FORGET about sophisticated treatment plants to clean up polluted water, just throw in some blue-green algae and let them get to work. These cyanobacteria can cleanse the water of organic compounds and heavy metals cheaply and efficiently, according to Judith Bender, a microbiologist at Clark Atlanta University.
Bender and her colleague Peter Phillips stumbled across the process in 1989 while developing fish foods as part of an aid project in the Dominican Republic 鈥� cyanobacteria are a rich source of protein. To hold the cyanobacteria fast, the researchers chose grass clippings because local farmers could lay their hands on them easily The cyanobacteria and clippings produce a 鈥渓eathery, slimy matrix鈥�, Bender told the AAAS. The result is what she called a 鈥渕icrobial mat鈥�.
The researchers noticed that the water in their experimental pool was cleaner after the microbial mat had built up. They abandoned the fish-feeding project and instead began to study the mats as a way of controlling pollution.
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Since then they have tested the mat鈥檚 properties against a variety of pollutants. Other microorganisms can be added to the mat, depending on which substances need to be removed. 鈥淚t degrades everything we give it. Everything. We can鈥檛 find a thing it can鈥檛 break down,鈥� Bender said. That includes a number of pesticides, the explosive TNT, and persistent industrial wastes such as PCBs. The mat concentrates metals such as selenium, manganese and zinc from the water in its top layer.
However, the researchers still do not know how the mat works 鈥� especially its ability to attract contaminants from remote parts of a pool. Bender speculates that the mat may generate a negative charge which binds to positively charged metal atoms attached to other bacteria already in the water.
Whatever the explanation, the process is so effective that Bender and Phillips have formed a company to commercialise it. They have already received contracts from the US government to clean up old coal, gold and silver mines, as well as soil contaminated with pesticides in banana fields on Saint Vincent in the West Indies.