Ballast Water Management Under the Ballast Water Management Convention - Global Maritime Transport and Ballast Water Management: Issues and Solutions - page 97

Ballast Water Performance Standard: D-2 Standard

The Ballast Water Performance Standard as outlined in Regulation D-2 stipulates
that ships meeting the requirements of the BWM Convention must discharge:

• less than 10 viable organisms per cubic meter greater than or equal to 50 μ m in

minimum dimension, and
• less than 10 viable organisms per millilitre less than 50 μ m in minimum dimen-

m in minimum dimension, and
• less than the following concentrations of indicator microbes, as a human health
standard:

sion and greater than or equal to 10 μ

- Toxigenic Vibrio cholerae (serotypes O1 and O139) with less than 1 colony
forming unit (cfu) per 100 ml or less than 1 cfu per 1 g (wet weight) of zoo-
plankton samples,
- Escherichia coli less than 250 cfu per 100 ml, and
-

Intestinal Enterococci less than 100 cfu per 100 ml.

This standard formed the basis for signifi cant discussions and continuing con-
troversy at IMO. The acceptable organism numbers and the method to determine
their size classes were debated intensively. This compromise was reached through
negotiations by various countries which ranged from an acceptable number of
organisms above 50

m in minimum dimension between 100 and 0.01 per cubic
meter. The current version of the D-2 standard is seen as a considerable reduction
compared to the amount of organisms discharged in unmanaged ballast water or
even that obtained by BWE.
The D-2 standard for both organism groups greater than or equal to 10

μ

m in
minimum dimension refers to all organisms, not per species, and not only for
non-indigenous or harmful organisms. As a result the individual taxonomic species
identifi cation is not required for purposes of compliance testing.
Also of note is the inclusion of a discharge limit for “indicator microbes” with a
human health impact in the D-2 standard. A number of delegations insisted on
incorporating these bacteria as they had specifi c issues, hoping this would result in
a strong signal to R&D interests. Existing and developing ballast water treatment
technologies are able to meet these standards using a combination of treatment
methods (see chapter “ Ballast Water Management Systems for Vessels ” ).
Although the D-2 standard results in a considerable reduction in organisms
being released we note that vessels carry up to 100,000 tonnes of ballast water or
more so that still a high number of organisms may be discharged with ballast
water being in compliance with this Convention. Assuming that 10,000 tonnes of
ballast water are discharged, the acceptable D-2 standard organism concentration
for individuals greater than or equal to 50

μ

m in minimum dimension is less than
100,000, which theoretically means 99,999. The number of organisms to establish
a founder population in new environments is largely unknown, but we suspect that
an inoculation of approximately 100,000 individuals (although of different spe-
cies) may not eliminate the risk of species introductions in all cases. Another

μ