Sludge concentration is mainly aimed at interstitial water. After concentration, the sludge has a moisture content of over 90% and is in a flowing state. The volume is still large, so dehydration is necessary. The purpose of sludge dewatering is to separate the capillary and water in the sludge.
The main methods of sludge dewatering by sludge dewatering machines include natural drying, mechanical dewatering, and heat treatment. In the method of sludge dewatering, natural drying occupies a large area, has relatively poor hygiene conditions, and is easily affected by weather conditions. Compared with heating dehydration, mechanical extrusion has a relatively low energy consumption, with an energy of 20MPa equivalent to 70kJ/kg and a vaporization heat of 2200kJ/kg. Therefore, mechanical dehydration is widely used in sludge dewatering. The moisture content of the sludge after mechanical dehydration is 65%~80%, in the form of mud cakes.
Sludge dewatering can greatly reduce the accumulation site of sludge during landfill and save costs incurred during transportation; When composting sludge, sludge dehydration can ensure smooth composting (during the composting process, sludge is generally required to have a low moisture content); If sludge incineration is carried out, a high sludge dewatering rate can greatly reduce heat energy consumption.
However, the complex composition, small relative density, fine particles, and often colloidal state of sludge determine its difficulty in dehydration. Therefore, further improving the degree of sludge dehydration has become a hot research topic at home and abroad.
There are currently three widely used sludge dewatering machines - centrifugal dewatering machines.
The centrifugal dehydrator has strong adaptability to sludge flow fluctuations, good sealing performance, large processing capacity, and small footprint. Most newly built sewage treatment plants in China use centrifugal dewatering machines, belt filter dewatering machines, and plate and frame filter presses, while small sewage treatment plants generally use concentration and dehydration integrated machines.
