Ceramic water filters (CWF) are an inexpensive and effective type of water filter that rely on the small pore size of ceramic material to filter dirt, debris, and bacteria out of water. This makes them ideal for use in developing countries, [1] and portable ceramic filters are commonly used in backpacking. [2]
Similar to other methods of filtering water, the filter removes particles larger than the size of the pores in the filter material. [3] Typically bacteria, protozoa, and microbial cysts are removed. However, filters are typically not effective against viruses since they are small enough to pass through to the "clean" side of the filter. Ceramic water filters (CWF) may be treated with silver in a form that will not leach away. The silver helps to kill or incapacitate bacteria and prevent the growth of mold and algae in the body of the filter.
Ceramic filtration does not remove chemical contaminants, per se. However, some manufacturers (especially of ceramic candle filters) incorporate a high-performance activated carbon core inside the ceramic filter cartridge that reduces organic and metallic contaminants. The active carbon absorbs compounds such as chlorine. Filters with active carbon need to be replaced periodically because the carbon becomes clogged with foreign material.
The two most common types of ceramic water filter are pot-type and candle-type filters. Ceramic filter systems consist of a porous ceramic filter that is attached to, or sits on top of a plastic or ceramic receptacle. Contaminated water is poured into a top container. It passes through the filter(s) into the receptacle below. The lower receptacle usually is fitted with a tap.
Contaminants larger than the minute holes of the ceramic structure will remain in the top half of the unit. The filter(s) can be cleaned by brushing them with a soft brush and rinsing them with clean water. Hot water and soap can also be used.
In stationary use, ceramic candles have mechanical, operational and manufacturing advantages over simple inserts and pots. Filter candles allow sturdy metal and plastic receptacles to be used, which decreases the likelihood of a sanitary failure. Since their filter area is independent of the size of the attachment joint, there is less leakage than other geometries of replaceable filter, and more-expensive, higher-quality gaskets can be used. Since they are protected by the upper receptacle, rather than forming it, they are less likely to be damaged in ordinary use. They are easier to sanitize, because the sanitary side is inside the candle. The non-sanitary part is outside, where it is easy to clean. They fit more types of receptacles and applications than simple pots, and attach to a simple hole in a receptacle. They also can be replaced without replacing the entire upper receptacle, and larger receptacles can simply use more filter candles, permitting filter manufacture to be standardized. If a filter in a multifilter receptacle is found to be broken, the filter hole can be plugged, and use can continue with fewer filters and a longer refill-time until a replacement can be obtained. Also, standardizing the filter makes it economical to keep one or a few filters on hand.
There are also portable ceramic filters, such as the MSR Miniworks, which work via manual pumping, and in-line ceramic filters, which filters drinking water that comes through household plumbing. Cleaning these filters is the same as with the clay pot filter but also allows for reverse-flow cleaning, wherein clean water is forced through the filter backwards, pushing any contaminants out of the ceramic pores.
The major risks to the success of all forms of ceramic filtration are hairline cracks and cross-contamination. If the unit is dropped or otherwise abused, the brittle nature of ceramic materials can allow fine, barely-visible cracks, allowing larger contaminants through the filter. Work is being done to modify clay/sawdust ratios during manufacture to improve the brittle nature and fracture toughness of these clay ceramic water filter materials. [4] If the "clean" water side of the ceramic membrane is brought into contact with dirty water, hands, cleaning cloths, etc., then the filtration will be ineffective. If such contact occurs, the clean side of the filter should be thoroughly sterilized before reuse.
