1. ARSENIC IN WATER

2. Introduction Arsenic occurs naturally in rocks and soil, water, air, and plants and animals. It can be further released into the environment through natural activities such as volcanic action, erosion of rocks and forest fires, or through human actions. Approximately 90 percent of industrial arsenic in the U.S. is currently used as a wood preservative, but arsenic is also used in paints, dyes, metals, drugs, soaps and semi-conductors. High arsenic levels can also come from certain fertilizers and animal feeding operations. Industry practices such as copper smelting, mining and coal burning also contribute to arsenic in our environment. Higher levels of arsenic tend to be found more in ground water sources than in surface water sources (i.e., lakes and rivers) of drinking water. The demand on ground water from municipal systems and private drinking water wells may cause water levels to drop and release arsenic from rock formations #Mining wastes from the processing of gold ore were deposited in Whitewood Creek, South Dakota, for more than 100 years. About 100 million tons of finely ground gold-mill tailings, containing arsenic and other trace elements, mixed with natural sediments and were deposited in channels and flood plains downstream. 3. Effect Exposure to inorganic arsenic can cause various health effects, such as irritation of the stomach and intestines, decreased production of red and white blood cells, skin changes and lung irritation. It is suggested that the uptake of significant amounts of inorganic arsenic can intensify the chances of cancer development, especially the chances of development of skin cancer, lung cancer, liver cancer and lymphatic cancer. A very high exposure to inorganic arsenic can cause infertility and miscarriages with women, and it can cause skin disturbances, declined resistance to infections, heart disruptions and brain damage with both men and women. Finally, inorganic arsenic can damage DNA. A lethal dose of arsenic oxide is generally regarded as 100 mg. Organic arsenic can cause neither cancer, nor DNA damage. But exposure to high doses may cause certain effects to human health, such as nerve injury and stomachaches. 4. CONTROL MEASURE Reverse Osmosis Systems The most cost-effective method for removing arsenic from a private water supply appears to be reverse osmosis, commonly called RO. RO can be thought of as filtration at a molecular level. It works by forcing water through a special, selective membrane. The membrane has microscopic pores that are specially sized to allow water molecules through, while trapping larger inorganic molecules like lead, iron, chromium and arsenic. Anionic Exchange Systems Anionic exchange systems use a physical/chemical process to exchange ions between a resin bed and water passing through. These systems soften water, remove iron and manganese, and lower nitrate and arsenic levels. These systems work by passing water through the resin bed, which is charged with chloride ions from dissolved salt. Arsenic molecules in the water replace these chloride ions by knocking them off and taking their place. This process continues until all of the sites on the resin are full. The resin is then backwashed with water that is super-saturated with dissolved salt. The chlorine ions in this backwash water strip the embedded arsenic molecules out of the resin and into the backwash wastewater. 5. Iron Oxide Filter Systems Iron oxide filters are a relatively new and promising method for lowering arsenic levels in private drinking water systems. Like activated carbon, these granular filters have large amounts of surface area and an affinity for arsenic to adhere to its surface. Although these filters are fairly new to the home treatment market, the principals behind them have been used by public water suppliers for many years. Iron oxide media can be housed in small inline filter cartridges (point-of-use) or in larger tanks like the ones used for ion exchange systems (point-of-entry). These filters can be used to enhance the performance of reverse osmosis systems that are not effectively removing As (III). The media can be disposed of as non-hazardous waste.