Ceramic water filters (CWF) are a low-cost and useful type of water filter. They work by using the tiny holes in ceramic material to remove dirt, small particles, and bacteria from water. This makes them a good choice for use in countries that are still developing, and portable ceramic filters are often used when people go hiking or camping.
Method of action
Ceramic water filters work by removing particles that are larger than the tiny holes, or pores, in the filter material. These filters usually remove bacteria, protozoa, and microbial cysts. However, they are not effective at removing viruses because viruses are too small to be blocked by the pores. Some ceramic water filters (CWF) are treated with silver that stays in the filter and does not wash away. This silver helps kill bacteria and stops mold and algae from growing inside the filter.
Ceramic filtration does not remove chemical pollutants directly. However, some ceramic candle filters include a special type of activated carbon inside the filter. This carbon helps reduce organic and metal contaminants by absorbing them, such as chlorine. Activated carbon filters must be replaced regularly because the carbon can become blocked by dirt and other materials.
The two most common types of ceramic water filters are pot-type and candle-type filters.
Ceramic filter systems include a porous ceramic filter that is connected to or placed on top of a plastic or ceramic container. Contaminated water is poured into a top container, passes through the filter, and collects in the container below. This lower container usually has a tap for drawing out the filtered water.
Particles larger than the tiny holes in the ceramic filter remain in the top part of the unit. The filters can be cleaned by brushing them with a soft brush and rinsing them with clean water. Hot water and soap may also be used for cleaning.
Ceramic candles have advantages over simple pots and inserts when used in fixed locations. They allow strong metal and plastic containers to be used, reducing the chance of contamination. The filter area in candles is not affected by the size of the connection point, so there is less water leakage. Higher-quality gaskets can be used because the filter is protected by the container. The clean side of the filter is inside the candle, making it easier to keep clean, while the outside, which is less sanitary, can be cleaned easily. Candle filters fit more types of containers and can be replaced without changing the entire container. Larger containers can use multiple filters, which makes manufacturing more efficient. If a filter breaks in a system with multiple filters, the damaged area can be sealed, and the remaining filters can continue working until a replacement is available. Standardizing filters also makes it easier and cheaper to keep spare filters on hand.
Portable ceramic filters, like the MSR Miniworks, use hand pumping to filter water. Inline ceramic filters are used in household plumbing to filter drinking water. These filters are cleaned the same way as pot filters, but they can also be cleaned by pushing clean water through the filter in the opposite direction to remove trapped particles.
The biggest risks for ceramic filters are tiny cracks and cross-contamination. If the filter is dropped or damaged, small cracks may form, allowing larger particles to pass through. Scientists are working to improve the strength of ceramic materials by adjusting the mix of clay and sawdust during production.
If the clean side of the filter touches dirty water, hands, or cleaning cloths, the filter may no longer work properly. If this happens, the clean side must be fully sterilized before the filter is used again.
Development and expansion
In 1827, Henry Doulton created the modern ceramic candle sanitary water filter. In 1835, Queen Victoria asked him to make such a device for her personal use. By 1846, Doulton ceramics was widely known as a top maker of an effective tool for treating infected water. In 1887, Doulton was knighted, partly because of his work with water filters. Research by Louis Pasteur about bacteria gave a clear reason for the filters’ success. Doulton’s original company for water filters still exists, though it has changed names and owners several times. "Doulton" is currently (2013) a registered trademark of Fairey Ceramics.
Many universities, such as MIT, the University of Colorado, Princeton University, the University of Wisconsin-Milwaukee, The Ohio State University, the Universities of Tulane, West Virginia, and North Carolina in the United States; the University of Delft and Strathclyde in Europe; USAID, UNICEF, Zamorano University in Honduras, Rafael Landívar University in Guatemala, Earth University, the Institute of Hydraulic Resources, the Red Cross, Engineers Without Borders, the United Nations, countries in Africa like Nigeria, Ghana, Burkina Faso, Kenya, and countries in Asia like Nepal, Bangladesh, Cambodia, Sri Lanka, India, Vietnam, Uganda, and others, along with NGOs, support the use of ceramic filters in drinking water projects. These filters are most often clay pot filters.
Fernando Mazariegos of Guatemala developed Ceramic Pot Filter technology in 1981 while working as Director of Water Research at the Central American Research Institute in Guatemala City. He later led research and development at Ecofiltro in Antigua, Guatemala. Ron Rivera studied under Fernando Mazariegos and helped spread the use of frustum-shaped (pot) ceramic filters globally. He also worked with Potters for Peace to support clay workers in developing countries.
In India, NGOs such as Enactus IIT Madras, Rupayan Sansthan, and Sehgal Foundation are promoting the use of locally made frustum-shaped ceramic filters called Matikalp for drinking water projects in Tamil Nadu, Rajasthan, Bihar, and other states.
In Africa, Uganda Spouts of Water works with local communities and partners to produce and distribute ceramic water filters (Purifaaya) made from locally available materials.