How to Use a Sludge Filter Press

The moisture in urban sludge can be classified into four types: free water, capillary water, surface-adsorbed water, and internal water.

Free water is unaffected by sludge particles and accounts for about 70% of the total water content. It is the main target of mechanical sludge dewatering.

Capillary water exists in the capillary spaces between sludge particles and accounts for about 20%. It is an important dewatering target for filter press machines.

Surface-adsorbed water adheres to particle surfaces or cell exteriors, while internal water is trapped within sludge particles, including intracellular water.

Challenges in Sludge Dewatering

Traditional dewatering equipment can only reduce sludge moisture to around 80%, at which point the sludge remains in a fluid-like state with extremely poor mechanical properties. Its compressive strength is below 20 kPa, making it difficult to handle.

When the moisture content is between 60% and 65%, the sludge enters a gel-like phase where water molecules are encapsulated by a colloidal layer. This phase, known as the "sludge gel phase region," is the most challenging stage for dewatering.

Sludge with a moisture content below 60% becomes solid and does not produce leachate, making it suitable for direct landfill disposal. Breaking through the sludge gel phase improves its dispersibility, laying the foundation for harmless disposal and resource recovery. Therefore, the sludge filter press is recommended for achieving effective dewatering.

Benefits of Reducing Sludge Moisture Below 60%

If the moisture content is reduced to 60%, composting treatment can halve the fermentation cycle, improving economic benefits.

Dried sludge cakes can be processed into solid fuel, which can then be burned for energy recovery or used as an additive in brick or cement production.

Sludge volume can be reduced by over 50%, improving sludge reduction efficiency while lowering transportation difficulty and costs.