The pH range applicable to aluminum sulfate is related to the hardness of raw water. When treating soft water, the suitable pH is 5 to 6.6. When treating hard water, the suitable pH is 6.6-7.2, and the high-hard water is treated. The suitable pH is 7.2-7.8. The water temperature range for aluminum sulfate is 20 ° C ~ 40 ° C. Aluminum sulfate is less corrosive, easy to use, and cost-effective.