Floc size distribution in a stirred suspension.
This paper focuses on the distribution of alumino-humic flocs found in a stirred suspension. Distributions were scaled using the transformation u = d/dL in which d is floc diameter and dL its arithmetic mean value and fitted by a gamma distribution. Flocs were treated as monofractal with solids mass concentration specified by C = A'rhos (d/do)D-3 in which A' is a packing coefficient, rhos the density of the floc solids, D the fractal dimension and do a reference size. It was shown that the overall solids concentration (M) complies with the dependence M proportional to NA'dDL-S(D) in which N is the number of flocs per unit volume and S(D) a distribution moment. Initial estimates of A' and D were obtained from analysis of floc sedimentation behaviour. From knowledge of the base parameters, the calculated value of M did not match the measured M and varied with shear. This was attributed to a kinematic influence on C over and beyond changes associated with the response of dL to shear. Issues of self-similarity were examined and it was concluded that distributions did not display strict self-similarity. Data are provided on the size distribution found in the flocculators of a treatment works at full scale.
Bache
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DH
Department of Civil Engineering, University of Strathclyde, Glasgow, UK.
Rasool
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D003627:Data Interpretation, Statistical; D005427:Flocculation; D006812:Humic Substances; D008956:Models, Chemical; D013535:Suspensions / Q000737:chemistry; D018508:Water Purification / Q000379:methods*
D006812:Humic Substances; D013535:Suspensions