Study On Fractal Structure Of Alum Floc And Removal Characteristics In Flotation

In the treatment process of domestic water and waste water, coagulation process (mixing,agglomeration,flocculation) is the most popular unit operation, used as pre-process of precipitation,flotation ,filteration and so on.the effect of flocculation decides the condition of operation, the quality of effulent and the cost. It is important research branch in the treatment of water and waste water, and flocculant is the key in application of flocculation technology. Polyaluminum chloride is one of the mature and popular inorganic polymer flocculants, so the deep study on the coagulation process have significance.The humic acid and the kaolin are removal object in this paper. Image analysis and a novel ES dissolved air flotation reactor(ES-DAF) are used in the study on fractal structure of alum floe and removal characteristics by flotation. The results of the experiment show that in varies conditions the fractal dimention of floe is between one and two. The correlation of the experiment data is good, which illustrates fractal characteristic of floe. When sweep flocculation acts as the main mechanism, floe tend to forming branch structure and have lower fractal dimention. The distributions of Elongation ratio show that the majority of the particles, approximately 80%, possessed ratios in the range between 1.2 and 2.5, which proves the irregular shape of floe. The fractal dimention of floe in Lake contrasting with man-made waste water's, are lower. The value is from 1.0314 to 1.4600. The type of pollutants, pH, form of PAC and coagulation mechanism have important influence on the density, regulation and fractal dimention of floe. The floccution of removal the humic acid and the kaolin by ES-DAF has better removal effect than the removal organic or clay respectively. But the quantity of flocculants is more. The industry PAC has high turbidity and organic removal. The removal efficiency is about 70% higher than the PAC made in lab, and is affected little. Contrast to coagulation precipitation, flotation exhibit the different phenomenon because of the size of bubble and Zeta potentials. At the same time, the type of pollutants, pH, form of PAC and coagulation mechanism have important influence on the removal characteristics in flotation..