DYNAMIC ANALYSIS OF COAGULATION WITH ALUM AND PACL

The coagulation kinetics of polyaluminum chloride (PACl) and alum appl ied to kaolin clay suspensions were compared in batch experiments. Inc reasing aluminium (Al) dosages reduced the time required for particles destabilization and increased the rate at which the number of primary particles decreased. PACl worked faster than alum. Photometric disper sion analysis showed that increasing Al dosages decreased the time req uired for floc to form. Again, this rate was faster with PACl than wit h alum. Increasing the Al dosage accelerated the flocculation rate bec ause it increased collision-attachment efficiency and increased partic ulate volume. The rates of particle destabilized primary particles, an d agglomeration varied with mixing intensity and water temperature. Al though lower temperature slowed the particle destabilization rate, sim ilar effects on the flocculation rate could be avoided by maintaining a constant G value. PACl was less sensitive to change in pH, implying that PACl performed better than alum in cold water.