With more than 30 years’ experience in the residential and commercial water treatment space, Mark Nelson is a Class 1 Drinking-Water Operator and a CBWA (Canadian Bottled Water Association) Certified Plant Operator. As founder and president of Nelson Water in Ottawa, Mark focuses on dealing with challenging water treatment system designs for problem water. He also heads the largest water bottling plant in the city of Ottawa with a delivery network throughout the Valley.
An activated carbon filter is a refined technique based on water filtration processes that have been in constant use for thousands of years. This filtration method produces water that tastes and smells great, and it reduces chlorine and chloramine (ammonia mixed with chlorine to boost efficacy). If you receive public water, the treatment plant adds chlorine or chloramine as a disinfectant to kill harmful microorganisms. But, chlorine imparts a “swimming pool” chemical taste and odor, and chlorine byproducts can be tentatively linked with certain types of cancer. In this article, we will take a closer look at activated carbon filters to help you make informed decisions.
What is a Carbon Filter?
All effective water filters offer a considerable barrier that water must pass through to remove contaminants. When there are organic compounds present in water, they make the water taste and smell bad. The first people to discover that carbon has detoxifying properties, and it’s used to this day to improve the taste and quality of foods and drinks. The incoming water passes through a carbon filter, and certain contaminants stick to the carbon.
How Does the Carbon Filter Work?
The aforementioned sticking process is known as adsorption, and it attracts certain organic compounds. This is because water and the contaminants that it may contain are polar compounds that are attracted to each other. But this is only one reason why carbon is so effective as a water filter.
The second characteristic of carbon is that it is extremely porous and has a very large surface area in relation to its actual size. This makes carbon an ideal filtration medium to trap organic compounds and certain other contaminants as the water flows through. Carbon has tiny pores that can only be measured in microns, and the smaller the pores, the more effective the water filtrations will be.
Small pores will reduce the flow rate and water pressure as the water passes through the filter. This may sound like a detriment, but it’s a good characteristic because it increases the length of the contact time for filtration. So, the larger carbon surfaces and the smaller pores will make the filtration more efficient.
What About Charcoal Filters?
When you hear people talking about carbon water filters, you may hear them use charcoal filters in an interchangeable fashion. This can cause considerable confusion, and some people may even try to use charcoal as a makeshift water filter. Although it is true that charcoal has historically been used as a filtration media, it doesn’t have the same filtering potential as carbon. A carbon filter is not made from the same type of coal that can be bought in a bag for grilling at the weekend.
What Does a Carbon Filter Contain?
Inside a carbon filter, you will usually find the following three different types of filter media: bituminous coal, coconut shell, and wood-based. Of these three, the most renewable is the coconut shell carbon media. This material doesn’t cause an allergic reaction or taste change to the filtered water. The ancient Egyptians used wood-based carbon by grinding burned wood into a pretty fine granule for the time period. In the recent past, the most common carbon was sourced from bituminous coal, and that fell out of favor after traces of arsenic in the media were discovered.
What is Activated Carbon?
Carbon is an interesting material, it can be activated by steam or heat, and this process actually opens the pores of the material. Essentially, this increases the overall surface area, and this, in turn, gives the carbon extra capacity to hold contaminants. Most modern carbon filters use activated carbon in one of the following forms: carbon block, radial carbon filters, and Granular Activated Carbon (GAC). Let’s take a look at these three carbon filter types in more detail:
1. Carbon Block
A carbon block is comprised of fine granules that are held together with a bonding agent. The incoming water flows through the side of the filter, and the cleaner water is forced out at the top. The carbon has been ground to a fine granule, and the surface area is increased with 7-10 more surface area than GAC. The compact carbon design prevents channeling, but it does restrict the water flow more.
2. Radial Carbon Filters
These combine the improved flow rate of a GAC filter with the extra surface area of the carbon block. The water flows into the side of the filter cartridge and out of the top in a similar way to the carbon block. But, the granules are much finer, and this increases the flow.
3. Granular Activated Carbon (GAC)
The GAC filters are filled with loose activated carbon granules that allow water to flow through the filter easily. The water can only flow in a single direction, and this guarantees even contact with the carbon. People like GAC filters because the water flow rate is faster. The main disadvantage is channeling, the water cuts a straight path through the carbon media, and this can allow contaminants to pass through the filter.
Which Contaminants Can a Carbon Filter Remove?
An activated carbon filter excels at the removal of chlorine, bad tastes, and odors, and it can remove certain other contaminants, too. Check the filter for NSF certification to check which contaminants the filter will remove from your incoming water supply.
Here are some common contaminants that they may be able to remove: trihalomethanes, lead, coliforms, cysts, herbicides, pesticides, iron, and heavy metals. Some of these contaminants will not adhere to the carbon, but the filter pores are so small that they cannot pass through. Additional materials can be added to a carbon filter to improve its capability to remove certain contaminants. An iron-reduction carbon filter has Kinetic Degradation Fluxion (KDF) to remove high concentrations of heavy metals. A carbon filter with added silver can be effective in killing microorganisms.
If you need a carbon water filtration system for your home, contact your local water treatment specialist today.