Sludge treatment technology sharing: concentration and dehydration

 

The function of sludge concentration is to remove part of the water in the sludge through gravity or mechanical means and reduce the volume; the function of sludge dehydration is to mechanically separate part of the interstitial water in the sludge to further reduce the volume. The moisture content of concentrated sludge can generally reach 94% to 96%. The moisture content of dewatered sludge can generally reach about 80%.

 

The sludge concentration and dehydration process should be comprehensively determined based on factors such as the sewage treatment process used, sludge characteristics, subsequent treatment and disposal methods, environmental requirements, site area, investment and operating costs, etc.

 

Main types and characteristics of concentration processes

 

The methods of sludge concentration are mainly divided into gravity concentration, mechanical concentration and air flotation concentration. At present, gravity concentration and mechanical concentration are often used.

 

Gravity concentration consumes less electricity and has strong buffering capacity, but it occupies a large area, easily releases phosphorus, and has a strong odor, so it requires additional deodorization facilities. The sludge in the primary sedimentation tank is concentrated by gravity, and the moisture content can generally be reduced from 97% to 98% to less than 95%; the remaining sludge is generally not suitable for gravity concentration alone; the primary sludge is mixed with the remaining activated sludge and then gravity concentrated. The moisture content can be reduced from 96% to 98.5% to less than 95%.

 

Mechanical concentration mainly includes centrifugal concentration, belt concentration, drum concentration and screw pressure concentration. It has the characteristics of saving space and avoiding phosphorus release. Compared with gravity concentration, the power consumption is higher and polymer coagulants need to be added. Mechanical concentration can generally reduce the moisture content of the remaining sludge from 99.2% to 99.5% to 94% to 96%.

 

Main types and characteristics of dehydration processes

 

Mechanical dehydration mainly includes belt filter press dehydration, centrifugal dehydration and plate and frame filter press dehydration.

 

Belt dehydration has low noise and low power consumption, but it requires a large area and a large amount of flushing water, and the workshop environment is poor. The moisture content of the incoming mud for belt dehydration is generally required to be below 97.5%, and the moisture content of the outgoing mud can generally be below 82%.

 

Centrifugal dehydration occupies a small area, does not require flushing water, and has a good workshop environment, but it has high power consumption, high dosage of chemicals, and high noise. The moisture content of the incoming mud for centrifugal dehydration is generally 95% to 99.5%, and the moisture content of the outgoing mud can generally reach 75% to 80%.

 

The moisture content of the plate and frame filter press dewatered cement cake is low, but the floor space and flushing water volume are large, and the workshop environment is poor. The required moisture content of the incoming mud for plate and frame filter press dehydration is generally below 97%, and the moisture content of the outgoing mud can generally reach 65% to 75%.

 

Screw press dehydration and rolling dehydration occupy a small area, have less flushing water, low noise, and good workshop environment. However, they have small single machine capacity and high solid content in the supernatant. There are not many domestic application examples. The required moisture content of the incoming mud for screw press dehydration is generally 95% to 99.5%, and the moisture content of the outgoing mud can generally reach 75% to 80%.

​

The sludge concentration and dehydration process produces a large amount of odorous gas. The main sources are sludge storage tanks, thickening tanks, sludge dehydration machine rooms, and sludge storage sheds or silos. The odorous gas in the dehydration machine room is not easily emitted and is the key area for odor treatment during the sludge concentration and dehydration process.

 

Deodorization measures should be taken according to the requirements of environmental impact assessment. The newly built sewage plant should adopt sealing measures for the concentration tank, sludge storage tank, dehydration machine room, and sludge storage and transportation room. The air should be extracted through supplemental air and sent to the deodorization system for deodorization treatment, and the discharge should meet the standard; the reconstruction project for deodorization should be based on The structure should be covered or sealed, and exhaust pipes and deodorization systems should be added. Biological deodorization methods are generally used, and chemical deodorization methods can also be used when necessary.

 

When purchasing equipment, please look for our professional sewage sludge treatment equipment manufacturer.