Polyaluminum chloride can remove organic matter, suspended solids, heavy metals and other harmful substances in drinking water and sewage. However, if some indicators of polyaluminum chloride are not up to standard, there may be residual free aluminum ions after water treatment with polyaluminum chloride. If these aluminum ions enter the human body excessively, they can lead to histological bone softening and inhibit the synthesis of bone matrix; if they combine with phosphate, fluorine, selenium and other elements in the human body, they will cause the loss of human elements; in addition, aluminum can also combine with transferrin to interfere with the distribution and metabolism of iron in plasma, resulting in non iron deficiency anemia, so the quality of polyaluminum chloride is not up to standard not only the effect of water treatment may not be good, but also it will cause damage to human body. In addition, because aluminum hydroxide is amphoteric compound, it has flocculation effect. If the content of aluminum hydroxide is too high in the process of using the equipment, it is easy to deposit on the metal surface of iron and copper, forming galvanic cell reaction, causing local corrosion and damaging the equipment. Therefore, Gongyi filter material company suggests that when purchasing polyaluminum chloride, we must choose regular manufacturers and obtain the report of national recognized inspection units to ensure that the heavy metal content does not exceed the standard.