Arsenic in water: invisible, natural and serious — how to recognize and remove it

Arsenic is one of the most serious health contaminants of drinking water, and at the same time completely invisible — without color, taste or smell. Unlike industrial pollutants, arsenic most often enters water naturally, geologically , and affects wells and water supplies in certain areas across Europe and the world. Since it is harmful even in very small, long-term doses and cannot be detected by the senses, this is a problem where analysis is key. This guide explains where arsenic comes from, why it is dangerous and which technologies reliably remove it.

Where does arsenic come from?

• Geological origin (most common). Arsenic is naturally found in certain rocks and sediments and dissolves into groundwater. In some regions (especially with deep wells and specific geology), natural levels exceed safe limits.
• Industry and agriculture — less common, local pollution (mining, some historical pesticides, industrial waste).

Important for treatment: Arsenic occurs in water in two forms — arsenite (As III) and arsenate (As V) . Trivalent As(III) is more difficult to remove, so for effective treatment it is often necessary to first oxidize it to As(V) . This nuance has a crucial impact on the choice and effectiveness of the solution.

How to identify arsenic in water

Unambiguously: not to the senses. Arsenic is colorless, tasteless, and odorless, does not stain or deposit, and does not damage devices. The only reliable method is a chemical analysis of the water . Increased caution and testing are recommended if:

• you live in an area known for geologically elevated arsenic ,
• use a deep well in such an area,
• the area has a mining or industrial history.

Why is arsenic dangerous to health?

Arsenic has been shown to be harmful with long-term exposure and is one of the most serious water pollutants. Chronic exposure to elevated levels of arsenic is associated with an increased risk of certain types of cancer (skin, bladder, lung) , with skin changes , and with effects on the cardiovascular system and other organs. Since the effects accumulate over years, the danger is greater the longer the problem goes unnoticed — and precisely because there are no external signs, it can go unnoticed for a long time. Because of this seriousness, the EU sets a very low limit and applies a precautionary approach.

What arsenic does (and doesn’t)

Arsenic leaves no visible trace — no color, stains, deposits, taste, or odor, and it doesn’t harm the installation. This, along with PFAS, nitrates, and other heavy metals, places it in a group of “invisible” risks where awareness and testing are the only way to detect it.

Limit values ​​(EU)

EU Directive 2020/2184 and national regulations set the limit value for arsenic at 10 µg/L (micrograms per liter). The value is deliberately very low because arsenic is already significant for health in trace amounts; water above it requires treatment.

1. Natural sources:

Arsenic can be released from rocks and soil through natural processes of erosion and dissolution. This natural arsenic can end up in surface and groundwater.

2. Anthropogenic sources:

Human activities, such as mining, industry, and agriculture, can contribute to the presence of arsenic in water sources. Industrial waste and the use of arsenic-containing pesticides can lead to contamination of water resources.

3. Arsenic in plumbing systems:

In some cases, the presence of arsenic in water may be due to corrosion of water pipes and equipment containing arsenic.

The concentration of arsenic in water varies depending on geographical area and local conditions. In most cases, the presence of low concentrations of arsenic in water does not pose a significant risk to health.

The starting point is an analysis that shows the concentration and, ideally, the form of arsenic (As III/As V) — only then is an effective technology and pre-oxidation selected.

However, long-term exposure to high concentrations of arsenic can have serious consequences for human health:

1. Chronic arsenic poisoning: Long-term exposure to low arsenic concentrations can cause chronic arsenic poisoning. Symptoms include skin lesions, changes in the nails, stomach pain, a feeling of fatigue and weight loss.
2. Cancer: Consuming arsenic-contaminated water can increase the risk of developing various types of cancer, including lung, skin, bladder and kidney cancers.
3. Cardiovascular problems: High concentrations of arsenic in water may be associated with an increased risk of heart disease, hypertension and other cardiovascular problems.
4. Neurological problems: Arsenic exposure can also affect the nervous system and cause neurological symptoms such as headaches, dizziness and sensory disorders.

Due to the serious health risks that arsenic poses, it is important to regularly test the water for the presence of this toxic element.

Technologies for removing arsenic from water include adsorption on activated carbon, reverse osmosis, and ion exchange. Proper water treatment can be key to ensuring a safe and healthy water source for consumption.

Arsenic can be removed from the water using various technologies to purify water. Here are some of the most common technologies used to remove arsenic from water:

1. Adsorption on activated carbon: Activated carbon has the ability to adsorption arsenic from water. Water passes through a layer of activated carbon where arsenic binds to the surface of the coal. This technique is effective for eliminating low concentrations of arsenic.

2. Ion exchange: Ion exchange is the process by which arsenic from water is replaced by other ions, usually sulfate or chloride. This technique is often applied to remove arsenic from drinking water.

3. Oxidation and filtration: Oxidation substances such as potassium permanganate or oxygen can be added to water to convert arsenic from dissolved to solid form. After oxidation, water is filtered to remove solid arsenic particles.

4. Reverse osmosis: Reverse osmosis is a technology that uses a membrane to filter particles and substances from water. It removes arsenic and other contaminants present in the water.

5. Iron oxide media: Adding ferrum (iron oxide) to water can cause arsenic to bind to ferum and create particles that are easy to precipitate and can be filtered.

6. Chemical treatments: Various chemical treatments can be used to remove arsenic from water, including the addition of calcium hydroxide or aluminum sulfate to form solid arsenic compounds that are deposited and can be removed.

It is worth noting that the choice of the appropriate technology depends on the concentration of arsenic in the water, local conditions and budget.

In some cases, it may be necessary to combine different technologies to achieve an optimal result. Regular water testing and collaboration with water experts will help ensure safe and clean water for consumption.