Effect of Calcium Ions on Dewaterability of Enzymatic-Enhanced Anaerobic Digestion Sludge

Abstract

Waste-activated sludge (WAS) solubilized remarkably after enzymatic-enhanced anaerobic digestion, but its dewaterability was deteriorated. In this study, a novel method was performed to improve the dewaterability of enzymatic-enhanced anaerobic digestion sludge by adding CaCl2 (0.01~1.00 g/g total sludge). The capillary suction time (CST), moisture content, and filtrate turbidity were employed to characterize the dewaterability of WAS, and the possible mechanisms involved were clarified. The results showed the dewaterability did not worsen when CaCl2 was added before sludge digestion, and the CST, moisture content, and filtrate turbidity were notably reduced with the increase of CaCl2 dosage. It also shown that calcium ions played an important role in the bioflocculation of digested sludge by neutralizing negative charges on the surface of sludge. In addition, soluble protein initially lowered a little and then observably improved with the addition of CaCl2, while soluble carbohydrate was reduced sharply first and then bounced back afterwards. The interactions between calcium ions and the biopolymer further enhanced the dewatering of sludge through bridging of colloidal particles together.

Feasibility and Mechanism of Combined Conditioning with Coagulant and Flocculant To Enhance Sludge Dewatering

“…Then the B-EPSs in the sludge were extracted by a heat extraction method , and analyzed according to Liu et al Both S-EPSs and B-EPSs were analyzed in terms of polysaccharide and protein contents. The polysaccharide and protein contents were determined by the anthrone–sulfuric acid and Lowry–Folin methods, respectively. , The ζ potential of the sludge was analyzed by a Zetasizer 2000 (Malvern Instruments Ltd., England) on the basis of previous studies . The compressibility coefficient was measured according to the methods proposed by Qi et al The microstructure was characterized with environmental scanning electron microscopy (Quanta 200, FEI Ltd., The Netherlands).…”

“…27,28 The ζ potential of the sludge was analyzed by a Zetasizer 2000 (Malvern Instruments Ltd., England) on the basis of previous studies. 29 The compressibility coefficient was measured according to the methods proposed by Qi et al 30 The microstructure was characterized with environmental scanning electron microscopy (Quanta 200, FEI Ltd., The Netherlands).…”

Applying rheological analysis to understand the mechanism of polyacrylamide (PAM) conditioning for sewage sludge dewatering

“…The supernatant was analyzed for zeta potential by a Nanosizer ZS instrument (Malvern Co., UK) at 25 C based on the previous studies. 24,25 The pH of the solution was determined by a pH meter (pHS-3C, LeiChi, China). The above measurements were determined at least six independent times and conducted at 25.0 AE 0.1 C.…”