1. A New Concept for Resolving the Ballast Water Management Problem - Buoyancy-control Type Ballast-free Ship -
Makoto Arai
Dept. of Systems Design for Ocean-Space, Faculty of Engineering
Yokohama National University, Japan

2. ・ Ballast water problems
Loading and discharging operation,
Impacts,
Ballast water convention,
Ballast water treatment technologies
・Proposed ballast-free ship concept
・ Model experiments and Numerical analyses
Model experiments
3-D numerical analyses
・Application to actual ship tank configurations
・Conclusions

3. Ballast water problems
Loading and discharging operation of ballast water
Possible impacts
Ecological: native biodiversity and/or ecological processes are disrupted
Economical: fisheries, coastal industry and other commercial activities and resources are disrupted
Human health: toxic organisms, diseases and pathogens are introduced

5. Ballast water management convention
The International Maritime Organization (IMO) adopted the “International Convention for the Control and Management of Ships’ Ballast Water and Sediments” in 2004.
Organism category
Regulation
Plankton, μm in minimum dimension
<10 cells/m3
Plankton, μm
<10 cells/ml
Toxicogenic Vibrio cholera (O1 and O139)
<1 cfu*/ 100ml
Escherichia coli
<250 cfu* / 100ml
Intestinal Enterococci
<100 cfu* / 100ml
D-2 Regulation： Ballast water performance standard
Mainly animal plankton
Mainly plant plankton
*colony forming unit: measure of viable bacteria numbers
Planktons gathered by a plankton net.
(Ohmura, Fukuyo: NTS, Sept. 2008)

6. solid-liquid separation
Ballast water treatment technology process options
・ Surface filtration
・ Hydrocyclone
Treatment:
・ Coagulation/ Flocculation
Chemical enhancement:
・ Chlorine dioxide
・ Vitamin K
・ Peracetic acid
・ Ozonation
・ Electrochlorination or electrolysis
・ Chlorination
Chemical treatment:
・ Cavitation
・ Ultrasonic treatment
・ Gas injection
・ Deoxygenation
・ UV + TiO2
・ UV irradiation
Physical treatment:
Physical enhancement:
・ Chemical reduction (sulphite/bisulphite)
Residual control:
Physical
solid-liquid separation
Disinfection OR
[Ref.] Lloyd’s Register, Ballast water treatment technology - Current status, 2007

7. Ballast water treatment system
Possible engineering problems:
Decrease of cargo space,
Increase of the electric generator capacity,
Storage of chemicals, sediment,..
Maintenance of filters, …
Reliability of the complicated system,
Supply of expendables, …
Example of the arrangement of a ballast water
treatment system for a container ship
( Ninokura, S., NTS, Sept. 2008)
A trial calculation:
In case of 220,000DWT Bulk carrier
System-A: Initial cost $4,200,000
Running cost $26,000/treatment
System-B: Initial cost $900,000
Running cost $19,000/treatment + overhaul $15,000/year

8. Volume of ballast water
Bulk carrier
Oil tanker
VLCC
Container ship
Cargo ship
D-2 standard:
VLCC with 110,000m3 ballast water:
Plankton, μm : <10 cells/m3
9cells/m3 x 110,000m3=1x106 cells
Plankton, μm: <10 cells/ml
9cells/ml x 110,000m3=1x1012 cells
Acceptable?

9. Is retrofit possible? An existing ship A newly-built ship
An existing ship
A newly-built ship

10. Summary
1. In order to fulfill the requirements of IMO’s Ballast Water Convention, lots of
　　 works, especially the development of BW treatment systems are being carried out.
2. However, there are a wide variety of ship types with different size, age, shape,
cargo type, operation system, etc., and one and only BW treatment system may not cover all of those ship types. Therefore, we believe it is worth studying the possibility of alternative systems in addition to the BW treatment system.

