Arsenic is a toxic chemical element that is widely present in nature. Long-term exposure to high levels of arsenic can cause serious harm to human health. Therefore, arsenic-contaminated water is an issue that people must pay attention to. In this article, you can learn about the hazards of arsenic, how to detect whether there is arsenic in water, and how to filter arsenic in water.
What is Arsenic?
Arsenic is a highly toxic non-metallic element widely distributed in water, air, land, and other environments, and exists in groundwater worldwide. Arsenic has three allotropic forms: gray, black, and yellow. Arsenic vapor has an unpleasant garlic smell. Arsenic easily reacts with fluorine and oxygen and can react with most metals and non-metals under heating conditions. Arsenic is insoluble in water, but soluble in nitric acid and strong alkali.
Arsenic in contaminated water for drinking, cooking, and crops generally poses the greatest threat to public health. Long-term exposure to arsenic may lead to chronic arsenic poisoning, as well as cancer and skin lesions.
According to data from the World Health Organization, many countries contain high concentrations of inorganic arsenic in groundwater, such as the United States, Mexico, Argentina, India, Bangladesh and other countries.
What are the effects of arsenic in water?
Long-term exposure to high levels of arsenic can cause health effects, so what effects does arsenic in water have? Here are the specific effects:
- Thickening and discoloration of the skin
- Stomach pain
- Nausea
- Vomiting
- Diarrhea
- Numbness in the hands and feet
- Partial paralysis and blindness
Is there arsenic in tap water?
No matter where you live in the United States, there is a chance that your tap water contains arsenic, but the concentrations vary from region to region. Drinking high levels of arsenic over a long period can affect your health, so here is information on arsenic levels for drinking and cooking, as well as information on arsenic levels in well water.
Arsenic in Drinking Water
Arsenic has been detected in groundwater in 48 states, so your tap water likely contains arsenic. However, the EPA requires that tap water contain less than 10 parts per billion (ppb). Therefore, drinking water with arsenic levels below 10 ppb is safe to drink.
Arsenic in Cooking Water
You are at risk if you cook with tap water that has high levels of arsenic. According to the Oregon Health Authority (OHA), drinking water used for cooking should contain less than 50 ppb of arsenic. Boiling concentrates the arsenic if the water evaporates during the cooking process. This absorbs a lot of water, which can lead to higher levels of arsenic ingested through the diet. Therefore, cooking water with arsenic levels above 50 ppb is very risky.
Arsenic in Well Water
Well, water is more likely to be contaminated with arsenic than municipal tap water because it comes from groundwater, which has very high arsenic levels. However, unlike municipal water supplies, well water is generally not regulated by the U.S. Environmental Protection Agency (EPA). Therefore, if you have a well at home, you need to test the well further. If it is determined that the well water contains arsenic, it should be treated with a reverse osmosis system before drinking.
What is the arsenic rule for drinking water?
The U.S. Environmental Protection Agency (EPA) sets the standard for arsenic in drinking water at 0.010 mg/L. This is equivalent to 0.010 parts per million (ppm), 10 micrograms per liter (µg/L), or 1 part per billion (ppb). Even with the standard for arsenic in drinking water, long-term drinking can have health effects. Generally, arsenic is not allowed in drinking water. Therefore, you need to test to determine whether your drinking water contains arsenic. If your drinking water contains arsenic, you should immediately take appropriate filtering measures to ensure that your drinking water is healthy.
How to test for arsenic in tap water?
Testing your tap water for arsenic is an important step to ensure that your drinking water is safe. You can use the following methods:
Home testing kits
You can test your water for arsenic with some arsenic-specific test kits. You prepare a clean container to collect your water sample, follow the kit's instructions, and then compare the color of the test strip or solution to the chart provided with the kit to determine the arsenic concentration. This method is suitable for home use, but it is not very accurate.
Laboratory testing
Contact a certified water testing laboratory to obtain a sample collection kit. Collect your water sample according to the lab's instructions. Send the sample back to the lab for analysis. The lab will use advanced technology such as ICP-MS (inductively coupled plasma mass spectrometry) to analyze the sample and provide a detailed report. This method is only available for laboratory testing and is very accurate, detecting very low levels of arsenic.
Professional water testing services
You can hire a professional to test your water. These services usually require a visit to your home, where a technician will collect the sample and handle the testing process. This method is very convenient and ensures that the sample is collected and analyzed correctly.
How to filter arsenic from water?
