What is an Activated Carbon Filter?

carbon filter detailed explanationA carbon filter is a reliable solution for purifying water from organic compounds as well as removing bad smells and tastes from water. Carbon filters are used in most water purifying systems like reverse osmosis, pitcher filters, or shower filters. Apart from detoxing drinking water, carbon filters are also used in the food industry or air purifying systems.

Compared to other water filtering systems, carbon filters’ working structure is based on using an adsorption process to trap contaminants. Similar to a magnet that attracts iron filings, the activated carbon attracts and holds organic chemicals like chlorine, pesticides, and many more.

A carbon filter is made out of a porous material that traps contaminants on its surface. These filtering media can be wood-based coal, bituminous coal, or coconut shells. Each media has its advantages and drawbacks, the most renewable being the coconut shell media, while the less used material is the bituminous coal since traces of arsenic were discovered. The wood-based coal carbon filters have been used since antiquity. Burned wood is the same material used by the ancient Egyptians to purify water.

Depending on the size of the pores, carbon filters are proven to remove even coliform bacteria, some cysts, or some heavy metals. However, carbon filters are not as effective against microorganisms as UV filters are. Nevertheless, the carbon filters remain a good option for disinfecting water, especially when used in conjunction with reverse osmosis or UV systems.

The average cost of installing a whole-house carbon-based water purifying system ranges between $500 and $2,800, depending on the size of the house and other factors like size or flow rates.

What is a Carbon Filter Used for?

Carbon filters have been used for purifying water since ancient times, and their usage became even more popular ever since. Some of the most important uses of carbon filters are:

  • Drinking water treatment
  • Pure water treatment
  • Industry water treatment
  • Beverage and food water purification
  • Removal of non-biodegradable pollutants from wastewater

Apart from purifying water, carbon filters have a wide range of applications in purifying the air. These filters are especially effective in removing bad odors, acid gases, or fumes.

How Do Carbon Filters Work?

benefits of using carbon filtersCarbon filters work by a principle called adsorption. While the compounds are assimilated to the filter media in the absorption process, the adsorption implies trapping the compounds to the filter media surface.

While the reverse osmosis purification process dissolves inorganic compounds and radionuclides, carbon filters do an excellent job for chlorine by absorbing it. Chlorine might damage the reverse osmosis membrane. Therefore a carbon filter should be used to protect this membrane.

Activated carbon has numerous crevices and pores where organic compounds pile up, thus blocking these nooks and crannies. The water is therefore purified.

Carbon filters function depending on several factors:

  • Surface area and pores’ size: The physical properties of the carbon filters have major importance on the filters’ effectiveness. Smaller pores mean better adsorption of the organic compounds. This size differs depending on the carbon source and the activation method used. A good thing to keep in mind is the fact that carbon filters work better on larger molecules.
  • The amount of oxygen and hydrogen in the carbon source: Adsorption results from the ion exchange between the carbon surface and the organic molecules of the organic compounds. This is how the activation method used affects the filters’ chemical properties and, ultimately, the effectiveness of removing specific compounds. For example, a carbon filter that holds a smaller amount of oxygen will work better in absorbing chloroform.
  • The chemical and concentration of the pollutants: Contaminants’ chemical properties are also important. Carbon filters tend to absorb larger particles better. Hence less soluble organic molecules are more likely to be retained. Regarding the concentration, carbon filters are less effective at filtering higher concentrations of contaminants.
  • Water’s pH and temperature: Chemical reactions highly depend on the water’s temperature and pH. Lower pH and temperature levels determine better adsorption of the organic compounds.
  • How long the water is exposed to the activated carbon: The length of exposure also affects the carbon filters’ effectiveness. The longer the contact, the better the adsorption. Other details that affect the filtration effectiveness are the carbon bed depth and the flow rate. A slower flow rate is more efficient than a faster one.
  • Although carbon filters do not remove all types of contaminants, they remain a great purification method, especially when used in conjunction with other purifying systems. Carbon filters have proven effectiveness in removing taste, odor, and chlorination from drinking water. Also, they are safe to use, and the rate of adsorption for a small amount of activated carbon is very high.

What Does a Carbon Filter Do?

Carbon filters are used for purifying drinking water, industrial water, but also wastewater. Using carbon filters in different types of water treatment systems has proven effective in removing chlorine and hydrogen sulfide, responsible for water’s bad smell and taste.

