Summary
Flocculation and sedimentation of fine particles are investigated here with emphasis on the correlation of flocculation with adsorbed polymer’s conformation, CAT scan determination of flocculation properties, and theoretical modeling of sedimentation process.
The conformational behavior of polymers and the extent of polymer adsorption are considered critical in flocculation process. Last year, we initiated a study of correlation of polymer conformation with flocculation as measured by the supernatant clarity. This year, we monitor other flocculation properties (settling rate, percent solid settled, and sediment volume) in order to have a complete description of the flocculation behavior: Effects of polymer concentration on both the polymer conformation and the flocculation behavior are also studied. The amount of polymer adsorption is measured by analyzing the residual polymer in the supernatant using carbon analysis technique.
In the CAT scan work, a technique is developed to evaluate flocculation proper- ties from the solid-concentration profiles measured during sedimentation. This new technique is shown to be superior to the traditional methods for measuring flocculation properties. More importantly, the CAT scan provides, for the first time, a method for in-situ determination of effective floe-size distribution.
Computer simulation of sedimentation, based on our discrete model developed last year, is extended to 3D and nonlattice cases. The nonlattice model is shown to simulate sedimentation process more realistically than the original lattice model. 3D simulation generates essentially the same results as 2D simulation for simple sedimentation; its potential for simulating channeling caused by movement of coarser particles or water lenses in real systems is recognized.