This first main section of the Handbook, which deals with fi ltration equipment, consists of a number of areas, each devoted to a type of fi lter. In accordance with the main theme of the book, more attention is paid to those fi lters used for clarification of gas or liquid streams than to those […]
Quite closely related to deep-bed filtration in principle is precoat filtration, which uses a bed of inert solids formed on the upstream surface of a relatively coarse filter medium to act as the actual medium. The most popular solids for this purpose are kieselguhr (diatomaceous earth) and perlite. These can only be used where the […]
The media used in deep-bed filters must be inert, resistant to fracture yet easily prepared in batches of graded particle size. Many different granular and crushed materials have been used to form the deep beds employed in the large gravity and pressure filters common to the water purification and sewage treatment industries. In addition to […]
The forms of filter media discussed in the previous parts in this section have all been constrained as pieces of material or structures. The remaining group of media materials, of particular interest to clarifying processes, are unconstrained (except by the walls of their containing vessel), being masses of coarse particulate substances, used as packed beds […]
Membrane separations began in the 1960s as an alternative means to distillation for the desalination of salt (i.e. sea) and brackish waters. This was called reverse osmosis because it works by applying a transmembrane pressure greater than the natural osmotic pressure between the two solutions (seawater, say, and desalted water). The various processes in which […]
Membranes are made in a variety of ways, according to how they are to be used, with basic formats as flat sheets, tubes of very different diameters and solid blocks, on the surfaces of which the membrane is later deposited. The various manufacturing processes can be broadly summarized as: ● sintering of fine graded particles […]
As the term is applied nowadays, membranes can be porous or non-porous, polymeric or inorganic. They can be used for a range of separations including solids from liquids, liquids from liquids, and gases from gases, but in particular it is the filtration of micrometre and sub-micrometre size particles from liquids and gases where membranes have […]
In terms of filtration and separation technology, membranes have become one of the most important components. It is almost impossible to separate membrane media from the processes and equipment in which membranes are used, so this is only the briefest of introductions to membranes, with more detailed coverage in Sections 3 and 4. In separation […]
A completely different constructed cartridge has a perforated cylindrical core around which is wound a continuous filament or yarn. With a plastic filament or metal wire, the core may be threaded and the first layer of the filament is wound into the threads, giving the required degree of spacing of consecutive turns. The cartridge may […]
Similar to the edge filter in appearance, in that it has an array of disc-shaped components held on a central core, the stacked disc filter differs because the discs are actually hollow, with filter media over the faces of the disc. It employs individual discs, porous on both sides – that are stacked over a […]
