Application of industrial filter cloth in belt press filter for pile foundation sludge treatment 

Against the backdrop of accelerating urbanization and continuous infrastructure development, ground improvement and pile foundation engineering have become standard practice in urban construction. During these processes, large amounts of slurry and waste mud are discharged, forming a special type of engineering sludge —— Pile foundation sludge. This type of sludge has fine particles, high water content, and complex composition. If not handled properly, it can easily have an adverse impact on the construction environment, urban drainage systems, and even the ecological environment. 

In order to achieve effective dewatering and resource utilization of pile foundation sludge, more and more engineering projects use belt press filter, a highly efficient solid-liquid separation equipment. During the operation of this equipment, the performance of the industrial filter cloth directly determines the efficiency of sludge dewatering, the dryness of the filter cake, the cleanliness of the filtrate, and the operating cost of the entire machine. Therefore, the research and application of high-performance industrial filter cloth suitable for pile foundation sludge treatment has become a focus of industry attention. 

I. Characteristics and Treatment Difficulties of Pile Foundation Sludge 

Pile foundation sludge mainly comes from underground continuous walls, rotary drilling piles, cast-in-place piles and other geotechnical engineering projects. Its components usually include bentonite, sand, cement residue, groundwater, and admixtures. This type of sludge has the following significant characteristics: 

• High water content ：The initial water content is generally as high as 75%-85% ，the slurry is stable and does not easily settle naturally; 
• Small particle size, high viscosity ：The mud is fine, highly dispersive, and contains a large amount of colloidal components; 
• Large fluctuation in organic content ：There are many construction admixture residues, which cause the sludge to become less dewaterable; 
• Easy to clog, difficult to press ：In filtering equipment, it is very easy to cause filter cloth clogging, turbid filtrate, and difficulty in forming filter cakes. 

Traditional sedimentation tanks and thickeners cannot meet the needs of fast and efficient treatment, while plate and frame filter presses, although having high dryness, have poor continuity and require much manual intervention. In comparison, belt press filter, with its automation, continuity, high throughput, and low energy consumption, is gradually becoming dominant in pile foundation sludge treatment. 

II. Working Principle and Advantages of Belt Press Filter 

Belt press filter uses multi-stage continuous action to gradually press and dewater the high-water-content sludge to finally form a filter cake. Its typical workflow includes: 

1. Gravity dewatering zone ：Sludge is transported on the filter cloth and drains freely under its own weight; 
2. Wedge pre-pressing zone ：The upper and lower filter cloths gradually converge, and slight pressure promotes further dewatering; 
3. Pressing and dewatering zone ：Multiple rollers form a “S” shaped path to strongly press and squeeze the sludge, increasing the dryness. 

Compared with other dewatering equipment, the significant advantages of belt press filter are: 

• Strong continuous operation capability ，suitable for large-scale processing tasks; 
• Low energy consumption, stable operation ，adaptable to the power supply and operating environment of the construction site; 
• High dewatering efficiency ，the water content can be reduced to 60% or so; 
• Clear filtrate recovery ，easy for recycling or discharge that meets standards. 

However, its performance is highly dependent on the quality and adaptability of the filter cloth. 

III. The Key Role of Industrial Filter Cloth in Pile Foundation Sludge Dewatering 

In belt press filter, the filter cloth is equivalent to the “ heart ” ”, it undertakes the direct task of solid-liquid separation, and its performance is related to the overall efficiency of the equipment and the sludge dewatering effect. For the particularity of pile foundation sludge, the matching filter cloth needs to have the following performance: 

1.  High permeability and excellent retention performance 

A good filter cloth should ensure sufficient permeability without sacrificing filtration accuracy, preventing slurry backflow or unstable equipment operation due to poor filtrate discharge. Considering the characteristics of pile foundation sludge with many fine particles and colloids, double-layer woven structure, modified monofilament filter cloth, etc., can effectively intercept fine particles and ensure clear filtrate. 

2.  Anti-clogging and easy cleaning ability 

Fine particles in pile foundation sludge are easy to deposit in the pores of the filter cloth, causing clogging and frequent “ filter cloth blinding ” phenomenon. High-strength monofilament fiber structure combined with hydrophobic surface treatment technology can effectively reduce filter cake adhesion, increase the filter cloth cleaning cycle, and reduce the cleaning frequency. 

3.  Wear resistance and tensile strength 

The belt pressing process involves repeated squeezing and stretching actions, which puts high demands on the mechanical strength of the filter cloth. Using high-tenacity polyester monofilaments or enhanced synthetic fiber materials, and using thickened edging and hot-melt sealing technology at the edges, can significantly extend the service life of the filter cloth. 

4.  Customizable processing to adapt to complex working conditions 

The structure of the filter cloth (such as mesh size, air permeability), size specifications, interface shape, tensile strength, etc., can be customized according to the actual engineering needs to ensure precise matching with the belt press filter and achieve optimal performance. 

IV. Shadiya Si (Xiamen Citius) Application Cases of Industrial Filter Cloth 

Xiamen Citius (Xiamen Citius) As a technological leader in the filtration materials industry, Xiamen Citius Filtration Materials Technology Co., Ltd. has long been committed to application innovation of industrial filter cloth in solid-liquid separation, especially accumulating rich practical experience in the sub-scenario of pile foundation sludge treatment. 

In a large-scale municipal rail transit project in South China, the contractor used a belt press filter to dewater pile foundation sludge. Initially, they faced problems such as easy filter cloth blockage, unformed filter cake, and turbid filtrate. After using Citius’s (Xiamen Citius) modified monofilament filter cloth designed for high-viscosity sludge, the equipment operating status was significantly improved: 

• The filter cloth service life was extended to 90 days or more; 
• The moisture content of the filter cake was reduced to 58%-62% and could be directly shipped; 
• The filtrate was clear and transparent, meeting the reuse standards; 
• The cost of sludge treatment per ton decreased by about 12%。

In addition, the company can provide customized suggestions and sample testing services for filter cloths based on different regional soil conditions and construction methods to ensure that customers can obtain stable and efficient dehydration performance under different operating conditions. 

V. Conclusion: Industrial Filter Cloth Promotes Green Pile Foundation Construction 

Pile foundation sludge treatment, as a part of infrastructure construction, may seem insignificant but is crucial. It is not only related to the cleanliness and safety of the construction site but also an important node affecting the city's environmental performance and the construction of a resource-saving society. 

With the assistance of belt press filters, high-performance industrial filter cloths have become a key weapon in solving the problems of pile foundation sludge treatment. With the continuous progress of filter cloth material technology and structural design, its performance in engineering applications will be even better. 

In the future, Xiamen Citius (Xiamen Citius) will continue to cultivate the field of engineering sludge treatment. Through material upgrades and service innovation, it will provide more efficient and greener solutions for building foundation construction, helping China's urban construction move towards a more sustainable development path.