Water Treatment

Water quality problems can be divided into two broad categories: (1) those that present aesthetic concerns, such as undesirable tastes, odors, or appearance, and (2) those that present a health risk.

Some water quality problems are caused by a contamination source that, if eliminated, could result in improved water quality. Generally, it is better to eliminate the cause of a water quality problem than to simply treat the contaminated water.

When treating the cause of a water quality problem is not possible—such as with naturally occurring geologic arsenic affecting groundwater—water treatment can be a good option.

Depending on what is being treated and how, water treatment equipment may be located at almost any stage within the well system. More often than not, water treatment is installed at the point of water use, such as the kitchen sink, or at the point where water enters the house, treating all the water. The most common types of water treatment are:

  • Continuous disinfection which kills bacteria and other microorganisms. The most common approach is the use of ultraviolet light, which requires proper installation, pre-treatment of the water, and maintenance. Another technology regularly releases a disinfectant into the well water.
  • Ion exchange is a physical-chemical process in which ions are exchanged between a solution phase and a solid resin phase. Ion exchange is most commonly used for water softening, but it also can be used for other purposes such as treating arsenic and nitrate in water.
  • Reverse osmosis (RO) is a process for the removal of dissolved ions from water, in which water is forced through a semipermeable membrane, retaining most ions while transmitting the water. When coupled with granular activated carbon filters before and after the RO treatment, this system can achieve a high degree of removal of many of the substances that cause water quality problems.
  • Whole-house sediment filters are installed in the water line coming into the house. They remove particulate from the water to enhance treatment effectiveness and reduce maintenance of other treatment systems that follow.
  • Adaptable automatic backwashing filters require relatively little maintenance because they backwash the filter media bed automatically. While these filters do not treat everything, they can be fitted with different types of media to address various water quality problems.

Check to see if the system you are considering has been certified effective by independent product testing laboratories, such as those operated by NSF International and the Water Quality Association.

How do I know if I need water treatment?

The first step is to determine what kind of water quality issues you have. Aesthetic water quality problems are noticeable. However, some contaminants that present a health risk have no odor, taste, or appearance.

The National Ground Water Association recommends that all well owners test their water annually for bacteria, nitrate, and anything of local concern. To find out what might be of local concern, check with your local health department, an area water well system professional, or an area drinking water testing laboratory.

The second step is to have the water tested by a certified drinking water testing laboratory. These labs can measure substances in parts per million or parts per billion. Depending on the type and number of substances for which you are testing the water, costs can range from less than $50 to hundreds of dollars.

Water test results are important to providing the information necessary to select the right system for what you need to treat in the concentration at which it exists in your water.

Learn more about water treatment here.

How do I know what kind of water treatment I need?

Selecting a water treatment system begins with water test results from a certified drinking water testing lab. Such test results should be compared to the water treatment product specifications to ensure that the treatment system being considered is designed to treat:

  1. The substances you want to treat
  2. In the concentrations at which they exist in your water.

There is no one-size-fits-all water treatment technology that addresses all water quality problems. In some cases, one treatment technology may meet all your specific needs. In other cases, you may need a “treatment train”—a series of treatment technologies in a sequence that treat one or more water quality problems. Again, when considering water treatment, use your lab test results as a guide and make sure the technology you are considering is designed to treat the problematic substances in your water.

Learn more about water treatment here.

How do you determine whether to treat water at the tap or for the whole house?

To decide whether to get whole-house treatment at the point where water enters the house (point of entry or POE) or at the tap (point of use or POU) it is helpful to ask yourself several questions:

  1. Which approach is necessary to protect health?
  2. Which approach is necessary to get rid of a taste, odor, or appearance problem?
  3. Which approach is necessary for my peace of mind?
  4. What can I afford?

Let’s consider the answers.

Protecting health—Most of the time, the substances that commonly present a health risk must be consumed to cause harm. Two examples are arsenic and nitrate. When the health risk comes through water consumption, treating water at the tap is sufficient to protect health.

Sometimes, however, a health risk can occur through means other than water consumption. For example, radon gas can be released from water when the water is agitated by clothes washing, dish washing, or passing through a showerhead or faucet, for instance. Once radon is released into the air, radon can be breathed. This released radon, when combined with radon gas coming up through the house foundation, can be a greater health threat than when radon in water is consumed.

Another example would be methane gas in water. When methane is released from water and accumulates in confined spaces within a house, it can present an explosion hazard. In the case of radon and methane gas, treating the water where it enters the house is recommended.

