When it comes to drinking water, you want to make sure that you’re taking all the necessary precautions to keep yourself and your family safe. One of the things you may be wondering is whether or not carbon filters remove VOCs.
Carbon filters are very effective at removing most VOCs from drinking water. Since VOCs are a group of many thousands of chemicals, the treatment efficiency varies according to the properties of each compound. In general, carbon adsorption can remove 90 to 99.999% of many common volatile organic compounds. Carbon filtration is a well understood and reliable treatment method for VOCs.
In this blog post, we discuss how well carbon removes VOCs and what factors can affect how effectively this technology works. Stay safe and drink clean!
What Are VOCs?
Volatile organic compounds (VOCs) are chemicals that vaporize into air and dissolve in water. They can come from many different sources, including cleaning products, paint, and even your furniture. VOCs can be harmful to your health if you’re exposed to them for too long.
There are a few different ways that you can be exposed to VOCs. They are widely used in many household products, such as:
- Hobby Products
The VOCs that are most troubling are those that persist in the environment and cause negative health effects. Here are the some of the most commonly encountered VOCs:
- Carbon tetrachloride
- Ethyl acetate
- Ethylene glycol
- Isopropyl alcohol
- Methyl ethyl ketone
- Methyl chloride
- Monomethyl ether
How do VOCs get into my drinking water?
Volatile organic compounds can enter the environment through both natural and human sources. These contaminants can come from several sources including:
- Leaking Underground Storage Tanks
- Wastewater Treatment Plants
- Industrial processes
- Dry Cleaners
Once released to the environment, these chemicals find their way to surface water and groundwater through runoff or infiltration. VOCs can also enter the air and eventually fall back to the ground in rain or snow, contaminating soil and water.
Health concerns with VOCs
VOCs are a group of chemicals, and each compound has specific health effects. These chemicals are known to cause a variety of health problems, including:
- Eye, nose and throat irritation
- Liver damage
- Kidney damage
- Allergic reactions such as skin rashes and asthma attacks
The health effects of VOCs are also dependent on the amount and length of exposure, as well as the compound itself. Some VOCs can be more dangerous than others. For example, formaldehyde is classified as a carcinogen by the EPA.
Drinking water standards
When it comes to drinking water, the EPA has established maximum contaminant levels (MCLs) for a variety of VOCs. The MCL is the highest level of a contaminant that is allowed in drinking water. MCLs are set at levels that protect public health.
The following table lists the drinking water standards (MCLs) for many of the most common VOCs.
Activated carbon adsorption is an effective and reliable water treatment process. It is considered a best available control technology by the USEPA and is a benchmark for other water treatment methods.
Carbon filters are widely used in residential and commercial water treatment systems to remove a variety of contaminants including taste and odor, chlorination byproducts, VOCs, and THMs.
Read my comprehensive Carbon Design Guide for a detailed explanation of this treatment technology.
How carbon adsorption works
Adsorption is a physical process where contaminants are removed from water by binding to the surface of the carbon media. Adsorption is different than absorption. Adsorption, which is how carbon filters work, is a physical attraction that attracts a contaminant to the surface of the carbon.
Absorption is a bulk process where the substance is taken into (absorbed) the media like a sponge. Adsorption onto activated carbon works because most organic molecules have a natural affinity for carbon. This means they will stick to the surface of the carbon. To increase the surface area available for adsorption, thousands of tiny pores are created by “activating” the carbon.
Carbon filter components
Carbon filters for residential applications are very simple. They include either a vessel filled with activated carbon (for whole-house systems) or a cartridge that contains carbon (point-of-use filters).
Granular activated carbon, also known as GAC, is the most commonly used type of carbon. GAC looks like the gravel in an aquarium. Some carbon filters include a particle pre-filter to remove sediment and suspended particles. This protects the carbon from fouling and extends the life of the media.
Many carbon filters, especially whole-house systems, include a bypass valve to allow the flow of water when the vessel is being serviced. Pressure gauges are often installed on the inlet and discharge side of the filter to allow you to monitor the amount of fouling that has occ
Types of granular activated carbon
Carbon is formed by converting organic materials like wood and coal into charcoal. The charcoal is then activating by exposing it to high temperature steam.
1 – Coal-based carbon
Most of the activated carbon used in water treatment is made from coal. The two main types use in carbon are bituminous coals and lignite coal. Coal-based carbon is very hard with pore sizes that make it ideal for removing many of the contaminants found in drinking water.
2 – Coconut shell carbon
Coconut shall carbon is highly prized for its ability to purify air and to remove difficult contaminants like PFAS and lead. This carbon is made from coconut husks. Coconut shell carbon is more expensive than coal-based carbon, but it lasts longer and is more effective at removing certain types of contaminants.
3 – Catalytic carbon
Catalytic carbon is activated carbon that has been modified through the addition of iron-hydroxide or through an enhanced activation process. It has several advantages over conventional carbon including a higher affinity for chlorine and chloramines.
