Summary of various sludge dehydrators

 Usually sewage treatment plants use a two-step process of sludge concentration and sludge dehydration to reduce sludge volume and volume. For sludge with a moisture content greater than 98%, concentration should generally be considered to reduce the moisture content to about 96% to reduce the sludge volume and facilitate subsequent treatment. Sludge concentration mainly increases the solid content of the sludge through the gravity concentration tank. However, through the concentration tank, the volume is proportional to the concentration time, and the sludge is left to stand and concentrate for a long time, and the organic matter in it is easy to decay under the action of microorganisms. It smells bad and affects the sanitary environment of the sewage treatment plant. Therefore, generally after the moisture content is reduced to 94-96% through gravity concentration, a mechanical dehydration process with higher dehydration efficiency is needed to further process the sludge, so that the sludge loses its flow state and the moisture content is reduced to 80%. The following facilitates transportation during sludge disposal.

 

1. Belt filter press

The belt filter press dehydrates sludge by directly applying pressure or tension on the filter cloth. It consumes less power. It has the advantages of mature and reliable technology and relatively low investment and operation and maintenance costs, and has achieved a high market share. Rate.

 

The belt filter press can reduce the moisture content of the sludge to 75-90%. It has relatively high requirements for the flocculation effect of the incoming sludge. It needs to be adjusted and modified by adding medicine to increase the permeability of the material to achieve the sludge dehydration effect. Equipment operating status It is greatly affected by the moisture content of the incoming mud and dosing. Its operating noise is 70-75dB, and its power consumption is 0.8 W/m3. The equipment occupies a large area and has requirements for floor height. Since the equipment structure is open, water and gas leakage cannot be avoided, and the workshop working conditions are poor. The key to the successful development of the belt filter press process was the development of the filter belt, a result of the development of synthetic organic polymers. However, its filter cloth structure requires regular maintenance, which not only limits the equipment's ability to operate continuously, but also requires continuous consumption of high-pressure water for flushing during operation. Single side dehydration, small dehydration area. The polyester mesh material filter belt can only withstand a tension of 10 kg/cm, and the highest pressure is only equivalent to 1 kg/cm. It cannot withstand the accumulated deformation caused by the instantaneous high pressure, causing the filter belt to bulge until it breaks. The polyester mesh has large holes, so the amount of flocculant is larger, otherwise it will be filtered. During actual operation, there is a force shift in the filter belt caused by uneven feeding, causing horizontal and vertical mud running, thus affecting the dehydration effect. Therefore, the technical level of the operator is required, and the maintenance labor cost is high.

 

2. Centrifugal dehydrator

There are many types of centrifuges, and horizontal spiral discharge drum centrifuges are mainly used in sludge treatment. It is suitable for solid-liquid phase separation with a certain difference in specific gravity, especially for the dehydration of oily sludge, residual activated sludge and other difficult-to-dewater sludge. The principle of sludge centrifugal dehydration is to use rotation to separate solids and liquids in sludge (sludge conditioning and adding coagulant). The centrifuge is mainly composed of a conveyor and a screw conveyor with a hollow rotating shaft. After the sludge is sent into the drum through the hollow rotating shaft, it is immediately thrown into the drum cavity under the action of centrifugal force generated by high-speed rotation. The sludge particles are thrown onto the inner wall of the drum to form a solid layer; the water forms a liquid layer inside the solid layer. The sludge in the solid layer is slowly pushed by the screw conveyor and is transported to the conical end of the conveyor, and is continuously discharged through the outlet around the conveyor. The liquid overflows and is discharged outside the conveyor, and is collected and discharged from the dehydrator.

 

The moisture content of the sludge produced by the centrifugal dehydrator is 60%~75%, and the dosage of flocculant is small, which does not affect the subsequent sludge drying or incineration process. The power consumption per cubic meter of sludge dehydration is 1kW/m3. The noise is 85dB, and the centrifugal dehydrator takes up less space. The dehydration process is automatically and continuously controlled in a closed space, which can fully ensure the hygiene of the workshop and provide a good working environment for construction workers. During actual operation, there will be no clogging that affects the sludge dewatering efficiency, and there is no need to use high-pressure water guns for cleaning operations, so it has high work efficiency. Among the related components that make up the centrifugal dewatering machine, the maintenance cycle of the discharge screw pusher is more than 3 years. The high performance of the bearings and seals can ensure the high-intensity operation of the centrifugal dewatering machine. After regular and correct maintenance, it can be effectively extended The maintenance cycle of the centrifugal dehydrator is low, and the equipment failure rate is low. During the working process of the centrifugal dewatering machine, sludge is continuously input, and the dewatered cement cake is automatically discharged after efficient dehydration operation, requiring low manual maintenance.

3. Plate and frame filter press​

The moisture content of the mud produced by the high-pressure plate and frame filter press can reach less than 60%. Although the plate and frame filter press is generally operated intermittently, due to its high solid content in the filter cake, clear filtrate, and high solid material recovery rate, it is suitable for needs Transportation, further drying or incineration, and sanitary landfilling of sludge can reduce transportation costs, reduce fuel consumption, and reduce landfill space. Therefore, it is also widely used in some places. The disadvantage is that the pressure resistance of the polypropylene filter material filter plate is difficult to exceed 3MPA. When the deformation is large, the diaphragm has safety hazards. Low-quality diaphragms have hidden dangers of bursting under high pressure. The raised-point filter plate blocks the filtration channel under high pressure, affecting the dehydration effect. The plate and frame filter press cannot operate continuously, and the filter cloth consumes a lot of wearing parts. It requires more manpower and material resources to clean the filter cloth. In addition, the plate and frame filter press dehydrator itself is heavy and occupies an area Larger, so there are higher requirements for workshop floor height, and the hygienic environment of the workshop cannot be effectively guaranteed.

 

To sum up, sewage treatment plants should choose sludge dehydration equipment based on their actual conditions and usage requirements. The belt filter press can meet the requirements of sludge dehydration, with low project investment, and is a relatively economical sludge dehydration equipment; if subsequent disposal requires higher moisture content of dewatered sludge, a plate and frame filter press can be selected; The centrifugal dehydrator equipment is more expensive, but it has many advantages such as small floor space, convenient operation and maintenance, high degree of automation, clean and sanitary working environment, small separation effect affected by human factors, and low daily operating costs. Taking into account the operation and maintenance costs and Stability, it is recommended to be selected in sludge dewatering projects. The selection should be based on the actual situation. Our company provides tracking sewage and wastewater care equipment and can provide you with customized solutions. Welcome to purchase!