Effects of Cationic Polyacrylamide Characteristics on Sewage Sludge Dewatering and Moisture Evaporation

Abstract

The effects of the molecular weight (MW) and charge density (CD) of cationic polyacrylamide (CPAM) on sludge dewatering and moisture evaporation were investigated in this study. Results indicated that in sludge conditioning, the optimum dosages were 10, 6, 6, 4, and 4 mg g−1 CPAM with 5 million MW and 20% CD, 5 million MW and 40% CD, 3 million MW and 40% CD, 8 million MW and 40% CD, and 5 million MW and 60% CD, respectively. The optimum dosage of CPAM was negatively correlated with its CD or MW if the CD or MW of CPAM was above 20% or 5 million. In the centrifugal dewatering of sludge, the moisture content in the conditioned sludge gradually decreased with the extension of centrifugation time, and the economical centrifugal force was 400×g. The moisture evaporation rates of the conditioned sludge were closely related to sludge dewaterability, which was in turn significantly correlated either positively with the solid content of sludge particles that were >2 mm in size or negatively with that of particles measuring 1 mm to 2 mm in diameter. During treatment, sludge moisture content was reduced from 80% to 20% by evaporation, and the moisture evaporation rates were 1.35, 1.49, 1.62, and 2.24 times faster in the sludge conditioned using 4 mg g−1 CPAM with 5 million MW and 60% CD than in the sludge conditioned using 4 mg g−1 CPAM with 8 million MW and 40% CD, 6 mg g−1 CPAM with 5 million MW and 40% CD, 6 mg g−1 CPAM with 3 million MW and 40% CD, and 10 mg g−1 CPAM with 5 million MW and 20% CD, respectively. Hence, the CPAM with 5 million MW and 60% CD was ideal for sludge dewatering.

Effective sludge dewatering technique using the combination of Fenton's reagent and CPAM

“…Hereinto, the part of the dissolved organics was further oxidized to small molecular substances . The concentrations of protein and polysaccharide were used as an index to measure the degree of EPS degradation . The Fenton reaction system generated hydroxyl radicals (•OH) with the existence of H 2 O 2 and the catalysis of Fe 2+ under acidic conditions, and the amount of Fe 2+ and H 2 O 2 directly influenced the production of •OH .…”

“…[29] The concentrations of protein and polysaccharide were used as an index to measure the degree of EPS degradation. [30][31] The Fenton reaction system generated hydroxyl radicals (•OH) with the existence of H 2 O 2 and the catalysis of Fe 2þ under acidic conditions, and the amount of Fe 2þ and H 2 O 2 directly influenced the production of •OH. [32][33] The generation of hydroxyl radicals (•OH) was deficient under low H 2 O 2 concentration, which inhibited the effect of sludge dewatering.…”

Preparation, Characterization, and Sludge Conditioning of Cationic Polyacrylamide Synthesized by a Novel UVA-Initiated System

“…Zhu et al [4] determined that the best sludge dewatering performance is obtained by CPAM with the highest MW. Zhou et al [9] indicated that the optimum dosage of CPAM is negatively correlated with its MW if the MW of CPAM reaches above five million. Thus, studies focusing on the preparation technology of CPAM constantly optimize MW synthesis conditions [10,11].…”

Preparation, Characterization, and Sludge Conditioning of Cationic Polyacrylamide Synthesized by a Novel UV-Initiated System

“…Zhu et al determined that the best sludge dewatering performance is achieved by CPAM with the highest MW [4]. Zhou et al indicated that the optimum dosage of CPAM is negatively correlated with its MW if the MW of CPAM reaches above 5 million [9].…”