Apart from the substances mentioned above, carbon filters are also used to remove volatile organic compounds (benzene, toluene, xylene, etc.), nitrates, or pesticides. Some carbon filters with smaller pores’ sizes are known to remove coliform bacteria, cysts, lead, arsenic, or iron.

Despite their effectiveness, carbon filters cannot be used for removing water hardness, but they should be installed before the water softener because if chlorine is removed by the carbon filter first, the softener resin lasts longer.

How Effective are Carbon Filters?

High-quality carbon filters are 95% effective in removing chlorine, and they reduce chloride by 50-70%. Also, a carbon filter can remove 70-90% of phosphates and Lithium.

According to numerous studies, carbon filters can remove between 60 – 80 chemicals, effectively reduce another 30, and moderately reduce 22. Among these chemicals, 14 most common pesticides and 12 herbicides can be removed with the help of an activated carbon filter. Nitrates are typically reduced by 50% – 70%, depending on the carbon filter quality.

The most important factors that influence the effectiveness of a carbon filter are the water temperature and flow rate. However, choosing the most efficient carbon filter also depends on the pollutants present in a specific geographic area.

What are the Parts of Carbon Filters?

Most water carbon filters come in the shape of cartridges. The main components of a carbon filter cartridge are:

  • The carbon bed: This is the core of the cartridge and consists of a carbon block. Its role is to filter the water. The dimensions of the carbon block determine the contact time between the water and the carbon.
  • Outer wrap: The outer wrap is usually made of propylene, and its role is to help prefiltration. It also has some aesthetic purposes.
  • Inner wrap: Some cartridges use an inner wrap also for minimizing the carbon particles entering the water.
  • Netting: The fine outside mesh is usually made of propylene, and its purpose is to ensure the cartridge’s integrity. It also plays an important role in appearance.
  • End-caps: These components ensure the carbon block is safely locked inside the cartridge, and they are commonly made of thermoplastic rubber.

Do Carbon Filters Remove Viruses?

Carbon filters do not remove viruses from water. These microorganisms have sizes ranging between 0.0004 to 0.1 micron (1-100 nanometers). Most carbon filters used for water filtration contain carbon blocks with pores’ sizes between 0.5 microns to 10 microns.

Although carbon filters are very effective in removing or reducing a wide range of chemical compounds, they cannot remove viruses. These tiny microorganisms are simply too small and will easily pass through the carbon pores.

For virus removal, one of the most common methods is chlorine water treatment. Removing this substance and its byproducts are done with carbon filters.

Are Carbon Filters Safe?

Yes, carbon filters are safe to use for water purification. Carbon is a natural, harmless material that is often used as a health supplement. Ingesting carbon flecks does not harm health. Moreover, running water will remove these carbon specks that usually appear when the cartridge is replaced. Typically, carbon filters are rated for material safety, another confirmation that they are safe to use.

What Are the Advantages of Using Carbon Filters?

Some of the most important advantages of using carbon filters for water purification are:

  • Contaminants removal: Due to its porosity, carbon can retain, thus removing harmful chemical compounds such as chlorine, pesticides, herbicides, lead, or some volatile organic compounds.
  • Preserving minerals: Carbon filters do not remove helpful minerals from water. Additionally, they add calcium, magnesium, and iron, which are well-known supplements for health.
  • Easy to install and maintain: Carbon filters are easy to install as they come with thorough installation guides. Maintaining them is also simple. Depending on the average water consumption, a carbon filter needs to be replaced every three months.
  • Low cost: Carbon filters are the cheapest filters on the market since carbon is a natural material.
  • Eco-friendly: Using a carbon filter for purifying water means that tap water can be consumed. Instead of purchasing plastic bottles, the existing recipients can be refilled. A carbon filter is the equivalent of 300 plastic water bottles.
  • Electricity not needed: Carbon filters do not require electrical power to function. The gravity is enough to have water flowing through the carbon cylinder. In case of power outages, water purification is not an issue.
  • Portability: Most water purification systems that use carbon filters are portable and can be used when traveling or camping.
  • Compatibility with other water purification systems: Carbon filters can be used in conjunction with other water disinfection systems, such as reverse osmosis or UV. The purified water will have a better taste and quality.

What Are the Disadvantages of Using Carbon Filters?

