INTERNATIONAL MARITIME ORGANIZATION
E
IMO
MARINE ENVIRONMENT PROTECTION
COMMITTEE
52nd session
Agenda item 2
MEPC 52/INF.3
1 July 2004
ENGLISH ONLY
HARMFUL AQUATIC ORGANISMS IN BALLAST WATER
Compliance with the International Convention for the Control and Management of Ships'
Ballast Water and Sediments
Submitted by Dominica
SUMMARY
Executive summary:
This document provides information on Ballast Water Treatment
Systems including one utilizing de-oxygenation with elevated CO2 by
infusion of inert gas from a marine inert gas generator
Action to be taken:
Paragraph 15
Related documents:
None
1
In responding to questions from Dominica shipowners relative to compliance with the
new International Convention for the Control and Management of Ships’ Ballast Water and
Sediments, 2004, Dominica has reviewed a number of ballast water treatment technologies to
enhance its ability to advise its ship owners. A persistent question is on the availability of
credible treatment methods apart from ballast water exchange.
2
To that end information on the available systems were explored and the types identified
are summarized in the CD-ROM1 provided together with this document. The list of treatment
methods includes: Ballast Water Exchange; Filtration-Mechanical; Ultraviolet (UV) Radiation;
Ultrasound; Electro-Ionization; Magnetic/Electric Field; Biocide; Ozone; Heat; De-Oxygenation
By Vacuum (Aquahabistat Tm); De-Oxygenation by Venturi Oxygen Stripping Tm ; and
De-Oxygenation with Elevated CO2 using a Marine Inert Gas Generator. Discussion of their
relative merits as well as information on availability of additional methods are welcome.
1
The CD-ROM also contains:
(i)
A Scripps Institution Oceanography of Explorations (April 2004) article regarding testing of ballast water
system utilizing de-oxygenation with elevated CO2 with a marine inert gas generator.
(ii)
A paper presented to the 2nd International Ballast Water Treatment R&D Symposium, July 2003, IMO,
London, entitled “Ballast water treatment by de-oxygenation with elevated CO2 for a shipboard
installation – a potentially affordable solution.”
One copy of the CD-ROM will be available for each delegation on request from IMO’s Documents Desk.
For reasons of economy, this document is printed in a limited number. Delegates are
kindly asked to bring their copies to meetings and not to request additional copies.
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3
In the course of the review, a detailed evaluation of the shipboard design of a ballast
water treatment (BWT) system based on de-oxygenation with elevated CO2 using a marine inert
gas generator, was made. The inert gas is obtained from a marine inert gas generator. The
system appears to have considerable promise. The views and experience of others relating to this
system are sought.
4
This System has been laboratory tested at the Scripps Institution of Oceanography of
San Diego, California, USA and a summary of results of the tests are presented below and in
greater detail in the CD-ROM. Additional tests in subscale and full scale are anticipated.
5
The tests and analyses show that the system effectiveness meets or exceeds the standards
for ballast water treatment, as stated in the BWM Convention as well as those in draft legislation
in the United States.
6
The ballast water treatment method focuses on bubbling inert gas, from a shipboard inertgas generator, via a row of pipes located at the bottom of the ballast tanks. The infusion of the
inert gas, a tri-mixture of about 2% oxygen, 12% to 14% carbon dioxide, and the rest nitrogen
achieves de-oxygenation (resulting in hypoxia), elevated level of CO2 (resulting in hypercapnia)
and acidic pH. The combined effects of hypoxia, hypercapnia and acidic pH on marine
organisms are very promising.
7
The research methods used are summarized below. Several different marine invertebrates,
plankton and a representative bacterium, Vibrio cholerae, were incubated in experiments to
determine their survival. The parallel incubations were gassed with nitrogen (anaerobic control)
or “trimix” (2% oxygen, 12% carbon dioxide, balance nitrogen). Aerobic controls, which were
gassed with air, were done in parallel for each incubation. The test results show that the treatment
objectives are met. All organisms tested died within few hours after incubation by the “trimix”
inert gas. The survival rate appears to be significantly shorter than in anaerobic incubation. All
invertebrates showed no mortality in aerobic incubations. Vibrio cholerae was non viable
(>99%) after an incubation period of 24 hours. Special consideration is given to the development
of methods to determine unequivocally the time of death of plankton, microorganisms, and
macro algae.
8
The other systems described in the available literature, including ballast transfer, have left
untreated the sediment buildup in the bottom of the tanks. With this system, if the orifices in the
lattice work of piping pointed down, the sediment is stirred up facilitating the kill of the
embedded Aquatic Nuisance Species (ANS).
