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Thick mud irrigation

Introduction of vertical flow sedimentation tank

Vertical sedimentation tank, also known as vertical sedimentation tank, is a sedimentation tank in which the wastewater in the tank flows vertically. The flat shape of the pool body is round or square. Water enters the pool from top to bottom through an inlet pipe located in the center of the pool (the flow rate in the pipe should be less than 30mm / s). An umbrella-shaped baffle is arranged below the pipe to uniformly distribute the waste water in the pool. The entire cross section of the backwater slowly rises (usually 0.5-0.7mm / s for domestic sewage, and the sedimentation time is 1-1.5h). The suspended matter settles into the conical sink at the bottom of the pond, and the clarified water flows from the periphery of the pond along the periphery. The overflow weir flows out. Baffles and scum tanks are set in front of the weir to trap scum to ensure the quality of the effluent. One side of the pond is provided with a drainage pipe (diameter greater than 200mm) by the wall of the pond, and the mud is regularly discharged by hydrostatic pressure. The advantages of the vertical flow sedimentation tank are the small floor area and the easy drainage of mud. The disadvantages are the large depth, difficult construction and high cost. It is often used in sewage treatment plants with water volume less than 20000m3 / d. Theoretical basis: In the vertical flow sedimentation tank, the direction of water flow is opposite to the direction of particle precipitation, and its retention speed is equal to the rising speed of the water flow. The particles whose rising speed is equal to the sedimentation speed will be suspended in the mixed liquid to form a suspension layer. Block and filter. Therefore, the efficiency of the vertical flow sedimentation tank is higher than the horizontal flow sedimentation tank.

2 working principle

The working principle of the vertical flow sedimentation tank: In the vertical flow sedimentation tank, the sewage flows vertically from top to bottom at a flow rate v. The suspended particles in the sewage have the following three movement states:
① When the particle sinking speed u> v, the particles will precipitate downward with the difference of uv and the particles will be removed;
② When u = v, the particles are in a random state, neither sinking nor rising;
③ When u <v, the particles will not settle down, but will be taken away by the rising water.
3 Construction
Structure of the vertical flow sedimentation tank: The vertical flow sedimentation tank can be circular, square or polygonal in plane. In order to make the water evenly distributed in the pond, the diameter of the pond should not be too large. Generally, 4 ~ 7m, not more than 10m is used. In order to reduce the total height of the pond, the sludge area can adopt multi-bucket dredging. The ratio of the diameter of the vertical flow sedimentation tank to the effective water depth is generally not greater than 3.

Features

1.Small footprint
2. Convenient drainage and simple operation management
Theoretical basis
In the vertical flow sedimentation tank, the direction of water flow is opposite to the direction of particle precipitation, and its retention speed is equal to the rising speed of the water flow. The particles whose rising speed is equal to the sedimentation speed will be suspended in the mixed liquid to form a suspension layer. filter. Therefore, the efficiency of the vertical flow sedimentation tank is higher than the horizontal flow sedimentation tank.