| Along with the economy development and the advance of the people's living-standard, more and more wastewater has been produced and there are more and more wide use of phosphorous detergents but there are still very serious neglect of removing the nitric and phosphorous from wastewater. Eutrophication has become one of the most serious problems in water pollution because the higher the phosphorus-content is, the more difficult the wastewater to be dealt with. In this paper, the complex flocculation has been applied in the dealing of wastewater to make it be in accordance with the discharging standard.Chitosan is a kind of inartificial organic compound of macromolecule in nature, and its annual production in China is the second in the world. The advantages of chitosan can be listed as: abundance, high yield, with no poisonous side-effect, complete biological decomposition, powerful sorption adsorbing of metal-ions, dyeing-ions, halo'gen, protein, amoino-acid, clay grain and so on. And it is a powerful germicidal and germ-repressing compound, which makes it can be used as a multifunctional flocculent in the treatment of wastewater.The writer of this paper tried to enhance the capability of removing electionegative grain from the wastewater on the way of altering the natural structure of chitosan and using its chemical sorption effect. Furthermore, the study provides the method through which, the manufacturing of chitosan complex flocculation with the powdered coal ash to remove phosphorus from wastewater under the general pH-value range can be carried out. At the same time, we can integrate its powerful adsorbing capability with its capabilities of phosphate, COD and SS and metal-ion removing.The results of numerous experiments indicate, when we use chitosan(CTS") seperately, the effect of flocculation capability of phosphorus removal is lower at general acid condition (pH=7-8). If we complex the measurable Fe3+ and chitosan, and adjust the measurable acidity to promote the hydrolyzing of complex compound of Fe3+, we can make the acidity of Fe-CTS" lower than previous CTS", make the hydrolyzing weaker, and get the more stabile solution; what's more, we can achieve a better flocculating efficiency and enhancing removing double phosphorus in dealing with the wastewater. But if we compound Fe-CTS and FMa, we can enhance the flocculating capability of it, and increase the removal of phosphorus. In the end, this paper indicates that the capability of complexing flocculating phosphorus removal ability is the bestwhen the concentration ratio of the complex flocculent is: CTS:Fe:FM is 2:1:32 (in weight), it's efficiency is twice the CTS" and four times the Fe-CTS. The result is that we can meet the I wastewater discharge standard when the concentration of complex flocculent is 24.7ml/l, and we can meet the II discharge standard when the concentration of complex flocculent is 19.0ml/l. If there is a trace concentration of CuSO4 in the wastewater, we can reduce the dosage of complex flocculent by 10% and 20% to get the same result because the existence of the ion of SO42" and Cu2+ can promote the complexing and bridge-linking abilities of flocculent and can enhance the capability of the chitosan-complex-flocculation.
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