentration and the optimum polymer dose (OPD) measured for a number of different sludge types. The thermophilic sample had the greatest polymer demand, followed by mesophilic anaerobic, aerobically digested, and activated sludges. The polymer charge density and molecular weight also impacted the OPD. The greater charge density of the polymer resulted in increased polymer demand when the polymer demand is expressed on an equivalent charge basis, while higher molecular weight polymers had lower polymer demand. The results can be applied by practitioners to understand the factors which will affect polymer dosages and ultimately polymer costs.