Arsenic Toxicity: Why and How to Remove It from Drinking Water
By Gary Battenberg, Argonide Corporation
What is arsenic toxicity?
Arsenic toxicity, also referred to as chronic arsenicosis in humans, occurs when one is exposed to high levels of arsenic more than 0.01 mg/L (10 parts per billion). Effects of arsenic ingestion in small amounts appear slowly and may take several years before poisoning becomes apparent. When ingested in large amounts, chronic arsenicosis manifests itself in many ways in different parts of the world.
Arsenic can be inhaled or absorbed through the skin. For example, those working in the smelting industry may be exposed to airborne inorganic arsenic which may be present in coal emissions. Therefore, it is prudent to wear appropriate breathing apparatus to prevent inhalation. Most plants now have air-emission scrubbers to eliminate toxic gasses and chemicals. Dermal exposure to products treated with chemicals containing arsenic can cause arsenic poisoning as well.
Where is arsenic prevalent?
Countries where high levels of arsenic in the groundwater has been confirmed include: the United States, Mexico, China, India and Taiwan. Western US states typically have arsenic levels that exceed .01 milligrams per liter (mg/L) or 10 ppb compared to the rest of the US. In fact, many water wells across the US contain arsenic where pump depths approach and/or exceed 200 feet (60 meters).
What are symptoms of arsenic poisoning?
Health effects range from mild to very severe symptoms. What makes arsenic so dangerous is that it has no taste or odor, which means one can be exposed to it without knowing it. Some of the symptoms include:
-Tingling of fingers and toes, red or swollen skin and changes such as lesions or warts
-Muscle cramps and abdominal pain
-Diarrhea, nausea, vomiting and persistent digestive problems
-Persistent sore throat
-Damage to cardiovascular and nervous systems
Arsenic has been shown to cause cancer of the skin, bladder, prostate, kidney, liver, lungs and nasal passages. The most common cause of arsenic poisoning is contaminated groundwater, where it is abundant in the earth and leaches from natural deposits. Additionally, arsenic seeps into groundwater from industrial plant runoff as well as from other sources, such as:
-Living near industrialized areas, exposed landfills or waste sites
-Breathing contaminated air containing arsenic from plants or mines that use arsenic
-Breathing in smoke or dust from treated wood or waste products
-Smoking tobacco products
There are several treatment methods available that are generally recognized as being effective in reducing arsenic to meet or exceed the maximum contaminant level. A look at some of the available methods may be helpful.
Where arsenic is present in municipally treated water with measurable free available chlorine (FAC), it will be in the oxidized state of arsenate. In this state, arsenic is easy to remove from water. Pre-coated or impregnated iron-based media will reduce both species from water when properly applied within application guidelines. These types of media have a specific service life based on the calculated capacity within a specific volume of media, relative to the total arsenic levels in the water.
Before treatment can begin you must first identify which species are present in the water, then determine how much of each for your total arsenic level. The two types are Trivalent (A3) and Pentavalent (A5). To be able to remove the Trivalent you must convert it to Pentavalent, this is usually done with Chlorine. Once it is converted to Pentavalent it can be removed from the water by filtering it through exposure tanks. The water that is exposed to the media has the arsenic removed allowing the clean water to pass through the tanks. Yearly service is required to maintain the media in the exposure tanks and insure the full removal of the arsenic.