The disadvantages of using carbon filters for water purification are:

  • Certain pollutants are not removed: Carbon filters do not remove toxic minerals, fluorides, nitrates, and microorganisms. The chemicals are not attracted by carbon, while the microorganisms are too small to be trapped in the carbon pores.
  • Harbour pathogenic bacteria: Due to the extended contact with water, some bacteria pill up inside the carbon pores, thus contaminating the water. Although the silver impregnated carbon filters sorted this issue, replacing the filter every three months is recommended. Flushing the filter daily also helps to prevent bacteria growth.
  • Short lifespan: Carbon filters get filled with contaminants quickly. Thus they stop working and require replacing more often than other media.

What Are The Types of Carbon Filters?

The two types of carbon filters commonly used for purifying water are granular activated carbon and carbon block filters.

The main difference between granular activated carbon and carbon block filters is that one is made of completely loose carbon while the other is composed of compressed carbon granules. Both types of filters are highly effective in removing a variety of contaminants, including smaller particles. Moreover, some high-quality carbon block filters can remove some microorganisms such as cysts or coliform bacteria and reduce asbestos, arsenic, or mercury.

2. Granular Activated Carbon (GAC)

Granular activated carbon filters are made of small loose carbon particles. These are used to purify water, especially for improving taste and odor. Their high adsorption capabilities help remove a series of contaminants such as pesticides, herbicides, volatile organic compounds, hydrogen sulfides, etc.

The loose carbon particles of granular activated carbon allow water to flow at a higher rate compared to the carbon block filters. This is particularly useful for gravity filtration systems.

Water flows in one direction through the cartridge, and this might be a drawback. Activated carbon is highly porous. Thus, GAC filters have no specific limit. Examples of some GAC products can be found in the granular activated carbon water filter buying guide.

What Are the Advantages of Granular Activated Carbon (GAC)?

The main advantages of using granular activated carbon filters are:

  • High adsorption properties: GAC is very effective in removing a series of contaminants, nitrates, pesticides, volatile organic compounds, and hydrogen sulfide (responsible for the bad odor of water). These filters are also very efficient in removing chlorine and its byproducts.
  • Eco-friendly: Granular activated carbon can be reactivated through thermal oxidation so that it can be used again for numerous applications.
  • Versatility: GAC filters can be used in conjunction with other water purification systems, such as reverse osmosis. These filters will remove bad odor and taste while the reverse osmosis systems purify water from the remaining pollutants and bacteria. Moreover, due to the internal pores’ size, the GAC filters can be used in different applications, depending on the contaminants present in the water.
  • High flow rate: Due to its composition, a GAC filter will allow water to flow much easier through the cartridge.

What Are the Disadvantages of Granular Activated Carbon (GAC)?

Although the granular activated carbon filters represent an efficient and cost-effective method for water treatment, there are also some disadvantages:

  • Enhances bacteria growth: Due to their internal structure, the GAC filters allow bacteria growth. While water flows through channels, it leaves behind small carbon pockets. The bacteria present in the water start growing and multiplying, thus making the water unfit for drinking.
  • Frequent replacing due to channeling: Since water flows through the cartridge and meets no resistance, channels form, so many carbon granules remain unused. This is a significant drawback of the GAC filters as the cartridge will require replacing since it becomes exhausted.

2. Solid Block Carbon

Solid block carbon filters are obtained by compressing the loose carbon particles. Due to the compression and carbon properties, the solid carbon blocks represent the most absorbent material known.

A bonding agent holds the fine carbon particles together, which does not take up too much from the filter’s surface area. Due to this, solid block carbon filters have greater adsorption properties as the particles are grounded to finer granules. Moreover, the adsorption area increases.

Due to the internal structure of the carbon blocks, the water flows at a lower rate in solid block carbon filters than GAC filters. There is an increased possibility to capture impurities and pollutants. Also, the same structure helps to avoid the channeling issue present in GAC filters. Examples of some solid block carbon filters can be found in the solid block water filter buying guide.

What Are the Advantages of Solid Block Carbon?

The main advantages of the solid block carbon filters are:

  • Remove a wider range of contaminants: Due to the smaller sizes of the carbon pores, solid block carbon filters remove and reduce more contaminants than GAC filters. They are capable of filtering out even microorganisms such as cysts and some bacteria.
  • Preserve useful minerals: Although they remove many compounds, solid block carbon filters do not remove helpful minerals like calcium, magnesium, or iron. Moreover, they add small concentrations of these minerals.
  • Elimination of the channeling issue: In solid block carbon filters, every carbon granule is used to its maximum efficiency. This way, no channels form, and there is no risk of bacteria growth.
  • Do not require frequent replacing: Since every carbon particle is used, the solid block carbon filters do not require to be replaced as often as GAC filters.
    Cost-effective: This type of carbon filter does not imply high costs. A replacement cartridge has an average price of $15, and they need to be changed every six months or once per year.
  • Specific pores size: Solid carbon blocks have pore sizes ranging between 0.5 and 10 microns. Due to this specificity, more contaminants are being filtered compared to the GAC filters. The most common solid block carbon filters are between 1 to 5 microns.

