The preparation and dosing methods of coagulants can be divided into two types: dry dosing and wet dosing.

① Dry dosing refers to the direct injection of chemicals into the treated water. Dry feeding has high labor intensity, and the dosage is difficult to control, requiring high requirements for mixing machinery and equipment. At present, this method is rarely used domestically.

② Wet addition refers to the process of first preparing a solution of a certain concentration of chemicals, and then adding them to the treated wastewater. The wet dosing process is easy to control and has good uniformity in dosing. Equipment such as metering pumps, water jets, and siphon quantitative dosing can be used for dosing.

Mixing refers to the process in which a chemical is added to wastewater and undergoes hydrolysis, resulting in the formation of differently charged colloids that come into contact with colloids and suspended solids in water, forming small flocs (commonly known as alum flowers).

The mixing process is completed within approximately 10-30 seconds. Mixing requires stirring power, which can be either hydraulic or mechanical. Hydraulic stirring commonly uses methods such as pipeline, perforated plate, and vortex mixing; Mechanical devices such as variable speed stirring and water pump mixing tanks can be used.

When the mixing is completed in the mixing reaction equipment, small flocs have already been generated in the water, but the particle size of natural sedimentation has not yet been reached. The task of the reaction equipment is to gradually coagulate the small flocs into large flocs for sedimentation. The reaction equipment has a certain residence time and appropriate stirring intensity, allowing small flocs to collide with each other and preventing the precipitation of large flocs produced. But if the strength of the agitator is too high, it will cause the generated flocs to break, and the flocs will break. The larger the flocs, the easier it is to break. Therefore, in the reaction equipment, the stirring strength along the direction of water flow decreases.

After dosing, mixing, and reaction, the wastewater completes the flocculation process and enters the sedimentation tank for mud water separation. The sedimentation tank can adopt various forms of results such as advection, radial flow, vertical flow, and inclined plate.

To ensure the effectiveness of the vehicle, regardless of the type of coagulant or dosing equipment used, attention should be paid to the following points when operating the dosing equipment.

Ensure the smooth operation of all equipment and sufficient supply of individual chemicals. Quantitatively calibrate the measuring device of the dosing equipment to ensure that the dosage of the medication meets the process requirements.

Ensure that the chemicals meet the quality standards required by the process. Regularly inspect the water quality of the raw sewage to ensure that the dosage adapts to changes in water quality and effluent requirements.

It is necessary to record the concentration of the storage tank and dosing tank clearly. Regularly inspect the dosing pipeline to prevent blockage or breakage, and ensure the normal operation of the pumping system.

When there is a disconnection phenomenon, it should be checked and repaired as soon as possible.

The addition of coagulants can be divided into two methods: dry and wet. The dry injection method is to directly inject solid chemicals that have been crushed and easily dissolved into the treated water. The advantage of this method is that it occupies less land, but requires higher particle size of the agent, making it difficult to control the dosage, requiring higher mechanical equipment, and having poor working conditions. Therefore, this method is now less commonly used. The commonly used method at present is wet dosing, which involves dissolving the agent and preparing it into a solution of a certain concentration before adding it to the treated water.