A water filter removes impurities from water Water is a ubiquitous chemical substance that is essential for the survival of all known forms of life.[citation needed] In typical usage, water refers only to its liquid form or state, but the substance also has a solid state, ice, and a gaseous state, water vapor or steam. Water covers 71% of the Earth's surface. On Earth, it is found mostly in by means of a fine physical barrier, a chemical process or a biological process. Filters cleanse water to various extents for irrigation Irrigation is an artificial application of water to the soil. It is usually used to assist in growing crops in dry areas and during periods of inadequate rainfall. Additionally, irrigation also has a few other uses in crop production, which include protecting plants against frost, suppressing weed growing in rice fields and helping in preventing, drinking water Drinking water is water of sufficiently high quality that it can be consumed or used without risk of immediate or long term harm. Such water is commonly called potable water. In most developed countries, the water supplied to households, commerce and industry is all of drinking water standard, even though only a very small proportion is actually, aquariums An aquarium is a vivarium consisting of at least one transparent side in which water-dwelling plants or animals are kept. Fishkeepers use aquaria to keep fish, invertebrates, amphibians, marine mammals, turtles, and aquatic plants. The term combines the Latin root aqua, meaning water, with the suffix -arium, meaning "a place for relating to&, and swimming pools A swimming pool, swimming bath, wading pool, or simply a pool, is an artificially enclosed body of water intended for swimming or water-based recreation. There are many standard sizes; the largest and deepest is the Olympic size. A pool can be built either above or in the ground, and from materials such as metal, plastic, fiberglass or concrete.
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Methods of filtration
Main article: Filtration Filtration is a mechanical or physical operation which is used for the separation of solids from fluids by interposing a medium through which the fluid can pass, but the solids (or at least part of the solids) in the fluid are retained. It has to be emphasized that the separation is not complete, and it will depend on the pore size and theFilters use sieving, adsorption Adsorption is the accumulation of atoms or molecules on the surface of a material. This process creates a film of the adsorbate on the adsorbent's surface. It is different from absorption, in which a substance diffuses into a liquid or solid to form a solution. The term sorption encompasses both processes, while desorption is the reverse process, ion exchanges Ion exchange is an exchange of ions between two electrolytes or between an electrolyte solution and a complex. In most cases the term is used to denote the processes of purification, separation, and decontamination of aqueous and other ion-containing solutions with solid polymeric or mineralic 'ion exchangers' and other processes. Unlike a sieve In general, a sieve separates wanted/desired elements from unwanted material using a tool such as a mesh, net or other filtration or distillation methods, but it is also used for classification of powders by particle size, or for size measurement as an analytical technique. The word "sift" derives from this term. A strainer is a type of or screen, a filter can remove particles much smaller than the holes through which the water passes.
Types of filters
Water treatment plant filters
Types of water filters include media filters A media filter is a type of filter that uses a bed of sand, crushed granite or other material to filter water for drinking, swimming pools, aquaculture, irrigation, stormwater management and other applications, screen filters A screen filter is a type of filter using a rigid or flexible screen to separate sand and other fine particles out of water for irrigation or other applications. These are generally not recommended for filtering out organic matter such as algae, since these types of contaminants can be extruded into spaghetti-like strings through the filter if, disk filters, slow sand filter beds, rapid sand filters and cloth filters Developed for use in Bangladesh, the cloth filter is a simple and cost-effective appropriate technology method for reducing the contamination of drinking water. Water collected in this way has a greatly reduced pathogen count - though it will not necessarily be perfectly safe, it is an improvement for poor people with limited options.[1]
Point-of-use filters
Filters for home use include granular activated carbon filters Activated carbon, also called activated charcoal or activated coal, is a form of carbon that has been processed to make it extremely porous and thus to have a very large surface area available for adsorption or chemical reactions. The word activated in the name is sometimes substituted by active. Due to its high degree of microporosity, just one (GAC) used for carbon filtering Carbon filtering is a method of filtering that uses a piece of activated carbon to remove contaminants and impurities, utilizing chemical adsorption. Each piece of carbon is designed to provide a large section of surface area, in order to allow contaminants the most possible exposure to the filter media. One pound of activated carbon contains a, metallic alloy filters An alloy is a partial or complete solid solution of one or more elements in a metallic matrix. Complete solid solution alloys give single solid phase microstructure, while partial solutions give two or more phases that may be homogeneous in distribution depending on thermal history. Alloys usually have different properties from those of the, microporous ceramic filters, carbon block resin (CBR) and ultrafiltration Ultrafiltration is a variety of membrane filtration in which hydrostatic pressure forces a liquid against a semipermeable membrane. Suspended solids and solutes of high molecular weight are retained, while water and low molecular weight solutes pass through the membrane. This separation process is used in industry and research for purifying and membranes. Some filters use more than one filtration method. Jug filters can be used for small quantities of drinking water. Some kettles In the United States, '"kettle" usually refers to a teakettle, a roughly pitcher shaped metal vessel used to heat water on a stovetop or hod. Kettles usually have a handle on top, a spout, and a lid. Sometimes stove-mounted kettles also have a steam whistle that indicates when the water has reached boiling point. Kettles often resemble have built-in filters, primarily to reduce limescale Limescale is the hard, off-white, chalky deposit found in kettles, hot-water boilers and the inside of inadequately maintained hot-water central heating systems. It is also often found as a similar deposit on the inner surface of old pipes and other surfaces where "hard water" has evaporated buildup.
