COMPRESSION AND CHANNELING IN GRAVITY SEDIMENTING SYSTEMS

In-situ solid concentration measurements and observations during the s edimentation of calcite, talc and aragonite suspensions showed that th e top of the channel region coincided with a solid concentration chara cteristic propagating from the base of the column. The solid concentra tion of this characteristic represented the first significant increase in concentration over that of the original suspension, and not a uniq ue characteristic value for each mineral. The region above the top of the channels diluted, and this increased the suspension/supernatant in terface velocity. Further rapid acceleration occurred when the top of the channels reached the interface, prior to the consolidation period when the interface slowed and compression resulted. Stirring the suspe nsions could completely suppress the channels and, under these conditi ons, the maximum sediment concentration was substantially increased. T he sedimentation velocity and, therefore, flux at the interface was gr eater in the presence of channels. However, for concentrations below t he interface stirring improved the batch sedimentation flux as well as the sediment concentration. Hence, the settling flux limiting value d uring continuous thickening may be improved by more rapid stirring tha n is currently employed.