Sludge Thickening and Dewatering

What is Sludge Thickening ?

Sludge thickening is a process of reducing sludge water content and thickening sludge by gravity or air flotation. Sludge concentration is an effective method to reduce sludge water content and sludge volume. Sludge concentration mainly reduces interstitial water of sludge. After concentration, the sludge is almost pasty and still keeps fluidity.

There are three kinds of sludge thickening processes: gravity concentration, mechanical concentration and air flotation concentration. Among them, gravity concentration for separating sludge by natural gravity is the most widely used and simple method.


LDHB provides you with the best sludge thickening equipment.

LDHB high-efficiency paste thickener is based on the traditional vertical flow sedimentation equipment. The structure of the internal feed cylinder is improved, and the efficiency of sedimentation is greatly improved. The plane of the tank body is circular and suspended. It settles into the conical sludge tank at the bottom of the tank under the action of gravity, and the clarified water is discharged from the overflow weir around the upper end of the tank. The overflow port is provided with a scum filter device and a baffle to ensure the effluent water quality, the underflow concentration is up to 70%, and the treatment capacity is 3-8 times higher than that of the conventional concentrator.

What is Sludge Dewatering ?

Sludge dewatering is a kind of sludge treatment method, which removes water from fluidized sludge and transforms it into semi-solid or solid sludge. After dewatering, the water content of sludge can be reduced to 55-80%, depending on the properties of sludge and sediment and the efficiency of dewatering equipment.

Mechanical dewatering is the most commonly used method of sludge dewatering. Usually, sludge is pretreated to improve dewatering performance before dewatering. The sludge is filtered with a filter layer, so that the leachate leaches into the filter layer, while the cake is intercepted on the filter layer. The commonly used sludge dewatering machinery and equipment are plate and frame filter press and belt filter.

Two types of filter press for sludge dewatering.


Ⅰ. Frame Filter Press

Frame filter press is to make water in sludge discharged through filter cloth through the extrusion of frame, so as to achieve the purpose of dewatering. When selecting equipment, the following aspects should be considered:

ⅰ. Requirements for solid content of mud cake. Comparing with other types of dewaterers, frame filter press have the highest solid content of mud cake, which can reach 35%. If considering the factors of reducing the area occupied by sludge stacking, frame filter press should be the preferred option.

ⅱ. Material of frame.

ⅲ. Material of filter plate and cloth. Corrosion resistance and tensile strength of filter cloth are required.

ⅳ. Moving mode of filter plate. Requirements can be completed automatically or semi-automatically by hydraulic-pneumatic device to reduce the labor intensity of operators.

ⅴ. The filter cloth oscillating device is used to make the cake easy to fall off.


Ⅱ. Belt Filter Press

Belt filter press is a new type of filter. The sludge layer is entrained by two tensioned filter belts. It passes through a series of rollers arranged regularly in the shape of S. The pressure and shear force on the sludge layer are formed by the tension of the filter belt itself. The capillary water in the sludge layer is squeezed out to obtain mud cake with high solid content to dewatering the sludge successfully.

Belt filter press developed by LDHB has less affect by the fluctuation of sludge load. It also has the characteristics of low water content of sludge, less stable start-up, relatively simple management and control, and low requirements for the quality of operators.

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