Ballast Water Management Under the Ballast Water Management Convention - Global Maritime Transport and Ballast Water Management: Issues and Solutions - page 98

weak point regarding the D-2 standard is that it does not address organisms below
10 m (in minimum dimension), but a considerable number of species, including

bloom forming harmful algae, are smaller than 10

μ

μ m (e.g., Phaeocystis spp.,

Pfi esteria spp. and Chrysochromulina spp.).

How to Achieve Compliance with the D-2 Standard?

The D-2 standard is based on a limited number of organisms that can be dis-
charged with ballast water, and is not considering only non-indigenous or harm-
ful organisms, but all viable organisms in relevant size classes, or limited
number of cfu per indicator microbes. Indicator microbes are in general present
only in coastal environments, into which these may be discharged with untreated
river run-offs contaminated with human infl uence or due to improper sewage
treatment plants. Therefore BWE may still be effi cient to manage ballast water
according to the D-2 standard in terms of indicator microbes as in open ocean
these organisms are absent. However, the open ocean concentration of viable
organisms greater than or equal to 10 μ m in minimum dimension, and especially

those greater than or equal to 50 m in minimum dimension, may be higher

in BWEA than the D-2 standard (Gollasch and David, own observations).
Consequently BWE is not an option to manage ballast water to comply with the
D-2 standard. With this the on board installation of ballast water treatment sys-
tems, so called BWMS, became a viable option and requirement. It is interesting
to note that a recent summary of existing and developing BWMS revealed more
than 100 such systems. However, some of these are not considered realistic, but
if only half of those make it to the market, a large variety of BWMS becomes
available so that all vessel types with their specifi c BWM requirements can be
equipped with BWMS. As of the December 2013, 33 BWMS have been type
approved. Details about BWMS are given in chapter “ Ballast Water Management
Systems for Vessels ” .
Issues which further may need to be considered are the possible regrowth of
organisms in ballast tanks after treatment and also that organisms may remain in the
tank from previous ballast water operations and may become re-suspended during
ballast water operations (Murphy et al. 2008 ). Consequently, upon discharge, treated
water may contain unacceptably high organism numbers although the treatment
systems proved that the D-2 standard was met during water uptake. To ensure that
ballast water discharges always meet the D-2 standard it is recommended to treat the
water during uptake and discharge and also to develop BWMS which by far exceed
the standards set forth in the BWM Convention.
In the case of fresh water ecosystems, some countries such as Canada are exam-
ining the possibility of continuing the use of BWE to take advantage of the salinity
shock imposed on fresh water organisms when vessels travel between freshwater
donor and freshwater recipient ports, i.e., in cases when vessels ballast in freshwa-
ter, a marine water BWE would provide a salinity shock to the originally pumped in
freshwater organisms. At the same time, marine organisms pumped on board during

μ