Does Reverse Osmosis Remove Arsenic From Water?

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Does Reverse Osmosis Remove Arsenic_Best RO For Arsenic Treatment At-Home

Arsenic has a long history of being feared for its deadly toxicity. It has no smell or taste, so it can harm people without their awareness. Since it can cause some terrifying health risks, you might be asking what’s the best way to treat arsenic. Does reverse osmosis remove arsenic from drinking water?  

In this post, we’ll uncover how arsenic gets into your water, how to detect if you have an arsenic problem, and how effective is RO filtration in treating it. Let’s dive in!

What Exactly Is Arsenic In Drinking Water?

Arsenic is a naturally occurring element in rocks, soil, and even our drinking water [1]. Excessive amounts of inorganic arsenic can easily enter soil and surface water due to mining, agriculture, and other industrial activities. It generally enters drinking water in the following ways:

  • Pesticide runoff can spread and leak into the groundwater nearby. 
  • Rainwater transports inorganic arsenic to groundwater from factories’ excessive environmental releases of the substance. 
  • Wells close to natural deposits, industrial activity, mining, or agriculture are particularly vulnerable to arsenic pollution.

Acceptable Arsenic Amounts in Water

A concentration of 10 parts per billion (ppb) arsenic is considered safe by the Environmental Protection Agency. However, it was originally believed that 15 ppb of lead in drinking water could be considered acceptable over the long term, but we now know the safe maximum contaminant level for lead is zero [1]. If the arsenic concentration in your water supply is even minor, you should consider treatment options. 

This is especially true for those with well water. Since the EPA doesn’t regulate private wells, the owners of those wells should test their water to get rid of any and all contaminants, not just arsenic.

Shockingly, the United States Geological Survey found that concentrations of arsenic exceeded the EPA maximum contaminant levels in 16% of drinking-water aquifers sampled in the Southwest [2].  

Does Reverse Osmosis Remove Arsenic_Arsenic Treatment Map Infographic
Source: United States Geological Survey

Potential Health Impacts Of Ingesting Arsenic

Arsenic exposure can cause symptoms like stomach discomfort, diarrhea, vomiting, nausea, skin discoloration, blindness, numbness of the hands and feet, and partial paralysis [3]. If you are exposed to this poisonous substance for a long time, you may have more chronic symptoms and may even die.

Furthermore, a long-term study in the Journal of Urology demonstrated the high correlation between bladder cancer and high arsenic concentrations in drinking water.

“Our study confirms the results of the significantly high bladder cancer specific mortality rates in this well-known arsenic exposed region”

Journal of Urology

Children are also at heightened risk from arsenic exposure. Long-term health effects include adverse impacts on cognitive development, lower IQ scores, and increased deaths for adolescents [4].

How Does Reverse Osmosis Remove Arsenic? 

Reverse osmosis, or RO for short, is a process that utilizes pressure to push water through a particular semi-permeable membrane in order to filter out dissolved contaminants. These are then expelled through the reject stream, also called the concentrate or brine stream. 

The wastewater can then be flushed down the drain or returned to the feedwater supply enabling the system to reuse and save water. Small pores in the layer let water molecules through while trapping bigger particles such as arsenic. 

How Much Arsenic Will Reverse Osmosis Remove?

Reports have found that point-of-use RO filtration systems can reduce arsenic contents by as much as 80% to 99%. A better reverse osmosis water filtration system will provide your home with better quality fresh, clean water every day.

The effectiveness of RO filters used in real life may differ from that done in research facilities. Poor maintenance, improper setup and use, water chemistry, and variances between filter types by brand may provide a different result

Do RO Systems Remove Arsenic From Well Water?

Unfortunately, the highest levels of arsenic are found in well water. One of the best arsenic water treatments for well water is reverse osmosis. In fact, many states known for high inorganic arsenic contamination will recommend NSF certified RO systems as their preferred solution. Aside from arsenic, reverse osmosis can reduce or eliminate contaminants in well water such as heavy metals, magnesium, nitrates, sulfates, and more.  

In order to prolong the lifespan of your reverse osmosis system in your well water, you may need to install an additional pre-sediment filter.  

