During the process of filteration ,should we use more number of filters with progressively smaller pore size or use one filyer with small mesh size ? Explain the reasons for your answer ??
Answers
Answer:
We must use more filters with progressively smaller pore size as this reduces the posibility of blockage of the pores that may occur in a filter with small pores.
By using more filters, the amount of particles will decrease gradually while moving to another filter and prevents any kind of blockage of the pores,
Explanation:
Filtration is a process that removes particles from suspension in water. Removal takes place by a number of mechanisms that include straining, flocculation, sedimentation and surface capture. Filters can be categorised by the main method of capture, i.e. exclusion of particles at the surface of the filter media i.e. straining, or deposition within the media i.e. in-depth filtration.
Strainers generally consist of a simple thin physical barrier made from metal or plastic. In water treatment they tend to be used at the inlet to the treatment system to exclude large objects (e.g. leaves, fish, and coarse detritus). These may be manually or mechanically scraped bar screens. The spacing between the bars ranges from 1 to 10 cm. Intake screens can have much smaller spacing created by closely spaced plates or even fine metal fabric. The latter are usually intended to remove fine silt and especially algae and are referred to as microstrainers.
Filters, as commonly understood in water treatment generally consist of a medium within which it is intended most of the particles in the water will be captured. Such filters might be manufactured as disposable cartridge filters, which can be suitable for domestic (i.e. point-of-use treatment) and small-scale industrial applications. Larger forms of cartridge filters exist which can be cleaned. One version is precoat filtration in which a porous support surface is given a sacrificial coating of diatomaceous earth, or other suitable material, each time the filter has been cleaned. Additionally, a small amount of the diatomaceous earth is applied continuously during filtration. However, in most cases, filters used in municipal water treatment contain sand or another appropriate granular material (e.g. anthracite, crushed glass or other ceramic material, or another relatively inert mineral) as the filter medium. Filtration using such filters is often referred to as in-depth granular media filtration.
Granular media filters are used in either of two distinct ways which are commonly called slow-sand filtration and rapid gravity or pressure filtration. When the filters are used as the final means of particle removal from the water, then the filters may need to be preceded by another stage of solid-liquid separation (clarification) such as sedimentation (Sedimentation Processes), dissolved-air flotation (Flotation Processes) or possibly a preliminary stage of filtration.
Other processes take place in vessels similar to those used for granular media filtration, and in some respects the processes do have similarities with filtration but filtration is not their sole or primary purpose. Therefore, such processes are not considered further in this article. Examples include vessels filled with granular activated carbon for removal of dissolved organic substances, and vessels filled with ion exchange resin for removal of inorganic and organic ions. There are applications of filters that whilst filtration (removal of particles) does take place a secondary process is intended to also occur, e.g. iron and manganese removal, and arsenic removal.