simple, and there is no need to bring potentially 

 harmful chemicals on board ship. "All you need 

 is electricity and air," Cooper notes. 



A stream of oxygen-rich air is sent through 

 an electrode, exposing the gas to 10,000 volts of 

 electricity. The ozone gas that emerges is then 

 sent to the 1 5 ballast tanks on board through a 

 system of 1,200 diffusers, which Cooper 



While ozone kills microorganisms like 

 bacteria and viruses almost immediately, larger 

 organisms often escape treatment. However, 

 when ozone reacts with bromide naturally 

 present in seawater, bromine is formed. Bromine 

 extends the effects of ozone treatment because it 

 also can disinfect — and bromine does not 

 degrade as rapidly as ozone. 



TESTING THE WATERS 



As one group of scientists monitors the 

 effectiveness of the Tonsina 's ozone treatment 

 technology, another gathers samples of ballast 

 water organisms. This means gaining access to 

 each ballast tank through a service hatch, or 

 manway — an access secured with many bolts, 

 some rusted in place since last time the ship was 



LEFT TO RIGHT, TOP TO BOTTOM: Russ Herwig holds a zooplankton sample bottle, with student Kim MacDonald in the background. Samples are 

 "fixed" with preservative so they can be examined by scientists in other labs. Scientist handles one of the smaller tubes of treated ballast water. An open 

 hatch leads to ballast tanks. Banks of ozone generator tubes. Connected to a microscope, this monitor offers enlarged views of the critters. 



compares to aerators in fish tanks. The gas 

 bubbles through the ballast water continuously 

 while the ship is in transit. Ozone oxidizes the 

 tissues of any ballast water organisms inside, 

 destroying them. 



According to Cooper, the ideal ballast 

 water treatment system would kill organisms of 

 all sizes, a requirement that many potential 

 technologies have failed to meet. "We're looking 

 at every trophic level in the water system, from 

 viruses and bacteria all the way up to fish," the 

 UNC-W chemist says. 



This combination of ozone and bromine 

 has the potential to eliminate entire populations 

 of microbes and planktonic organisms within the 

 ballast water tanks. Initial tests, conducted in 

 Long Beach, Calif, and Port Angeles, Wash., 

 have shown that the ozone treatments can kill 

 up to 99.99 percent of the bacteria and phyto- 

 plankton in ballast water. 



The system was somewhat less effective at 

 destroying zooplankton, but the success rate was 

 still above 90 percent. 



serviced. "The ship's crew has been extremely 

 cooperative and very interested in watching our 

 sampling efforts," Herwig says. 



Once the crusty hatches are cracked open, 

 the team collects plankton samples, pulling a 

 small plankton net, or "tow," through the tank. 

 One tow will amass about 5,000 planktonic 

 organisms in its stocking-shaped sieve. Microbe- 

 laden water samples also were collected in five- 

 liter Niskin bottles for subsequent lab analysis. 



"Collecting samples is the fun part," 



Continued 



COASTWATCH 9 



