Since the particle size distribution of sludge is difficult to observe, and the fractal structure and the efficiency of flocculation are rarely considered in previous simulations, we established an improved aggregation model to simulate the mechanism of sludge particle aggregation and finally carried out three-dimensional simulation of flocculation-settling of sludge based on population balance model and two-phase flow mixture model. Results revealed that the established mathematical model and simulation method could well reflect the regularity of flocculation-settling of sludge. Furthermore, the particle size distribution range of floccules is widened with the decrease of fractal dimension, the number of large diameter floccules grows rapidly, and the number of small diameter floccules reduces gradually; the decay rate of initial particle number increases with the rising of fractal dimension, and the number of floccules generally increases and then decreases with time, but the maximum floccules number increases with the rising of fractal dimension, the occurence time of the maximum floccule number is shortened with the rising of fractal dimension.
Key words
improved aggregation model /
population balance model /
sludge flocculation /
settling /
particle size distribution /
fractal dimension /
numerical simulation
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References
[1]常 青,傅金镒,郦兆龙.絮凝原理[M].兰州:兰州大学出版社, 1992.
[2]杨铁笙,熊祥忠,詹秀玲,等.粘性细颗粒泥沙絮凝研究概述[J].水利水运工程学报,2003,6(2):65-77.
[3]FALCONER K J.The Geometry of Fractal Sets[M].Cambridge: Cambridge University Press, 1985.
[4]DU G L. Modeling Coagulation Kinetics Incorporating Fractal Theories: A Fractal Rectilinear Approach[J]. Water Research, 2000,34(7): 1987-2000.
[5]LOGAN B E, GROSSART H P, SIMON M. Direct Observation of Phytoplankton, TEP, and Aggregates on Polycarbonate Filters Using Brightfield Microscopy[J]. Journal of Plankton Research, 1994, 16(12): 1811-1815.
[6]JIANG Q, LOGAN B E. Fractal Dimension of Aggregates Determined from Steady-state Size Distributions[J]. Environmental Science and Technology,1991,25(12):2031-2038.
[7]赵 明.黏性细颗粒泥沙的絮凝及对河口生态的影响研究[D].北京:清华大学,2010.
[8]LUO H. Coalescence, Breakup and Liquid Circulation in Bubble Column Reactors[D]. Trondheim, Norway: Norwegian Institute of Technology, 1993.
[9]KRANENBURG C. The Fractal Structure of Cohesive Sediment Aggregates[J]. Estuarine, Coastal and Shelf Science, 1994,39(6):451-460.
[10]DE CLERCQ J, JACOBS F, DAVID J. Kinnear. Detailed Spatio-temporal Solids Concentration Profiling During Batch Settling of Activated Sludge Using a Radiotracer [J]. Water Research, 2005, 39(10): 2125-2135.
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