OLD DOMINION RESEARCHERS DEVELOP TECHNIQUE TO PROTECT WATERWAYS

Two Old Dominion University researchers believe they have found a cheaper, more effective way of killing microorganisms being spread into the Chesapeake Bay and other coastal waters by ships from overseas.

Mounir Laroussi, an electrical engineering research professor, and Fred Dobbs, associate professor of oceanography, have developed the technique using a concentrated type of ultraviolet (UV) light to kill harmful organisms found in ballast water within the hulls of cargo ships.

Funded by a grant from the National Seagrant College Program of the National Oceanic and Atmospheric Administration(NOAA), they created a reactor built around a specially designed UV lamp. To date, tests have been conducted using a table-top prototype, which needs only to be plugged into an ordinary wall outlet.

The device's electrical power consumption is relatively low -- less than 300 watts per lamp -- and the light source can be produced for about $7,000, compared with more powerful but less productive sources that cost five times that amount, the researchers said.

Kill rates achieved by the reactor are equal to or better than those in other known UV systems, according to Dobbs. Tests have been performed on organisms including E.coli and hard-to-kill forms of Bacillus subtilis and dinoflagellates, all of which perished in the UV light.

Dobbs and Laroussi believe the system could be used in any water treatment application: drinking water processing; water and sewage treatment; decontamination of waste water; decontamination of waste water from the animal-production industry; and chiller water for food and meat processing industries.

Dobbs co-authored an article in the Nov. 2 issue of the journal Nature, detailing how ballast water in the hulls of cargo ships traveling around the world is spreading harmful bacteria.

Since the 19th century, ships have used ballast water for stability, discharging water both in port and at sea. The United States receives more than 79 million tons of foreign ballast water each year. The water can carry a diverse community of organisms, including those harmful to humans, plants and animals.