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International Journal of Environment Science and Technology
Center for Environment and Energy Research and Studies (CEERS)
ISSN: 1735-1472 EISSN: 1735-1472
Vol. 7, No. 1, 2010, pp. 37-46
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Bioline Code: st10005
Full paper language: English
Document type: Research Article
Document available free of charge
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International Journal of Environment Science and Technology, Vol. 7, No. 1, 2010, pp. 37-46
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Experimental and modeling investigation of sewage solids sedimentation based on particle size distribution and fractal dimension
Wu, J. & He, C.
Abstract
Sewage solids are usually characterized by non-specific parameters such as suspended solids. The
suspended solids has been shown to be an inadequate index for advanced water treatment processes. In this study, the
sewages solids particle size distribution was used to provide more detailed information on sewage characteristic. It is
hoped that, by introducing particle size distribution, the mechanism of sewage solids sedimentations can be better
understood. The particle size distribution of the domestic sewage was measured by the Malvern® laser scattering
technique to link to its settlement efficiency. Experimental results show that 77 % of particle volume was removed
during the 90 min settling, of which 71.2 % of particle volume was removed in the initial 30 min. The submicron
particles were found to be removed by co-settling with large particles. The fractal dimensions of sewage solids could
also be derived from the laser scattering measurement. The fractal dimension could also provide useful information on
the shape and density of sewage solids. A mathematical model considering the particle sizes, shapes and density changes
was then constructed to simulate the settlement of raw sewage particles. Comparison of the modeling results based on
discrete and flocculant settling theory shows that settlement can be better predicted by considering the fractal nature of
particles. The particle size distribution and fractal dimension data measured by Malvern® laser scattering technique
have been shown to be valuable data for in-depth understanding of the mechanisms of sewage solids sedimentation.
Keywords
Discrete settling; Flocculant settling; Laser scattering; Solids sedimentation mechanism; Suspended solids
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