Does Reverse Osmosis Remove Other Contaminants?

Yes, reverse osmosis can remove other contaminants besides arsenic. Note that the pores of a reverse osmosis filter are typically around 0.0001 micron in size. Thus, they are highly efficient at filtering out the following:

  • protozoa such as Cryptosporidium and Giardia
  • Bacteria such as Campylobacter, Salmonella, Shigella, and E. coli
  • Pathogens such as Enteric, Hepatitis A, Norovirus, and Rotavirus.
  • Chemical contaminants such as sodium, chloride, copper, chromium, and lead.
  • Elements or compounds such as fluoride, radium, potassium, nitrate, sulfate, calcium, magnesium, and phosphorous.

Where Is A Reverse Osmosis System Installed?

While the typical placement for a reverse osmosis system is beneath the kitchen sink, it is possible to put the system elsewhere, there are also countertop and whole-house RO units. Here are the three different types of reverse osmosis systems.


The under-sink area is perfect for securing the RO filter. You can apply this system with enough space under your kitchen sink. Having this hooked up to the mains water line ensures that everyone in the house can access clean water.  A tank is not required for some under-sink units (tankless), whereas others do (with a tank).

Tankless reverse osmosis systems may be the best option for people who live in apartments or other dwellings with less storage capacity. You won’t need to worry about building a large tank under your sink.


This RO system is designed to fit neatly on a kitchen counter, consisting of individual filter units connecting to purify water through a series of purification processes. This filter can be attached to a sink’s faucet or a water container. 

Whole House

The RO system is set up where the water supply enters the house. This system will filter and purify all the water in your house, making it suitable for human consumption. A whole-house RO system consists of a RO membrane cartridge, carbon postfilter, and sediment filter.

How To Test For Arsenic In Drinking Water

There are a few reliable ways to detect if your drinking water contains arsenic. Here are the best methods to check:

Get A Home Water A Lab Test

Tap Score’s lab test is the most reliable at-home method for detecting arsenic in water. This comprehensive water test kit provides all the tools necessary to collect a representative sample of your tap water for examination by a certified laboratory. Results will include a comprehensive evaluation of total arsenic among dozens of other contaminants.

Check The Environmental Working Group (EWG) Database 

The Environmental Working Group (EWG) database can be used to get a free in-depth report on the quality of your local water supply. By entering a ZIP code, users may search for their water provider and learn what toxins are in their water and how those levels compare to state and national standards and health guidelines.

Check The Consumer Confidence Reports (CCR)

Consumer Confidence Reports (CCRs) are a great resource for learning more about the safety and quality of your local water supply. Some of the water quality information in the CCR report will help you comprehend how drinking water affects your well-being. 

For instance, the report may reveal that your water supply can be contaminated with bacteria, chemicals, or minerals that are bad for you.

What Water Filter Will Remove Arsenic Other Than RO? 

Although reverse osmosis is most recommended, other water filtration alternatives can also work to treat arsenic in your drinking water. These at-home options include:

Granular Activated Carbon (GAC or Charcoal Filters)

Granular activated carbon filters are produced from ground-up carbon held together loosely in a cartridge or container. GAC filters are capable of reducing arsenic in water, however, not as effective as the reverse osmosis system.

A recent study conducted at Duke University found carbon block filter performance to be erratic.

“Effectiveness of activated-carbon filters used in many pitcher, countertop, refrigerator, and faucet-mounted styles was inconsistent and unpredictable.”

Duke University Study on Drinking Water Filters

This is not to say that GAC and charcoal filters are categorically poor performers at removing arsenic. But, getting a higher quality unit and changing the filter more frequently is probably a good idea.

Carbon Block Filters

In a carbon block filter, the carbon is crushed into a fine powder and squeezed to create a solid block. Carbon block filters typically use carbon particles that are five to twenty times smaller than those found in GAC filters. 

Since the blocks are packed much more densely than GAC filters, they can remove a greater quantity of contaminants.

