Effects of thermal hydrolysis temperature on the physical properties of municipal sludge was further studied by a series of experiments. There was a decrease in bound water content with an increase in hydrolysis temperature, while there was an increase in pH at temperatures below 120 °C, and a decrease at temperatures exceeding 120 °C. An analysis of settleability, centrifugation and vacuum filtration of the treated sludge indicated that the threshold temperature was 120 °C, which was the same as the temperature for the bound water content and particle size. In addition, raw sludge with a solids content of 100 g/L, exhibited significant non-Newtonian fluid characteristics. At thermal hydrolysis temperatures exceeding 120 °C, non-Newtonian fluid characteristics including liquid and solid characteristics were significantly weakened. The consistency index (k) decreased from 5.90 Pa·s to 0.068 Pa·s, while the flow index (n) increased from 0.31 to 0.74, suggesting that thermal hydrolysis sludge was much closer to Newtonian fluids compared to raw sludge. Modification of bound water content, particle size and viscosity with hydrolysis temperature, revealed the nature of improved dewaterability by thermal hydrolysis. The fractal dimension of the sludge floc increased from 2.74 to 2.90, meaning that the floc became more compact after thermal hydrolysis.
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Research Article|
August 11 2015
Effects of thermal hydrolysis temperature on physical characteristics of municipal sludge
Guohong Feng;
Guohong Feng
1School of Environment & Safety, Taiyuan University of Science & Technology, Taiyuan, 030024, China
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Yabing Guo;
Yabing Guo
1School of Environment & Safety, Taiyuan University of Science & Technology, Taiyuan, 030024, China
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Wei Tan
2School of Chemical Engineering & Technology, Tianjin University, Tianjin, 300072, China
E-mail: wtan@tju.edu.cn
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Water Sci Technol (2015) 72 (11): 2018–2026.
Article history
Received:
April 18 2015
Accepted:
July 29 2015
Citation
Guohong Feng, Yabing Guo, Wei Tan; Effects of thermal hydrolysis temperature on physical characteristics of municipal sludge. Water Sci Technol 1 December 2015; 72 (11): 2018–2026. doi: https://doi.org/10.2166/wst.2015.425
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