Basic Introduction to Plate and Frame Filter Press

The plate and frame filter press was the first mechanical equipment applied in chemical dehydration. Although typically operated intermittently, requiring significant capital investment in infrastructure, and having lower filtration capacity, it is still widely used in small wastewater treatment plants due to its advantages such as strong filtration force, high solid content in the filter cake, clear filtrate, high solid recovery rate, and low consumption of conditioning chemicals. After sludge is concentrated and digested, it still has a moisture content of about 95% to 97%, with a large volume. Dewatering the sludge can further remove interstitial water and capillary water, reducing its volume. After dewatering treatment, the moisture content of the sludge can be reduced to 70% to 80%, with a volume 1/10 to 1/4 of the original, which is beneficial for subsequent transportation and disposal. Dewatering methods for sludge include filtration, centrifugal, and squeezing; filtration dewatering includes vacuum and pressure filtration; centrifugal dewatering uses centrifugal separators; and squeezing dewatering uses screw or roller presses. The most commonly used methods are pressure filtration and centrifugal dewatering. Sludge filtration dewatering utilizes the pressure difference across the filter medium as the driving force, forcing sludge moisture through the medium to form filtrate, while solid particles are retained on the medium to form a filter cake, thereby achieving sludge dewatering. Despite being generally operated intermittently, requiring significant infrastructure investment, and having lower filtration capacity, the plate and frame filter press is still widely used in small wastewater treatment plants due to its strong filtration force, high solid content in the filter cake, clear filtrate, high solid recovery rate, and low consumption of conditioning chemicals.