3. Filter cake pressing

3.1 Principle

After the cake-forming filtration stage, the cake may remain heavily impregnated with residual liquid. When this medium is compressible, subsequent pressing is carried out to improve the dryness of the filtration cake, following a process of expression of the porous medium. The combination of filtration and pressing operations has undergone significant technological development over the last twenty years, stemming from two decisive factors. The first was the urgent need in Europe for high-capacity urban wastewater treatment plants, designed to reduce wastewater to a sufficiently concentrated sludge to be either pelletizable or self-combustible. The filters developed for wastewater treatment plants are generally horizontal belt press filters, designed to achieve the best...