11. Concept Ship’ advance speed
Buoyancy control tank
In the lightweight condition, sea water is drawn into a buoyancy control tank by using the pump system. As a result of the weight of the water taken into the tank, the ship loses some of its buoyancy and gains sufficient draft for navigation. The sea water in the tank is circulated by utilizing the advance speed of the ship. In order to accelerate the circulation of the water in the tank, the shapes of the sea water intake and exit vents are designed appropriately. Also, the locations of the intake and exit are determined considering the pressure distribution on the ship’s bottom. Through the circulation of the water, the components of the water inside the tank are kept identical to those of the local sea water outside the ship’s hull. Together with the opening and closing operation of the air drain system, the tank can be fully filled with sea water even if the tank’s top ceiling is located above the ship’s draft line.
In the full load condition, the intake and exit vents of the tank are closed, and the tank is emptied by the ship’s pump system to give sufficient buoyancy to the ship.

12. Intake and exit shapes Possible variants of intake and exit shapes
Inside the buoyancy control tank
Bottom plate
High
pressure
Outside the ship
Low pressure
Flow direction
Possible variants of intake and exit shapes
Intake
Exit

13. Numerical analyses Water locality ratio
In this study, we analysed the seawater circulation in the tank by using ANSYS-FLOTRAN.
Before opening the intake and exit
After opening the intake and exit
Water locality ratio
Flow
In order to examine the performance of the water circulation, we compared the water locality ratio (R) of each tank.
R=(Volume of fluid A in the tank)/(Tank volume)
R is defined as the ratio of exchanged fluid volume inside the tank.
In this system a higher water locality ratio is desirable.
I.e., R=1.0 (100%) 　　　　
Composition of the seawater inside the tank is the same as that outside it.

14. Model experiments at the circulating water channel
VTR camera
Dummy stern
Model tank
Dummy bow
Flow direction
Model tank
2,026mm
Model experiment setup

15. Measurement of the water locality ratio (high speed playback: 8x)
A small amount of colourant was added to the water inside the tank, and the change
of colour density in time was measured.

16. Analyses of actual ship tank configurations
Side tank
Bilge hopper tank
Double bottom tank

17. Double bottom tank of a 1,600TEU container ship (v=23.3 knots)
Computed time change of the water locality ratio (v=23.3kn)
T=500s., R=17.3%
T=5000s., R=85.5%
Double bottom tank of a 1,600TEU container ship (v=23.3 knots)

18. Bilge hopper tank and side tank (1,600TEU container ship, v=23.3knots)
Original
Modification 2
[6000s] 51.5%
Bilge hopper tank and side tank (1,600TEU container ship, v=23.3knots)

19. Design criterion of the proposed ballast-free ship
Comparison of measured number of organisms in Tokyo
Bay and IMO's D-2 standards
Organism category
Tokyo Bay [Ref.: Kuno]
IMO standards
m in minimum dimension
Plankton, 50
105 cells/m3
< 10 cells/m3
99.99% dilution
m in minimum dimension
103 cells/ml
< 10 cells/ ml
Plankton, 10-50
99.0% dilution
Toxicogenic Vibrio cholera (O1 and O139) -
< 1cfu/100ml
Escherichia coli -
< 250 cfu/100ml
Intestinal Enterococci -
< 100 cfu/100ml
Example of the relation between the voyage distance and the sea water locality ratio
Cf.

20. Conclusion
In this presentation, we proposed a ballast-free ship concept and showed the results of model experiments and numerical analyses carried out to enhance the performance of the proposed system. In order to evaluate the ballast-free system, we proposed a criterion that accords with the IMO’s D-2 regulation. The proposed ballast-free ship can be an efficient and environmentally friendly alternative to cope with the ballast water problems on ships. The system is especially effective for retrofitting since it can be applied to existing ships without serious structural modifications.

21. As a matter of fact, this technology has been used by some
Wind
Upogebia major
We also use this tech!
Ventilation inside the nest of
Prairie dogs
As a matter of fact, this technology has been used by some
wild animals and crustaceans.