Why Activated Carbon used in Water Purifiers
Activated Carbon is used in water filter purifiers because activated carbon removes from the water most toxic organic compounds in water like pesticides and heavy metal organic compounds. So passing water through an activated carbon water filter purifier improves the taste of drinking water and also makes water safe to drink by removing most toxic organic compounds in water like pesticides and heavy metal organic compounds. Activated carbon also removes smells in water and makes cloudy water clear by removing color causing compounds in the water. So activated carbon is a very efficient purifier of water and is widely used in water filter purifiers.
How Activated Carbon water purifier works
How Activated carbon water filter works is because activated carbon is an extremely porous material that attracts and holds on its surface harmful chemicals by a process known as 'Adsorption'. Adsorption happens due to electrostatic forces of attraction known as 'Van der Waals forces' or 'chemisorption'.Activated carbon is very effective in removing bad odour from air or water. Activated carbon can also remove bad taste from water. This is why is activated carbon used in air and water purifiers.
Activated carbon water filter works by removing chlorine and most of the harmful organic chemicals in the water passing over the activated carbon and thus improves the taste of water and also removes bad smells in water.
There are many different types of Activated Carbon depending on the raw material from which it is made. Each type of activated carbon has its advantages in certain applications, like Coconut Shell Activated Carbon is the best type of Activated Carbon for water filter purifiers.
How long can Activated Carbon Water purifiers filter be used
Activated carbon filter in water purifiers has a limited ability to adsorb contaminants from water, and so the activated carbon filter in water purifiers should be changed when it has been depleted and cannot purify water anymore. The pore structure of the activated carbon gets filled or saturated with the adsorbed pollutants and it cannot adsorb any more.
At this stage the activated carbon will start rejecting some of the previously adsorbed pollutants back into the water flowing over it. This is called ‘breakthrough’. When this happens, the concentration of pollutants in the treated water will be higher than in the raw water being treated. The activated carbon filter cartridge must be replaced well before this happens. Most of the activated carbon filter elements are sold saying that they are good for so many litres of water. This quantity is based on a previously fixed standard quantity of contaminants in the incoming water. Your water may have more contaminants and so it is important to know the quality of your incoming water.
How good is activated carbon water purifier
Activated Carbon water filter purifier does not remove microbes and dissolved inorganic chemicals like Nitrates, Fluorides and hardness in water. Generally not all the heavy metal contaminants like Lead and Mercury salts are removed by activated carbon, though some organic heavy metal salts are adsorbed by activated carbon. So activated carbon filters should not be used for removal of heavy metal salts like Arsenic in water.
One big disadvantage of activated carbon water filter is that it can be a breeding ground for microorganisms on the surface of the activated carbon filter media, especially when there is no running water over the activated carbon in the water filter, like when it is not being used for a long time. Some of the organic chemicals adsorbed by the activated carbon become the food for these bacteria. Since the dangerous disease causing germs like typhoid, cholera and dysentery are not present in tap water of public water distribution system, it is safe to use activated carbon filters on such city water. Activated Carbon water filters should not be used on well water or other sources of water that has not been disinfected.
It is safe to use bleach like Clorox to disinfect well water and then use an activated carbon filter to dechlorinate or remove the bad tasting chlorine from the water. This method of well water purification is described in more detail in our page on well water purification
What is Activated Carbon, How Activated Carbon is made
Activated Carbon is made from many materials like Bituminous Coal, Lignite coal, Coconut shell and wood charcoal, etc. The raw carbon has to undergo many treatment process as described below, before it becomes a good grade of activated carbon. How is activated carbon made from coconut shell described as follows
The raw un-activated Coconut shell charcoal is filled in a tank and inert gases like Argon or Nitrogen is introduced into the tank. The Coconut shell charcoal is blanketed by the inert gas and is subjected to high temperatures of about 1200 degrees Celsius. Then the Coconut shell carbon is exposed to superheated steam and oxygen. With these high temperature activation process, the raw Coconut shell Carbon becomes Activated Coconut Shell Carbon and pore surface area of the Coconut Shell Carbon is greatly increased. The quality of the finished Coconut Shell activated carbon very much depends on how well the activation process was carried out.
