Cleaning Drinking Water with Bacteria

Bacteria and drinking water are not two things that usually go together very well, but according to a new study, certain species of microbes may help remove trace minerals such as zinc, selenium and even arsenic from your drinking water in the future. In nature, sulfate-reducing bacteria (SRB) play an important role in binding sulfate in water. But scientists have disputed their role in binding trace minerals. Among other reasons, it was thought that SRBs could exist only in oxygen-free environments.

An international team of scientists, led by Matthias Labrenz of the University of Wisconsin-Madison, recently sent scuba divers into a flooded lead and zinc mining tunnel in Tennyson, Wis., where they retrieved a type of SRB that behaved a differently from the rest. Bacteria of the Desulfobacteriaeceae family, they found, can handle a low-oxygen environment. They reported the results in the December 1 issue of Science.

Using x-ray experiments, the researchers discovered that the bacteria formed mineral deposits from the water that surrounds them, binding them in the form of tiny spheres. In this particular case, the bacteria bound zinc and sulfate, and they did it so effectively that the zinc concentration in the spheres became a million times higher than that in the surrounding water. Indeed, the spheres consisted almost entirely of zinc sulfide (see image). This ability makes the tiny life-forms potentially very useful in the process of water treatment. They could be used to remove zinc, selenium and even arsenic traces from contaminated water, as in the mining tunnel, or even from drinking water supplies.