3.2 Experiment results and evaluation
Figures. 2 and 3 show test results in terms of phytoplankton and zooplankton, respectively. Concerning phytoplankton, results of armored dinoflagellates, to which toxic plankton belong, are specially extracted and shown; regarding zooplankton, results are shown of crustacean larvae, including those of barnacles, which adhere to ships' bottoms, in the subclass Cirripedia.
As for phytoplankton, about 50% disappeared only by one-time treatment, showing the effectiveness of mixer pipes in sterilization. Phytoplankton which lives on photosynthesis is doomed to die in the darkness. In the recent experiment many cells died by the storage for two weeks. Comparison was made after storage for two weeks between original water and treated water; in the original water (without treatment), about 60% of the remaining cells retained their normal conditions, while, in the treated water, only about 20% were normal. This comparison also proves the effectiveness of the treatment with the mixer pipes. An additional treatment of these waters after storage naturally reduced the number of normal cells further. Particularly after the treatment of sea water which had been treated once before storage, any normal cells did not exist at all. The effectiveness is more conspicuously evident in the case of armored dinoflagellates.
This means that the mixer pipes are capable of killing almost all cells of phytoplankton by their use upon either ballasting or deballasting and that they are expected to achieve a nearly perfect sterilizing effect by their use on both occasions.
The device has the same effect against zooplankton and crustacean larvae as in the case of phytoplankton. The test result shows that a complete sterilizing effect, more effective than against phytoplankton, was obtained in the treatment after storage of original water for two weeks, i.e., treatment upon assumed ballast discharge.
On the other hand, this device did not show conspicuous effects against cysts of Alexandrium sp., toxic plankton amazingly tough, and other minute, general heterotrophic bacteria of about 1 ? m, posing a problem which must be solved. However, in an experiment where water was treated ten times, the device proved to be very effective against general heterotrophic bacteria. When the suspended sediment was observed according to size, it was found that a large proportion of particles smaller than 22 ? m in size disappeared. These results suggest that this device, when improved in structure or system, will be sufficiently effective also for cysts and bacteria.
As seen above, it is confirmed that the treatment of seawater with mixer pipes is effective against plankton at the current stage of study and it is considered that it has the potential to prove to be an effective method against other aquatic organisms.
4. Future Study
JAMS intends to proceed with the study, with a view to improving the device to make it effective even against bacteria or aquatic organisms with strong survival force, including cysts of Alexandrium sp. and to devising a proper structure and system for its installation on board actual ships. JAMS also intends to conduct research and development of technology to use the device in combination with other methods, considering, e.g., that the mixer pipe has the potential to intensify its marine organism-killing capacity by injecting a gas other than air, such as ozone; and that the particle-destructive effect of the device may be used as a method for pre-treatment of sea water before electrochemical processes or filtering measures.
