How to Remove Mercury From Water

Posted by
John Woodard on January 09, 2024

Mercury possesses some unusual properties that makes it one of the most unique metals on earth. It is the only metal that is liquid at room temperature and is extremely slippery to the touch. Mercury is also heavy; one tablespoon of the element weighs about one-half pound. However, the unique properties of mercury also make it hazardous to humans. Liquid mercury gives off vapors that can easily be inhaled and cause major health issues. It can also find its way into water supplies and cause problems due to long-term exposure. Fortunately, some water filters can eliminate the risk of mercury poisoning induced by water contamination. In this article, you can find information on what mercury is, the symptoms of mercury poisoning, and how to remove mercury from water.

What is mercury?

Mercury (denoted Hg), historically known as quicksilver, is the only metal that holds a liquid state at room temperature. It is a neurotoxin, meaning exposure to mercury can affect how the brain and nervous system operate. When an object containing mercury breaks, elemental mercury breaks into droplets and evaporates into a toxic, odorless gas. In the past few decades, the dangers of mercury have become more well-known, and certain products are no longer allowed to contain the metal. The most popular mercury ban involves fever thermometers. Since 2001, many state and city governments have passed restrictions on the manufacturing of thermometers containing mercury because of the threat they pose when broken.

How does mercury get into water?

Most mercury that finds its way to water sources does so through atmospheric deposition, the falling of gasses from the atmosphere in rain, snow, or dry particles to the earth. Other sources include industrial waste, mining waste, volcanic activity, and natural deposits. Mercury can be found in everyday electronic and electrical products, such as fluorescent lights, thermostats, automotive parts, certain batteries, and LCD screens. Thermometers and certain other manufactured products in many states no longer contain mercury due to the health threat it poses. However, the electronic and electrical industries, alongside coal-fired power plants, are still responsible for most of the mercury found in industrial waste.

products containing mercury

Is mercury in water dangerous?

Mercury is toxic to the body, causing unpleasant side effects at low blood-mercury levels and potentially fatal results at high levels. Mercury is particularly dangerous because it does not need to be directly ingested to poison the body. Rather, mercury poisoning is most often caused by inhaling mercury vapors, but it can also be absorbed through the skin. Mercury absorbs into skin very slowly, so mercury vapor is much more hazardous than elemental mercury on bare skin.

Mercury poisoning

Mercury poisoning occurs due to slow long-term exposure to mercury or rapid high levels of exposure. The symptoms of mercury poisoning vary due to the age of the exposed person, length of the exposure, prior medical issues of the exposed person, the amount of mercury in the exposure, and the form of mercury involved.

Symptoms of methylmercury poisoning

Methylmercury is a form of mercury most found in fish and shellfish. It is particularly dangerous to infants and children because of its effects on the nervous system and brain. Expecting mothers can expose their unborn infants to high levels of methylmercury when consuming certain kinds of seafood, affecting the development of the infant’s brain and nervous system. Well water is also susceptible to high levels of methylmercury. City-treated water is tested for mercury, but the water in a well may contain dangerous levels of the metal. Those with a blood-mercury level of over 100 parts per billion are most likely to experience symptoms of mercury poisoning.

While methylmercury is most harmful to infants and children, adults can still experience side effects when exposed to too much. Common side effects of methylmercury poisoning include:

  • Vision loss
  • Lack of coordination
  • Muscle weakness
  • Lung impairment
  • Hearing loss
  • Cerebral palsy in infants

Symptoms of elemental mercury poisoning

Elemental mercury poisoning is caused by exposure to spilled metallic mercury. Many household items contain metallic mercury, including old thermometers, thermostats, fluorescent light bulbs, barometers, and blood pressure gauges. Too much exposure to elemental mercury can lead to the following side effects:

  • Mood swings
  • Insomnia
  • Tremors
  • Headaches
  • Reduced mental cognition
  • Decreased nerve responsiveness

broken thermometer

Can I bathe in water that contains mercury?

If levels of mercury are too high in your water, you may need to avoid using your home’s water altogether until a filter is implemented. Mercury is absorbed into the skin very slowly. However, if your water contains high enough levels of mercury, mercury poisoning can result from long-term exposure to even skin contact. You can bathe in water with higher than 2 ppb of mercury, but you will not want to expose yourself to high levels over a long period of time.

Does tap water contain mercury?

To meet the EPA’s standard for mercury in drinking water, tap water must contain fewer than 0.002 parts per million (ppm), or 2 parts per billion (ppb), of mercury. At these levels, mercury is not known to pose any health threats, even over long-term consumption. The most likely victims of mercury in water are those that receive their water from a well, not those with city-treated water.

Learn more: How does city water treatment work?

Does well water contain mercury?

