Water Treatment Using Carbon Filters

Water Contaminants and Your Health

Children at hand pump.Clean and safe drinking water is an important part of a healthy environment and protecting public health. Many of us depend on groundwater as our primary source for drinking water — whether we use a private well, public water supply, or some other groundwater source.

A filter with granular activated carbon (GAC) is a proven option to remove certain chemicals, particularly organic chemicals, from water. GAC filters also can be used to remove chemicals that give objectionable odors or tastes to water such as hydrogen sulfide (rotten eggs odor) or chlorine.

What is Activated Carbon?

  • Material: Activated carbon is a form of carbon that is processed to have small, low-volume pores.

  • Adsorption: These pores increase the surface area available for adsorption, effectively removing contaminants like chlorine, volatile organic compounds (VOCs), and other substances from water.

  • Types: Activated carbon filters can come in various forms, such as powdered, granular, or block carbon.

Why Use Activated Carbon Filters for Well Water?

  1. Remove Contaminants: It helps in removing various contaminants, including chlorine, pesticides, herbicides, and industrial solvents.

  2. Improve Taste and Odor: It can significantly improve the taste and odor of well water by removing impurities and chlorine.

  3. Protect Health: By removing certain harmful contaminants, it helps in protecting health.

How Does an Activated Carbon Filter Work?

  • Adsorption: The primary mechanism is adsorption, where contaminants adhere to the surface of the carbon particles.

  • Catalytic Reduction: A process in which an electron is transferred between chemical species, converting a contaminant to a non-hazardous substance.

  • Size Exclusion: Larger particles are excluded from entering the pores of the activated carbon, effectively filtering them out.

Installation and Maintenance:

  • Point of Entry (POE) System: Installing a whole-house activated carbon filter system at the point where the well water enters the home ensures all water is treated.

  • Point of Use (POU) System: Alternatively, activated carbon filters can be installed at specific points of use, such as under the sink, for targeted water treatment.

  • Maintenance: Regular maintenance, including filter replacement, is crucial to ensure the system remains effective. The frequency of maintenance depends on water quality and usage.

Considerations for Well Owners:

  1. Water Testing: Before installing a filter, have your well water tested to identify specific contaminants and determine the most effective treatment solution.

  2. Filter Size: Ensure the filter size and design are suitable for your water usage and contamination level.

  3. Additional Treatment: Depending on the water test results, additional treatment methods (e.g., water softeners, UV purifiers) may be needed in conjunction with activated carbon filters.

  4. Professional Installation: Consider professional installation and regular service to ensure the system operates effectively and adheres to local regulations.

  5. Emergency Preparedness: Have a plan for alternative water sources or treatments in case of well contamination that cannot be addressed by the activated carbon filter.

Water Quality/Well Testing/Well Disinfection
Well Management Program

Well Testing Information

As a private well owner, you are responsible for regularly testing your well water. Minnesota Department of Health (MDH) recommends:

activated carbon filter

However, other chemicals, like iron and nitrate, are not attracted to the carbon and are not removed and another type of filter, such as reverse osmosis (RO) or green sand may be needed. RO filters will also remove certain organic chemicals. This information only addresses GAC filters.

Granular Activated Carbon

Granular activated carbon is made from raw organic materials (such as coconut shells or coal) that are high in carbon. Heat, in the absence of oxygen, is used to increase (activate) the surface area of the carbon; this is why these filters are sometimes referred to as “charcoal” filters. The activated carbon removes certain chemicals that are dissolved in water passing through a filter containing GAC by trapping (adsorbing) the chemical in the GAC.

It is very important that the type and concentration of contaminants, and average water use, be known in order to determine the correct size and components of the system. All treatment systems require proper installation and periodic maintenance. Eventually, the ability of the GAC to bind and remove chemicals is used up and the GAC needs to be changed. How often the GAC should be changed needs to be based on contaminant levels and water use. While some filters may last for several years if contaminant levels and/or water use are low, higher levels or use may require more frequent change-outs.

Types of GAC Filter Systems

There are two types of GAC filter systems:

1. Whole-House Filters or Point of Entry:

GAC water filter system

A whole-house filter is installed at a point on the home's water supply plumbing that will result in treatment of all water that travels to any faucet or fixture in the home (but typically will exclude outside faucets to prolong the life of the carbon). It removes the chemicals before they can be ingested, breathed in, or absorbed by the skin during washing or bathing.

The filters are usually cylindrical in shape. The example shown in the photo is about 4-feet tall and 15 inches in diameter. The filters are usually installed as a pair, although more may be required in some situations. Two filters arranged in sequence ensure that any chemical that might get past the first filter is trapped by the second.

When the first filter is used up, the second filter is moved to the first position and a new filter is placed in the second position. Sample ports located before, between, and after the filters allow for testing of the water at each location (see diagram on the next page).

Most systems also have a bypass switch that allows the water flow to bypass the system when needed for chlorination or certain plumbing activities. When the system is bypassed, the water entering the home is NOT being filtered.

GAC water filter diagram

2. Point of Use Filters:

A point of use (POU) filter is installed in the water supply pipe just before the faucet where people get water.

One example is an under-sink unit; water passes through the carbon filter and travels to a separate water tap, next to the main faucet. Water from the separate tap will be GAC-treated, and water from the main faucet (hot or cold) will be untreated.

Other examples of point of use filters are the GAC pitcher filters commonly sold in grocery stores or GAC filters that are a part of a refrigerator’s icemaker.