Activated Carbon Filters for VOC Removal
Activated carbon is very effective at removing most VOCs from water. The US EPA considers carbon filtration to be a benchmark technology – they compare the performance of other treatment technologies to carbon filters.
How well do carbon filters remove VOCs?
Carbon filters do a very good job of removing VOCs from water. Since VOCs are a group of chemicals, the affinity carbon has for each compound will vary.
The following table summarizes how well activated carbon adsorbs specific VOCs.
|Contaminant||How Well Does Carbon Remove This Compound|
|Methyl ethyl ketone||Fair|
|Methyl Isobutyl Ketone||Excellent|
Considerations for VOCs and carbon filtration
Removing VOCs from drinking water with activated carbon is a very well understood and reliable treatment method. However, there are some considerations that must be made when using carbon filters for VOC treatment:
- VOCs can breakthrough carbon filters – this means that the VOCs are not completely removed and can still be present in the treated water. The rate at which VOCs breakthrough a carbon filter depends on several factors, including the type of VOC, the amount of VOCs in the water, and the type of carbon filter.
- Biological fouling – a common issue with VOCs and activated carbon filters is biological fouling. This happens when microorganisms (such as bacteria) grow on the surface of the carbon media. As a result, the VOC removal efficiency decreases and the pressure increases.
- Disposal – Once the carbon filter is fully loaded with VOCs, it must be removed from the vessel and disposed of. This spent carbon is a waste that must be properly managed. Disposal can be expensive.
Factors to Consider with Carbon Filters
If you are considering a carbon filter for your home, there are some factors you should keep in mind before making a decision.
A carbon filter can be installed as a point-of-use (POU) unit or as a whole-house system. Whole-house systems are also known as point-of-entry (POE) systems.
POU systems are less expensive to install, but they only treat water at the sink where they are installed. Whole-house systems are more expensive to install, but they will treat all of the water in your home. Typical installation costs for POE carbon filtration are between $1,300 to $5,000.
The biggest cost is the labor to install the filter. If you’re handy, you can install the system yourself. An under-sink carbon filter can be installed for less than $100. However, a filter this small would not remove all of the radon from your water.
Carbon filters require maintenance to keep them operating properly. The primary maintenance is replacement of spent carbon – spent carbon is media that has no remaining adsorption capacity.
Small, under-sink filters need to be replaced every few months. Large whole-house filters can last for 6 months to as long as 2 years before they need to be replaced. Often, the carbon will become fouled with sediment or biological growth which would require replacing it more frequently.
For a whole-house carbon unit, you have to remove the carbon from the filter vessel. This is difficult to do and, most people hire a specialty company to do this.
How often do I need to change the carbon
You need to replace the carbon when it becomes spent. This is the point where the media can no longer remove the contaminant from your water. For a typical residential system, a carbon filter has a service life of 6 months to 1 year. If your carbon becomes fouled with solids or biological growth, you may have to replace it sooner than this.
How much do replacement filters cost
POU carbon filters have a carbon cartridge that is replaced when the media is spent. The cost of an under-sink carbon cartridge is $30 to $350, depending on the size of the unit. Whole house carbon filters require removing the spent carbon and adding fresh media to the vessel. The cost for this service is $1.40 top $4.50 per pound. A typical whole-house carbon system contains between 100 and 400 pounds of carbon – the cost for this service varies from $140 to more than $2,000.
Whole-house versus under-sink
You have two options when it comes to carbon filtration – whole-house and under-sink. Whole-house systems treat all of the water entering your home. They are more expensive to install, but they provide clean, safe water to every faucet and shower in your house.
Under-sink systems are less expensive to install, but they only treat the water at the sink where they are installed.
If you are planning to install a carbon filter for your home, you should look for NSF certification. The NSF certification mark means that the water filter has been tested for safety and to verify the manufacturer’s claims. Here are the NSF certifications that apply to caron filters:
- NSF/ANSI 42: Certified to reduce aesthetic impurities such as chlorine and taste/odor.
- NSF/ANSI 53: Certified to reduce a contaminant with a health effect. Health effects are set in this standard as regulated by the U.S. Environmental Protection Agency (EPA) and Health Canada.
- NSF/ANSI 401: Certified for emerging contaminants.
Do Brita filters remove VOCs?
Britia filters use activated carbon as part of the treatment process. As discussed throughout this article, activated carbon is very effective at removing VOCs from water. Although Brita filters contain carbon, they aren’t designed to purify water contaminated with VOCs and should not be used as the primary treatment.
Do reverse osmosis filters remove VOCs?
Reverse osmosis filters do not effectively remove VOCs from drinking water. Dissolved organic compounds like VOCs pass through the RO membrane. However, most RO systems include a carbon pre-filter that will remove some of the VOCs.
Carbon filters are an effective and reliable treatment method for VOCs in drinking water. Although there are some considerations that must be made, carbon filters are a great option for removing VOCs.
If you have any questions about VOCs or carbon filtration, please leave a comment below and I’ll be happy to answer them!