Polyaluminum chloride chemical principles sometimes need to be used in the treatment of sewage coagulant and flocculant used in combination will achieve satisfactory results. Then the organic polymer flocculant polyacrylamide is the leading disadvantage of its disadvantages are high prices, and inorganic polymer coagulants in the high efficiency of polyaluminium chloride is the best water treatment agent, which not only can handle a variety of concentrations of sewage, but also with The amount of high efficient PAC is 50% less than the same concentration of ferrous sulfate and 10% less than the same concentration of PAC, so the high efficiency and low dosage are the highlights of high efficiency PAC . Because the general iron salt, aluminum salt water treatment agent in the hydrolysis process can only generate AL (OH) 2 +, Fe (OH) 2+, and other simple hydrolysis of hydroxyl ions, and high efficiency PAC itself is AL3 +, Fe3 + In addition to the above-mentioned hydroxyl ions, it can mainly generate a large amount of polyhydroxyl cation such as AL4 (OH) 4 +8 and Fe4 (OH) 4 + , To neutralize colloidal particles in the water charges and compress the electric double layer, at the same time hydroxyl bridging, crosslinking, surface adsorption and other series of reactions, in the corresponding collision, condensed into large alum, in order to play the role of rapid precipitation.