The water we drink is not drinkable in the state it is found. Freshwater is often contaminated through human activity, such as agriculture and pollution, and it can contain germs, chemicals, and other harmful bacteria. For municipalities and other places to provide clean water, it has to be filtered.
For that process, carbon filtration systems are a common medium through which water is filtered from impurities, and here we will discuss how they work.
Water Treatment Systems
Most water treatment systems do not simply filter impurities from water and render it drinkable. There are processes involving several other steps as well.
These steps are as follows:
As can be seen, the filtration process has other prerequisites as well. Coagulation is used to remove dirt particles from the water, and along with Flocculation, it helps form larger particles. These larger particles can make the subsequent sedimentation and filtration processes easier.
Sedimentation is the process of separating solids from liquids, which allows the solid parties from the preceding steps to form at the bottom because they are much heavier than the water. Filtration is then used to clear the water through different filters, the size of which depends on the contaminants. In some cases, if chlorine is used during filtration, it may require additional disinfection.
Carbon is often used in water filtration, but how exactly?
Typically, carbon filtration systems are only referring to the medium of filtration, that is, a carbon-based method. The actual method through which it is used differs.
That is not to say that carbon is not used frequently. In fact, it is among the most common medium of filtration, from the water filter you use for hiking to a complete reverse osmosis water filter. All of these areas utilize carbon for water treatment, which is typically produced by grinding up a carbon source.
The source of carbon can vary, from coconut shells to coal. Each has its own uses, though coconut shells are the most widely used due to their renewable properties.
To make a carbon filter, the carbon material that is to be used has to be heated in a chamber without any oxygen present. It is typically heated to 1000 degrees as it removes any impurities present within the material. The carbon is then activated by treating it with steam at 1600 degrees, which allows the carbon material to form fragments with cracks in them, which help with the actual filtration process and keep out impurities from the system.
How Do They Work?
When contaminated water is filtered through carbon filtration systems, the process occurring is called adsorption. The carbon, when activated by treating it with steam, acts almost like a magnet to attract the impurities and bring them to the surface of the carbon material, which then holds on to them.
Some of the impurities also change their composition when they react with the carbon, which acts as an activating agent for the change itself. Contaminants such as chlorine, pesticides, and many other insolvents are often used to filter water with carbon filtration systems.
There are two major types of these systems:
- Caron Block Filtration Systems
- Granular Activated Carbon (GAC) Systems
Carbon Block Filtration Systems
In this system, the filter is made of pieces of carbon, which are then pressed together to create the filter itself. The pieces of carbon, when compressed, significantly add to its absorbent properties, though it also means that the water passing through it does so slowly.
However, the level of compression also determines how fine the impurities have to be that it filters. A carbon block filter with a very small micron rating, such as 20 microns, will have a much lower flow rate than one rated for 100 microns.
Granular Activated Carbon (GAC) Systems
GAC systems are a type of carbon filtration system that is made of small carbon granules and particles. These filters are typically used as polishing filters, designed to improve the quality and taste of the water being filtered during treatment. GACs are known for having a much better taste and odor of the water after filtration, especially compared to other methods.
GAC can be considered an uncompressed filter of carbon particles, which are then compressed together to form a solid carbon block.
GACs also have very high adsorption properties and remove a wide range of impurities, which is especially useful for drinking water. The reason is that if a municipal filtration plant is using chlorine or disinfectant, they can make the water have less than preferable odor and taste. GAC allows the filtration process to improve the taste and odor even further.
Comparing Carbon Blocks and GACs
One important thing to note is that neither are mutually exclusive filtration systems. In fact, most carbon filtration systems use both to be as effective as possible.
Of course, GACs are loose and are not designed for as fine materials, whereas a carbon block is compressed together and can filter dust and bacteria if they are rated for it. Carbon blocks are often used in pre-filter processes in reverse osmosis filtration.
The two also have a different flows of water. As carbon blocks are highly compressed, water is slow to pass through, whereas GACs are designed loosely and can pass water much faster.
Carbon filtration systems are not the only aspect of water treatment, but they are crucial in removing contaminants and impurities from the water, allowing it to be cleaned for drinking, cooking, and other purposes. Different water filtration plants also have varied purposes, from filtering wastewater to rainwater. Different impurities and contaminating materials require different filtration systems as well.
Most filters are made using carbon, and here we have also discussed how they work, in addition to two types that have very different properties. These filtration systems, which are carbon blocks and GACs, can both be used in tandem, allowing for greater efficacy in water filtration.