Chinese researchers use bacteria to remove toxic chemicals from water

BEIJING, June 20 (Xinhua) -- Escherichia coli, commonly known as E. coli, a bacteria that can cause severe food poisoning, diarrhea, and septicemia, could be useful in removing toxic chemicals from water, according to a new study by Chinese researchers.

Researchers from Xinjiang Institute of Ecology and Geography under the Chinese Academy of Sciences found the bacteria could remove toxic mercury ions and selenite from water.

Mercury contamination is a global concern because of its high toxicity, persistence, and wide distribution in the environment. Mercury in water is mainly in the form of divalent mercury ion, which can be easily converted into highly toxic methyl mercury by organisms. Eating seafood contaminated with mercury can damage the central nervous system and is particularly dangerous for pregnant and nursing women and young children.

Selenium is a necessary and beneficial element for humans, but the gap between selenium deficiency and excess is very small. Selenite, a compound that contains selenium ion in water, is a common pollutant.

In some areas, the mercury and selenium levels in the earth's crust and water are very high, and the mining of mercury and selenium contaminates surrounding areas.

Researchers put E. coli in water and found that with a divalent mercury ion concentration of 40 micrograms per liter, about 93.2 percent of the toxic chemical was removed. Of the total mercury removed, about 3.3 percent was adsorbed on the bacterial surface, 2 percent accumulated inside the bacteria, and 80.6 percent converted in the form of nontoxic chemical compound.

Meanwhile, E. coli also reduced selenite to harmless precipitates in the water.

The research, published in the journal Science of the Total Environment, indicated that the bacteria would have great application prospects in removing mercury and selenium contamination.