| The flocculation has a very important role in the process of water and wastewater treatment. The perfect degree in flocculation processes directly affect the treatment effect in the following treatment,such as sedimentation and filtration and so on. The theoretical basis about the flocculation researches rather more in foreign countries. But in the forepassed research,the people all abstracted the colloid in the water as the sphericity and explained it by the known theory of the colloid chemistry. Moreover some people modified the result by the grain coefficient. But this assume had more difference on the observed phenomena in the experiment,so it was not perfect in theoretical speaking.In this paper, we use the SCD and on-line TV-microscope to study the dynamic properties of Al-flocs, which were formed of kaolin and humic acid. Through a lot of experiments, we obtained the streaming current and fractal dimension of aluminum sulfate and PAC on different hydraulic condition or different dosage. The result shows: the fractal dimensions all distribute during 12-1.8 on different condition, and R2 of the data are bigger than 0.95. this suggested flocs are in accord with fractal character. Associating with streaming current, we found : aluminum sulfate mainly act with compressing double electric layer and charge neutralization, so the effect is affected by colloid potentials mostly; PAC coagulant act with bridge-work accompanying charge neutralization, and the effect is affected by morphology more.At the same time, we apply the particle counter in coagulation process. As it is shown that particle counter can display flocs distribution. The particle amount's variety in slow stirring evening reflects the turbidity of settled water. Moreover we introduce the fractal theory into particle distribution, and work out the fractal dimension of particle. We found that the fractal dimension of particle can also reflect the effect of flocculating very well. |
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