Charcoal Filtration

30^th December, 2023.

In this post, we will see the concept of activated carbon filter or charcoal filter.

Filters are a very important part of any water treatment system in secondary stage. Basically, there are so many types of filters used that it literally gets confusing as to which one to use for what. If you have a clear idea of each and every filter in terms of it’s purpose, then you can easily choose one of them. One of the most used filter technologies in water treatment is an activated carbon technique. You may think that how this black material helps in purifying water, when it can either add it’s colour or smoky properties to it. Well, it is not like that. Carbon that we are talking about here is a very advanced form of material that is first treated upon before using it for water. So, it is an interesting topic and curious to learn. In this post, we will see the concept of activated carbon filter or charcoal filter.

·       How does charcoal filter water?

There are two basic methods for capturing things – absorption and adsorption. Suppose you have a sponge. When you pass water through it, sponge will capture it. But when it is squeezed, it will just pour the water out. But, if you want to trap it permanently, then it is called adsorption. Means, when some impurity passes through an adsorption material, it generally gets trapped on it as it bonds with it and gets attached through chemical reaction. Charcoal works on the principle of adsorption.

Carbon as we know is a gaseous property. For getting activated carbon, two materials are used – charcoal or coconut shell. Here, we will discuss about charcoal. Charcoal is very high in carbon. It is first treated with oxygen due to which millions of pores of carbon atoms are opened up (this method is also called as superheating, usually done at 1000°F). As pores increase, the surface area of the charcoal material increases. It can typically go up to 2000 square metres per gram. Because it becomes porous and large in surface area, the holes are such a size that major chemical impurities which are bond compatible with carbon get merged quickly with it and gets trapped on the carbon layer. Due to this, a large amount of clean water passes through activated charcoal layer.

But it is to be noted that not all chemicals bond with carbon (like sodium or nitrate or lead). So, some impurities which have non-carbon bonding properties will not stick on it and will pass through it instead. So practically, it is not completely possible to purify water with activated carbon filter. But yes, your work will be done maximum with the help of it.

In practical purposes, carbon is filled inside a trapping body vessel through which water passes and impurities are removed. This looks very similar to a normal filter housing body that you have everywhere. One thing to note that mere backwash is not the remedy for cleaning this filter, as is done in other filters. Carbon properties are such that impurities will not be removed easily from it’s layers once stuck. Yes, backwash will help, but only to some extent. So, they are usually replaced after period of use.

·       Carbon filter benefits:

1.     Due to carbon properties, it is able to merge a large type of chemicals on it’s layers. So, water becomes much pure with the use of this type of filter. The chemical composition of carbon atom is such that the healthy minerals of water remain as it is and only impure chemical properties are merged on it’s pores.

2.     The main merit is that it removes chlorine, which is responsible for odour in water. Additionally, removal of chlorine is advantageous as many bacteria survive on it. This makes the water tastier.

3.     The cost of activated carbon filter is much less than other types of filters.

4.     Activated carbon can add back important minerals like manganese, calcium or iron back into the water.

5.     Because pores are responsible for holding the impure chemicals, it gets choked after some point of time, maybe one year. So, it too requires maintenance; but the important advantage is that it is easy to replace and maintain than other filters.

6.     Due to it’s features, activated carbon is used in many critical areas like odour removal, organic matter removal, de-colourisation of sugar molasses, and high toxic gas removal.

I have covered some general principles related to activated carbon technology. I have also not attempted to cover all the methods, as it can vary from case to case and there is no end to it. Once you are familiar with this filter technique, you can easily tackle all types of problems in it.

Thank you for reading the post. I hope you liked it and will find a new way in this type of technology.