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Russian Application of Membrane Filter Press in Seawater Desalination
Desalination is a technology that removes salt and impurities from seawater and converts it into fresh water. It is mainly used to alleviate the shortage of freshwater resources. This technology plays an important role in coastal arid areas, islands, and industrial water use.
Sludge is produced during the desalination process, mainly from the pretreatment stage (such as coagulation, flocculation, and sedimentation) and the suspended matter is carried during the discharge of concentrated brine. These sludges need to be dehydrated to reduce the volume, facilitate transportation and disposal, and meet environmental emission requirements. The application of a membrane filter press in desalination sludge treatment is critical. The following is a detailed introduction.
Characteristics of Desalination Sludge
High water content: The initial water content is usually 85%-95%.
High salt content: The sludge contains a large amount of dissolved salt and solid particles, which is corrosive.
Complex composition: Including inorganic particles (such as sand, soil), organic matter, chemical flocculant residues, etc.
Easy to scale and clog: The sludge particles are small and easy to clog pipes and filter cloths.
Importance of Desalination
97% of the water on the earth’s surface is seawater, and less than 1% is fresh water for direct use. Droughts and uneven rainfall caused by extreme weather have made freshwater resources more scarce. With the increase in population and the development of industrialization, the demand for freshwater continues to rise.
Desalination of seawater can provide drinking water for coastal cities and provide available water sources for arid areas. It can also provide industrial water to support high-water-consuming industries such as power generation and chemical industry.
Specific Applications in the Treatment Process
Pretreatment
Add flocculants (such as PAM, and PAC) to promote sludge flocculation.
Adjust pH and salt concentration to improve sludge dewatering performance.
Filter pressing stage
Preliminary filter pressing: Separate free water and part of bound water in sludge to form a preliminary filter cake.
Diaphragm pressing: The diaphragm plate is inflated (usually compressed air) to apply additional squeezing pressure to the mud cake to further remove bound water.
Post-treatment
Filtrate treatment: The filtrate contains dissolved salts, which can be recovered as freshwater or safely discharged through reverse osmosis or evaporation concentration processes.
Mud cake disposal: High-salt filter cakes can be landfilled or incinerated, and some areas try to use mud cakes as building material additives.
Advantages of Diaphragm Filter Press in Desalination Sludge Treatment
Significant dehydration effect
The diaphragm pressing stage can reduce the sludge moisture content to 30%-60%, which is more efficient than ordinary filter press.
Secondary extrusion is particularly suitable for treating fine particles and high water content components in desalination sludge.
Excellent corrosion resistance
The filter plate can be made of polypropylene filter plate or stainless steel material, which can effectively resist corrosion in high-salt environment.
The filter cloth can also be made of special materials, which are acid and alkali-resistant and anti-clogging, extending the service life of the equipment.
Save operating costs
Due to the low moisture content of the filter cake, the sludge volume is greatly reduced, reducing transportation and final disposal costs.
No additional flocculant is required in the secondary pressing stage, further reducing the cost of chemical agents.
Conclusion
The application of membrane filter press in desalination sludge treatment has become an ideal choice for treating high-salinity sludge due to its high-efficiency dehydration, corrosion resistance, and automation advantages. By optimizing operating parameters and material selection, the operating cost can be significantly reduced, and environmental emission requirements can be met, providing strong support for the sustainable development of the desalination industry.