Most well water contains some level of mercury, but many times the concentrations of mercury are below the threshold of danger. However, some states, such as those on the east coast, are more prone to higher levels of mercury than others. Factors that influence the levels of mercury in water include natural deposits, mining waste, air pollution, industrial waste, and volcanic activity. According to the EPA, Texas, Ohio, and Pennsylvania contribute to mercury pollution more than other states due to coal-fired power plants. Mercury pollution in the air eventually settles to the ground in a process called atmospheric deposition. This allows mercury to find its way into surface water sources, soil, and eventually groundwater. To know whether your well water contains safe levels of mercury, you will need to use a test kit. Mercury test kits are simple to use and provide results in a matter of minutes. If your test determines your water mercury level is too high, you will need to incorporate one of the filters listed below into your water system.

Learn more: How to install a whole house water filter for well water

Best water filters for removing mercury

Many types of water filters and water purifiers can reduce levels of mercury in water. However, some are more effective than others. Some of the best water filters for removing mercury are reverse osmosis systems, activated carbon filters, and water distillers.

Reverse osmosis systems

Reverse osmosis (RO) systems use at least three stages of treatment to filter contaminants from water. These stages include a sediment filter, a carbon filter, and a reverse osmosis membrane.  The activated carbon stage in an RO system removes a high percentage of mercury from water, and the rest is dealt with by the tiny pores in the RO membrane. RO filtration removes about 95% to 97% of mercury from water, virtually eliminating the risk of mercury poisoning by consumption or absorption.

Advantages of reverse osmosis for removing mercury

  • Available in whole-home configurations
  • Removes almost all other contaminants alongside mercury
  • Ideal for well water, the most likely water source to be high in mercury
  • Can be customized to solve your individual water needs

Disadvantages of reverse osmosis for removing mercury

  • Less simple installation than carbon filters and water distillers
  • Typically more expensive than carbon filters
  • Produces wastewater in the filtration process
  • Requires an appropriately sized storage tank to ensure it can produce and collect enough water for your household’s needs

Learn more: What Is a reverse osmosis system? | Reverse osmosis vs distilled water

Carbon filters

Both activated carbon and carbon block filters are capable of reducing levels of mercury in water. Both filter types work in generally the same way, but they perform very differently. Activated carbon filters and carbon block filters use ground-up activated carbon granules that attract contaminants, such as mercury, chlorine, and lead, as water passes through the filter. The carbon in carbon block filters is ground down even further into a fine powder and mixed with a binder to create a solid block. Because of the composition of carbon block filters, water takes much longer to pass through than in activated carbon filters. This allows for more contaminants to be removed, but it also reduces the flow rate of the filter. Some activated carbon filters require more contact time with water, making them more effective yet slower. Activated carbon filters are often used in conjunction with other filtration systems, but they are also used in standalone systems like refrigerators and water pitchers.

There are also many under-sink systems that combine carbon with other filtration technologies to eliminate mercury, as well as other common contaminants like lead, VOCs, and chlorine. Some of these employ ultrafiltration membranes to give them increased contaminant reduction capabilities. While these will not solve your household’s problem if you are drawing water from a mercury-ridden well, they can provide safe and highly pure water from the individual taps they are installed beneath.

It is important that you locate a carbon filter that has been tested and certified to remove mercury. While many carbon filters are engineered to eliminate this contaminant, it is not inherent to all carbon filters. Make sure to read the accompanying literature to ensure the filter you are installing has been specifically tested for the removal of mercury.

Advantages of carbon filters for removing mercury

  • Available for whole-home applications
  • Simple to install and maintain
  • Higher flow rate than RO or water distillation
  • Available in many configurations

Disadvantages of carbon filters for removing mercury

  • Do not remove as many contaminants as reverse osmosis or water distillation
  • Does not make water microbiologically safe
  • Removes significantly less arsenic than RO or water distillation from well water, the most likely water source to contain mercury

Learn more: Activated carbon filters 101

Water distillers

Water distillers produce extremely pure water. In fact, so many contaminants are removed during distillation that the finished product has a flat, unpleasant taste. Water distillers are used in applications, such as hospitals and laboratories, where water must be free from as many impurities as possible. Water in a distiller is housed in a boiling chamber, where it is heated up until it turns into water vapor. As the water evaporates, almost all contaminants, including mercury, are left behind in the boiling chamber. Once the vapor reaches the ceiling of the distiller, it condenses back into liquid form and drops into a collection container. Because water takes so long to boil, evaporate, and finally condense into liquid form, water distillation is not capable of purifying enough water for uses other than drinking at the home level.

Advantages of water distillation for removing mercury

  • Produces highly pure water
  • Creates microbiologically safe water
  • Easy to install and maintain

Disadvantages of water distillation for removing mercury

  • Can only be practically used for potable applications
  • Purifies water very slowly
  • Finished product has a flat taste

Learn more: What Is distilled water and is it safe to drink?

Does boiling water remove mercury?

No, boiling water does not remove mercury. It will only increase the levels of mercury and other contaminants as water is lost in the form of steam. Boiling water also adds to the risk of releasing certain forms of mercury into the air.

 Learn more about eliminating common water contaminants: Lead | Chloramines | Nitrates | Arsenic | Water Hardness | Microplastics | Fluoride | Copper | PFAS | VOCs | Bacteria


If you have any further questions, please do not hesitate to contact us.

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