The grit tank is composed of an inlet, an outlet, a grit area, a sand hopper, a turbine drive device and a sand discharge system. The sewage flows tangentially from the inlet into the gritting area. A drop weir is installed in the water inlet channel to allow the sand that may be deposited at the bottom of the channel to slide downward into the gritting tank. A baffle is also provided to allow the water flow and sand to flow toward the bottom of the gritting tank when it enters the gritting tank, and to enhance the wall-coating effect. There is an adjustable speed paddle in the middle of the grit settling tank to keep the water in the tank circulating. The paddles, baffles and inlet water flow are combined together. The rotating turbine blades cause the sand particles to flow in a spiral shape, promoting the separation of organic matter and sand particles. Due to the different centrifugal forces, the relatively dense sand particles are thrown towards the wall of the pool and sink into the sand bucket under the action of gravity; while the lighter organic matter is separated from the sand in the middle part of the grit settling tank, and the organic matter is taken out of the pool with the vortex of the outlet water. By adjusting the rotation speed, the best sand settling effect can be achieved. The trapped sand in the sand hopper can be removed by air lifting, sand discharge pump, etc., and then through sand and water separation to achieve clean sand discharge standards.
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Advantages and disadvantages of cyclonic grit chamber
The cyclonic grit chamber (Zhong's and Bee's) has the characteristics of saving space, high sand removal efficiency, good operating environment, and reliable equipment operation. However, it has a strict application range for changes in water volume and requires higher operating effects of fine grids. The key equipment is foreign products and the price is very high, so it is too early for this pool type to be popularized in the country.
Its advantages and disadvantages are as follows:
advantage:
1. Strong ability to adapt to traffic changes;
2. The water head loss is small, the typical loss value is only 6mm;
3. The fine sand removal rate is high, and the 140 (0.104mm) mesh fine sand can also reach 73%;
4. High kinetic energy efficiency.
shortcoming:
1. Proprietary products and design technologies of foreign companies;
2. Fibrous objects will be wrapped around the stirring paddle;
3. It is difficult to pump out the sand in the sand hopper because it is compacted. High-pressure water pumps or air are often required to stir the sand. Air lift pumps often cannot effectively pump out the sand;
4. Although the pool itself occupies a small area, due to the requirement of tangential water inlet and long straight line of the inlet channel, when there are more than two pools, water distribution is difficult and the area is large.
