Study of sludge moisture distribution and dewatering characteristic after cationic polyacrylamide (C-PAM) conditioning

Abstract

Dewatering is a key step in sludge handling, and flocculant conditioning is the commonest way to improve the sludge dewatering. The sludge dewatering performance is largely affected by the sludge moisture distribution. But changes of sludge moisture distribution by flocculants were unclear and literature findings were controversial to each other. This paper investigated the changes of sludge moisture distribution and sludge dewatering characteristics after flocculant conditioning, and the flocculant used was cationic polyacrylamide (C-PAM). Results showed that C-PAM conditioning effectively changed the sludge moisture distribution, sludge viscosity, specific resistance of filtration (SRF), particle size, extracellular polymeric substances (EPS) concentration, and filtrate liquid viscosity. Especially, free water was increased by C-PAM conditioning and the highest value reached 95.04%. On the other hand, the interstitial water content was decreased by C-PAM conditioning. The optimal dosage was 3 mg g⁻¹ TS considering both effects and cost. After C-PAM conditioning, the mean sludge particle size increased to 219.1 μm, the sludge SRF reduced by 87%, and the supernatant EPS decreased. Specifically, the filtrate liquid viscosity could also determine the optimal dosage of C-PAM and an equation was proposed for the correlation between filtrate viscosity and C-PAM dosage.

Keywords:

• Sludge moisture distribution
• SRF
• Coagulation
• Extracellular polymeric substance

Acknowledgment

This research was funded by the National Natural Science Foundation of China (51178047, 51578068).

Notes

Presented at the 8th International Conference on Challenges in Environmental Science & Engineering (CESE-2015) 28 September–2 October 2015, Sydney, Australia