Henry Doulton invented the modern form of ceramic candle sanitary water filter in 1827. In 1835, Queen Victoria commissioned him to produce such a device for her personal use. By 1846, Doulton ceramics was widely recognized as a premier manufacturer of an effective prevention device for treating infective water. In 1887, Doulton was knighted, in part for his work with water filters. Louis Pasteur's research concerning bacteria also had provided a demonstrable reason for the filters' effect. Doulton's original organization for water filters remains in existence, although it has been sold and renamed several times. "Doulton" is currently (2013) a registered trademark of Fairey Ceramics. [5]
Several universities including MIT; Universities of Colorado; Princeton University; University of Wisconsin-Milwaukee; The Ohio State University; Universities of Tulane, West Virginia, North Carolina in the US; University of Delft, Strathclyde in Europe, USAID, UNICEF, Zamorano University in Honduras, Rafael Landívar University in Guatemala, Earth University, Institute of Hydraulic resources, the Red Cross, Engineers Without Borders, United Nations, countries in Africa like Nigeria, Ghana, Burkina Faso, Kenya, etc. and countries in Asia like Nepal, Bangladesh, Cambodia, Sri Lanka, India, Vietnam, Uganda etc. and NGOs are supporting the expansion of the use of ceramic filters in drinking water development initiatives; most commonly, in the form of clay pot filters. [6]
Fernando Mazariegos of Guatemala was responsible for developing Ceramic Pot Filter technology in 1981 while Director of Water Research at the Central American Research Institute in Guatemala City. He was the Director of Research and Development at Ecofiltro in Antigua, Guatemala. Ron Rivera studied under Fernando Mazariegos of Guatemala and was a key proponent and innovator in the field as part of the group to take the ceramic frustum shaped(pot) filter across international borders and helped developing nations to provide cheap high quality potable water. Ron Rivera also worked with Potters for Peace worldwide for the good and benefit of clay workers in developing nations to sustain their businesses. [7]
The latest development is in India, NGOs such as Enactus IIT Madras, Rupayan Sansthan, Sehgal Foundation are supporting the expansion and use of indigenized frustum shaped ceramic water filters called Matikalp for drinking water development initiatives in Tamil Nadu, Rajasthan, Bihar and other states. [8] [9]
In Africa, Uganda Spouts of Water works in collaboration with local communities and partners to produce and distribute ceramic water filters (Purifaaya) made from locally available materials.
Filtration is a physical separation process that separates solid matter and fluid from a mixture using a filter medium that has a complex structure through which only the fluid can pass. Solid particles that cannot pass through the filter medium are described as oversize and the fluid that passes through is called the filtrate. Oversize particles may form a filter cake on top of the filter and may also block the filter lattice, preventing the fluid phase from crossing the filter, known as blinding. The size of the largest particles that can successfully pass through a filter is called the effective pore size of that filter. The separation of solid and fluid is imperfect; solids will be contaminated with some fluid and filtrate will contain fine particles. Filtration occurs both in nature and in engineered systems; there are biological, geological, and industrial forms. In everyday usage the verb "strain" is more often used; for example, using a colander to drain cooking water from cooked pasta.
Filter paper is a semi-permeable paper barrier placed perpendicular to a liquid or air flow. It is used to separate fine solid particles from liquids or gases.
Water purification is the process of removing undesirable chemicals, biological contaminants, suspended solids, and gases from water. The goal is to produce water that is fit for specific purposes. Most water is purified and disinfected for human consumption, but water purification may also be carried out for a variety of other purposes, including medical, pharmacological, chemical, and industrial applications. The history of water purification includes a wide variety of methods. The methods used include physical processes such as filtration, sedimentation, and distillation; biological processes such as slow sand filters or biologically active carbon; chemical processes such as flocculation and chlorination; and the use of electromagnetic radiation such as ultraviolet light.
Water treatment is any process that improves the quality of water to make it appropriate for a specific end-use. The end use may be drinking, industrial water supply, irrigation, river flow maintenance, water recreation or many other uses, including being safely returned to the environment. Water treatment removes contaminants and undesirable components, or reduces their concentration so that the water becomes fit for its desired end-use. This treatment is crucial to human health and allows humans to benefit from both drinking and irrigation use.
Microfiltration is a type of physical filtration process where a contaminated fluid is passed through a special pore-sized membrane filter to separate microorganisms and suspended particles from process liquid. It is commonly used in conjunction with various other separation processes such as ultrafiltration and reverse osmosis to provide a product stream which is free of undesired contaminants.
A media filter is a type of filter that uses a bed of sand, peat, shredded tires, foam, crushed glass, geo-textile fabric, anthracite, crushed granite or other material to filter water for drinking, swimming pools, aquaculture, irrigation, stormwater management, oil and gas operations, and other applications.
A water filter removes impurities by lowering contamination of water using a fine physical barrier, a chemical process, or a biological process. Filters cleanse water to different extents, for purposes such as: providing agricultural irrigation, accessible drinking water, public and private aquariums, and the safe use of ponds and swimming pools.
Sand filters are used as a step in the water treatment process of water purification.
Nanofoams are a class of nanostructured, porous materials (foams) containing a significant population of pores with diameters less than 100 nm. Aerogels are one example of nanofoam.
Ceramic foam is a tough foam made from ceramics. Manufacturing techniques include impregnating open-cell polymer foams internally with ceramic slurry and then firing in a kiln, leaving only ceramic material. The foams may consist of several ceramic materials such as aluminium oxide, a common high-temperature ceramic, and gets insulating properties from the many tiny air-filled voids within the material.
