Composition and Dewatering Properties of Biological Sludges

摘要

This study was designed to determine the role of biopolymer in sludge dewatering. Free biopolymer was measured as the high molecular weight fraction (excluded by Sephadex G-50 gell) in the supernatant liquor fraction. The study showed that as the fraction of high molecular weight material increased, sludge dewatering rates decreased. This suggested that the resistance to filtration of activated sludge is due to or influenced by the high molecular weight fraction. The supernatant biopolymer also varied with pH. As the pH increased over the natural sludge pH, biopolymer levels increased. Lowering the pH reduced biopolymers. This study indicates that biological floc contains large quantities of adsorbed biopolymer. Adsorption is pH sensitive, being strongest at pH levels near 3. Treatments which reduce biopolymer levels improve sludge dewatering and selective coagulation or precipitation of supernatant biopolymer appears to be the chief role of sludge conditioning agents.