How Do Carbon Water Filters Work?

Carbon is one of the most abundant elements on the planet. It resides in all living things including human beings, animals, and plants.

It is also one of the planet’s most active elements, moving through the atmosphere, the oceans, living entities, and within the earth itself in a process called the carbon cycle.

The abundance of carbon has led humans to develop thousands of ways to use it, from building structures and fuelling our cars, to providing heating and growing crops. It’s an essential element for human survival.  

One of the most exciting uses for carbon can actually be found in the world of water filtration.

Carbon can be used to remove a huge range of contaminants from water including chlorine, heavy metals, pesticides, insecticides, PFAs, and petrochemicals.

It can transform contaminant water dramatically, making it cleaner, safer and more enjoyable to consume.

In this guide, we are going to delve into the world of carbon filtration. We’ll be:

• Explaining why carbon excels at contaminant removal
• Identifying the different forms of carbon
• Answering common questions about activated carbon
• Sharing some of the best carbon filters in Australia

If you have any questions at all, contact Clarence Water Filters via 02 6646 8565 or sales@clarencewaterfilters.com.au.

Contents 

1. How Do Carbon Water Filters Work?
2. What Is Activated Carbon?
   Thermal Activation
   Chemical Activation
3. Types Of Activated Carbon
   Powdered Activated Carbon (PAC)
   Granular Activated Carbon (GAC)
   Extruded Activated Carbon (EAC)
   Impregnated Carbon
   Catalytic Carbon ORC
4. What Do Carbon Filters Remove From Water?
   Chlorine
   Chloramines
   Disinfection by products
   Bad tastes and odours
   Per- and polyfluoroalkyl substances PFAs
   Herbicides and insecticides including Glyphosate Round-up
   Heavy Metals
   Polychlorinated biphenyls PCBs
   Volatile Organic Compounds VOC
   Petrochemicals
   Steroid hormones including Estrogen
   Pharmaceuticals and antibiotics
   Microplastics
5. What DON’T Carbon Filters Remove From Water
   Dissolved Minerals
   Certain Microbiological Contaminants
   Inorganic contaminants partial removal
   Radionuclides
6. Frequently Asked Questions
   How Long Does a Carbon Water Filter Last?
   How Do You Know When Your Carbon Filter Needs To Be Replaced?
   Can Carbon Remove Heavy Metals?
   Are There Any Charcoal Water Filter Side Effects?
   What Are The Disadvantages Of Activated Carbon In Water Treatment?
   Can You Use A Carbon Filter For Well Water?
   Is Carbon Water Filter Replacement Hard?
   How Much Does Carbon Filter Cost?
   What Is The Best Activated Carbon Water Filter?
   Is A Carbon Water Filter Jug All I Need?
7. Wrapping Up

How Do Carbon Water Filters Work?

Carbon has been used to filter water for thousands of years. It primarily works using the scientific principle of ‘adsorption’.

Adsorption is the capability of any material to attract and hold onto molecules.

When water flows through a material with a high adsorption capacity some of the contaminants it contains can become ‘stuck’ to its surface and removed from the water.

Carbon has a particularly strong adsorption capacity, which makes it extremely useful for filtration purposes.

The pores on the carbon’s surface can also catalyse (break apart) more complex chemicals. Certain forms of carbon are more effective at catalysing chemicals than others.

Blocks of compressed carbon will also use mechanical filtration to remove contaminants. The carbon will block large sediment particles from passing through, like a sieve.  

Many types of carbon can be used to filter water including wood, coal, coconut shells, bamboo, sawdust, willow peat, peach pits, and coir.

Back to top.

What Is Activated Carbon?

Most modern carbon water filters will use activated carbon, also called activated charcoal.

Activated carbon refers any form of carbon that has been modified to have more pores on its surface. This gives the carbon a larger surface area, which provides for improved absorption capacity and chemical catalysing capabilities.

In other words, it makes the carbon faster at removing impurities and increases the total chemical reduction capacity of the carbon.

The amount of surface area on activated carbon is astounding. A single gram of activated carbon has about 3 kilometres of surface area. This provides plenty of room for capturing contaminants. 

Activated carbon can be made from virtually any carbonaceous source material. However, the most common choices are crushed coconut shells, wood, and coal.

There are two methods for activating carbon: thermal and chemical activation.

Back to top.

1. Thermal Activation

With this form of activation, hot gases are applied to the carbon which causes additional pores to. This increases its adsorption and chemical catalysation ability. This process is carried out using an inert gas like carbon dioxide, nitrogen or argon.