9
Results: the oxygen concentrations were measured at “non-detectable” for the nitrogen
incubations and 10% air saturation (=16Torr partial pressure) for the “trimix”. The pH value of
the water bubbled with trimix reached 5.5 after the initial 10 min of vigorous bubbling. The
aerobic and nitrogen bubbled seawater maintained their pH at 8. The incubations showed clearly
that “trimix” kills organisms considerably faster than incubations in pure nitrogen Table 1. All
organisms except of Vibrio cholerae showed no mortality in aerobic conditions. The shrimp and
crabs incubated in “trimix” were dead after 15 min and 75 min, respectively. Even a transfer into
aerated water did not result in any movement. The brittle stars incubated under nitrogen started to
move again after transferred into aerated water. All the mussels incubated in nitrogen and
“trimix” were open after 95 min but only the ones in nitrogen still responded to tactile stimuli by
closing their shells. The barnacles were judged dead after incubation in “trimix” when they did
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MEPC 52/INF.3
not withdraw their feet when disturbed, the ones incubated in nitrogen still behaved normally.
The plankton sample mainly contained copepods. They stopped moving after 15 min and could
not be revived in nitrogen and “trimix” incubations. The results are summarized in Table 1.
Table 1. Effects of “trimix” on Marine Species
Crab
Number/
Nitrogen
Incubation
7/inc
Normal
Mussel
10/inc
Pollicipes
polymerus
Megabalanus
californicus
Sebastes
diplopora
Ophionereis
annulata
Barnacle
10/inc
Barnacle
5
Rockfish
2
Brittle star
5-10
Ophioderma
panamanse
Unidentified
Brittle star
8/inc
Caridean
shrimp
6
Unidentified
Caridean
shrimp
6
Mysolopsis
californica
Lysmata
californica
Plankton
mix
Tigriopus
californicus
Mysid
shrimp
Shrimp
25
Var.
copepods
Copepod
lots
Vibrio
cholerae
Bacterium
2.5
x106/ml
Species
Mimulus
foliatus
10/inc
8 - 10
Open but
Responding
Normal
Dead after
84 h
Dead after
19 min
Most survive up
to 3 h, most
dead after 26 h
“trimix”
Dead after
75 min
6 dead after
95 min
Dead after
60 min
Dead after
48 h
Dead after
7 min
Most
Mean
of
survive up experiments
to 3 h,
several
dead after
26 h
Dead after
50 min
Dead after
25 min
Not moving but
Revivable by air
Affected
but
alive after
30 min
2 dead after
5 dead
30 min
after
45 min
Dead after
Dead after
15 min
15 min
Normal
Dead after
20 min
Dead
Dead after
15 min
Dead after 2 h
Many
dead after
2h
>>99%
dead >>99%
after 24 h
dead after
24 h
*trimix (2% oxygen, 12% CO2 and 86% nitrogen)
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Comments
Mean
of
experiments
4
3
Aerobic: 30%
dead after 24 h
MEPC 52/INF.3
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10
Shipboard installation review of the various systems indicates that installing a cost
effective, practical and viable ballast water treatment system on-board a ship is challenging
because of the huge amounts of ballast that must be treated. There are at least half a dozen
systems that may be effective in “killing” ANS, but are impractical on board a ship, costly to
operate, dangerous or grossly inadequate to treat large amounts of ballast water in a given time
frame.
11
The data related to the system reviewed utilizing de-oxygenation with elevated CO2 by
infusion of inert gas from a marine inert gas generator is based on a 300,000 dwt tanker, which
carries about 128,000 tons of ballast. The system requires only off-the-shelf components which
can be installed at pier side, without dry-docking and can be fully automated. Installing pH and
oxygen sensors at multiple locations inside the tank can assure continuous remote monitoring of
the ballast water. Figure 1 shows a schematic of a 300,000 dwt tanker ballast water treatment.
Figure 2 shows a ballast water treatment schematic and Figure 3 shows the necessary piping
system on a double hull tanker.
12
A cost estimate for the installation of the system on a 70,000 dwt tanker was also
performed indicating that the system is economical to operate: less than 4 cents per ton of ballast
water treated. The cost of retrofit installation may vary between $1.5 million to $2.7 million for
tankers from 75,000 dwt to 300,000 dwt.
13 The economic analysis shows, for a 300,000 dwt tanker utilizing its own inert gas
generator, that installation cost of the ballast water system is approximately $2.7 million and the
operating cost of treating per ton of ballast water is 3.8 cents. Similarly, for a 70,000 dwt tanker
the installation cost is approximately $1.5 million and the operating cost is 3.5 cents per ton.
14
Shipboard System Description: each ballast tank has rows of pipes at the tank floor with
downward pointing nozzles. The pressurized inert gas is jetted downward out of the piping. The
bubbles rise through the ballast water to the space above the surface, which has been (optional)
previously under-pressurized to – 2 psi. Based on the 300,000 dwt tanker design, which carries
128,000 tons of ballast, the system described can effectively treat that ballast in approximately
48 hours. The pacing events in the establishing of the lethality in ballast water are the times
required to elevate the concentrations of CO2 and its ionic forms and the decrease of the oxygen
level.
Action requested of the Committee
15
The Committee is invited to note the information provided.
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Figure 1
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Figure 2
Figure 3
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