Environmental Engineering Reference
In-Depth Information
the data requirements for existing and new biocides within the EU. Antifoul-
ing agents are included in this directive (Product Type 21). Any antifouling
agent seeking registration was required to notify in 2002 and provide a base
set of data. Time-scales for submission of additional necessary data have not
been established; however they will be part of the 10-year plan to fully imple-
ment the directive. It has been suggested that antifouling agents are likely to
be reviewed in 2006 [25].
6
Future Developments
Clearly there is a need to protect non-target organisms in the environment
from antifouling agents. However, antifoulants are critical for shipping, and
withanimminentbanonTBT,alternativestrategiesmustbefound.Yebra
et al. [1] have reviewed this topic.
In the short term, the most feasible option is to utilize copper-based for-
mulations with the most environmentally friendly booster biocides. Whilst
substantial data on the biocides is presented within this volume, there remain
deficits in our knowledge concerning the environmental behaviour and ef-
fects of these compounds. Persistence is an important feature of the agents,
but needs to be tempered with longevity of antifouling performance. In the
slightly longer term, some companies are addressing this issue through poly-
mer research, which controls the release of active compounds and affords
self-polishing capabilities to maintain the active ingredient in the surface
layer. This challenge is substantial, as it needs to maintain a constant, and ide-
ally a small release, that is adequate for antifouling the vessel (even during
stationary periods), whilst maximizing the lifetime of the coating.
An alternative strategy to the polymer option relates to the use of natu-
ral products (or synthesized analogues), which prevent fouling of organisms
in the wild. Usually, these compounds act enzymatically by interfering with
the metabolism, or dissolving adhesive materials of the fouling organisms.
Structures include terpenoids, steroids, heterocyclics, alkaloids and poly-
phenolics. This approach to the prevention of fouling is, however, far from
commercial exploitation.
Another important area of technological development of antifouling re-
lates to non-stick fouling-residue coatings that prevent adhesion by the foul-
ing organisms. The demands of this type of material, presently, restricts
choice to two families of compounds: the fluoro-polymers and silicones. This
option, from an environmental viewpoint, is appealing. Results from per-
formance tests for currently available coatings indicate modest performance,
requiring comparatively high speeds to remove fouling organisms. Coupled
with expense, poor adhesion qualities to the hull and susceptibility to dam-
age, further advances will be necessary [1].
