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Review of two decades of progress in the development of management options for reducing or eradicating phytoplankton, zooplankton and bacteria in ship's ballast water
Citation
Gregg, M and Rigby, G and Hallegraeff, GM, Review of two decades of progress in the development of management options for reducing or eradicating phytoplankton, zooplankton and bacteria in ship's ballast water, Aquatic Invasions, 4, (3) pp. 521-565. ISSN 1798-6540 (2009) [Refereed Article]
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Copyright Statement
Copyright © 2009 The Author(s) This is an Open Access article
Official URL: http://www.aquaticinvasions.net
DOI: doi:10.3391/ai.2009.4.3.14
Abstract
The worldwide transfer and introduction of non-indigenous invasive aquatic organisms via ships’ ballast water has been amply
demonstrated to cause significant ecological, economic and human health impacts. Possible solutions to the problem include: 1)
treating ballast water to remove or destroy unwanted organisms; 2) re-designing new vessels to eliminate the need to discharge
ballast water; and 3) retaining ballast water onboard. Ballast water exchange is currently the only widely acceptable and
suggested (sometimes even required) procedure to minimise the risk of ballast water mediated invasions but the variable efficacy
and operational limitations of this approach have led to significant financial investment in the last two decades in the research
and development of more effective shipboard and shore based ballast water treatment technologies. Specific technologies under
consideration include mechanical separation, heat treatment, UV irradiation, cavitation, de-oxygenation and active substances.
To date, no single treatment option has proved to be universally effective and increasing attention has focused on multicomponent
treatment systems. The high flow rates and volumes of ballast water that must be treated pose significant
technological challenges, and the presence of sediment in ballast tanks reduces the efficacy of many treatment options as this
provides a habitat for resistant organisms such as resting stages of phytoplankton and zooplankton. Mechanical separation
devices would best be used as a primary stage of a treatment system comprising multiple technologies because free-living
organisms and sediment below a certain size are likely to be largely unaffected. UV treatment systems are unlikely to eliminate
all ballast water organisms, as they are not able to deliver a stable lethal dose across a wide range of water quality conditions and
many organisms are resistant to UV exposure or can recuperate after treatment. At the current stage of development, cavitation
would not be considered appropriate for the shipboard treatment of ballast water due to high capital and operating costs and high
power requirements. The heating of ballast water using waste heat from ships’ engines has been claimed to be a practical and
cost effective treatment options for eliminating ballast water zooplankton and phytoplankton (including resting stages) but
concerns have been expressed that attainable temperatures may not eliminate all bacterial pathogens, that this approach does not
apply to ships traversing colder seas and may impact on the integrity of vessel structures. Promising research has been conducted
on several systems that are able to achieve temperatures capable of eliminating bacteria but these technologies are still under
development. De-oxygenation by the addition of glucose or reducing agents are not effective treatment options, however deoxygenation
technologies based on the injection of an inert gas are more promising (notably against larval and adult
zooplankton) as they could be cost effective and do not impact on the aquatic environment as ballast water is re-oxygenated prior
to discharge. Biocide dosing systems have low capital costs and power requirements but the costs of active substances are
significant. Chemical treatment costs and space requirements can be significantly reduced by using onboard chemical generators
but the capital cost of these systems is significant and all have biological efficacy, safety, operational and environmental (poor
biodegradation) concerns. Treatment systems that produce free hydroxyl radicals would be favourable over other chemical
treatments as they are claimed to produce less or no toxic by-products at ballast discharge but these technologies have high
power requirements. Each treatment option requires further research on their biological and operational efficacy and safety under
full-scale shipboard conditions. As of July 2009, 16 promising systems u
Item Details
Item Type: | Refereed Article |
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Keywords: | ballast water treatment, invasive species, bacteria, phytoplankton, zooplankton |
Research Division: | Biological Sciences |
Research Group: | Plant biology |
Research Field: | Phycology (incl. marine grasses) |
Objective Division: | Transport |
Objective Group: | Water transport |
Objective Field: | Coastal sea freight transport |
UTAS Author: | Gregg, M (Mr Matthew Gregg) |
UTAS Author: | Hallegraeff, GM (Professor Gustaaf Hallegraeff) |
ID Code: | 59944 |
Year Published: | 2009 |
Deposited By: | Plant Science |
Deposited On: | 2009-12-23 |
Last Modified: | 2017-01-24 |
Downloads: | 34 View Download Statistics |
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