What Are the Disadvantages of Solid Block Carbon?

The drawbacks of the solid carbon block filters are:

  • Lower water flow rate: Due to the internal structure of these filters, the water flow rate is much lower than GAC filters. This means that it takes a longer time to purify water. Moreover, for smaller carbon particles sizes, even the water particles struggle to pass through.
  • Size: Solid block carbon filters are bigger compared to GAC filters. Due to their size, they might not fit in any house as they take some space.
  • Slow filtration process: Depending on the size of the pores, the water filtration is much slower than the GAC filters.

Are Carbon Filters Washable?

Yes, activated carbon filters can be washed between replacements. However, when the carbon becomes exhausted, the cartridge will need to be changed as it loses its adsorption properties.

How to Clean a Carbon Filter?

To effectively clean a carbon filter, one needs to follow these steps:

  1. Soak the carbon filter in clean distilled water or aquarium water.
  2. After three or five minutes, the debris from the filter surface becomes dislodged. Use fresh distilled or aquarium water to rinse the filter that can be utilized again.

How We Can Understand That Our Carbon Filter is Bad?

Replacing the carbon filter depends on a series of factors such as its lifespan, manufacturer’s recommendation, or the amount of contaminants in the water.
The durability of carbon filters depends on how heavily they are used, and they will show some symptoms that need to be replaced.
Some of these symptoms are:

  • The water has an unpleasant taste and/or odor.
  • Water pressure decreases.

There is no visibility with the activated carbon filters, so the appearance of the previously mentioned symptoms should not be ignored. The manufacturer’s instructions are also a good reference regarding the replacement time.

Do Carbon Filters Smell?

Typically water purification carbon filters do not smell, compared to air purifying filters, where the bad smell is a sign that the filters require replacing. However, if an unpleasant odor is sensed, it is a sign that something does not work or the filter is clogged. It will have to be changed as soon as possible.

Do Carbon Filters Need to be Replaced?

Yes, carbon filters require replacement as they become exhausted and will no longer purify water. The reasons for which carbon bed becomes exhausted are: contaminants clogging up the filter, poor quality tap water, frequent usage of the filter.

Changing the carbon filter cartridge is easy, and most manufacturers provide instructions on how to perform this operation.

How Often Should Carbon Filters Be Changed?

Carbon filters require replacing every six months or at least once per year. Some manufacturers recommend changing the carbon filter cartridge every four months, but this depends on the quantity of pollutants present in the water and how heavily the filter is used.

Using a filter for more than a year is not recommended as the carbon particles will no longer retain the contaminants.

How To Change Carbon Filters?

To safely replace the carbon filter, some steps must be followed:

  1. Turn the input valve to the water filter off.
  2. Open the housing that holds the carbon cartridge by rotating it clockwise.
  3. After the old cartridge is removed, clean the housing with mild soap.
  4. Place the new cartridge inside the housing.
  5. Screw the housing back by using a wrench.
  6. Turn on the water, and check the whole system for leaks.

How Much Does a Carbon Filter Cost?

carbon filter using tipsThe average cost of a carbon filter water purification system is about $2,500. The price of replacement cartridges is added to the cost, about $100 per year for a family using 25 liters of water per day. Also, depending on the water purification system and the accessories, the installation costs of a carbon filter range between $100 and $1,000.

The cost of a carbon filter is influenced by several factors, such as the type of filter needed, whether the house plumbing system requires modification, the existing pollutants in water, and the labor.