Aquarium filters are critical components of both freshwater and marine aquaria. Aquarium filters remove physical and soluble chemical waste products from aquaria, simplifying maintenance. Furthermore, aquarium filters are necessary to support life as aquaria are relatively small, closed volumes of water compared to the natural environment of most fish.
Electrokinetic phenomena are a family of several different effects that occur in heterogeneous fluids, or in porous bodies filled with fluid, or in a fast flow over a flat surface. The term heterogeneous here means a fluid containing particles. Particles can be solid, liquid or gas bubbles with sizes on the scale of a micrometer or nanometer. There is a common source of all these effects—the so-called interfacial 'double layer' of charges. Influence of an external force on the diffuse layer generates tangential motion of a fluid with respect to an adjacent charged surface. This force might be electric, pressure gradient, concentration gradient, or gravity. In addition, the moving phase might be either continuous fluid or dispersed phase.
A Berkefeld filter is a water filter made of diatomaceous earth (Kieselguhr). It was invented in Germany in 1891, and by 1922 was being marketed in the United Kingdom by the Berkefeld Filter Co. Berkefeld was the name of the owner of the mine in Hanover, Germany, where the ceramic material was obtained.
A Chamberland filter, also known as a Pasteur–Chamberland filter, is a porcelain water filter invented by Charles Chamberland in 1884. It was developed after Henry Doulton's ceramic water filter of 1827. It is similar to the Berkefeld filter in principle.
Depth filters are filters that use a porous filtration medium to retain particles throughout the medium, rather than just on the surface of the medium. Depth filtration, typified by multiple porous layers with depth, is used to capture the solid contaminants from the liquid phase. These filters are commonly used when the fluid to be filtered contains a high load of particles because, relative to other types of filters, they can retain a large mass of particles before becoming clogged.
Ronald Rivera was an American activist of Puerto Rican descent who is best known for promoting an inexpensive ceramic water filter developed in Guatemala by the chemist Fernando Mazariegos and used to treat gray water in impoverished communities and for establishing community-based factories to produce the filters around the world.
A vacuum ceramic filter is designed to separate liquids from solids for dewatering of ore concentrates purposes. The device consists of a rotator, slurry tank, ceramic filter plate, distributor, discharge scraper, cleaning device, frame, agitating device, pipe system, vacuum system, automatic acid dosing system, automatic lubricating system, valve and discharge chute. The operation and construction principle of vacuum ceramic filter resemble those of a conventional disc filter, but the filter medium is replaced by a finely porous ceramic disc. The disc material is inert, has a long operational life and is resistant to almost all chemicals. Performance can be optimized by taking into account all those factors which affect the overall efficiency of the separation process. Some of the variables affecting the performance of a vacuum ceramic filter include the solid concentration, speed rotation of the disc, slurry level in the feed basin, temperature of the feed slurry, and the pressure during dewatering stages and filter cake formation.
Potters for Peace, which has changed its name to Good Foundations International, is a nonprofit organization that has created a network of potters and other relevant parties to improve quality of life and preserve tradition using local skills and materials. PFP primarily works in Central America and has headquarters in Boulder, Colorado. PFP manages projects that help local potters to improve and market their products. PFP is best known for their work in water treatment, which has influenced water treatment systems worldwide. The treatment strategy follows a Point-of-Use (POU) water treatment design that uses ceramic water filters to remove pathogens and other contaminants from the water. This is generally a very effective method to remove bacteria from water, though there are some concerns about the ease of use and maintenance of the filtration units. Unlike other similar organizations, PFP does not manufacture these filters, but instead helps local communities to set up independent filter workshops to produce and sell the filters.
Membrane technology encompasses the scientific processes used in the construction and application of membranes. Membranes are used to facilitate the transport or rejection of substances between mediums, and the mechanical separation of gas and liquid streams. In the simplest case, filtration is achieved when the pores of the membrane are smaller than the diameter of the undesired substance, such as a harmful microorganism. Membrane technology is commonly used in industries such as water treatment, chemical and metal processing, pharmaceuticals, biotechnology, the food industry, as well as the removal of environmental pollutants.
José Fernando Mazariegos Anleu was a Guatemalan inventor, recognized in several countries in Latin America, Asia and Africa, for the creation of the drinking water filter called "Ecofilter", which was developed in 1990 as part of a project of the Central American Institute of Industrial Research and Technology.