Australia has presented a study to IMO MEPC 81 to evaluate the performance of ballast water management systems (BWMS) fitted on board ships that visited Australian ports between 2021 and 2023.
In particular, between 2021 and 2022, sampling was conducted on a voluntary basis from ships that were intending to discharge treated ballast water in Australian ports. For these, sampling was conducted on 19 individual ships across two Australian states, at the ports of Dampier and Walcott in Western Australia, and Gladstone in Queensland. The 10 ships sampled in Gladstone were also previously included in document MEPC 78/4/1.
In 2021 and 2022, sampling activity was conducted on a voluntary basis with prior notification given to the ship before the arrival of the sampling team. An additional 20 ships were sampled in 2023, which were attended by the sampling team with no prior notification to the ship, in the port of Newcastle, in New South Wales.
From the 39 ships, in total, 44 samples of ballast water were taken and tested against the D-2 performance standard using both indicative and detailed analysis methods.
According to the Australian submission to IMO for the next MEPC, of the 44 ballast water samples taken, non-compliances were observed for 36% (16) of detailed tests for biological compliance. This result is consistent with the previous observations reported in document MEPC 76/INF.56 (which was 33% non-compliance using detailed analysis).
As clarified, all identified instances of non-compliance were detected in the largest organism size category of the discharge standard (with a minimum diameter of ≥50 µm), except for one case exceeding the limit for Enterococci (which also surpassed the limit in the ≥50 µm size class). This result indicates, in line with findings from other studies, that organisms in the ≥50 µm size category are more susceptible to posing a non-compliance risk in treated ballast water compared to other size categories.
Australia concludes that non-compliance was sometimes linked to operational issues, such as the introduction of untreated ballast water through an open valve or while clearing an air lock in the ballast line during the sampling process. However, for many ships there were no obvious operational difficulties, suggesting other factors, such as lack of preparation or cleaning of the tanks prior to the installation of the BWMS, BWMS not working as intended or regrowth in the tanks of existing populations that were introduced from BWMS bypass operations.
"There is currently not enough data to conclude which of these potential sources of organisms are responsible for exceedances, however this study provides further evidence that BWMS in global operation do not consistently meet the regulation D-2 standard."
…says Australia in the report submitted to IMO for MEPC 81, calling the Committee to take note of the findings from this study and evaluate the performance of BWMS installed on board ships against the D-2 standard of the BWMC as part of the experience-building phase.
Source: Safety4sea