Eliminating taste, odor, or appearance problems—To a large degree, ridding water of taste problems can be treated at the tap. Often homeowners treat water at the kitchen tap where most water is drawn for drinking and food preparation. For many homeowners, it is not practical to treat water at every tap in the house.

When the problem is an unpleasant odor, cloudy water, or water that stains orange or black, treating water at the tap would only be a partial solution since it would not address water in the toilet, washing machine, or dishwasher, for instance. Odor problems can be caused by hydrogen sulfide gas, and staining can be caused by iron (orange or brown) and manganese (black). In these cases, treating the water where it enters the house may be a better overall solution.

Whole-house treatment also is standard when treating “hard” water, which is water with a high mineral content related largely to calcium and magnesium.

Peace of mind—While treating water at the kitchen tap may be adequate for some homeowners, others may choose more treatment so as not to worry about health risks or aesthetic issues. For instance, some homeowners get continuous water disinfection systems because they don’t want to worry about harmful bacteria in their water—even though periodic water testing and disinfection when necessary may be adequate to protect against bacterial problems.

Affordability—Whole-house systems are more expensive than point-of-use treatment. If either approach can be used to address your water quality issues, your budget may dictate which approach you take.

Learn more about water treatment here.

Is there one treatment technology that will take care of all water quality problems?

No. Of all the home water treatment technologies, reverse osmosis (RO) and distillation cover the widest range of substances. Reverse osmosis and distillation are not effective in treating everything. RO, for instance, does not treat some pesticides, solvents, and volatile organic chemicals, including ions and metals such as chlorine and radon. RO is popular because of its ease of installation, reasonable cost, and relatively minimal maintenance. Distillation is highly effective but uses significant amounts of energy.

Learn more about types of home water treatment.

How do water treatment systems work?


There are a variety of system designs to treat various constituents in water:

  • Particle filtration: There are various filters to remove particles from water. This type of filtration removes particles ranging in size from more than 1,000 microns to fewer than 10 microns. The width of a human hair is about 100 microns.
  • Chemical treatment—This form of treatment creates chemical reactions that address various water quality problems such as hardness, pH imbalances, and sulfides.
  • Ultrafiltration and nanofiltration—These approaches are used to remove total dissolved solids, which include salts, organics, and heavy metals such as arsenic and lead. Ultrafiltration removes such constituents in the range of less than 1 micron to as small as less than one-tenth of a micron. Nanofiltration removes constituents 1/10,000th of a micron or smaller.
  • Disinfection—Disinfection is used to kill microorganisms such as bacteria, viruses, and protozoa.

Often, more than one type of treatment will be used in sequence to address water quality issues.

Learn more about water treatment here.

What kind of maintenance do water treatment systems require—and can I do the maintenance myself?

Some maintenance is simple, such as the replacement of a cartridge in a whole-house sediment filter.

Other maintenance is more complicated and may best be done by a professional. Take the removal of uranium. For each type of uranium treatment—reverse osmosis, ion exchange, and distillation—filters or membranes can accumulate high concentrations of this radioactive substance. These filters or membranes must be handled carefully and disposed of properly.

Maintenance also can become more challenging if there is a “treatment train,” where multiple treatment technologies are used.

Discuss the maintenance requirements of your treatment system with your water well professional or water treatment professional to decide how much maintenance if any is feasible for you to perform.

Take a free online water treatment system maintenance lesson or view a recorded webinar.

How much do water treatment systems cost?

There are two sets of costs involved: the purchase/installation costs (capital costs) and operating costs. In the cost ranges below, the higher ranges tend to apply to whole house treatment while the lower ranges tend to apply to point-of-use treatment.

The capital costs of the most common types of water treatment generally range from less than $100 to $3,000 or more.

Operating costs for the most common home water treatment systems generally range from less than $100 a year up to $1,000 annually.

Learn more about water treatment here.

How do I treat arsenic in my water?

Three different water treatment technologies can be effective in treating arsenic:

  • Reverse osmosis (RO): This is a nanofiltration system often accompanied by granular activated carbon filtration as the water enters and exits the RO membrane.
  • Ion exchange: This is a physical-chemical process in which ions are exchanged between a solution phase and a resin phase.
  • Adsorption media: This is a physical process involving the adherence of a contaminant to the surface of a porous medium.

Learn more about treating arsenic.

How do I treat bacteria or other microorganisms in my water?

