Plate and frame filter presses were initially applied in chemical dehydration. Although they typically operate intermittently, require significant capital investment in infrastructure, and have lower filtration capacity, they are still widely used in some small wastewater treatment plants due to their advantages such as high filtration driving force, high solid content in the filter cake, clear filtrate, and high solid recovery rates.

After concentration and digestion, the sludge still has a moisture content of about 95% to 97%, and its volume remains large. Dewatering the sludge can further remove interstitial and capillary water from the sludge, reducing its volume.