WO2003002406A1

WO2003002406A1 - Management of water ballast in marine vessels

Info

Publication number: WO2003002406A1
Application number: PCT/GB2002/002966
Authority: WO
Inventors: David Peters
Original assignee: Wilson Taylor & Company Ltd
Priority date: 2001-06-29
Filing date: 2002-06-27
Publication date: 2003-01-09
Also published as: GB0115968D0

Abstract

In order to reduce risks of bio-contamination being transmitted in ballast water, ballast water in a ballast tank is subjected to copper ions of a concentration such as to render a significant proportion of marine organisms non-viable. The treatment is carried out using copper or copper clad anodes to which current is impressed.

Description

Manaqement of Water Ballast in Marine vessels

This invention relates to the management of water ballast in marine

vessels, particularly for the purpose of limiting the transportation of viable bio-

matter between habitats.

It is now recognised that the discharge of water ballast from marine

vessels is a source of bio-contamination of marine and sometimes fresh water

habits by the introduction of species to foreign environments. This poses a substantial ecological threat, as introduced species can proliferate at the

expense of existing species, or produce vigorous hybrids with local similar species which disturb the balance of the ecology adversely.

This problem is being increasingly recognised, and is summarised in the UNDP and International Marine Organisation leaflet "Stopping the Ballast Water

Stowaway" (March 2001). The program will result in international agreements,

and national legislation which will regulate the discharge of water ballast with the

objective of effectively reducing or preventing the accidental introduction of

invasive species.

Accordingly, it is desirable to be able to provide an effective method and

apparatus for management of water ballast in marine vessels which can meet this objective, and which is not unduly burdensome on ship operators.

Marine organisms almost all have a life cycle stage where they form part

of the zoo-plankton, as larvae or eggs for example. Filtration, however, is not a

viable method of eliminating this material as the pressure drop across a filter medium having a pore size sufficiently small to trap the smallest plankton, such

as eggs, leads to a significant slowing of the intake and/or discharge of water to

or from the ballast tanks, and in addition, the filter elements must be cleared by

removal of filtrate and are also vulnerable to bio-encrustation. It is thus necessary to consider non-mechanical methods of eliminating

viable marine organisms from ballast water and it is an object of the invention to

provide a method and apparatus for management of ballast water in marine

vessels which will effectively eliminate, or substantially reduce contamination of

ballast water discharges by viable marine organisms. Treatment with

hypochlorite is effective, but handling the material such as avoiding contact with

acids, whilst well understood, places a burden on operators and runs the risks of'

damage or casualties should there be any failure. An object of the invention is

to provide a safer alternative to the use hypochlorite.

In accordance with the invention, a method of management of ballast

water in marine vessels includes the steps of admitting ballast water to one or more ballast tanks, subjecting the ballast water during admission to the tank or

tanks to a concentration of metal ions in the water sufficient to render a

significant proportion of marine organisms non-viable, containing the water in

the tanks as required and discharging the ballast water with marine organisms

present in non-viable forms.

The invention also provides apparatus for management of ballast water in

marine vessels comprising one or more ballast tanks in a marine vessel, means for admitting ballast water to each of the ballast tanks, means for subjecting the ballast water during admission to the tank or tanks to attain a concentration of

ions in the water sufficient to render a significant proportion of marine

organisms non-viable, and means for discharging the ballast water from the tank

or tanks with marine organisms present in non-viable forms.

The metal ions provided in the ballast water to render marine organisms

non-viable are preferably copper. The copper ions may be maintained at a

concentration in the water of from 2 micro grams per litre to 100 micro grams per

litre, preferably up to 45 micro grams per litre.

The copper ions may be released into the water in each ballast tank from

a copper device which is immersed in the ballast water.

The current impressed on the copper alloy anodes is preferably controlled

so as to attain a concentration of copper ions in the ballast water within the range of 2 micro grams per litre to 100 micro grams per litre, preferably up to 45

micro grams per litre. A control circuit may be provided to vary current applied

to the anodes to increase or reduce the output of copper ions in direct proportion

to the level of current applied.

The means for admitting ballast water to the ballast tanks, and for

discharging ballast water from the tanks may comprise inlet and outlet ports in

the hull of the vessel, which are preferably dual purpose , with a coarse screen

cover to prevent ingress of large particle size floating or swimming matter or

organisms, conduits connecting the inlet and outlet ports to the ballast tanks, and pumps for impelling the ballast water to fill or empty the ballast tanks.

The copper ion concentration maintained in the ballast tanks is such that

whilst a significant proportion of marine organisms in the tanks are rendered

non-viable (that is either killed, or prevented from growing or reproducing) on

discharge of the ballast water, the concentration will be diluted well below

hazardous levels in the wider marine environment, and also the ions will be

quickly neutralised and thus reduced in effectiveness as a poison.

A preferred method and embodiment of apparatus according to the

invention for management of ballast water in marine vessels will now be

described by way of example, with reference to the accompanying, wherein:-

Figure 1. is a sectional view of a marine cargo vessel;

Figure 2. is a diagram showing the general arrangement of a ballast tank

equipped with means according to the invention.

