Application of Horizontal Decanter Centrifuge in Wastewater Treatment

With the rapid development of industrial production and the concentration of population to the city, a large number of industrial wastewater and domestic wastewater are discharged to rivers, which exceeds the natural purification capacity. Environmental pollution has become a very prominent social problem, seriously threatening the life safety of the people. Therefore, wastewater treatment has attracted extensive attention.

Wastewater treatment is roughly divided into three stages. Stage one: natural settlement, removing the separated pollutants. Stage two: biological and chemical treatment, add biological bacteria or drugs to the wastewater, so that the harmful ingredients become harmless. Stage three: physical and chemical treatment, in-depth treatment based on the first two stages. After three-stage treatment, the water quality can meet the discharge and even drinking standards.

In the three-stage treatment, there are a large number of sediment - sludge in each stage. Some of these sludge can be recycled, some will pollute the environment. Its water content is generally more than 90%, which needs to be dehydrated to reduce the water content to about 60% - 80%, so as to be transported and utilized. For the sludge used to improve the soil, high temperature and biochemical treatment are also needed to prevent the spread of bacteria and viruses in the sludge, which will harm the growth of plants and animals. After high temperature and biochemical treatment, the sludge with more than 95% water content also needs to be dehydrated.

Sludge dewatering is an important part of wastewater treatment, which has great significance in economic value and prevention of environmental pollution. The traditional dehydration method is to use the drying field to dehydrate by natural evaporation and osmosis. This method needs a large area of land, high labor intensity, greatly affected by the weather, and unbearable odor emission. It is a very backward method. In the past, vacuum filtration, which is widely used in mechanical dehydration, has many advantages over drying field, but it still has many disadvantages, such as many auxiliary equipment, easily blocked filter net, low production capacity, odor leakage and difficult to seal. In recent years, a large number of experimental studies have shown that horizontal decanter centrifuge is an ideal device for sludge dewatering, which has the trend of replacing vacuum filter.

The horizontal decanter centrifuge consists of two high-speed rotating rotors. One rotor is a cylindrical cone-shaped drum without holes, the other is a conveyor with spiral blades, and there is a certain differential speed between the two. The drum is horizontally installed between the two bearings, one end is connected with the pulley to be driven by the motor, and the other end is connected with the gear differential to realize the differential speed between the drum and the screw conveyor.

The suspensions (with a certain concentration of mud water) are fed from the central pipe of the screw conveyor and injected into the drum space through the nozzle. Under the action of centrifuge, the sludge particles are deposited on the drum wall and discharged from the slag discharge hole of the small head of the drum by the conveyor with a certain differential speed. The liquid forms a certain liquid layer in the drum. When the liquid level exceeds the overflow hole on the large head of the drum, the clear liquid flows out of the overflow hole, therefore the solid and liquid phase in the suspensions are separated. The flow direction of the clarified liquid is opposite to the discharge direction of sediment, so it is also known as counter flow horizontal decanter centrifuge, which is currently used in many fields.

The horizontal decanter centrifuge has been used for sludge dewatering for more than 30 years. Compared with other sludge dewatering machines, it has many advantages:

1. Compact structure, small footprint.

2. Less ancillary equipment and lower equipment cost.

3. It can dehydrate under closed condition with less odor.

4. It is suitable for sludge dehydration with a large number of fine particles and a large change in solid phase concentration.

5. It can operate automatically and continuously for a long time without regular supervision.

6. As a sedimentation type machine, it is convenient for maintenance and does not need to clean or replace the filter cloth and screen.

Therefore, the centrifuge is widely used in food factory, beer factory, paper factory, electroplating factory, foundry factory, printing and dyeing factory, chemical factory and other industrial wastewater sludge dewatering and domestic wastewater treatment.