Polyaluminum chloride different doses of sediment produced Different polyaluminum chloride different doses caused by the formation of aluminum hydroxide precipitation in water is divided into four stages, namely the formation of 0.1,1,10,100 mgA1 / L. In the first stage, the dosage of <0.5mgA1 / L, from the curve A is the formation of dissolved aluminum compound state. The dosage of Ⅱ ~ 0.5 ~ mgA1 / L generated a small amount of colloidal aluminum hydroxide precipitation. The dosages of Ⅰ and Ⅱ were less than 1.0mgA1 / L, the treated filtrate did not see any change, but the turbidity of Ⅱ slightly increased (1.2NTU). Section III dosage increased to 1 ~ 10mgA1 / L, with the dosage increases, the water PH lower but still higher than 6, so completely generate aluminum hydroxide precipitate. At this point of treatment of filtered organic C reduced to 0.1mg / L, turbidity 0.2NTU, that is, to achieve good water coagulation effect. Ⅳ dosage of 10 ~ 25mgA1 / L, PH value of water dropped below 6, below the minimum solubility of aluminum hydroxide precipitate PH, generate a certain amount of dissolved aluminum compound state, the amount of filtered aluminum water increased. The positive charge of the precipitate tends to disperse, resulting in deteriorating treatment. The curves in the figure are plotted against the chemical equilibrium of the titration and do not correspond exactly to the slow dissolution of aluminum hydroxide. The above example is the analysis of the treatment of low-colored water, aluminum sulfate treatment is more emphasis on the role of aluminum hydroxide precipitate, which represents part of the PAA manufacturers point of view, you can participate in old comparisons.