As shown in Figure 1. , a marine cargo vessel 10 has a hull 11 divided by

internal bulkheads into spaces such as a cargo hold 12, propeller shaft tunnel

13, and ballast tanks 14 in the lower part of the hull. Ballast tanks 14 are

arranged to be filled and discharged by conduits 15 with pumps 16 opening to

the underwater environment at 17. These openings are closed by mesh grills in

the usual way to exclude large sized water borne matter and fish.

As shown in Figure 2., each ballast tank 14 has an inlet conduit 15, an

overflow conduit 18, and an inspection access 19. The top of the tank 14 is

closed by a cover 20, through which protrude an array of electrodes, in the form of copper or copper-clad anodes 21. These are connected to a controller 23

which controls the current supplied to the electrodes in order to attain a

preferred optimum concentration of copper ions in the ballast water during

admission to the tank. A combination of CU+ or CU++ ions is preferably in the range of 2 micro

grams per litre to 100 micro grams per litre, for example about 45 micro grams

per litre. This is sufficient to render a significant proportion of marine organisms

such as algae, larvae, eggs, mirco organisms and other plankton non viable, in

the sense that they either killed or rendered incapable of further development -

ie. eggs will not hatch, nor larvae proceed to the adult stage, or adult organisms

are effectively sterilised. It is to be noted that it is unlikely that even the most

effective biocide will render 100% of all organisms non-viable in every trial.

Typical results in various circumstances range from about half, to well over 90%.

This copper ion concentration is attained at the time of admission of the

ballast water to the tank, to provide a once and for all dose to render bio matter

non viable. The ion concentration can then be allowed to decline, to render eventual discharge low enough in toxcity to meet environmental standards.

By use of this method, it is possible to meet current and expected future

requirements for preventing contamination of environments by accidental

introduction of invasive species from marine vessel ballast water.

The levels of copper ions in discharged ballast water is well below levels

considered to represent even a low level risk, so that the method can be used repeatedly to prevent invasion by foreign species.

The method is applicable not only to use with sea water, but also with

fresh water such as might be taken in on the American great lakes, or inland

ship canals.

Details of the electrode materials are set out below: -

Anode Materials:

Copper: 99.9% pure electrolytic copper C101 as taken from BS2874 C101

ELECTRICALLY TOUGH PITCH HIGH CONDUCTIVITY COPPER.

Chemical Composition

COPPER (Sliver being counted as copper); Not less than 99.09%

Last 0.01% are called impurities. The British standard states the material must

not contain impurities in excess of the amounts stated for:

BISMUTH Not more than 0.0010%

LEAD Not more than 0.005%

TOTAL (Excluding Sliver SOxygen) Not more than 0.03%

Claims

1. A method of management of ballast water in marine vessels

including the step of:-

- admitting ballast water to one or more ballast tanks;

subjecting the ballast water during admission to the tank or tanks to a

concentration of metal wires in the water sufficient to render marine organisms non-viable,

containing the water in the tanks as required; and

- discharging the ballast water with marine organisms present in non-

viable forms.

2. A method according to claim 2 when the metal ions to which the

water is subjected are copper.

3. A method according to claim 2 when the copper ions are maintained

at a concentration in the water of from 2 micrograms per litre to 100

micrograms per litre.

4. A method according to claim 3 wherein the copper ions be

maintained at a concentration of in the order of 45 micrograms per

litre. 5. A method according to claim 2, 3 or 4 wherein the copper ions are

released into the water in each ballast tank from a copper anode

device which is immersed in the ballast water.

. A method according to claim 1 , wherein the ballast water is substantially

diluted on discharge, from the tanks.

7. Apparatus for management of ballast water in marine vessels, comprising

one or more ballast tanks in a marine vessel; means for admitting ballast

water to each of the ballast tank; means for subjecting the ballast water

during admission to the tank or tanks to attain a concentration of ions in

the water sufficient to render marine organisms non-viable, and means

for

discharging the ballast water from the tank or tanks with marine

organisms present in non-viable forms.

8. Apparatus according to claim 7 wherein copper urns are released into the

water by one or more copper alloy anodes immersed in the ballast water.

9. Apparatus according to claim 8 wherein control apparatus is provided to

control the current control impressed upon the alloy anodes to attain a

concentration of copper ions in the ballast water within the range of 2

micrograms per litre to 100 micrograms per litre.

10. Apparatus according to claim 8 wherein the control apparatus comprises

a control circuit to vary current applied to the anodes to increase or reduce the output of copper ions in direct proportion to the level of

current applied.

11.Apparatus according to claim 7 wherein the means for admitting ballast

water to the ballast tanks and for discharging ballast water from the tanks compose inlet and outlet ports on the hull of the vessel, each having a coarse screen cover to prevent ingress of large particle size floating or swimming matter or organisms; conduits connecting the inlet and outlet ports to the ballast tanks and pumps for impelling the ballast water to fill or empty the ballast tanks.