For the Planet

Drinking water filters and active carbon

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.

As this article includes technical language, there are some key terms to define before we start:

  • pH level: A measure of how acidic or alkaline water is
  • Adsorption: when atoms, ions or molecules stick to a solid, liquid or a gas

What is active carbon?

Carbon is made from organic material like coconut, coal or wood.

Carbon is made from organic material such as coconut, coal, or wood and is formed by heating the material in the absence of air. Carbon has been used throughout history as an adsorbent for contaminants and is considered the most powerful adsorbent known to man. Its use dates back to 2000 BC. It is used in drinking water filters because it’s a very porous material. This means other substances such as impurities in water get attached to it easily.

How does active carbon work?

Active carbon removes contaminants using two processes:

Adsorption (Van der Waals force):

Contaminants 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 contaminant 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

Catalytic reduction:

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

Active carbon removes a great many contaminants from water including:

  • Chlorine
  • Radioactive chemicals
  • Carcinogens
  • Herbicides
  • Pesticides
  • Limited arsenic
  • Heavy metals

Not reduced or removed

Active carbon does not remove the following contaminants from water:

  • Sodium
  • Microbes
  • Hardness minerals
  • Asbestos
  • Some metals

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 by many as a breeding ground for microorganisms. However, as the UK water authorities do a great job bringing safe water to our homes, the likelihood that microbes will enter the water filter system is small. The public water system treats the water to prevent harmful 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

Summary

Active carbon in water filters is a safe, effective way of improving the taste, appearance and smell of your water. It removes a wide range of contaminants through either catalytic reduction or adsorption, leaving you with water that you know is free of herbicides, pesticides and other harmful chemicals.

Are you interested in getting a drinking water filter in your home? Have a look at our drinking water filters page.

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