Ion Exchange Resins

By flowing water through a resin bed, ions are physically and chemically exchanged. This process is known as anionic exchange. Water softening, iron, manganese, nitrate, and arsenic reduction are all possible with the aid of ion exchange systems. 

The type of impurities that can be eliminated is dependent on the resin bed’s chemical makeup. Anion exchange can lower arsenic levels by approximately 90%. If heavy contamination exists in the water source, pre-filtration may be required for the process to be effective [6].

Distilling Water

Water contaminants can be removed by a physical process called distillation. The distillation process is capable of removing arsenic, and other heavy metals like lead and copper. Contaminated water is boiled, and the steam is collected in a separate container. Once the cleaned steam has been cooled, it condenses back into the water [5].

The drawback of distilling water vs reverse osmosis is that distillation takes a considerable amount of time. The average distiller takes four hours to purify one gallon of water. But because distillation is a natural process, there are ways to make it at home for free.

Drawbacks of Using Reverse Osmosis For Arsenic Treatment 

Wastes Water

Water is lost in the process of reverse osmosis. As a result of RO’s impressive level of filtration, some water will be wasted. In fact,  seventy-five percent of the water that is delivered to water stations is wasted, while only around twenty-five percent is really recovered. The most practical method of preventing this from being squandered is to save it for later use for gardening or flushing purposes. 

Filter Replacement Costs

When you factor in the initial investment and maintenance fees, the system’s cost per gallon of water produced is modest. However, routine maintenance and frequent filter replacements are expensive and necessary. Although RO systems are low-maintenance, they still need to be cleaned and sterilized once a year.

Higher Purchase Price

Reverse osmosis may be quite pricey, especially if you opt for whole-house systems. That surely costs thousands of dollars!  While the hefty price tag reduces the time needed to filter water, it also results in significant water waste.

Requires Installation

Before having a reverse osmosis system installed, there are a few things you should think about. Consider the wiring, water supply, the amount of room needed, the accessibility of an electrical outlet, and any other important parts.

How much does An RO System cost to operate and maintain?

The average price for a point-of-use reverse osmosis system ranges from $250 to $1,000. Depending on the size and features of the unit, larger point-of-entry systems that treat a complete house or building can cost as much as $6,000.

The sediment pre-treatment cartridge needs to be updated approximately every 6 months at a cost of about $45. The actual membrane has a life expectancy of up to 24, although this will vary with the quality of your water supply and costs around $100 to buy a replacement membrane.

Roughly half of the water used in a reverse osmosis system is wastewater, which is then discharged. That rejected water can be reused in some setups. The impurities that the membrane has trapped are flushed away with the rejected water to a drainage system as well.

FAQs For Reverse Osmosis Arsenic Removal 

Does reverse osmosis remove lead and arsenic?

Yes, reverse osmosis will remove lead and arsenic from water using a semi permeable membrane process. Using reverse osmosis to purify your home’s water supply from harmful chemicals and metals like lead is the best solution. 

Can you shower in what with arsenic?

It could be okay to use the water for cleaning and bathing unless it contains more than 500 parts per billion of arsenic. This level of arsenic in water does not easily pass through the skin or evaporate. If the levels in your water exceed 500 ppb, you should seek guidance from your local health authority or the Department of Health.

Does boiling water remove arsenic?

No, boiling water will not remove arsenic. Arsenic does not evaporate. Do not boil the water in an effort to get rid of the arsenic, as boiling water could increase arsenic concentration.

Article Sources

Freshnss uses only the highest-quality sources to support the facts used in our articles including: government organizations, independent studies, peer-reviewed journals, and lab testing results. Read our editorial review guidelines here to learn more about how we verify and fact-check our writing to keep our content reliable, accurate, and trustworthy.

  1. Arsenic And Drinking Water, United States Geological Survey (USGS)
  2. Water Quality in Principal Aquifers of the United States, United States Geological Survey (USGS)
  3. Arsenic In Drinking Water, Washington State Department Of Health
  4. Arsenic Fact Sheet, World Health Organization (WHO)
  5. How to Lower the Levels of Arsenic in Well Water, University of Arizona
  6. Arsenic Virtual Trade Show, Environmental Protection Agency (EPA)
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