Invasive Species in Ballast systems – Eradication Methods
1. The exchange of ballast water in mid-ocean.
This is carried out by discharging the original ballast and refilling with the mid-ocean seawater, before entering the cargo discharge port.
2. Purification by UV or Ozone
The use of UV lamps or ozone on the ballast water to kill the invasive species has been suggested.
3. Mechanical control
This involves the use of fine mesh screens (50 Micron) and a backwash system located in the ballast suction inlets. It is designed to trap any invasive species before they can enter into the ballast system.
4. Biological control
Once the invasive species have been identified, the use of a species which control them in their own habitat can be introduced to manage their extermination in their new environment.
5. De-oxygenation of ballast water
This method entails the injection of nitrogen into the ballast tank water, thus starving it of oxygen. De-oxygenation is deemed to not only to eradicate any invasive species, but also mitigate the corrosion of the internals of the ballast tanks.
6. Use of fresh water as ballast
This would require the ballast tanks to be well washed out before filling with fresh water. The fresh water ballast could then be pumped ashore and used for irrigation in arid countries.
7. Coating of ballast tank internal surfaces
There are numerous anti-corrosion tank coatings available today, and these can incorporate anti-fouling additions such as silicon PDS (polydimethyelsiloxanes) to reduce the formation and reproduction of invasive species on the tank surfaces.
However most of the successful anti-fouling coatings are toxic and would be detrimental to indigenous aquatic species if discharged along with the ballast water.
- IMO approved ballast water treatments.
Earthtrends - ballast water control