Abstract
We conducted a shipboard ballast water test using seawater of extreme turbidity collected from Shanghai Port (China) (>300 mg total suspended solids (TSS)/L), and normal seawater collected in other ports (<100 mg TSS/L). All three types of International Maritime Organization (IMO)-approved ballast water management system (BWMS) tested failed to properly operate because of filter clogging or insufficient generation of oxidants under near-fresh water conditions with extremely high concentration of suspended solid during ballasting. It was also found that the number of microorganisms increased with longer ballast water retention time, with higher numbers in the treated discharge water. The results suggest that when operating a BWMS involving a filter unit in areas with water having high concentrations of suspended solids, the filter unit should be used during ballast water discharge, rather than during ballasting. This method has the advantage of removing ≥50 µm organisms at discharge that could not be removed by a filter during ballasting. For ballast water retained for long storage times, the results suggest the use of BWMSs involving UV units or electrolysis during deballasting. In addition, BWMSs involving electrolysis units provide the opportunity to maintain residual total residual oxidant (TRO) levels, using a partial ballast tank. Although the BWMSs tested are a small subset of the large number of IMO-approved BWMSs, the results demonstrate that there is a significant gap between the technology currently available and capacity to meet IMO and US Coast Guard standards.
Highlights
Invasive aquatic species can disrupt native ecosystems of affected regions
The BWMC came into force on 8 September 2017, and under Regulation B-3 it requires that most ships moving among international ports from that time to 8 September 2024 have installed a type-approved ballast water management system (BWMS)
When the ballast water, which was pumped on board from Shanghai Port with no BWMS, was discharged at Pusan Port in the 10th test cycle, the total suspended solids (TSS) concentration decreased from an average of 351 mg L−1 during ballasting to 42.0 mg L−1 during deballasting
Summary
Invasive aquatic species can disrupt native ecosystems of affected regions. Biofouling and ballast water are major mechanisms in the movement of exotic species among ocean ecosystems. An experience-building phase (EBP) from 2018 to 2022 was approved by the Marine Environment Protection Committee (MEPC) to monitor implementation of the BWM Convention, with the aims of identifying those aspects of the convention’s implementation that are working well, and to shed light on issues that require further attention [8,9]. To this end, the EBP is structured in three stages: a data gathering stage, a data analysis stage, and a review stage. Another important goal of the EBP is to develop standardized sampling and analysis procedures
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