Date of Award
Doctor of Philosophy
Civil, Construction, and Environmental Engineering
J. L. Cleasby
This research is intended to give the water treatment industry a better understanding of how the coagulation/flocculation process can be optimized for treatment of cold waters. The following work was performed during this study: (1) Two particle/floc measuring techniques were evaluated; The HIAC particle counter, and fully automated image analysis. (2) An investigation of the effect of reactor geometry, mixing intensity, and pH on flocculation efficiency in a batch reactor at high (20°C) and low (5°C) temperature;The testing performed on the floc measuring systems has established that the HIAC automatic particle counting system has some severe limitations, and under certain conditions the HIAC causes severe floc breakup;The flocculation tests were performed using two impeller geometries; the turbine and the stake and stator. The primary particles were kaolinite and they were flocculated using alum, ferric sulfate, or a cationic polymer (MagniFloc 573C). The flocculation was carried out in the adsorption/destabilization region. The following conclusions are drawn: (1) Temperature and geometry both have a significant impact on the kinetics of primary particle removal, the structure of the floc formed, and the strength of the floc formed. (2) The primary particle removal efficiency of the turbine geometry is less effected by temperature than the efficiency of the stake and stator geometry. This difference is related to the structure of the turbulent flow field produced by the two impellers. (3) When using metal salts as the primary coagulant it is appropriate to hold the system pOH constant, rather than the system pH, as the temperature changes. (4) The particle removal characteristics of the polymer and metal salts were radically different, with the salts performing better than the polymer in sweeping up the primary particles. The polymer produced larger, stronger floc, but left more primary particles.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Adrian T. Hanson
Hanson, Adrian T., "The effect of water temperature and reactor geometry on turbulent flocculation " (1989). Retrospective Theses and Dissertations. 9129.