INFLUENCE OF PACL COAGULATION CONDITIONS ON ZETA POTENTIAL AND PARTICLE NUMBER OF MESO-PARTICLES

Abstract

 This study classified tiny-particles into three categories: meso-particles (20 nm-0.5 μm), sub micro-particles (0.5 μm-1.0 μm) and micro-particles (larger than 1.0 μm). We newly developed the optical microscope equipped with a violet laser and investigated zeta potential and particle number of meso-particles formed in various coagulation conditions. Generally, particles are neutralized at pH7 when using PACl as coagulant, but the meso-particles were found to be neutralized at around pH5. This indicates that under the general coagulation condition (i. e., pH7), meso-particles still remain with negative charge. The second-stage coagulation could not neutralize the remaining meso-particles but contributed to the decrease in their particle number. This gave us the suggestion that meso-particles would be removed by co-precipitation with the self-aggregated coagulant formed in high PACl dose condition.