Will Reverse Osmosis Remove Arsenic – Trivalent And Pentavalent

According to the USGS, approximately 2.1 million people in the United States are exposed to arsenic in their drinking water, and particularly those who are consuming water from domestic wells. Reverse Osmosis systems are an effective method of water purification and may help remove arsenic.

Reverse osmosis systems can remove arsenic from water with an efficiency of 80 to 99 percent, although the performance of the system varies depending on its design. The semipermeable membrane with microscopic pores allows water to pass through, while trapping larger molecules, including arsenic.

This article will take you through what arsenic is, how it enters our drinking water, and its effects on the human body. The guide will also explain how reverse osmosis removes arsenic in water.

What is arsenic?

According to the CDC, Arsenic (As) is a white to grey, brittle solid that occurs naturally in water and soil. Arsenic is an extremely toxic metallic element that can be found in rocks, soil, plants, air, and even water. 

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

Copper smelting, mining, and coal combustion all produce arsenic as a by-product. Arsenic can also be combined with other elements to create compounds that can be used to preserve wood and kill insects in cotton and other agricultural crops.

There are two types of arsenic – trivalent (arsenic III) and pentavalent (arsenic V)

Trivalent arsenic is considered more toxic than pentavalent arsenic.

Types of arsenic compounds

Arsenic compounds come in two major divisions. They include:

  1. Inorganic arsenic

Inorganic arsenic compounds are ones that do not contain carbon and are simple molecules. These chemicals are extremely dangerous, and a good example is Arsenic trioxide. The chemicals can be found in industries, building items, and water that has been contaminated. Inorganic arsenic, which is bonded to oxygen atoms, can be found in groundwater.

  1. Organic arsenic

Organic arsenic is a type of arsenic that has been mixed with carbon and other components. These arsenic compounds are far less hazardous than inorganic arsenic compounds. Some foods, such as fish and different kinds of marine life can contain these compounds, because they feed on algae that contain arsenic compounds.

How reverse osmosis removes arsenic from water

Reverse osmosis uses pressure to force water through a series of filters. Water is forced through a pre-filter, carbon filter, post-filter, and a reverse osmosis membrane with microscopic pores that are specifically sized to allow water molecules to pass through, while trapping bigger inorganic compounds, like arsenic. 

The membrane is made up of thousands of tiny pores of roughly 0.0001 microns in diameter, which are too small for arsenic to fit through (Arsenic is typically 5 microns in diameter).

Though the performance of the reverse osmosis system varies depending on its design, most reverse osmosis systems can remove arsenic with an efficiency of 80 to 99 percent according to EPA – making reverse osmosis one of the best water treatment solutions for removing arsenic.

According to the CDC, reverse osmosis systems can remove typical chemical pollutants (metal ions, aqueous salts) such as sodium, chloride, copper, chromium, and lead, as well as pentavalent arsenic by up to 95%.

Reverse osmosis units are extremely capable of removing arsenic V; however, other forms, such as arsenic III, require a pre-treatment to convert arsenic III to Arsenic V. Once converted to arsenic V reverse osmosis can effectively filter it. For treatment, potassium permanganate, ferric chloride, and chlorine are effective at converting arsenic (III) to arsenic (V).

Which reverse osmosis systems can remove arsenic from water

The Waterdrop G3 Reverse Osmosis Water Filter System.

The Waterdrop G3 reverse osmosis system includes three filters that can reduce arsenic and other contaminants by more than 99.2 percent. The activated carbon block filter also employs high-precision activated carbon granules derived from natural coconut shells to improve the taste of the water.

The cross filtration technology utilized in the Waterdrop G3 Reverse Osmosis Water Filter System avoids bacteria and virus build-up.

It is NSF 58 and 372 certified, as it has been tested and certified by NSF International in accordance with the NSF/ANSI standard.

The American National Standard for point-of-use (POU) reverse osmosis (RO) systems is NSF/ANSI 58, whereas NSF 372 is compliant with the Safe Drinking Water Act and meets the requirements of various states, including California.

2. Waterdrop G2P600 Reverse Osmosis Water Filtration System.

The Waterdrop G2P600 Reverse Osmosis Water Filtration System employs innovative composite filter technology, which effectively mixes the properties of multiple filter materials to provide greater filtration.

This Waterdrop reverse osmosis system can remove 99.99 percent of pollutants, including arsenic, from your drinking water with its composite filter. The brand’s post activated carbon block filter also improves the taste of water by reducing bad taste and odor caused by pollutants in your drinking water.

Is arsenic in water bad for you?

Arsenic exposure is detrimental to the human health. According to CDC, people are exposed to arsenic in hazardously high or even small amounts from the air they breathe, the water they drink, or the food they consume.

Some man-made products can also expose people to arsenic.

Globally, the majority of human arsenic exposures occur from drinking water, and despite the amount, it has negative short and long term negative effects on human health.

As a result, the EPA established a lower arsenic in drinking water standard that applies to both community and non-transient, non-community water systems. The new 10 parts per billion (ppb) arsenic standard replaces the previous 50 ppb standard, which protects consumers against the effects of long-term, chronic arsenic exposure.

