Arsenic Water Treatment
Arsenic is a semi-metal element in the periodic table. Arsenic is odorless and tasteless. It enters drinking water supplies from natural deposits in the earth or from agricultural and industrial practices, including copper smelting operations, mining, coal burning, use of certain pesticides and fertilizers, and industrial waste disposal. Arsenic compounds have been shown to produce acute and chronic toxic effects which include systemic irreversible damage. Arsenic has been linked to cancer of the bladder, lungs, skin, kidney, nasal passages, liver, and prostate. Non-cancer effects can include thickening and discoloration of the skin, stomach pain, nausea, vomiting, diarrhea, numbness in hands and feet, partial paralysis, and blindness. See more information on arsenic below.
There are two types of arsenic: Trivalent = III (3) and Pentavalent=V (5). Trivalent arsenic is generally more difficult to remove from drinking water than pentavalent arsenic. Trivalent arsenic can be converted to pentavalent arsenic in the presence of an effective oxidant such as free chlorine. In other words, if the supply water is chlorinated the trivalent arsenic is converted to pentavalent arsenic which is easier to remove. If the water supply is not chlorinated, the trivalent arsenic will remain as trivalent arsenic which is more difficult to remove.
The EPA has classified Arsenic as a known human carcinogen. The EPA has set the arsenic standard for drinking water at .010 parts per million (10 parts per billion) to protect consumers served by public water systems from the effects of long-term, chronic exposure to arsenic.
Reverse osmosis can treat water containing up to 0.160 mg/L of arsenic. Reverse Osmosis has approximately a 90% removal rate.