Water treatment technologies commonly used in treating microorganisms in water include:

  • Reverse osmosis (RO): This is a nanofiltration system often accompanied by granular activated carbon filtration.
  • Chlorine compounds: This is the most convenient, effective, and economical method of disinfecting large volumes of water. Chlorine for residential well systems is available either in liquid, granular, or tablet form. Continuous chlorine feeding into the water can create potential damage to the well system.
  • Ozone: Ozone is a gas that can be dissolved in water to produce an excellent disinfectant. It is a more effective disinfectant than chlorine but must be produced on site and administered by the ozone treatment system.
  • UV irradiation: This technology has been used for years in disinfection. Some pre-filtering of the water may be necessary to enhance the disinfection process, UV bulbs must be kept clean, and there are some forms of bacteria that are more resistant to UV disinfection.

Note: When addressing bacteria, it is important to determine whether the bacteria’s presence is an isolated incident or the result of a more persistent problem—for instance, a breach in the well system or an overloading of the groundwater with bacteria from a concentrated source such as an animal enclosure or a failing septic system.

If the bacteria’s presence is due to an isolated incident, disinfection of the well system should get rid of the bacteria. The way to confirm this is to retest the water a week or so after the disinfection process has been completed to see if the bacteria returns. Until the water tests negative for coliform bacteria, drinking bottled water is a safe alternative.

If the presence of bacteria is persistent, consult with a water well system professional, who can inspect your well system and the area around the well to look for a cause that can be addressed. It is better to keep bacteria out of your well system in the first place than to simply treat its presence.

Learn more about treating microorganisms.

How do I treat hydrogen sulfide in my water?

Technologies used in treating hydrogen sulfide are:

  • Aeration, which mixes air with water to separate out sulfide
  • Carbon filters
  • Chlorination to reduce the bacteria that produce hydrogen sulfide
  • Ion exchange in which a resin absorbs hydrogen sulfide
  • Manganese greensand filtration
  • Oxidizing filters that change the hydrogen sulfide gas to sulfur for removal
  • Ozone treatment in which a chemical reaction separates out sulfur for removal.

Work with a water treatment service provider to determine which treatment technology is the best approach to treating the hydrogen sulfide in your water.

Learn more about treating hydrogen sulfide.

How do I treat iron and manganese in my water?

There are two technologies used for the treatment of iron and manganese:

  • Ion exchange: A physical-chemical process in which ions are exchanged between a solution phase and solid resin phase. A standard household water softener may effectively remove iron and manganese at certain concentrations.
  • Oxidation and filtration: This involves oxidation of iron and manganese into forms which can then be filtered out.

Learn more about treating iron and manganese.

How do I treat methane in my water?

Any water well with methane present should have a gas venting system installed at the well to vent gas to the atmosphere. This may allow a portion of methane gas to escape before it can accumulate in the water distribution lines, pressure tanks, water heaters, water treatment equipment, or well houses. This option is most effective for dealing with free gas bubbling through the water. However, this method is unlikely to be fully effective against the portion of gas dissolved in groundwater.

If groundwater with methane is pumped into a pressurized tank, in rare circumstances when a faucet or similar valve is opened, the water can flame when ignited as the gases are released from the water. In this case, a venting system installed in the water tank is required.

It may be possible to release methane outside of the building, using a specially configured pressurized water storage tank that vents the gas to the atmosphere. In such a system, the vent pipe needs to extend above the eave height of the well house or home where the tank is located. Using a combination of venting at the well casing, as well as installing aeration equipment in the water storage tank, will decrease the potential for methane.

Aeration at the point of water entry into the house can also help remove methane gas. Aeration releases gas from suspension in the water so it can be vented into the atmosphere through a pipe. Aeration equipment must be specially designed or modified by the manufacturer to safely remove methane gas. A totally closed system should be provided to prevent any methane gas from leaking out of the system and into the building interior.

Learn more about treating methane.

How do I treat nitrate in my water?

Water containing nitrates can be treated by a variety of methods, including reverse osmosis and ion exchange.

Reverse osmosis or a disposable mixed-bed deionizer work best on point-of-use systems installed in places such as the kitchen sink where water is used mostly for drinking or cooking. Ion exchange, along with a water softening system, can provide a whole-house solution for nitrate contamination.

Learn more about treating nitrate.

How do I treat radon in my water?

The primary source of radon exposure is from breathing contaminated air in the home. Therefore, water should be treated as it enters the house to prevent radon from being released into the air anywhere inside water is being used. Point-of-use devices, such as those installed on a tap or under the sink, treat only a small portion of the water in the home and are not as effective in reducing radon.