The entire process involves several steps:

1. Cleaning/processing
2. Moisture reduction
3. Removal of volatile compounds
4. Carbonisation
5. Final steam treatment (activation)

2. Chemical Activation

Chemicals are added to the raw source material before it begins the carbonisation process. In most cases, it will involve salt, acid or a strong base solution. The carbon is then exposed to heat which causes it to develop more pores, activating it.

Types Of Activated Carbon

There are many forms of carbon available, categorised by processing method, application, and size. The most common forms include:

Granular Activated Carbon (GAC)

Granular activated carbon consists of clumps of carbon, typically 0.4 to 3mm in size. GAC is ideal for water filtration applications where a fast flow rate is needed. Also useful for absorption of vapours and gasses from the air.

Granular activated carbon is often used inside of refillable filter cartridges. The cartridge has sediment pads to keep the carbon from flowing through into the filter head.

Powdered Activated Carbon (PAC)

Very fine particles of ground or crushed carbon that can be added directly to water or used in a water processing unit.

Extruded Activated Carbon (EAC)

Also referred to as carbon block filters. Combines powdered activated carbon with a binding agent to create a solid piece of carbon filter media.

Carbon block filters have a low pressure drop, minimal dust content, and excellent mechanical strength. Compression of the carbon can also make the filter capable of blocking fine sediment particles, which can include heavy metal particles on filters with smaller micron ratings, like the WC04.

Most carbon block filters are cylindrical, with a hollow core. The incoming water will move through the walls of the filter, then through the hollow core and out of the filter head outlet.

Impregnated Carbon

Carbon can be impregnated with a variety of materials to enhance its capabilities. Common types of impregnated carbons include:

• Silver impregnated carbon
  Silver is bacteriostatic, so it can kill or incapacitate bacteria inside of the filter media and filter housing. This reduces the risk of bacterial growth occurring in your filter system when treating unchlorinated tank/bore water.
• KOH Impregnated Coal Based Carbon (Potassium Hydroxide)
  Excels at reducing sulfide-rich odours typical of municipal sewage treatment, pulp and paper mills, and refineries. Also reduces Nitrogen Dioxide and Nitrogen Oxides.
• Copper Impregnated Carbon
  Copper impregnated carbon is more resilient against high temperatures compared to standard carbon. Often used to filter volatile organic compounds and other chemicals from air.

Catalytic Carbon (ORC)

Catalytic carbon is a form of activated carbon which has received additional processing to further increase the number of pores it contains.

The additional pores make it capable of removing chemicals faster and having greater storage capacity. It can also catalyse complex chemicals like chloramines more easily.  In fact, if chloramines are of concern to, catalytic carbon should be used in your filtration system. 

Back to top.

What Do Carbon Filters Remove From Water?

Carbon filters can reduce a wide range of contaminants from air and water. From water, this includes:

Chlorine

Chlorine is added to treated water supplies to kill or incapacitate bacteria, protozoa, algal spores, viruses, and cyst parasites (cryptosporidium, giardia etc). Unfortunately, it gives the water a bad taste/odour. Disinfection by-products (DBPs) are also created as the chlorine interacts with decaying matter and other chemicals (more on those in a moment)

Chloramines

Chloramines are a combination of chlorine and ammonia. Water authorities are increasingly turning to chloramination as it provides longer residual protection, so water remains sanitised for longer. Unfortunately, chloramine molecules are harder to remove from water than chlorine, because they are more complex. If you have chloramines in your water, we’d recommend the use of Catalytic Carbon (ORC) as it has more surface reactive sites.

Disinfection by-products

Chlorination of water can generate hundreds of new compounds and chemicals. Some of the DBHs created are toxic, like Trihalomethanes. The good news is that carbon filtration can also reduce the levels of DBHs in the water.

Bad tastes/odours

Carbon is extremely effective at removing bad tastes and odours from water. There are also speciality carbons which remove unusual smells like Hydrogen Sulphide.

Per- and polyfluoroalkyl substances (PFAs)

Nicknamed ‘forever chemicals’ due to their ability to persist within the natural environment and the human body. PFAS can increase the risk of many conditions including Thyroid disease, Liver damage, Breast cancer, Kidney cancer, Inflammatory bowel disease, and Testicular cancer. Fortunately, Carbon is effective at removing PFAs from water.

