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

・ 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

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 Http://www.globallast.od.ua/eng/problem.asp

http://www.globallast.od.ua/eng/problem.asp

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, 50 μm in minimum dimension <10 cells/m3 Plankton, 10-50 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)

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

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

Volume of ballast water Bulk carrier Oil tanker VLCC Container ship Cargo ship D-2 standard: VLCC with 110,000m3 ballast water: Plankton, 50 μm : <10 cells/m3 9cells/m3 x 110,000m3=1x106 cells Plankton, 10-50 μm: <10 cells/ml 9cells/ml x 110,000m3=1x1012 cells Acceptable?

Is retrofit possible? An existing ship A newly-built ship http://www.jasnet.or.jp An existing ship A newly-built ship

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.

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.

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

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.

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

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.

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

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)

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)

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.

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.

As a matter of fact, this technology has been used by some Wind Upogebia major http://ja.wikipedia.org 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.