Ballast Water Treatment: More Dead Than Alive

The U.S. Coast Guard’s preliminary rejection of the most probable number (MPN) method for determining the effectiveness of ballast water treatment systems has come under increasing fire from the industry and researchers. The issues are set to be discussed at IMO later this month. Meanwhile, concerns are multiplying. 

Industry bodies, ICS and INTERTANKO, have made a submission to the upcoming IMO Marine Environment Protection Committee highlighting the problems as they see them. With the Ballast Water Management Convention inching closer to ratification, the U.S. Coast Guard’s decision challenges the concept of viability in the context of the type approval of systems and port sampling and analysis. ICS and INTERTANKO assert that the decision negatively impacts treatment systems based on UV and “halves the number of systems shipowners can select from if they wish to operate globally.” This is expected to create substantial equipment supply issues, should the Convention come into force soon.

UV treatment can sterilize organisms without killing them. The MPN method does not determine if an organism is alive or dead. Rather it evaluates the ability of an organism to reproduce and hence its ability to colonize a new environment. As such, it does not provide a result equivalent to that of the Coast Guard’s preferred method - vital staining.

Since the ICS and INTERTANKO submission, the science behind vital staining has been called into question. In a presentation at the IMO GloBallast Forum in March, Dr Hugh L. MacIntyre concluded that the vital stain method is seriously flawed and unable to accurately classify phytoplankton as either live or dead. 

MacIntyre investigated 24 species of marine and fresh water phytoplankton, including eight species known to cause harmful algal blooms, and found that a great majority had significant error rates in the classification of live versus dead organisms using vital stains, thus indicating that vital staining might not be a preferable alternative to the MPN method.

“Dr Hugh MacIntyre is a recognized world expert in phytoplankton ecology,” says Mark Kustermans, Market Manager for UV system manufacturer Trojan Marinex. “This comprehensive study places serious doubt that vital stains are protective of the environment, particularly when compared to the MPN method, which can be used to effectively assess viability for all ballast water management systems, not just UV-based systems.”

The choice of methods is not the only issue plaguing the Convention. Also to be discussed at the MEPC meeting is a study on the implementation of the performance standard described in regulation D-2 of the Convention. The study results suggest that ballast water management system testing and type approval approaches currently employed follow the guidelines. However, due to divergent interpretation of the guidelines, several differences exist in how testing is carried out and how type approval is granted. 

In addition, lack of publicly available documentation on processes and verifications hinders transparency and may impair confidence in the testing and approval regime. While the majority of test facilities use validated procedures, some may also use methods that have yet to be reviewed or validated. Moreover, not all facilities have been audited by an accredited body.

The ways challenge conditions of test waters are achieved vary significantly, which could lead to differences in testing results. Some test facilities do not manipulate biological challenge conditions while others do in varying ways and to varying levels. It also appears that most test facilities manipulate physical/chemical challenge conditions to some extent but the specific parameters differ and the methods used to make adjustments also vary greatly.

The issues will be discussed at MEPC 69 which will be held between April 18 to 22.