The quality control of pretreatment process should follow the following provisions: 1. According to the changes of water source, water quality and water temperature, the hydraulic retention time, water level, washing cycle, gas water ratio and biochemical hydraulic load should be controlled. 2. According to the raw water quality and effluent requirements, the dosage, dosing point, muffler manufacturer and mode of powdered activated carbon should be strictly controlled to meet the following requirements: 1) dosing point: the mutual offset and synergistic action of PAC and other chemicals should be considered, and the dosing point of PAC should be reasonably determined. Powdered activated carbon has a high selectivity for the adsorption of oxidants such as chlorine. Should the adsorption point of powdered activated carbon and the adsorption point of chlorine and other oxidants be fixed at a certain distance. The sampling point should be set to ensure sufficient adsorption time. 2、 Dosing mode: dust proof and explosion-proof measures must be taken. The principle of fast and uniform dispersion of powdered activated carbon in water was studied to reduce the agglomeration of powder and improve the utilization rate of powder. Wet feeding generally requires special equipment, which is prepared into slurry and mixed evenly before feeding.