Coagulation process in drinking water treatment is mainly to remove organic matter and suspended particles in water. There are many factors affecting the coagulation effect, mainly including: the matching degree between the selection of coagulant type and the nature of raw water, the dosage of coagulant, the water quality and pH value of raw water, the compound use and dosing sequence of coagulant aids, etc. Enhanced coagulation technology is mainly through taking certain measures to determine the best coagulation conditions to achieve good coagulation effect, that is, to remove turbidity, odor, algae, organic pollutants and chlorine.

The common methods to enhance the coagulation effect are as follows:

1. First of all, the types of coagulants should be determined according to the water quality. At present, there are three kinds of coagulants commonly used in drinking water purification process: aluminum salt, iron salt and synthetic organic polymer coagulants.The common ones are polyaluminum chloride and polyferric sulfate. In theory, the coagulation effect of aluminum salt and iron salt is better than that of synthetic organic polymer coagulant, and the coagulation effect of iron salt is better than that of aluminum salt. But in the actual production and application, different water quality and on-site process are different, so the coagulants that need to be selected can not be generalized, and the types of coagulants need to be determined after on-site small-scale test.

2. Determine the dosage of coagulant. Although the coagulation effect of various coagulants is different, there is an optimal dosage for the determined water quality under the condition of a certain pH value of raw water. Therefore, the coagulant should be selected according to the specific water quality, and the optimal dosage should be determined by using the relationship between the dosage of coagulant and the utilization efficiency. It is suggested to select a small range as small as possible after on-site small-scale test, and then carry out large-scale test on the computer.

3. Adjust the pH of water. The pH of water has a significant effect on the removal of organic matter. Generally, when there are more organic matter, the pH of 5-6 is conducive to the formation of humic acid polymer.

4. Add coagulant aid. Adding a certain amount of coagulant aids can enhance the coagulation effect of coagulant, and the commonly used coagulant aids are polyacrylamide,

5. Improve the mixing and flocculation facilities, and improve the water conditions, so that the coagulant can give full play to its role.