Does Reverse Osmosis Remove Heavy Metals from Water?

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Not just a fun genre of music, heavy metal can also be present in your drinking water supply. And that is not as cool as it sounds! Heavy metals can accumulate in your body over time, causing a range of health issues.

The presence of heavy metals in water is one of the main reasons why people turn to reverse osmosis as a possible filtration solution.

But why? Is reverse osmosis really that good at removing heavy metals from water?

Key Takeaways

  • Reverse osmosis is one of the best methods to remove heavy metals from water.
  • Not only does reverse osmosis remove a broad spectrum of heavy metals, but it also does so with a very high percentage of effectiveness. For example: Lead is removed to around 96%, nickel to 97%, iron to 96%, and mercury to 97%.

Does Reverse Osmosis Remove Heavy Metals from Water? How?

So, does reverse osmosis remove heavy metals from water?

Yes, reverse osmosis does remove heavy metals or metals in general from water, and it is highly effective doing so.

How does RO remove heavy metals exactly? Simply put, when the water is being pushed through the reverse osmosis membrane, the metals are too big to fit through the tiny pores, and they remain on the other side of the membrane to be disposed of with the wastewater.

blue reverse osmosis membrane

If a reverse osmosis system is well maintained and working effectively, then it can remove up to 98% of metal content from water.

How Effective Is Reverse Osmosis at Removing Heavy Metals?

Reverse osmosis is a highly effective method of removing heavy metals, and metals in general, from your water supply. It can remove most metals into a percentage of the high 90s, including:

  • 98% of aluminum
  • 96% of arsenic
  • 96% of barium
  • 96% of cadmium
  • 94% of chromium 6
  • 97% of copper
  • 96% of iron
  • 96% of lead
  • 96% of manganese
  • 97% of mercury
  • 97% of nickel
  • 95% of selenium
  • 97% of zinc

Other Ways to Effectively Remove Heavy Metals from Drinking Water

While reverse osmosis may be the broadest and most effective way to filter out heavy metals from your drinking water, there are also some other processes you could use if your water is high in certain metals only.

Ion Exchange

Ion exchange uses ion exchange resin that your household water passes through. When it does, specific metal ions will stick to the surface of the resin.

Ion exchange filtration works for nickel, mercury, lead, cadmium, chromium, and copper. The downside is that this method can’t usually handle very high concentrations of metals without exhausting its ion exchange supply quickly.

Chemical Precipitation

Chemical precipitation involves adding a chemical to the water to extract the metals, turn them into solids, and then physically remove them. It works for lead, arsenic, and mercury for example and is one of the most widely used methods in water treatment plants for heavy metal removal.

KDF Filtration

KDF filters use a chemical reaction called an oxidation/reduction reaction to remove metals from water, such as copper, lead, mercury, chromium, and nickel. Some KDF filters might be combined with other filter elements, such as activated carbon, to remove even more than just heavy metals from your drinking water.

KDF filtration is a relatively cost-effective filtration method too.


Ultrafiltration filters have a pore size of around 0.01 microns. While this is not as small as a reverse osmosis membrane, it is small enough to remove some heavy metal particles from water, as well as protozoa, bacteria, and viruses among other stuff.

Ultrafiltration is not great at removing chemicals, however, and should not be used for this purpose.

Does Activated Carbon Remove Heavy Metals?

Some activated carbon filters, such as granular activated carbon, can remove heavy metals such as cadmium, copper, and zinc. However, carbon filters have a lower success rate percentage-wise than let’s say reverse osmosis.

What Are Heavy Metals and Why Remove Them from Water in the First Place?

Heavy metals are elements found in abundance in nature, mainly in soils and rocks. While they don’t pose health risks by being present there, rainwater can often break them down, causing them to seep into drinking water supplies, where ingestion over time at high doses can be toxic (they accumulate in your system and vital organs).

They can also get into drinking water through industrial/manufacturing waste.