Classification of Activated Carbon
The surface area within the pores of Activated carbon is huge, one gram of activated carbon can have surface areas of 500 to 1500 meter square depending on the of Classification of the Activated Carbon. The selection of pore size of Activated Carbon is very important in relation to its application. The classification of Activated carbon is done depending on their pore size and is as follows:
- Macropores (greater than 50 nm or Nanometre in diameter)
- Mesopores (2-50 nm diameters)
- Micropores (less than 2 nm diameter)
Activated Carbon can also be classified depending on the form or type of Activated Carbon. Some of the common classification of Activated Carbon is as follows
- Granular activated carbon (GAC)
- Extruded activated carbon (EAC)
- Powdered activated carbon (PAC)
- Impregnated carbon (chemicals added for special applications)
- Polymer coated carbon
Different types of Activated Carbon
There are many different types of Activated Carbon depending on the raw material used for making the activated carbon. Activated Carbon can be termed as for example Coal based Activated Carbon, Coconut shell based Activated Carbon or wood based Activated Carbon.
One of the best Activated Carbon for water purification purpose is coconut shell activated carbon. Coconut shell based activated carbons are of the microporous type and they are best for removal of chlorine and it's by-products called TTHM's and volatile organic compounds or VOCs in water.
Most popular forms of activated carbon used in drinking water filters are granular activated carbon (GAC), extruded solid carbon block (CB) and powdered activated carbon (PAC). Activated Carbon in the form of solid Carbon Block is generally considered the most efficient for water treatment.
Factors affecting performance of Activated Carbon purifiers
How effective is activated carbon filter in purifying water by adsorption depends on several factors and one of the most important factor is the contact time between the water and the activated carbon media. By increasing contact time of water and activated carbon, more contaminants can be removed from the water. Contact time can be increased in two ways by allowing the water to flow more slowly over the activated carbon or by increasing the amount of activated carbon media in the filter. When there is more of the activated carbon in the filter the better it is, because the water will flow over more area of carbon and also the cartridge will last longer. The slower the flow of the water over the carbon, the more time the contaminants in the water will be in contact with the activated carbon and it gives more time for absorption to take place. Lower water temperatures improve the performance of activated carbon filters.
Problems of Activated Carbon water purifiers
the main problem of Activated Carbon water filters is that it will not remove bacteria, dissolved salts and water hardness from the water. Bacteria can grow on the activated carbon media in the water purifier. Some ways of overcoming these problems in Activated carbon filters are described below.
Silver impregnated Activated Carbon water filter purifier
Some manufacturers counter the bacterial growth on the surface of activated carbon by impregnating the activated carbon with nano-silver particles. Silver ion is a bactericide and will be helpful in preventing this bacterial growth. UV after activated carbon filter is another way of preventing the germs growing on the activated carbon to pass through to your drinking water.
How to buy Water Purifiers in India
The best way to buy Water Purifiers in India is to first look at all models of Water Purifiers available online at the leading online Retailers in India. For example on the online webpage of All Water Purifiers available in India on Amazon.in, you will find the full range of Indian Water Purifiers complete with their best discounted price and full specifications. This is great information, and you can decide on which model of water purifier to buy. With the model of water purifier you want to buy finalised, you can go to local shops to try and find the model of water purifier you have chosen and see if you can get at similar price of that at Amazon.in. In most cases the price from Amazon will be cheaper, because they buy in bulk from the manufacturers direct and they sell huge volumes because they are the world's largest and most trusted online retailer. If you buy from Amazon, they will arrange to have the water purifier installed in your house, usually free of charge.
Warranty and other facilities offered through Amazon are usually better than what you can get from local agents of water purifiers.
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