Analysis On Morphological Characteristics And Strength Of Humic Flocs For A Given Shear Rate

In resource water and waste water treatment system, the size, shape and structure of floc play an important role on contamination and removal. Whether floc with good structure can be formed has great influence on the following operation and the last water quality. Therefore, morphological characteristics and strength of the floc are very important factors in the process of liquid-solid separation .Using the microscopic and image analysis technique, the morphological character of floc in water was described in this paper. Morphological character of. Fe- humic flocs and Al- humic flocs were analyzed and compared at slightly acid (pH=5.0) and neutral (pH=7.0) condition, and the fractal shape characteristic of the humic flocculation was pointed out.Cementing power and the breakage stress under small flocculation were calculated by using increasing velocity gradient which resulted from Increasing velocity of flow, and weak change situation was shown directly by computer whose results came from output of photometric dispersion analyzer(PDA).Analysis computational method of floc strength was established combining with humic floc fractal nature. Morphology and strength characteristic of al-humic floc and Fe-humic floc under different conditions.were analyzed and compared.The results indicated that the shearing strength had very important influence on morphology of humic floc. Under a certain chemical condition, the breakage force of floc was proportional to the strength size and the velocity gradient change. The velocity gradient played a decisive role. The shearing strength of floc became high with the increase of velocity gradient Once floc was broken, its fractal dimension can be increased obviously, it showed that the structure of floc tended to compact.The cementing power and the breakage strength of Al floe and Fe-floc under the low-acid condition was than that of the neutral condition. Under the same chemical condition, the cementing power of Al- floe was smaller than that of Fe- floe.