The above has explained how to detect whether drinking water contains arsenic, but how to filter arsenic in water has become a concern. Commonly used methods include adsorption, reverse osmosis, ion exchange, chemical precipitation, etc. These four methods can effectively filter arsenic in water. Filtering arsenic in water can ensure the health of drinking water and reduce harm to human health. The specific method you choose depends on your water quality and requirements. Let's take a brief look at the four treatment methods:
Adsorption method
The adsorption method is a commonly used drinking water treatment method. Its principle is to use the adsorption effect of adsorbents to adsorb harmful substances in water on the surface, thereby filtering them out of the water. Commonly used adsorbents include activated carbon, alumina, etc. These adsorbents have a large surface area and pore size, and can effectively adsorb trace arsenic in water.
Reverse Osmosis
Reverse osmosis is one of the most effective water treatment methods. It uses advanced reverse osmosis technology and uses the osmotic principle of semipermeable membranes to filter out most of the harmful impurities in the water. Such as sodium, chlorine, copper, lead, arsenic, and many other contaminants. The RO system filters arsenic V faster than arsenic III, So the best reverse osmosis filters are ideal for filtering arsenic.
Water passes through the semipermeable membrane under pressure, while particles, ions, and organic matter larger than the membrane pore size cannot pass through the membrane and be filtered. Since the reverse osmosis membrane has a high filtration accuracy, it can effectively filter trace arsenic in the water. Reverse osmosis requires high operating pressure and backwashing cycle. At the same time, you need to regularly replace the water filter cartridge and clean the reverse osmosis system regularly to ensure the normal operation of the equipment.
Related: How reverse osmosis works
Ion exchange
Ion exchange is a method of filtering harmful ions in water using the ion exchange reaction of ion exchangers. Commonly used ion exchangers include anion and cation exchange resins. These resins have high exchange capacity and selectivity and can effectively filter trace arsenic in water. The ion exchange method requires regular regeneration and replacement of ion exchangers to ensure its treatment effect.
Chemical precipitation
The chemical precipitation method is to add chemical agents to the water to make the arsenic in the water react with the agents to form insoluble precipitates, thereby filtering it from the water. Commonly used chemical agents include ferric chloride, calcium sulfate, etc. In the chemical precipitation method, it is necessary to reasonably control the dosage of the agent and the reaction conditions to avoid secondary pollution.
By taking the above treatment methods, I believe you can filter out the arsenic in the water, thereby ensuring pure and healthy drinking water.
Distiller
The working principle of the distiller is to heat water to its boiling point, evaporate it, and then cool the vapor to a liquid state. During the distillation process, contaminants with a higher boiling point than water will remain. Since arsenic has a higher boiling point than water, impurities such as arsenic will remain in the heated container.
Both the distiller and the RO system can remove soluble minerals and heavy metals such as lead, arsenic, and mercury. Therefore, the distiller and RO system are also an option for arsenic removal.
Related: Difference between reverse osmosis and distilled water
Advantages
- Efficient impurity filtration: It can efficiently filter most impurities in water, such as arsenic, heavy metals, bacteria, and viruses.
- No chemical reagents are required: Distillation does not require the addition of chemical reagents, which can reduce the risk of chemical pollution.
- Applicable to various water qualities: Distillation can filter different water qualities.
Disadvantages
- High energy consumption: Long-term use will result in high energy costs.
- Slow speed: The distillation process is slow and the water output is limited, which is not suitable for the demand for rapid and large-scale supply of drinking water.
- Equipment cost: The distiller is expensive and requires regular cleaning and maintenance.
- Demineralization: Distilled water is very pure and does not contain any minerals.
Frequently Asked Questions
Does boiling water get rid of arsenic?
No, boiling water does not remove arsenic. Water evaporates when heated, and arsenic is not removed with evaporation. Also, boiling water may increase the concentration of arsenic in the water.
Is there arsenic in bottled water?
The arsenic content in bottled water is very low and meets the drinking water safety standards of various countries. Most countries have strict regulatory limits on the arsenic content in bottled water. For example, the US Environmental Protection Agency (EPA) stipulates that the arsenic content in drinking water must not exceed 10μg/L.
Do water softeners remove arsenic?
No, a water softener cannot remove arsenic. However, a water softener can remove calcium and magnesium ions from the water.
Can hydrogen peroxide remove arsenic from water?
No. Because hydrogen peroxide is mainly used as a disinfectant and oxidant, it can remove organic matter and metal impurities such as iron and manganese in water.
