MEPC 44/INF.9
ANNEX
Page 2
2 Actions and Effects
The mixer pipe has the following excellent actions and effects:
・ There is no possibility of causing secondary pollution of the environment or giving adverse effects to the ship's hull since the method does not produce chemical substances as in the use of chemicals or electrical reactions;
・ As a result of its simple structure and low energy consumption, a relatively small space is required only;
・ There is no possibility of the pipe being clogged; and
・ It is economical (both in initial and running costs).
The effect of damaging marine organisms is presumed to be attributed to the following actions:
・ Destruction caused by turbulent flows generated by the spiralling motion of water; and
・ Destruction caused by collision of marine organisms with projections or turbulent flows created downstream of projections.
3. Shore Experiment
3.1 Experiment method
The experiment was conducted with an installation set on the shore, using natural sea water found in a harbor area.
The effect to destroy marine organisms was evaluated on the basis of a change in the state of such organisms in sea water after every passage of the water through mixer pipes. With the actual shipboard operations of ballasting and deballasting in mind, the state of aquatic organisms was examined 1) immediately after the treatment of natural sea water (original water) (treatment upon assumed ballasting), 2) immediately after treatment of original sea water stored for two weeks (in a dark condition; hereinafter the same) (treatment upon assumed deballasting), and 3) immediately after treatment of seawater which was first treated and then stored for two weeks (treatment twice upon ballasting and deballasting). The parameters of observations of aquatic organisms were: 1) the state of phytoplankton cells and individual zooplankton, 2) the state of cysts of Alexandrium sp., toxic plankton, and the concentration of general heterotrophic bacteria.
The conditions of treatment of sea water per time were as follows:
・ Number of mixer pipes connected in series: 3
・ Pipe inlet pressure: 4.8 to 5 kg/cm2
・ Sea water flow rate: 340 l/min.
・ Injected gas: natural air
・ Air injection rate: 25.5% of the seawater flow rate (75.5 l/min.) =7.5% of the water flow rate/mixer pipe x 3 pipes