A novel application of dissolved ozone flotation on sewage sludge thickening: Performance and mechanism investigation

Sludge thickening in sewage treatment plants is an essential step to reduce the sewage sludge volume and provide space for collaborative anaerobic digestion of sludge and other urban organic wastes. Dissolved ozone flotation (DOF) is a novel choice worthy of application in the field of sludge thickening. In order to investigate the effect of DOF thickening, the total solid content (TS %) was used to characterize the thickening performance under different O-3 dosage. The optimal condition was determined to be polyacrylamide (PAM) dosage = 3 %o TS, air floatation time = 2 h and O-3 dosage = 12 mg/g TS, under which the TS % of raw-sewage sludge (RS) increased from 0.33 +/- 0.01 % to 8.03 +/- 0.06 %. In this study, the relationship between the sludge thickening performance, physicochemical properties, and the changes of organic matter (content, structure and molecular weight) in extracellular polymers (EPS) was systematically clarified. The results indicated that the DOF couple with PAM could change the sludge surface properties, destroy the sludge floc structure, release intracellular organic matter, and increase moisture fluidity. The surface hydrophilicity/hydrophobicity, protein (PN) secondary structure and moisture distribution were mainly responsible for sludge thickening performance. Moreover, the change of TS % during the DOF thickening process was mainly caused by the variations of the organic matter content in EMPS layer. The identification of key influencing factors was conducive to the further regulation and upgrading of the novel application for enhanced sludge thickening in sewage treatment plants.

Automated summary

This study investigated the thickening performance of sludge using dissolved ozone flotation (DOF). The results showed that DOF can change the surface properties of sludge, destroy the floc structure, release organic matter, and increase moisture fluidity. The key influencing factors were found to be surface properties, protein structure, and moisture distribution.