what is ballast water ?
A ship discharges ballast water.
Ballast water is the water used to fill tanks around cargo holds in order to ensure a ship’s stability on water.
A merchant ship is built to transport huge volumes of cargo, which wighs it down considerably. When it has unloaded part or all of its cargo, a ship becomes less heavy, which can make navigation dangerous. The ship must be deep enough in the water to ensure efficient propeller and rudder operation and to avoid the bow emerging from the water, especially in storm conditions in heavy seas.
Ballast water is pumped directly into the ballast tanks from the sea. The amount of water that needs to be pumped into the ballast tanks depends mainly on weather conditions, how much cargo is on the ship, and the vessel’s itinerary. When the vessel is loaded, it must discharge part or all of its ballast water in order to maintain ideal buoyancy. This ballast water is discharged into the sea.
Precautions must be taken when taking on ballast water. It can carry bacteria and other microbes, micro-algae and various stages of aquatic plant and animal species from where the water was pumped. When discharged with the ballast water, some can acclimatize to their new environment. If they have no natural predators, they can reproduce very quickly. They can become invasive and negatively impact native fish species.
For example, ballast water is thought to have been the source for the introduction of an oyster parasite called MSX to Cape Breton, which then spread to Prince Edward Island, where the oyster industry is more firmly established. The economic impact to the oyster industry from damages, and the potential future loss of revenues to the industry could extend into the future and reach millions of dollars.
Ballast water can be treated in order to neutralize all types of organisms. But the best available option, according to Transport Canada, is mid-ocean ballast exchange that occurs 200 nautical miles from shore in waters that are at least 2,000 metres deep.
In 2004, the International Maritime Organization adopted the International Convention for the Control and Management of Ships’ Ballast Water and Sediments. Once in force, the Convention will require all ships to carry a Ballast Water Record Book and carry out ballast water management procedures to a given standard. Transport Canada is active at IMO working on the preparation of guidelines for implementation of the Convention.
Canada: the best system in North America
Canada did not wait for regulations in order to act. Today, it has the best ballast water management system in North America. Ships arriving by sea in Canadian waters must:
- Exchange the ballast water offshore and, if heading for the Great Lakes, flush any residual waters, and/or
- Treat the ballast water, and/or
- Retain the ballast water on board, and/or
- Transfer it to a port reception facility.
All ships must send in a Ballast Water Reporting Form before entering Canadian waters. Transport Canada inspectors go aboard ships to check the vessel’s documents and that the crew is aware of ballast water management procedures. One hundred percent of ballast water reports are checked, 365 days a year.
No invasive species have been identified since the flushing measure was applied to ocean-going ships in 2006.