The Characteristic Floc Growth in Coagulation and Flocculation Processes

The characteristic floc growth of Al-based coagulants was investigated in the aspect of mixing intensity and visualization of generated flocs during coagulation and flocculation processes. Zeta potential of turbid particles in the artificial water nearly approached to zero at pH 8-9, in which TDS and conductivity were minimized. The removal rate of turbidity and phosphate was maximized at the optimal mixing intensity of rapid and slow mixing stages. After the rapid mixing stage of coagulation process, small particles (3-5 mu m) were abruptly generated, and higher mixing intensity made more numbers of flocs. With the progress of slow mixing stage, the number of small particles were decreased with the simultaneous increase of intermediate particles (7-21 mu m). The number of large particles (>23 mu m) were maximized at the lowest rapid mixing intensity of 95.1 sec(-1), whereas small particles (<5 mu m) were maximized at the highest rapid mixing intensity of 760.7 sec(-1).