Management of Ships’ Ballast Water and Biofouling - Prevention of Pollution of the Marine Environment from Vessels - page 71

miles from the nearest land and in water at least 200 m in depth. 41 When this is not
possible, ballast water exchange must be conducted at least 50 nautical miles from
the nearest land and in water at least 200 m in depth. 42 In sea areas where the nearest
land or depth does not meet these parameters, the port State may designate ballet
water exchange areas. A ship shall not be required to deviate from, and delay, its
intended voyage to comply with these requirements.
The effectiveness of ballast water exchange is questionable. 43 Ballast water
exchange will not guarantee complete removal of harmful organisms. Due to the
design of ballast tanks, certain water and sediments will always remain in the
ballast water tank. Moreover, the 95 % volumetric exchange level does not neces-
sarily equate to a 95 % rate of organism removal. It has been shown in some studies
that there are even more organisms present after an exchange of ballast water in the
high seas. 44 Moreover, water-depth requirements for ballast water exchange cannot
be fulfilled in many areas and circumstances. However, it should be noted that
ballast water exchange has been introduced merely as an interim measure which
will gradually be replaced.

4.2.4.2 Ballast Water Performance Standard (Regulation D-2
Standard)

The Ballast Water Performance Standard introduced specific biological criteria to
ensure performance. According to Regulation D-2, ships are allowed to discharge:

￿ less than ten viable organisms per cubic metre greater than or equal to 50 μ min

minimum dimension; and

￿ less than ten viable organisms per millilitre less than 50 μ m in minimum

dimension and greater than or equal to 10 μ m in minimum dimension; and

￿ the indicator microbes not exceeding the following concentrations as a human

health standard:
- Toxicogenic Vibrio cholerae (01 and 0139) with less than one colony forming
unit (cfu) per 100 mL or less than 1 cfu per 1 g (wet weight) zooplankton
samples;
- Escherichia coli less than 250 cfu per 100 mL;
- Intestinal Enterococci less than 100 cfu per 100 mL. 45

41 BWM Convention, annex, reg. B-4.
42 BWM Convention, annex, reg. B-4.
43 Gollasch et al. ( 2007 ), p. 588.
44 Ibid.
45 BWM Convention, annex, reg. D-2.