Abstract

Activated sludge dewatering is of great importance in sludge treatment and disposal. To enhance the dewaterability, a novel method was performed by treating the sludge under mild temperature (50-90 °C) in CaCl(2) solution (3.7-1110.0 mg/g dry sludge). The capillary suction time, zeta potential, Fourier-transformed infrared spectra, concentration of soluble protein and carbohydrates were employed to characterize the dewaterability and influencing mechanism. The sludge dewaterability was deteriorated with single thermal treatment, but significantly promoted in CaCl(2) solution and advanced further together with thermal treatment. An increasing CaCl(2) dosage reduced the surface charge remarkably, and a higher temperature could strengthen this impact. The spectra indicate that Ca(2+) could interact with the protein, phenols and O-H functional group in the flocs. The thermal treatment could cause the solubilization of protein and carbohydrates, providing more binding sites for Ca(2+) to establish a strong bridging among the flocs. As CaCl(2) dosage elevated, the soluble carbohydrates showed a reduction trend, while the soluble protein lowered firstly and then bounced back except that remained unchanged at room temperature. A bridging equilibrium is presumed to exist between Ca(2+) and the soluble protein. And the bridging between Ca(2+) and the soluble carbohydrates plays a more important role in the dewatering. The sludge dewaterability was successfully and economically improved by thermal treatment in CaCl(2) solution.

Links

Publisher Full Text

Authors

Guan B, Yu J, Fu H, Guo M, Xu X

Institution

Department of Environmental Engineering, Zhejiang University, Hangzhou 310058, China. guanbaohong@zju.edu.cn

Source

Water research 46:2 2012 Feb 1 pg 425-32

MeSH

Calcium Chloride
Carbohydrates
Flocculation
Hot Temperature
Proteins
Sewage
Solubility
Spectroscopy, Fourier Transform Infrared
Waste Disposal, Fluid

Pub Type(s)

Evaluation Studies
Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

22119238