Analysis of the basic process flow of coagulation and sedimentation treatment

2019-07-05

In the sewage treatment process, a chemical is added to the sewage to mix the sewage and the medicament, thereby causing coagulation or flocculation of the colloidal substance in the water. This comprehensive process is called a coagulation process.

The coagulation and sedimentation treatment process includes several parts of administration, mixing, reaction and precipitation separation:

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1. Drug delivery

The preparation and dosing method of coagulant can be divided into dry dosing and wet dosing.

1 dry method of adding dry method refers to the direct injection of the agent into the treated water. Dry labor is labor intensive, the dosage is difficult to control, and the requirements for mixing machinery are high. Currently, this method is rarely used in China.

2 Wet method Adding Wet method refers to first adding the agent into a certain concentration of solution and then putting it into the treated sewage. The wet feeding process is easy to control, and the uniformity of drug delivery is also good. It can be dosed by means of metering pumps, ejector, siphon quantitative dosing and the like.

2. Mixing

Mixing refers to the process of hydrolyzing and generating an iso-charged colloid that contacts the colloid and suspended matter in the water to form fine flocs.

The mixing process is completed in approximately 10 to 30 seconds. Mixing requires stirring power. The stirring power can be either hydraulic stirring or mechanical stirring. Hydraulic mixing is commonly used in pipeline type, perforated plate type, vortex mixing, etc. Mechanical type can adopt variable speed stirring and water pump mixing tank.

3. Reaction

When the mixing is completed in the mixing reaction equipment, fine flocs have been produced in the water, but the particle size of the natural sedimentation has not yet been reached. The task of the reaction equipment is to gradually flocculate the small flocs into large flocs to facilitate precipitation. The reaction equipment has a certain residence time and appropriate agitation strength, so that the small flocs can collide with each other and prevent the production of large flocs. However, if the strength of the agitator is too large, the flocs formed will be broken, and the flocs will be broken, and the larger the flocs, the more easily broken, so that the stirring strength in the reaction device is smaller and smaller along the water inflow direction.

4. Precipitation

After the wastewater is added, mixed, and reacted, the flocculation process is completed, and the sedimentation tank is entered to separate the mud water. The sedimentation tank can adopt various forms of results such as advection, radial flow, vertical flow, and sloping plate.

Problems that should be paid attention to during the operation of the dosing system

In order to ensure the effect of the vehicle, regardless of the type of coagulant or drug delivery equipment used, the following points should be observed when handling the dosing device.

Ensure that all equipment is in good condition and that there is sufficient medicine. The metering device of the dosing device is quantitatively corrected to ensure that the amount of the drug input meets the process requirements.

Ensure that the pharmacy meets the quality standards required by the process. Regularly check the original sewage water quality to ensure that the dosage is adapted to the water quality changes and water requirements.

It is necessary to record the concentration of the storage tank and the drug pool. Check the dosing line frequently to prevent the pipe from being blocked or broken, and to ensure the normal operation of the pumping system.

When there is a current interruption, the repair should be checked as soon as possible.


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