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INTERNATIONAL COOPERATION
ON MARINE ENGINEERING SYSTEMS
Paper presented at the 9TH International
Conference on Marine Engineering Systems
at the Helsinki University of Technology (HUT) Ship
Laboratory and on board MS SILJA SERENADE
19-21 May 2003
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| Ballast
Water Treatment by De-oxygenation with Elevated CO2 for
a Shipboard Installation - An Affordable Solution |
No.
B10 |
M. Husain,
President, MH Systems, Inc., San Diego, CA
H. Felbeck,
Professor, Scripps Institution of Oceanography, University
of California, San Diego, CA
R. Apple,
Sr. Vice President, MH Systems, Inc., San Diego, CA
D. Altshuller,
Control System Engineer, MH Systems, Inc., San Diego,
CA
C. Quirmbach,
Analyst, MH Systems, Inc., San Diego, CA |
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| ABSTRACT |
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This
paper describes a shipboard design to combat the
Aquatic Nuisance Species (ANS) invasion resulting
from ballast water discharge. Treatment standards
and various treatment concepts are briefly reviewed.
Two effective methods of treatments, deoxygenation
and carbonation, have been tested and are summarized.
A ballast water treatment system design, which
combines these two methods, is then described.
The testing and analyses, which support the effectiveness
of this design, are presented. A chemical and
physical analysis of the bubble and underpressure
inert gas method of obtaining hypoxia is presented.
The results of tests at the Scripps Institution
of Oceanography are described using a tri-mixture
of 86% Nitrogen, 12% Carbon Dioxide and 2% Oxygen,
which approximates the discharge of marine inert
gas generators. These tests proved the effectiveness
of these methods for 6 different types of marine
invertebrates. In the experiments, trimix is significantly
more lethal than pure nitrogen. The shipboard
practicality of the design is discussed and a
first approximation economic analysis is presented
for affordability review.
Key
Words: ballast water treatment, deoxygenation
and carbonation, pH reduction, inert gas, aquatic
nuisance species, bubbled through ballast water,
elevated CO2
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| NOMENCLATURE |
| c |
concentration of
carbon dioxide in the water, including ions
produced by electrolytic dissociation. |
| g |
acceleration
due to gravity. |
| h |
concentration of
hydrogen ions in the water. |
| K |
dissociation constant
of carbonic acid
( = 4.3 x 10-7 mol/liter). |
| k |
reaction rate constant. |
| kH |
Henry's
Law constant for oxygen
(= 39.79 x 10-6). |
| N |
total number of
bubbles generated. |
| n |
total number of
gas moles in the bubble. |
| nCO2 |
number of moles
of carbon dioxide in the bubble. |
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| nN |
number of moles of nitrogen
in the bubble. |
| p |
total pressure
inside the bubble. |
| pCO2 |
partial pressure
of carbon dioxide in the bubble. |
| Q |
gas weight flow
rate. |
| t |
time. |
| u |
bubble speed. |
| Vt |
volume of the tank. |
| x |
molar fraction
of carbon dioxide in the bubble. |
| Y |
weight fraction
of oxygen in the water. |
| y |
molar fraction
of oxygen in the bubble. |
| rho |
density of the
ballast water. |
| Superscript 0 refers
to quantities in the gas bubble when it is
first introduced into the tank. Subscript
0 refers to quantities in the water at the
time t=0. |
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