Many people who own water softeners will also choose to improve the taste and quality of their drinking water by using drinking water filters. There are many different types of water filters but most will use active carbon.
What is active carbon?
Carbon is made from organic material eg: coconut, coal, wood and is formed by heating the material in the absence of air. Carbon has been used throughout history as an adsorbent for contaminates and is considered the most powerful adsorbent known to man. Its use dates back to 2000 BC. The reason carbon is used in drinking water filters is that it is a very porous material. Active carbon has been activated by a chemical process which gives it a slight positive electrical charge. Active carbon used in drinking filters will be more efficient because the positive electrical charge makes it more porous than normal carbon.
How does active carbon work?
Active carbon removes contaminates using two processes:
Adsorption (Van der Waals force):
Contaminates are attracted by this force into the pores of the active carbon where they stay attached to the walls. The process depends on:
- the type of source material of the active carbon to determine the size of the pores and thus the contaminate type and removal level
- the chemical nature of the source material
- the chemical composition and concentration of the contaminant
- the temperature and PH of the water
- the contact time, determined by the flow rate and volumes of active carbon
The positively charged active carbon attracts the negatively charged contaminations. The level and type of contaminant removal is determined by the activation process. For example the level of oxygen, level of electrical charge. Active carbon is most effective in removing organic contaminates from the water and so improving the aesthetic appears of the water (colour, taste and odour).
What is removed by active carbon?
Reduced or removed
Large organic molecules, Radon, Ozon, Chlorine (including cancer causing by-products trihalomethanes like Bromoform, Dibromochloromethane, Bromodichloromethane, chloroform etc), Carbon Tetrachloride, Toluene, Tetrachlorethylene, Trichloroethane, Vinyl chlorides, Methyl tert-butyl ether (MTBE), many (54) volatile organic chemicals (VOC), pesticides, Phenol, herbicides, benzene, solvents, Xylenes, some heavy metals. Limited arsenic, limited sediment.
Not reduced or removed
Microbes, sodium, nitrates/nitrites, fluoride, minerals/salts (hardness) halogenated hydrocarbons, polychlorinated biphenyls, polcyclic aromatic hydrocarbons, asbestos, barium, beryllium cadmium, chromium, copper, mercury, nickel, selenium, sulfate, thallium.
NOTE: The above listing is purely indicative and is based on data provided. The actual removal/reduction of contaminates depends on many factors such as type of active carbon, temperature, contact time, PH, level of contamination. The exact removal or reduction can only be confirmed by lab testing.
Active carbon and bacteria
Active carbon is seen as a breeding ground for microorganisms. However, the UK water authorities do a great job bringing safe water to our homes, so the likelihood that microorganisms will enter the drinking filter system is small. The public water system treats the water to prevent pathogenic microorganisms being in the water.
‘Studies of activated carbon units, have not shown this medium to encourage pathogenic bacterial growth’ – (WQA Water Processing by Wes McGowan)
Are you interested in getting a drinking water filter in your home? Have a look at our drinking water filters page.