Why remove heavy metals from your drinking water? Well, due to the fact that they can accumulate in your body over time, frequent ingestion may result in toxicity, which can cause:

  • Gastrointestinal symptoms like abdominal pain, diarrhea, nausea, and vomiting.
  • Weakness and fatigue.
  • Brain damage, causing memory loss or even convulsions.
  • Kidney and liver damage.
  • Difficulty breathing.
  • Increased risk of cancers.
  • Increased risk of miscarriage.

Five heavy metals are of relatively serious concern for poisoning: Mercury, lead, arsenic, chromium 6, and cadmium.

Aside from health effects, the presence of heavy metals in water can affect the taste and color of the water. For example, excess iron can produce rusty-colored water with a metallic taste, which is rather unpleasant.

woman sitting in front of water glass

Health Effects

Let’s look at a few metals found in our water supplies these days in more detail:


Mercury toxicity can cause symptoms such as mood changes, irritability, depression, impaired vision and hearing, and developmental delays in children. Elemental and methylmercury are toxic to the nervous system. Neurological and behavioral symptoms include tremors, memory loss, insomnia, headaches, and cognitive and motor dysfunction.


Lead poisoning can cause gastrointestinal distress, such as abdominal pains, cramps, and children’s behavioral and learning problems. Children under 6 years are especially vulnerable. At high levels, lead poisoning can be fatal.

Unfortunately, signs and symptoms of poisoning often don’t show until dangerous amounts are present in the body. Lead poisoning in children can look like

  • Developmental delay
  • Learning and behavioral difficulties
  • Weight loss
  • Fatigue
  • Abdominal pain, constipation, vomiting, constipation
  • Hearing loss
  • Seizures
  • Eating things that aren’t food (pica)

In adults, lead toxicity may look like

  • High blood pressure
  • Joint and muscular pain
  • Difficulties with memory or concentration and mood changes
  • Headache
  • Abdominal pain
  • Reduced sperm count
  • Miscarriage, stillbirth, or premature birth


Some inorganic arsenic compounds are highly toxic and have been linked to many adverse health effects, including cancer.

Contaminated drinking water is one of the primary causes of arsenic toxicity and happens to around 140 million people globally. Long-term exposure to arsenic may cause toxicity that takes years to develop and can cause severe symptoms such as

  • Skin pigmentation changes, warts, and lesions
  • Hard patches of skin on the palms and soles
  • White lines on your nails
  • A persistent sore throat
  • Digestive issues


Chromium poisoning from hexavalent chromium can cause respiratory problems, various cancers, kidney and liver problems, and reproductive issues. Oral intake of chromium 6 may cause

  • Intense gastrointestinal irritation and ulceration, and corrosion, along with epigastric pain
  • Diarrhea, vomiting, nausea, and fever
  • Vertigo
  • Muscle cramps and fatigue
  • Kidney toxicity
  • Liver damage or failure
  • Circulatory system collapse


Cadmium poisoning can cause kidney damage and renal failure, bone softening, an increased risk of fracture due to fragile bones, increased risk of certain cancers, and damage to the reproductive system and infertility.

While most cadmium toxicity comes from cigarette smoke, it is possible to ingest toxic levels from contaminated water.

How Do I Know If My Water Has Heavy Metals?

The best way to test for the broad spectrum of heavy metals is to send a sample of your water to a lab for a professional assessment.

You can also check your latest water quality report, which will be available from your water utility supplier for free.

At-home test kits are the last option. These are cheap and deliver instant results, but reliability is to be questioned.

If you have any thoughts about the question, does RO remove heavy metals, please don’t hesitate to leave a comment below!

About the Author Gene Fitzgerald

Gene Fitzgerald is one of the founders of BOS and currently head of content creation. She has 8+ years of experience as a water treatment specialist under her belt making her our senior scientist. Outside of BOS, Gene loves reading books on philosophy & social issues, making music, and hiking.
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