A study on the deep dewatering of urban dewatered-sewage sludge by aluminum chloride

Abstract

Due to its composition and biological nature, dewatered sludge (water content was 80%) is usually highly compressible and known to be difficult to dewater. In this paper, deep dewatering of urban dewatered-sewage sludge (DD-UDSS) using different dosages of inorganic flocculant AlCl₃ was investigated. Dewaterability of the DD-UDSS was determined in a series of sludge dewatering tests. Their physicochemical characteristics were evaluated in terms of thermogravimetry, zeta potential, transmission electron microscope, and particle size analysis. Results revealed that the moisture content (MC) of DD-UDSS was decreased, at the same time the positive electricity on surface of DD-UDSS gradually increased with the increase in AlCl₃ dosage. The minimum MC was observed at 54.03% (8 g AlCl₃/300 g UDSS), which was relatively low as compared with the urban dewatered-sewage sludge (UDSS) of 81.2%. Additionally, the structure of the microstructure as well as the particle size was also changed by the addition of AlCl₃. These results suggested that with the addition of AlCl_3, the physicochemical characteristics of the DD-UDSS were improved; thus, its dewaterability was improved.

Keywords:

• Sludge
• Dewatering
• AlCL₃
• TG
• Zeta potential
• Particle size
• TEM

Acknowledgments

This research was supported by the National Science and Technology Support (2011BAC02B04) of China and the Natural Science Foundation of Shandong Province, China.