Currently, there are different methods of water treatment available today. For the purpose of this article we shall classify the treatment plants based on size meaning the conventional treatment plants and the small treatment plants and this include under sink water filters and drinking water filters.
Conventional treatment plants are used exclusively for large communities and cities. Their main source of water is the surface water or water coming from the rivers, lakes and streams. This water is usually stored in large dams.
The pre-treatment process involves the use of bar racks. This is the removal of larger solids two inches in diameter or larger. Most treatment plants have both mechanical racks and hand cleaned bar racks. Next the water will go to the so-called screen where the removal of solids smaller than .01 to .25 inches is done. Then, lastly it will go to the micro screens where solids no greater than 23 to 65 microns are removed.
Next comes the gas transfer called aeration. This process is used for the addition of oxygen to oxidize dissolved iron and manganese, the removal of carbon dioxide, the removal of hydrogen sulfide to eliminate odors and tastes and the removal of volatile oils and similar odors and taste producing substances released by algae and similar microorganisms. This process is also available in smaller water filters.
Then comes the flocculation or the coagulating chemicals are added to water to form flocs from suspended and dissolved solids and colloidal matter. Then, the water will undergo sedimentation and filtration where the water passes through the filter; suspended particles and flocculant material come in contact with the sand and adhere to them. The filter materials could include anthracite and sand.
Then comes the disinfection thru chlorination, ozonation or by uv radiation. Uv water filters also does this disinfection. Another method used in large treatment plants is the backwashing where this consists of fluidizing the filter media either by water, air or a combination of the two so that the individual grains will be suspended and be subject to abrasion by their contact with each other and thus be cleansed of material which has accumulated during filtration. Then finally the disposal of sludge's is the last stage of the process.
For small treatment plants the main sources of water are basically shallow well which is drilled hole less than 200 feet deep and protected by a casing and wherein a pump is installed for the purpose of drawing the water from the aquifer. Deep wells meanwhile are drilled holes which are more than 200 feet deep.
Yet most households today have sources of water coming from the faucets and since most of our water had already undergone treatment from the treatment plants we usually utilize water filter systems for household use. These are enclosed type of water purification devices that uses granulated or minute pore materials to decrease or remove impurities.
The removal of impurities coming from the tap water consists of a transport and attachment process. The transport process involves the transport to the surface of the filtration media thru diffusion, interception, settling, impingement or hydrodynamic carriage. The transport process is aided by flocculation in the interstices of the filter.
Next the water would have to undergo the filter media where the size and uniformity of a filter media are specified by the so-called effective size which is the sieve size in mm which permits 10% of the medium by weight to pass and uniformity coefficient which is the ratio between the sieve size which permits 60% by weight and the effective size to pass thru. Most water filter cartridges have this feature also.
Then the water would have to pass thru granular media of sand and anthracite. And lastly most water filters have activated carbon features included in them. This is a physical and biological filter media that uses adsorption process in the removal of taste, odor and chlorine residues.
