Mechanism and Application Prospects of Sewage Sludge Conditioning with Fly-Ash

Abstract

The effects of fly-ash on dewatering of sewage sludge were studied according to sludge specific resistance (SSR), dehydrated speed, and moisture content of sludge cake as investigation indexes through single-factor experiments by contrasting to cationic polyacrylamide (PAM). The results showed that SSR kept decreasing with the rising of fly-ash dosage. When the dosage of fly-ash was 0.02 g/(ml sludge), SSR reduced by 65.2%. When the dosage of fly-ash was over 0.03 g/(ml sludge) adding with PAM, the dehydrated speed will be increased by three fourths. Through the analyses of Zeta potential, scanning electron microscope (SEM) observation, combined with the dehydration experiments, it was thought that the mechanism of fly-ash on dewatering of sewage sludge was that their particles evenly dispersed in sludge floc skeleton structure and thus decreased the SSR and improved the permeability of the sludge cake. The disposal of dewatering sludge and recycling approaches after fly-ash condition were also discussed. They can be used as landfill or as raw materials in building fields.