Portable water filters
Water filters are used by hikers, by aid organizations during humanitarian emergencies, and by the military. These filters are usually small, portable and light (1-2 pounds/0.5-1.0 kg or less), and usually filter water by working a mechanical hand pump, although some use a siphon A siphon is a continuous tube that allows liquid to drain from a reservoir through an intermediate point that is higher, or lower, than the reservoir, the flow being driven only by the difference in hydrostatic pressure without any need for pumping. It is necessary that the final end of the tube be lower than the liquid surface in the reservoir drip system to force water through while others are built into water bottles. Dirty water is pumped via a screen-filtered flexible silicon tube through a specialized filter, ending up in a container. These filters work to remove bacteria The bacteria [bækˈtɪərɪə] (singular: bacterium)[α] are a large group of unicellular microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals. Bacteria are ubiquitous in every habitat on Earth, growing in soil, acidic hot springs, radioactive waste, water, and deep, protozoa While there is no exact definition of the term "protozoan", most scientists use the word to refer to a unicellular heterotrophic protist, such as an amoeba or a ciliate. The term algae is used for microorganisms that photosynthesize. However, the distinction between protozoa and algae is often vague. For example, the alga Dinobryon has and microbial cysts that can cause disease. Filters may have fine meshes that must be replaced or cleaned, and ceramic water filters must have their outside abraded when they have become clogged with impurities.
These water filters should not be confused with devices or tablets that are water purifiers, some of which remove or kill viruses A virus is a microscopic infectious agent that can only reproduce inside a host cell. Viruses infect all types of organisms: from animals and plants, to bacteria and archaea. Since the initial discovery of tobacco mosaic virus by Martinus Beijerinck in 1898, more than 5,000 types of virus have been described in detail, although most types of virus such as hepatitis A Hepatitis A is an acute infectious disease of the liver caused by the hepatitis A virus (HAV), which is most commonly transmitted by the fecal-oral route via contaminated food or drinking water. Every year, approximately 10 million people worldwide are infected with the virus. The time between infection and the appearance of the symptoms, (the and rotavirus Rotavirus is a genus of double-stranded RNA virus in the family Reoviridae. It is the leading single cause of severe diarrhoea among infants and young children, and is one of several viruses that cause infections commonly known as stomach flu, despite having no relation to influenza. By the age of five, nearly every child in the world has been.
Homemade water filters
A homemade waterfilter for making drinking waterWater filters can be made on-site using local materials such as grass, charcoal Charcoal is the blackish residue consisting of impure carbon obtained by removing water and other volatile constituents from animal and vegetation substances. Charcoal is usually produced by slow pyrolysis, the heating of wood, sugar, bone char, or other substances in the absence of oxygen . The resulting soft, brittle, lightweight, black, porous (e.g. from burned firewood), and sand. These filters have been used by soldiers and outdoor enthusiasts.[2] Due to their low cost they can be made and used by anyone, including the poor Poor is an adjective related to a state of poverty, low quality or pity, who often do not have access to safe drinking water Drinking water is water of sufficiently high quality that it can be consumed or used without risk of immediate or long term harm. Such water is commonly called potable water. In most developed countries, the water supplied to households, commerce and industry is all of drinking water standard, even though only a very small proportion is actually. Regrettably such filters do little if anything to mitigate against pathogens and other harmful constituents and can give a false sense of security that the water so produced is potable.
See also
- Backwash (physical phenomenon)
- Water purification Water purification is the process of removing undesirable chemicals, materials, and biological contaminants from raw water. The goal is to produce water fit for a specific purpose. Most water is purified for human consumption but water purification may also be designed for a variety of other purposes, including to meet the requirements of medical,
- Reverse osmosis Reverse osmosis is a filtration process that is often used for water. It works by using pressure to force a solution through a membrane, retaining the solute on one side and allowing the pure solvent to pass to the other side. This is the reverse of the normal osmosis process, which is the natural movement of solvent from an area of low solute
- Distillation Distillation is a method of separating mixtures based on differences in their volatilities in a boiling liquid mixture. Distillation is a unit operation, or a physical separation process, and not a chemical reaction
- Carbon filtering Carbon filtering is a method of filtering that uses a piece of activated carbon to remove contaminants and impurities, utilizing chemical adsorption. Each piece of carbon is designed to provide a large section of surface area, in order to allow contaminants the most possible exposure to the filter media. One pound of activated carbon contains a
- Sand separator
- Settling basin
- Swimming pool sanitation Swimming pool sanitation refers to both visual clarity and levels of microflora, such as bacteria and viruses in swimming pools. The goal of sanitation is to prevent the spread of diseases and pathogens between users. Unsanitized water may also support the growth of algae which will present as a greenish tinge initially, then if left unchecked may
References
- ^ "Types of Filters". Mountain Empire Community College. http://water.me.vccs.edu/concepts/filters.html. Retrieved on 2008-10-01.
- ^ "Water". woodcraftwanderings.org. http://www.woodcraftwanderings.org/water.html. Retrieved on 2008-10-01.
External links
- Filter vs Purification and other filtration information
- Filtration info from New Mexico State University
Categories: Water filters | Irrigation | Hiking equipment