Herbicides and insecticides including Glyphosate (Round-up)

Although Australian water authorities do their best to limit agricultural activities around water reservoirs, herbicides and pesticides can still make their way into town water. If you have a tank, you may have this type of chemical contaminant due to aerial spraying. Fortunately, carbon does a fantastic job of adsorbing both herbicides and pesticides.

Back to top.

Heavy Metals

Fine carbon block filters are capable of removing lead, mercury and other heavy metals. It’s important to note that standard granular activated carbon cannot remove heavy metals.

Polychlorinated biphenyls (PCBs)

PCBs are carcinogenic chemical compounds, which were often used in industrial and consumer products prior to the 1980s. Activated carbon is very effective at removing it from water, with high-quality carbon blocks having a removal rate of up to 99.99%. Read more about the effectiveness of carbon on Polychlorinated biphenyls (PCBs).

Volatile Organic Compounds (VOC)

Volatile organic compounds are organic chemicals that have a low boiling point and high vapor pressure. You can find VOCs in many solvents, adhesives, cleaning supplies, paints, and other chemical solutions. Some VOCs are been found to be hazardous to humans. Fortunately, carbon filtration has been shown to effectively reduce Volatile Organic Compounds (VOC) in water.

Petrochemicals

Petrochemicals refer to any chemical developed from natural gas or petroleum. You can find petrochemicals in detergents, polyester fibres, nylon, acrylics, polythene and man-made plastics. Activated carbon has been shown to remove most petrochemicals from water.

Steroid hormones including Estrogen

Steroid hormones are quite robust and can persist in water for a long time. Unfortunately, consuming them can have an unexpected impact on a person’s health. Carbon can trap a wide range of steroid hormones including Estrogen.

Pharmaceuticals and antibiotics

Our local waterways are increasing polluted by pharmaceutical compounds and anti-biotics. Unfortunately, this increases the risk that some of these compounds can make it into our drinking water supply. Fortunately, carbon has been shown to be capable of trapping both pharmaceuticals and antibiotics.

Microplastics

Microplastics are extremely small pieces of plastic debris created from plastic objects breaking down. Scientists believe that they may have a negative impact on human health if ingested.

Although most microplastics are between 2-5mm in size, they can eventually become quite small. As of 2017, the smallest microplastics found are 1.3 micrometres (1.3 microns) in size. A fine carbon block or sediment filter is very effective at trapping particles of this size.

Back to top.

What DON’T Carbon Filters Remove From Water?

Although activated carbon is one of the most effective forms of media for contaminant reduction, there are a few things it can’t do. It won’t remove:

Dissolved Minerals

Carbon doesn’t remove dissolved minerals like calcium, magnesium, phosphorous, potassium, and sodium. This is a good thing in one respect, as it means your water retains mineral content, which is good for your health.

However, if you are in a part of Australia with high TDS, you may be experiencing limescale build-up, which could damage appliances and plumbing fixtures. Your carbon filter won’t help to prevent this on its own.

Fortunately, there are some other options which can reduce limescale including KDF and Polyphosphate. Contact us to learn more.

Certain Microbiological Contaminants

Carbon filters will not remove very small bacteria and viruses, which can sometimes be found in untreated water. For their removal, you will need a UV system (kills all pathogens) or a ceramic filter (traps most bacteria).

Some pathogens can only be removed using specific types of carbon filters. For example, you would need to use a sub-micron carbon block (1 micron or smaller) to remove Cyst parasites like Cryptosporidium, Giardia, and Cyclospora.

If you are using untreated water, you could also chlorinate it to kill any pathogens, then use carbon filtration to remove the chlorine.

Inorganic contaminants (partial removal)

Only certain carbon filters are capable of removing inorganic contaminants like arsenic and asbestos. To reduce these contaminants, you’ll need a fine carbon block filter (1 micron or lower). A high quality carbon block filter is required to handle these contaminants.

Radionuclides

Radionuclides are unstable radioactive forms of elements including radon, uranium, radium, lead and polonium. There are specific carbon block filters designed to trap these types of contaminants.

Back to top.

Frequently Asked Questions

Back to top.

Wrapping Up

As you can see, carbon water filters are a very useful tool when it comes to removing chemical contaminants and improving the odour/flavour of water. If you would like to learn more, contact us today!

Clarence Water Filters

02 6646 8565

sales@clarencewaterfilters.com.au.

Back to top.

Categorised in: Product Features, Water Filtration

This post was written by Greg