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Organisms That Remove Arsenic From Water

Arsenic is well-known as a means for murder in more than a few stylish who-dun-its. So most people are aware that it is a poison, and some people are aware that arsenic has contaminated a great deal of the world's water. This positions the toxin to enter humans via cooking water, drinking water and irrigation water.

  1. Ates and Ites -- Bacteria, Algae and Plants

    • Arsenic contaminates water in two forms: arsenate and arsenite. Arsenate can be readily removed through a combination of filtration and treatment with chlorine. Arsenate can even be locally removed with duckweed and water hyacinths. Arsenite has proved more problematic; and this has led scientists to study bioremediation of arsenic-contaminated water. Bioremediation is the use of biological organisms to break down contaminants into benign elements. In the case of arsenic, the organisms under review are bacteria and algae.

    The NT-26 Enzyme

    • One bioremediation strategy is to use bacteria to convert arsenite into arsenate, so the latter can then be remediated using existing methods. NT-26 is the name given to one bacterium that apparently eats arsenite and excretes it as arsenate. An enzyme is responsible for this conversion. Scientists are now trying to locate the same enzyme in other bacteria to employ more than one organism in worldwide arsenic bioremediation efforts.

    Metal-Eating Algae

    • Arsenic is a metal. It is well-known that algae consume metals. Studies have been conducted in South Asia on the use of algae with rice growing to determine whether algae in the rice-growing water would lower the amount of arsenic absorbed into the rice. Results of the studies have shown as much as a 71 percent reduction in the uptake of arsenic from the algae-inoculated water. Blue-green algae, green algae and diatom algae have all been effective at absorbing arsenic from water; and some studies are testing the efficacy of algae for the remediation of soils that have been heavily irrigated with arsenic-contaminated water.

    Bio-Oxidizers

    • Iron and manganese are also common water contaminants, and bioremediation of these two pollutants has been practiced using a number of bacteria that oxidize both iron and manganese. Studies of groundwater remediation around Thessalonica, Greece, yielded the surprising result that these same organisms seemed to lower arsenic levels in the bio-oxidized water. It is believed that an enzyme which oxidizes iron (catalase) may actually convert arsenic into hydrogen peroxide.

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