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Reporting by Chris Swanson,
Managing Editor, CQD JournalAfternoon Sessions – A Ship Owner's Treasure If you are interested in learning about new technologies
for ballast water treatment, Wednesday afternoon provided some excellent insight into new technologies and regulations. Research findings were discussed on BW technologies including: Ozonation, UV Irradiation,
Natural Product Biocide and Deoxygenation.
The following reports are based on presentations made at the 11th International
Conference on Aquatic Invasive Species, February 27, 2002. Opinions and estimates are those of the Presenter's unless
otherwise noted. CQD Journal for the Maritime Environment Industry makes no assertions as to the validity of the statements or opinions and cannot be held responsible for any of the information or claims contained
therein. We make every effort to report as accurately as possible, as presented by the speakers during the session. Ozone, Seawater and Aquatic Non-indigenous Species: Testing a Full-Scale Ozone Ballast Water Treatment System on an American Oil Tanker
as presented by William J. Cooper
A Shipboard Trial for Ballast Water Treatment Options, as presented by David WrightBallast Water Deoxygenation can prevent species introductions while reducing ship corrosion
, as presented by Mario Tamburri
Ozone, Seawater and Aquatic Non-indigenous Species: Testing a Full-Scale Ozone Ballast Water Treatment System on an American Oil Tanker
as presented by William J. Cooper, Univ. of North Carolina at Wilmington, cooperw@uncwil.edu
Cooper spoke about full scale ballast water treatment tests performed aboard the oil tanker S/T Tonsina. The Tonsina can carry a water ballast load of 11 million gallons,
hence this is the largest field test to date on ballast water treatment technologies. Cooper and his team installed ozone generators that input ozone into 12 ballast
tanks via ceramic diffusers. Installation costs were approximately USD 3 million. The study was designed to compare ozone treatment technology against open ocean ballast water exchange.  The ozonation treatment yielded better than expected results in
killing bacteria, zooplankton and minnows. The treatment did not fare well against crabs, amphipods and shrimps; they had a 100% survival rate.
In terms of quality of the effluent,
Cooper did not find residual ozone but bromine and bromoform were formed. Bromine is toxic and researchers were not sure the chemical could cause corrosion of the ballast water tanks – a very
serious concern for ship owners. In initial tests, they did not find any corrosion. Although installation costs were high, Cooper felt the payback in time saved to
tanker owners would offset the costs. Ballast water exchange causes significant delays in voyage time and Cooper felt using a BW treatment technology such as
ozonation could add at least one voyage per year in time saved. A Shipboard Trial for Ballast Water Treatment Options, as presented by
David Wright, Univ. of Maryland, wright@cbl.umces.edu In the summer of 2001, the Maritime Administration (Marad) made their vessel the
USS Cape May available to test a battery of BW treatment technologies. Wright reported on some of the findings from those tests.
Voraxial Separation – the vendor was unable to get the centrifuge to operate and the technology was eventually discarded. Biocide – the natural biocide Peraclean Ocean resulted in an overall 75% mortality
rate among tested organisms in the ballast tanks. Researchers found the optimum dose to be 100 ppm. Ultra Violet (UV) Irradiation – the technology yielded a very good mortality rate of
90%-94% at a dosage of 200mW/sec/cm3, a pretty high dosage according to Wright. Pros & Cons: Biocide – worked fairly well at a reasonable cost. Wright said that biocide may be
corrosive and takes a considerable time to work effectively. UV Irradiation – UV system was very effective, however the dosage rate to achieve
the effectiveness is more powerful than is commercially available. If researchers tried to scale up to a bigger ship, the price could exceed USD 5 million and the
number of UV systems required would be too numerous to fit in a ship. By Ship Size /Type– Wright felt UV may be a real possibility for smaller ships.
Biocides may be one of the very few options available for larger ships. Ballast Water Deoxygenation can prevent species introductions while reducing ship corrosion
, as presented by Mario Tamburri, Monterey Bay Aquarium Research Institute, Mario@mbari.org
Tamburri introduced the novel concept of applying a technology used to prevent corrosion to treat ballast water for exotic species. Studies he is conducting involve
removing oxygen from ballast tanks by purging with Nitrogen gas. The removal of oxygen has been shown to be extremely effective at preventing rust problem in the tanks. 
Tamburri's team decided to see if their technology
would treat ballast water as well as preventing rust. His results indicated pretty fair kill rates for two days deoxygenation in the tanks. Tubeworms and zebra
mussels had an 80% kill rate and crabs 95%. They found that invertebrate larvae, some algae, bacteria and fungi are sensitive to anoxic conditions and will die off within 1-2 days.
Deoxygenation will not treat resistant organisms of concern such as the cysts stage of harmful algae, viruses such as vibrio cholera and anaerobic bacteria.
According to Tamburri, deoxygenation is effective, safe for the crew and environmentally benign. Most important, he points out the
technology saves money for the ship by preventing rust as it kills potential nuisance species. Return to top of page. |
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