Does Reverse Osmosis Remove Arsenic From Drinking Water?

If your household uses water from a domestic well, chances are, you are already exposed to arsenic. Inorganic arsenic is naturally present in groundwater and can easily contaminate drinking water.

And since exposure to this water contaminant is detrimental to your health, you need to find ways of eliminating it from your water.

So, does reverse osmosis remove arsenic from drinking water? The answer is a big yes. Reverse osmosis is one of the best technologies that help to eliminate arsenic from water. In fact, the efficiency rate is 80 to 99%.

The RO membrane has microscopic pores that allow water to pass through as it traps larger molecules, including arsenic.

What is Arsenic?

Does Reverse Osmosis Remove Arsenic From Drinking Water

Arsenic is a whitish-grey, brittle solid that occurs naturally in the soil and water. It is highly toxic and can be found in the air, soil, rocks, plants and even water.

Some industrial and agricultural sources can also discharge it into the environment.

There are 2 types of arsenic; trivalent (arsenic iii) and pentavalent (arsenic v). Trivalent arsenic is considered more toxic.

How Does Arsenic Enter Your Water Supply?

Arsenic can enter your water supply naturally or through human activities. When arsenic-containing rocks dissolve, arsenic enters oceans, lakes, rivers and underground water.

It can also get into the water through human activities like mining or contamination from agriculture.

It also enters lakes, streams and groundwater through agricultural waste discharge.

And since it stays in the environment for a very long time after it’s emitted, arsenic can slowly enter the water.

It has no smell, taste or color hence not detectable in water. The only way to find out whether your water has excessive amounts of arsenic is by testing it using a total arsenic testing kit.

You can also choose to get the water tested in a certified laboratory by a professional.

How Does Reverse Osmosis Remove Arsenic From Water?

Reverse osmosis is the best technology to eliminate arsenic from water. Ro systems feature a semi-permeable membrane with microscopic pores.

These pores are specifically sized to let water molecules pass through and trap bigger inorganic compounds like arsenic.

The RO membrane comprises tiny pores, roughly 0.0001 microns in diameter. They are too small that arsenic can’t penetrate as it’s typically 0.1 microns in diameter.

To get rid of arsenic, water is forced through a sediment pre-filter, carbon filter, post-filter and an RO membrane at high pressure.

And although the performance of RO systems depends on their designs, most units can remove 80% to 99% of arsenic from water.

Arsenic and other contaminants removed from your water are flushed down the drain during the filtration process.

Are There Alternatives Methods of Removing Arsenic from Drinking Water?

Aside from reverse osmosis filters, other filters can help reduce arsenic from your tap water. In fact, a distillation unit can eliminate 90 to 100% arsenic hence just as effective as reverse osmosis. The only drawback back is that the process is quite expensive.

Ion exchange systems can also reduce arsenic from your water. In addition, an activated carbon unit can reduce up to 70% arsenic.

What Other Contaminants Does Reverse Osmosis Remove?

If your water has arsenic, the chances are that it has other contaminants. To make it clean, pure, safe and healthy for drinking, you’ll have to remove them from the water as well.

Reverse osmosis eliminates up to 99.99% of TDS (total dissolved solids) from the water.

Other contaminants that the water filtration method can filter from your water include chlorine, fluoride, lead, radium, magnesium, calcium, chloramines, sulfate, nitrates, phosphorus, copper and chromium.

Why is Arsenic in Water Bad for You?

Exposure to arsenic is very harmful to human health. However, its effect depends on various factors, which include:

  • The amount of arsenic you’ve been exposed to.
  • The type of arsenic you’ve been exposed to.
  • The period you’ve been exposed to arsenic
  • Your age

Generally, exposure to arsenic causes skin disorders such as discoloration, lesions and the development of corns. It also causes high blood pressure, nausea, irritated lungs, dehydration and shock, numbness, diarrhea and vomiting.

In worse case scenarios, it can lead to cancer of the bladder, colon, lungs, skin and the liver. It can also lead to death.

It’s also important to note that kids who have been exposed to arsenic for long can have low IQ. Pregnant women who drink water rich in arsenic risk giving birth to kids with respiratory infections or lung damage.

Research shows that inorganic arsenic causes developmental and reproductive issues.


A reverse osmosis system can remove heavy metals like arsenic from your drinking water. And not only arsenic, most contaminants that other water filtration methods cannot deal with, RO systems give the best results.

To find out whether your water has arsenic, just get a total arsenic testing kit. You can also get the water tested by a professional.

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