Radioactivity also can build up on the filters of these devices and become a hazard. The two most common treatment technologies are granular activated carbon and aeration:

  • Granular activated carbon: This technology will remove 95 percent of the waterborne radon. It works by adsorbing the radon onto the surface of activated carbon. There the radon continues to decay and give off radiation; however, the treatment equipment is usually not located in the living area of the home. Although the granular activated carbon system has few moving parts and should have a long, useful life, radon buildup over extended periods of time becomes a low-level radioactive source requiring special disposal. This technology has a lower front-end cost, but there are costs associated with disposal of radioactivity buildup over a period of years.
  • Aeration: Radon can be easily removed from water supplies by blowing air up through the water and venting the resulting vapor out through the roof. This is most commonly accomplished with an air diffuser mounted at the bottom of a storage tank filled with water to be treated. As the air bubbles rise through the water, they strip radon and carry it out of the top of the tank and through a vent pipe to above the roofline. A greater level of success—as much as 99 percent removal—can be achieved when selecting a unit that uses a mister or nozzle located at the top of the tank to fill the tank along with a bubbler. This technology has a higher front-end cost than granular activated carbon but has no associated disposal costs.

Learn more about treating radon.

How do I treat uranium in my water?

The following methods can be used to remove uranium from water:

Reverse osmosis (RO)—RO can remove up to 90 percent of uranium. Typically, RO is a point-of-use (POU) device installed where the water is used. It also can be used at the point-of-entry (POE) into the house so that all water is treated.

With POU RO units, a minimum three gallons of wastewater is discharged for every gallon of treated water produced. Since low concentrations of soluble minerals such as calcium, magnesium, iron, and manganese can foul an RO unit, some pretreatment device may be needed.

Maintenance involves replacement of filters and membranes. Filters should be handled carefully and disposed of properly due to potentially high uranium concentrations.

Ion exchange—This involves a physical-chemical process in which water passes through a specialized resin, inducing an exchange of ions removing uranium. Ion exchange is typically used in POE treatment systems.

Maintenance can involve replacement or regeneration of media and cartridges. Spent media and cartridges must be handled carefully and disposed of properly due to potentially high uranium concentrations.

Distillation—Distillation, involving evaporating water and condensing the vapor, requires significant heat energy and cooling capacity. It is generally used in POU systems. Residue disposal must be done according to applicable regulations. Filters should be handled carefully and disposed of properly due to high uranium concentrations.

Learn more about treating uranium.

How can I address unsafe levels of lead in my water?

First, try to determine the source of the lead in your water. In most cases, it is not the groundwater but rather the household plumbing pipes, fittings, fixtures, or solder. If it is not the groundwater, a water well system contractor can inspect your well system for any components that contain higher lead levels. A plumber may be able to help in identifying the sources of lead in the household plumbing.

If household plumbing or well system components are the source of unsafe levels of lead, the homeowner has four options to address the source:

  1. Replace the problem components with new components that meet current federal requirements.
  2.  Treat water that is being consumed with appropriate treatment technologies. The National Sanitation Foundation (NSF) recommends the following:“Potential treatment options for lead can include filters, reverse osmosis units, and distillers. Make sure the system is certified under NSF/ANSI standards for lead reduction, which means that the system has been independently verified to be able to reduce lead from 0.150 mg/L to 0.010 mg/L or less.
  3. When pH levels drop below 7.0, water becomes acidic which can cause lead to leach from plumbing pipes, fittings, fixtures, and solder, according to NSF, adding: “Acid neutralizing systems are generally used to correct this situation. By adding a chemical like soda ash to the water to boost pH above 7.0, the system can help reduce both lead and copper leaching attributable to low pH.”
  4. Flush water that has been sitting in your water system for a long time (such as overnight) to remove water into which lead has leached. Several water samples from different taps may be needed to determine how to effectively flush your system of lead-tainted water.

The preceding options vary in cost and ease of implementation, so what works best for one well owner may not have the same advantages for another.

Learn more about treating lead in this lesson or webinar.

Should I periodically test water that’s gone through my water treatment system? If so, how often should I test the treated water?

First, check the treatment system owner’s manual or product information for recommendations on water testing. If you do not have that information, contact the manufacturer or go online to see if you can find the maintenance information for your product’s make and model.

Generally, treated water should be tested after the treatment system is installed to make sure it is working. You also can test the water after the treatment system is serviced to make sure it is working properly. Another reason to test is if the treatment system has not been maintained according to the product maintenance recommendations. Neglecting maintenance such as the timely filter replacement or cleaning could impair the treatment system’s effectiveness.

Learn more about water treatment here.

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