What is the principle of sewage treatment in sedimentation tank?

What is the principle of its sedimentation tank in sewage treatment tank?

1. The principle of sedimentation tank is that when the downward sedimentation speed of water flow is greater than the downward velocity of water flow, or when the downward sedimentation time is less than the time when water flows out of sedimentation tank, suspended impurity particles in water flow can be separated from water flow.

2. The treatment structure for removing suspended particles with density greater than water by gravity sedimentation is one of the most widely used treatment units in wastewater treatment, which can be used for wastewater treatment, post-treatment and advanced treatment of biological treatment.

Opening mode of sewage sedimentation tank

1. grit chamber

The pretreatment device in sewage treatment is a pretreatment unit used to remove inorganic particles that are easy to settle in water and separate sand particles from water by physical methods.

Its function is to separate particles with relative density greater than 1.5 and particle size greater than 0.2 mm from water, mainly including inorganic sand, gravel and a small amount of organic particles with high density such as grains and seeds.

Grit chamber is generally set in front of lifting equipment and treatment equipment to protect pumps and pipelines from abrasion, prevent subsequent water structures from clogging and reduce the volume of sludge treatment structures, and at the same time reduce inorganic components in activated sludge and improve the activity of activated sludge.

2. Primary sedimentation tank

In the process of primary sewage treatment, suspended solids in water can be removed economically and effectively, and some suspended organic matter can also be removed to reduce the organic load of subsequent biological treatment structures. Sometimes the primary sedimentation tank is also used alone, and the water is discharged after primary treatment, which is generally set behind the grit chamber of the sewage treatment plant and before the aeration tank.

When the primary sedimentation tank is used to treat municipal sewage, the sedimentation time is generally 1.5-2h, the removal rate of influent BOD5 can reach 20%-30%, and the removal rate of suspended solids SS can reach more than 50%.

3. Secondary sedimentation tank

The secondary sedimentation tank is arranged behind the aeration tank and before advanced treatment or discharge, and includes five parts: water inlet area, sedimentation area, buffer area, sludge area and water outlet area.

Generally, if ammonia nitrogen, cod and other indicators exceed the standard, chemicals need to be added to meet the standard, and the dosing position of chemicals is behind this sedimentation tank.

4. The concentration of particles in the sewage pool of sludge concentration tank is high, which interferes with each other and stratifies. The concentration of suspended particles is high, and the particles support each other. The water between the lower particles is squeezed out under the gravity of the upper particles, and the sludge is concentrated.

There is an obvious interface between particles and water masses, but the water masses are dense and the interface settlement speed is very slow.