Normally, the health effects of arsenic exposure to human beings depend on various factors. These factors are:

  • The type of arsenic you are exposed to. Is it organic or inorganic?
  • The amount of arsenic you have been exposed to.
  • The period of time you have been exposed to arsenic.
  • Your age bracket.

According to the EPA, exposure to arsenic in water has the following effects on the human body:

  • Skin disorders and skin problems, such as lesions, discoloration, and the development of corns.
  • High blood pressure.
  • Cancers of the bladder, kidney, lung, skin, colon, and the liver.
  • Nausea.
  • Vomiting.
  • Diarrhea.
  • Dehydration and shock. 
  • Muscle weakness and cramping.
  • Irritated lungs.
  • Death.
  • Heart attacks.
  • Numbness.
  • EPA research shows that children who have been exposed to arsenic for a long time may have lower IQ scores, and pregnant women who drink water contaminated with arsenic risk giving birth to babies who have lung damage, respiratory infections, and are more likely to develop lung illness.
  • Recent research showed ingestion of inorganic arsenic (InAs) causes reproductive and developmental consequences, as well as non-malignant lung diseases.

How does arsenic enter our water supply?

Arsenic can enter our water supply by human activities or naturally. When mineral deposits, such as arsenic-containing rocks dissolve, arsenic naturally enters lakes, rivers, oceans, and underground water.

Arsenic can get into the water as a result of human activities, such as mining, or its diverse uses in industry, animal feed, as a wood preservative, and as a pesticide. Arsenic can also enter the water supply through contamination from industry and agriculture. 

It can enter streams and lakes, and the groundwater through industrial and agricultural waste discharge.

According to the CDC, inorganic forms of arsenic were used in pesticides and paint pigment in the past. People also used them as wood preservatives and as a cure for a number of ailments, and because arsenic has remained on the ground for such a long time, it has the potential to infiltrate the earth and contaminate water supplies.

  • When groundwater levels drop dramatically, it also dissolves out of some rock formations.
  • Arsenic levels in private wells can be elevated due to historical usage of arsenic-containing fertilizers or industrial waste.
  • It can also mean that the well was built incorrectly or that chemical fertilizers or herbicides were used excessively in the past. 

Arsenic can slowly permeate the earth in the ground or surface water because it stays in the environment for a long time after being emitted.

Arsenic is mostly found in water in inorganic forms such as trivalent arsenite (AsIII) oxyanions or pentavalent arsenate (AsV).

Note: Because arsenic has no smell, color, or taste, it’s not detectable in water. Get a Total Arsenic Testing kit and have your water professionally tested – it’s the only method to find out if your drinking water has excessive amounts of arsenic in it.

Which reverse osmosis systems waste less water?

There are now several reverse osmosis systems that have waste water to pure water ratios less than 4:1. The WaterDrop 800GPD Tankless RO system and N1 reverse osmosis system are the most water efficient and have a 1:3 wastewater to pure water ratio. This means for every 3 cups of pure water generated, only 1 cup of waste water is produced.

For a complete list of reverse osmosis systems that waste less water read this comprehensive guide.

Reverse osmosis removes a lot of pollutants from water in most cases. However, the amount of wastewater produced by reverse osmosis systems can be more than four times that of purified water, meaning these systems can generate a lot of wastewater. As a result, if you’re in the market for a new Reverse Osmosis system, you might want to look for one that creates less effluent.

Most reverse osmosis systems remove water on a ratio of 4:1 which means that the waste water produced is more than clean water but if you find one that can produce clean water and waste water on a ratio of 1:1, 1:2, 1:3, or 1:4 it is better because less water is wasted.

Can reverse osmosis remove fluoride?

Because fluoride molecules are bigger than water molecules, reverse osmosis successfully removes them from the water supply. It applies high water pressure to a semi-permeable membrane with microscopic pores that allow only water molecules to pass through, preventing bigger pollutants like fluoride molecules from passing through.

Reverse osmosis not only removes fluoride from water but it also filters other contaminants like PFAS, PFOA, chlorine, sodium, chloride, copper, chromium, and lead, among so many other pollutants.

A Reverse Osmosis system may remove 80 % of fluoride from your drinking water.


A reverse osmosis filtration system is ideal for removing harmful chemicals and heavy metals from drinking water, such as arsenic. As discussed above, reverse osmosis systems are capable of removing arsenic in water. The system is capable of removing a variety of contaminants, including chlorine, PFAS, lead, pesticides, and cysts, among others.

RO systems provide tailored filtration, which means they can use multiple filters to target different types of pollutants. While some filtering systems only have one type of filter, reverse osmosis systems have a number of filter options. The RO employs three or more filters to ensure that the majority of pollutants are removed from the water.

Ultimately, If you’re not sure about the state of your water or whether it contains arsenic, get a Total Arsenic Test Kit here to guarantee you don’t experience the long-term effects of arsenic in your water owing to a lack of knowledge. According to the WHO, some people drink water contaminated with high levels of arsenic without realizing it.

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