CHOOSING WATER FILTERS
Water Filtration is one of several methods of purifying water. The other methods are: Boiling, Distillation, Aeration, Chemical Treatment, and Radiation Treatment. These processes can be applied singly or in combination with each other, depending upon the nature of the contaminants and the extent of purity required of the processed water. For example, Boiling as a method of water purification, kills some pathogenic microorganisms such as bacteria and viruses, but is not effective in removing other contaminants like organic and inorganic chemicals, hardness, solids, etc. Water Distillation can be effective in eliminating inorganic chemicals, microorganisms, and solid contaminants, but may not be able to remove organic chemicals that boil off with water. Water Aeration involves getting the water into contact with the oxygen in the air to eliminate undesirable dissolved gases, some chemicals, and some microorganisms. In Water Chemical Treatment, water is doped with certain chemicals such as Chlorine (for Chlorination) and Iodine (for Iodination), to eliminate certain harmful microorganisms. Radiation Treatment is essentially Ultraviolet (UV) Water Sterilization employed to kill air-borne type microorganisms that contaminate water.
Choosing water filters is a rational process and it involves essentially determining the right filter, or combination of filters, for a specific purpose. It requires knowing 1) the various types of filters and how they work 2) the type and extent of the contaminants or impurities present in the input raw water, and 3) the type and extent of the impurities that is acceptable in the finished “purified” water. For example, water intended for drinking must be free from harmful microorganisms and harmful chemicals, and therefore the filter or filter combination to use should be able to eliminate these undesirable contaminants so that the trace amount left in the final product is within accepted levels.
Water filters are devices employing “strainer action” for the purpose of eliminating undesirable (harmful) substances and materials called contaminants from impure water. The contaminants are commonly inorganic and organic in nature such as chemicals, microorganisms, viruses, metals, rusts, and minerals. Filters are intended to remove most of these contaminants to the extent that the remaining levels of impurities in the water have become acceptable. To accomplish this, filtering devices are either in the form of mechanical filters whereby the contaminants are “screened out”, or the filters are in the form of a physical barrier whereby the contaminants are selectively “adsorbed”, thus purifying the water. In principle, the pores of the filter of mechanical filters are designed to be smaller in size relative to the contaminants to be eliminated, but big enough to allow the water molecules and other desirable substances to pass through. As the contaminated water is introduced, the impurities are retained but the water is allowed to pass through. On the other hand, the “adsorption” action of the physical type filters is based on their ability to chemically attract and hold certain contaminants while the water molecules which are unaffected are allowed to pass through. “Adsorption” described here is different from “absorption” in terms of their actions relative to the contaminants. (Adsorption and Absorption).
In choosing water filters it is important also to establish the criteria to be used in the selection process. Essentially, the criteria are: effectiveness, price, availability, and filter life. Ideally, the best choice will be the filter or combination of filters which is not only the most effective, but is also the cheapest, the most easily available and with the longest filter life. However, since it is not always possible to have everything ideal, the ultimate decision on which type of water filters to use has to involve optimizing or balancing of these criteria. Effectiveness refers to the ability to eliminate the undesirable contaminants taking into account the 1) expected use and desired quality of the filtered water, and 2) the type and nature of the contaminants in the water to be filtered. Price and availability depends on the locality and location relative to the suppliers. The source could be specialty high street outlets for water accessories and supplies, or hardware stores, home builders’ supply stores, home accessory shops, etc. Long life will depend on the nature and quality of the materials used in the manufacture of the filter, on the design and workmanship in the manufacture of the filter, on the degree of contamination of the raw water to be filtered, and on whether the filter can be back-washed or on whether it can be regenerated.