Compression Effects in Batch Settling Tests

by D. Christopher Dixon, Sr. Lect.; School of Chemical Engrg. and Industrial Chemistry, Univ. of New South Wales, Kensington, N.S.W. 2033, Australia,

Serial Information: Journal of the Environmental Engineering Division, 1982, Vol. 108, Issue 6, Pg. 1171-1191

Document Type: Journal Paper


The effect of compression resistance on terminal settling velocity results obtained from batch tests has been studied by means of dimensional and numerical analyses, and comparison with experiment. It is concluded that the Talmage and Fitch (single test) method is unreliable when compression effects are significant, because it only gives a satisfactory approximation when the terminal settling velocity - dilution relation is convex downwards, but whether this applies or not to the suspension under test cannot be determined from the tests. To determine whether compression effects are significant, repeat tests using different initial suspension heights are necessary, at least at the smallest dilution for which data are required. When significant effects are present, repeat tests (at each dilution) allow the corresponding terminal settling velocity and compressive stress values to be obtained from the intercept and slope of a plot of initial settling velocity versus reciprocal initial height (the Michaels and Bolger extension of the Coe and Clevenger testing procedure).

Subject Headings: Settling velocity | Dilution | Compression | Compression tests | Approximation methods | Load and resistance factor design | Numerical analysis | Comparative studies

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