Ceramic and activated carbon water filters use the porosity of ceramic material and charcoal respectively, to purify water. The following article provides some information about both these types of filters.
Water filtering is the method of separating impurities from water, and thus purifying it. The above mentioned water filters are commonly used for household water purifying purpose. They are very inexpensive and easy for maintenance. Though the working mechanism of both types is slightly different, the principle is same, that is blocking the impurities and allowing only water to pass through.
Ceramic Water Filters
They are divided into two components, filter and the receptacle. The former one can be of two types, pot or candle. Candle is the most commonly used type of filter. It is seated on the top of the receptacle, which is fitted with a tap. The ceramic material is highly porous. Most impurities are larger than the pores of the filter. When the water is added to one side of the filter, everything except water molecules are blocked by the filters. Thus, the water becomes free of any impurities, and is collected in the receptacle.
The impurities that accumulate in the top half or the filter region have to be removed timely, otherwise it may lead to the growth of algae and other micro-organisms. This can be done using soap solution with hot water and soft brush. These days, many ceramic water filters are treated with colloidal silver, which prevents the growth of bacteria and algae. Certain portable filters, like MSR Miniworks, require manual pumping for the filtering process. The in-line filters are used for drinking water coming through the household plumbing.
The main problem with ceramic filters is that it does not remove the chemical impurities. They are also prone to hairline cracking and chipping.
Activated Carbon Water Filters
Activated carbon is actually a charcoal that is processed to make it highly porous. Bituminous coal, lignite, wood, coconut shell, etc., are some of the materials used for making such type of carbon. Its extremely high porosity allows it to have a very high surface area. The surface area of 1 gram active carbon equals to around 500 m², which is 2.17 times that of a tennis court. The impurities of size 0.5 to 50 micrometers can be successfully removed by these filters. The chemical mechanism by which active carbon filters water is called adsorption. The carbon shows hydrophobic and oleophilic properties, which means that it shows repulsion to water and affinity for oil and other chemicals. Due to these properties, oil and other chemicals cling to the carbon filter, and water is allowed to pass through the pores.
Activated carbon filters are of two types, powdered block filters and granular activated filters. The former ones have an increased surface area, and hence are more capable of filtering large number of impurities. Carbon filters are used mostly for household water purification, however they can also be used in municipal water treatment plants. Sometimes, they are also used as devices for reverse osmosis systems in pre-treatment stages. They can be additionally treated with silver or KDF- 55 to restrict the growth of bacteria.
The problem with active carbon filters is that the impurities that cling to the filter tend to clog the pores, rendering them ineffective.
Both these filters are incapable of removing dissolved impurities or salts. Therefore, they cannot be used where high quality purification is required. However, they are a cheap, easy to use, and easy to maintain; hence, useful for small scale or for household purification.