Ballast Water and the IMO Convention

Ballast water is taken into special tanks of ships during loading / unloading processes as well as for the stabilization of ships during rough weather conditions. Natural seawater as well as seawater from harbors contains plankton organisms which enter the ballast water tanks and could, under optimal ecological conditions develop new populations when re-discharged into other marine areas. There these non-indigenous species could invade resident populations and generate massive ecological damages followed by huge economic losses.

The “Convention on the management of ship’s ballast water” elaborated by the International Maritime Organization (IMO) demands, that the natural seawater pumped into the ships should be adequately treated before it enters the ballast water tanks. Since the natural seawater is treated by different systems and technologies, the water bodies resident in the ballast water tanks have to defined as artificial water bodies.

When re-discharged into harbors or into natural marine areas this ballast water of artificial character has to meet quality standards set-up by the IMO:

  • The maximal allowable density of organisms with a size of >50µm is set to <10 viable organisms/m³.
  • The maximal allowable density of organisms with a size of >10µm<50µm is set to <10 viable organisms/ml.
  • The maximal allowable density of bacteria Vibrio cholera is set to <1 colony forming unit / 100ml
  • The maximal allowable density of bacteria Escherichia coli is set to <250 colony forming units / 100ml
  • The maximal allowable density of the bacterial group Enterococci is set to <100 colony forming units / 100ml

The fact, that the ballast water quality standards set-up by IMO encompasses not only three different organism size classes but also organisms of different trophic characters (autotrophic: algae; heterotrophic: planktonic crabs, worms, etc.; chemotrophic: bacteria) demands different analytical approaches and methods to detect the respective organism in a sample of ballast water and distinguish live from dead individuals.

In addition the ballast water pumping systems onboard ships represent complex pipe systems feeding several ballast water tanks of various shape. Moreover ballasting and de-ballasting procedures may last from a few hours to several days depending on the ship’s type and size.

Therefore it is crucial to identify sampling technologies, sampling procedures and adequate analytical methods which reflect these characteristics of the ballast water to be investigated for its compliance with the IMO convention.

More Information

Sampling of Ballast Water

Analysis of Ballast Water