Agglomerate Size Changes in Coagulation

by Robert K. Ham,
Russell F. Christman,

Serial Information: Journal of the Sanitary Engineering Division, 1969, Vol. 95, Issue 3, Pg. 481-502

Document Type: Journal Paper


A concentric cylinder apparatus utilizing an electronic particle size analyzer was used to study the coagulation of finely divided silica particles by alum and FeCl3 and the coagulation of natural color in water by alum. The unit was capable of indicating the agglomerate size distribution directly, from which information on the rate and extent of coagulation and on the strength and settling characteristics of the floc could be determined. Study variables included pH, coagulant dose, silica or color concentration, mixing rate, and the method of coagulant addition. The experimental results were used to formulate a theory of coagulation for the alum-silica system in which coagulation is thought to involve chemical interaction between the silica surface and Al(OH)3 precipitate to form small agglomerates called unit flocs. Further coagulation, according to the theory, would require chemical interaction between unit flocs, and is based largely on the collision dynamics of the system.

Subject Headings: Coagulation | Silica | Particle size distribution | Cylinders | Equipment and machinery | pH | Water management | Dynamic analysis

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