Water filter
A water filter removes impurities from water by means of a fine physical barrier, a chemical process or a biological process. Filters cleanse water to different extents for purposes like irrigation, drinking water, aquariums, ponds and swimming pools.
Filters use sieving, adsorption, ion exchanges, biological metabolite transfer, and other processes. Unlike a sieve or screen, a filter can remove particles much smaller than the holes through which the water passes.
Water filters can be made on-site using local materials such as grass, charcoal (e.g. from firewood burned in a special way). These filters are sometimes used by soldiers and outdoor enthusiasts. Due to their low cost they can be made and used by anyone. The reliability of such systems is highly variable. Such filters can do little, if anything, to mitigate germs and other harmful constituents and can give a false sense of security that the water so produced is potable. Water processed through an improvised filters should be undergo secondary processing such as boiling to render it safe for consumption.
Slow sand filters are used in water purification for treating raw water to produce a potable product. They are typically 1 to 2 metres deep, can be rectangular or cylindrical in cross section and are used primarily to treat surface water. The length and breadth of the tanks are determined by the flow rate desired by the filters, which typically have a loading rate of 0.1 to 0.2 metres per hour (or cubic metres per square metre per hour).
Slow sand filters, due to their simple design, may be created DIY. DIY-slow sand filters have been used in Afghanistan and other countries to aid the poor.
Simple techniques for treating water at home, such as chlorination, filters, and solar disinfection, and storing it in safe containers could save a huge number of lives each year. Reducing deaths from waterborne diseases is a major public health goal in developing countries.
A Biosand Filter (BSF) is a point-of-use water treatment system adapted from traditional slow sand filters. Biosand filters remove pathogens and suspended solids from water through a combination of biological and physical processes that take place in a sand column covered with a biofilm. BSFs have been shown to effectively remove heavy metals, turbidity and other contaminants such as bacteria, viruses and protozoa. BSFs also help to reduce discoloration, odor and unpleasant taste. Studies have shown correlation between use of BSFs and decrease in occurrence of diarrhea with an increase in general health. Due to their effectiveness, ease of use, and lack of recurring costs, biosand filters are often considered appropriate technology in developing countries. It is estimated that over 200,000 BSFs are in use worldwide.
Biosand filters are typically constructed from either concrete or plastic. The most widely used plans for the concrete biosand filter are produced and distributed by CAWST, and Hydraid Biosand Water Filter. Most biosand filters consist of similar components. At the top of the filter there is a tightly fitted lid, which prevents contamination and unwanted pests from entering the filter. Below is the diffuser plate, which prevents disturbance of the biofilm when water is poured into the filter. Water then travels through the sand column, removing pathogens and suspended solids. Below the sand column is a layer of gravel that prevents sand from entering the drainage layer and clogging the outlet tube. Below the separating layer is the drainage layer, which consists of larger gravel that promotes water flow by preventing clogging near the base of the outlet tube.
The Tata Swach is a water purifier developed by Tata Chemicals, a part of the Tata group in India. Swach was designed as a low cost purifier for Indian low-income groups, who lack access to safe drinking water.
Sujal was a very basic low-cost model which used rice-husk ash (produced from heating rice husk in combination with pebbles and cement). Activated silica and carbon is present in the ash; silica can reduce the turbidity of water, while activated carbon binds with and adsorbs non-polar impurities (such as pesticides and fertilisers).
Soma is a company that designs eco-friendly water filtration systems. The filters are made from Malaysian coconut shells, vegan silk, and food-based PLA plastic.
See also:
Water Filter
Water Purification
Tata Swach
Soma Company
Source: Wikipedia (All text is available under the terms of the Creative Commons Attribution-ShareAlike License)
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