Some of the best carbon water filters brands are:

  • Aquasana Inc.: This is maybe the most famous water purification systems manufacturer that offers a wide range of products. Although the Aquasana EQ-1000-AST-AMZn whole house water filter comes with a high price tag (up to $1,700), it can remove 97% of chlorine. It reduces lead, mercury, pesticides, herbicides, volatile organic compounds, and many more pollutants. The carbon cartridges need replacing every three months for better filtration and flow rate. Considering that two cartridges are required, and the average price of a replacement is about $30, the total cost for maintaining this unit goes up to $240 per year. Nevertheless, the system remains a premium choice, rated to last ten years.
  • iSpring: The second consumers’ favorite brand is iSpring and their WGB21B 2-stage heavy-duty water filtration system. This system uses carbon block filters and can remove up to 95% of sediment, chlorine, and other pollutants. Its cartridges require replacement every six months. Speaking of costs, the water purification system has a price tag of about $460, and the replacement cartridges have an average cost of $100 per year.
  • Express Water: Express Water heavy metal whole system water filter is another useful and reliable water filtration system. It includes a carbon block filter, a KDF fluxion, and a sediment filtration cartridge. This unit comes with a $500 price tag and can remove lead, aluminum, copper, sand, viruses, fungi, and many more. The cartridges require replacement every six months or at least once per year. So, the maintenance cost is about $185 per year.
  • Home Master: Home Master is another major player on the market, a manufacturer that brings high-quality products to their customers. The whole house three-stage water filtration system is a perfect example. This unit can remove up to 95% water contaminants, including manganese, iron, sediment, and other chemical compounds. The price of this water filtration system is about $600. Filters require replacement once a year, and the average cost for all cartridges is around $125.
  • Pelican: One of the high-end water filtration systems manufacturers is Pelican. Their products come with a high price tag but also with high-quality standards. The Pentair whole house water filtration system costs about $3,200, but the materials used in his manufacturing are top-notch. Carbon filters require replacement every 3 or 6 months, depending on the usage. Considering the price of a cartridge, the maintenance of the system goes up to $153 per year.

How to Make a Carbon Filter?

Several materials are required to craft a carbon filter: fresh charcoal, a cylindrical recipient, a large stone, and grass or sand.

The steps for making a carbon filtration system are:

  1. Crafting a funnel: The funnel acts as a filter and can be made of a large plastic bottle. Its top must be cut, and its cap must point down. A hole must be made in the bottle cap.
  2. Preparing charcoal: The charcoal must be crushed with the help of the stone. After the material Is grounded, it is placed inside the bottle. On top of the grounded charcoal, some grass or sand must be added to help the filtering process.
  3. Filtering water: The water is poured into the funnel, and it will slowly filter down into a recipient. This process must be repeated until the water has the desired clarity. After the filtering process, it should be boiled so harmful microorganisms are destroyed.

How to Use Carbon Filter?

Carbon filters have a wide range of applications. To fully benefit from these filters’ properties, they need to be correctly used.

  1. Fit for purpose: A specific type of carbon filter should be used for the application it was designed for. For example, the pores sizes differ, so a filter with larger pores will allow a series of contaminants with small particle sizes. Solid block carbon filters have a slower filtration process, so this type of filter is not an option if a higher water flow rate is needed.
  2. The amount of carbon: Some filters have a higher amount of ash, meaning the carbon content is lower. These filters will become exhausted faster. Currently, the carbon filters made of coconut shells have the lowest percentage of ash.
  3. External checks: Every carbon filter must be checked externally prior to installation. The presence of few black dust particles is normal. However, any cracks or a higher amount of carbon particles are the signs of a poor quality filter. Also, if the filter is too brittle, it will not resist.
  4. Performance parameters of the filter: Understanding the performance parameters such as capacity or chlorine reduction percentage is essential. These parameters show how long (in gallons or liters) a filter will remove contaminants. As soon as the flow volume is reached, the carbon filter will need to be replaced. Also, the iodine value is a good indicator as manufacturers use this value to express the adsorption performance. An iodine value higher than 1000 indicates a highly performant filter.
  5. Quality certification: Filters NSF, ANSI, and WQA rated are reliable and follow a specific standard. These are high-quality carbon filters that will not fail any time soon.

What are the Side Effects of Carbon Water Filters?

The most important side effects of carbon water filters are:

  • Limited filtration: Although carbon filters efficiently remove bad taste and odor from drinking water, they cannot remove bacteria or other microorganisms, fluoride, and heavy metals. Moreover, their short lifespan exacerbates the problem.
  • Slow filtration process: To be efficiently filtered, water needs to spend a certain amount of time in the filter. Unfortunately, most carbon filters do not allow for sufficient contact time.
  • Bacteria growth: Carbon filters might trap harmful bacteria at the charcoal’s surface. Moreover, these microorganisms contaminate the water. If the filter is not replaced at a certain amount of time, the bacteria grow and water is no longer properly filtered.
  • Replacement contaminants: Carbon filters are made differently. Poor quality filters might introduce impurities from the materials used in the water.

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