Determining What GAC Filter System to Use
Which system you need depends on:
  • The type and amount of contaminants in the water,
  • Other chemicals in the water,
  • Water use, and
  • Exposure pathways that need to be eliminated. (Exposure pathways are the ways that chemicals enter the body.)
Under-Sink Filter

An under-sink filter protects people from ingesting the chemical by treating the drinking or cooking water only from that tap. It will not protect people from inhaling the chemical while showering or bathing, prevent the chemical from being absorbed through the skin, or protect other water faucets. Inhalation is a concern when the chemical easily evaporates from the water into the air. Not all contaminants easily evaporate into the air or are absorbed through the skin.

Whole-House Filter System

A whole-house filter system treats all water traveling to any faucet or fixture in the home. It removes the chemical before it can be ingested, breathed in, or absorbed by the skin during washing or bathing.

  • For all work on your filter system, use only a licensed plumber or licensed water conditioning contractor.
  • For either type of filter system, consistent maintenance and periodic filter replacement is essential to ensure effectiveness and prevent bacterial build-up.
  • It is recommended that water treatment systems be tested and certified to national standards by a reputable testing laboratory, such as NSF.
  • The Minnesota Water Quality Association also has information about water treatment systems.

Owner's Guide to Wells
Well Management Program

A well that is properly located, constructed, maintained, and tested can provide a reliable and safe drinking water source and serve many domestic, agricultural, and commercial purposes.

You and your licensed well contractor have important roles in keeping your well safe. A safe well helps keep your household healthy and protects Minnesota’s groundwater. Remember your role by remembering TIPS.

Test your water. Inspect your well. Protect your well. Seal unused wells.

Keep all well records related to well construction, maintenance, repairs, disinfection, sediment removal, and testing.

1.2 million Minnesotans get their drinking water from a private well.

Your Licensed Well Contractor’s Responsibilities When Constructing Your New Well

Ensures proper well location.

  • Correct distance from contamination sources (see image below).
  • Good drainage away from the well.
  • Highest practical site on the property.

Complies with MDH regulations by using approved methods, products, and materials.

Disinfects your well to get rid of harmful bacteria.

Collects an initial water sample after construction is finished to test for coliform bacteria, nitrate, and arsenic before you start using your well water for drinking or cooking.

Gives you a copy of the water test results and the Well and Boring Construction Record.

For a complete list of isolation distances, see Isolation Distances from a Water-Supply Well http://www.health.state.mn.us/divs/eh/wells/construction/isolate.html Figure 1: Partial list of minimum isolation distances. Isolation distances keep pollutants away from your well to protect your water. Some sensitive wells will require greater isolation distances. For a complete list of isolation distances, see Isolation Distances from a Water-Supply Well.

Bacterial Safety of Well Water
Well Management Program

It is not practical to test water for every disease-causing microorganism, but it is easy to test for a group of indicator bacteria called total coliform bacteria. These bacteria are good indicators of sanitary protection of the well and water system because they are everywhere on the surface of the ground, but do not usually occur past a few feet into the soil. If they show up in a water test, they can indicate that surface contamination has gotten into the water and that disease-causing microorganisms may be present. Just as disinfection kills most disease-causing microorganisms, it also kills coliform bacteria.

Health Risks

While most coliform bacteria do not cause disease, their presence suggests there may be disease-causing microorganisms in your water. These microorganisms can cause diarrheas, dysenteries, salmonellosis, hepatitis, and guardians. Symptoms include diarrhea, vomiting, cramps, nausea, headaches, fever, fatigue, and even death sometimes. Infants, children, elderly people, and people with weakened immune systems are more likely to get sick or die from disease-causing microorganisms in drinking water.

Test for Coliform Bacteria Every Year

Water quality can change. Minnesota Department of Health (MDH) recommends you test every year for coliform bacteria, even if you have not noticed any changes in your water quality. MDH also recommends you test for coliform bacteria any time your well or water system is worked on or the water changes in taste, smell, or look.

Your Responsibilities

Test your water.

You are responsible for regularly testing your well water. Both natural sources and human activities can contaminate wells and cause short- or long-term health effects. You cannot taste, see, or smell most contaminants. MDH recommends using an accredited laboratory to test your water. Contact an accredited laboratory to get sample containers and instructions, or ask your county environmental or public health services if they provide well water testing services.

Inspect your well regularly.

  • Damage: Any cracks or holes in well casing, corrosion, loose wires, or soil settling?
  • Well cap: Is it securely attached to the well casing? Is it broken or missing?
  • Connections: Are the electrical conduit and other connections watertight?

Well in good condition.

Figure 2: Well in good condition.

Well casing has been cracked and damaged.

Figure 3: Damaged well.

Protect your well.

Do these things

  • Keep top of well at least 1-foot above ground.
  • Keep well area clear of debris.
  • Maintain minimum isolation distances from contamination sources (see isolation distances image above).
  • Mark your well with flags or posts to protect it from being hit by vehicles or machinery.
  • Take precautions before and after floods.

Do NOT do these things:

  • Allow water to pond around your well.
  • Use, store, or dispose of potential pollutants (such as animal wastes, fertilizers, pesticides, or hazardous chemicals) near your well.
  • Tie animals to your well.
  • Dispose of waste in unused wells.

Seal unused wells.

A well that you no longer use (unused well) can be a pathway for contaminants to get into groundwater and is a safety hazard. You are responsible for getting unused wells on your property sealed. Only a licensed well contractor can legally seal wells.

Contact a licensed well contractor if your well needs to be repaired or sealed.


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