We have co-sponsored a submission to MEPC 85 making the case for revising the IMO guidance related to ballast water management for ships operating in challenging water quality conditions.
Drawing on operational experience, the proposals seek clearer procedures and more consistent implementation, with the committee still to decide whether to take the revision forward.
For ships trading in ports and rivers with high sediment loads or poor water clarity, ballast water treatment can present recurring difficulties. Filters can clog, treatment capacity can fall and alarms or shutdowns can interrupt ballasting during busy cargo operations. Even a properly installed, maintained and operated ballast water management system (BWMS) can encounter conditions that limit its ability to treat the water.
These difficulties were reflected in BIMCO’s 2025 Ballast Water Management Survey, which gathered responses representing more than 3,200 ships. Operators reported recurring water-quality challenges, increased crew workload and uncertainty over the acceptance of contingency measures. The findings underline the need for guidance that crews can apply in practice and authorities can interpret consistently.
Progress at IMO has, however, required further work. At MEPC 84, there was insufficient support to revise the Interim guidance on the application of the BWM Convention to ships operating in challenging water quality conditions (Resolution MEPC.387(81)). Interested Member States and international organisations subsequently continued discussions through informal intersessional work. The new submission brings the outcome of that work back to the Committee as a consolidated package of proposed revisions.
Ahead of the next session of the Marine Environment Protection Committee (MEPC 85) taking place at the end of November, BIMCO has joined the Republic of Korea, the Marshall Islands and INTERTANKO in submitting proposals to improve the guidance for ships operating in challenging water quality (CWQ) conditions.
The proposals seek to make decisions on board clearer, from assessing conditions before arrival to managing treatment difficulties and recovering after a bypass. A proposed integrated pre-arrival assessment flow chart would guide crews through these stages, while revised wording would better reflect the ship’s operational needs and the system’s technical limitations. The paper also addresses the exceptional circumstances in which pre-emptive bypass might be considered, supported by documented evidence, approved procedures and prior agreement between the flag Administration and relevant port States.
Where bypass becomes necessary, ships need practical arrangements for decontaminating affected tanks and piping before subsequent discharge. The proposals encourage port States to identify suitable ballast water exchange options, particularly in enclosed or semi-enclosed seas, and to facilitate decontamination while minimising delay and deviation where practicable.
For members, another significant proposal concerns port State control. CWQ-related alarms, automatic shutdowns, flow reductions and bypass events should be assessed in their operational context, alongside the ship’s approved plan, operating instructions and records. The proposed wording recognises that such events should not, by themselves, be treated as evidence of non-compliance.
The submission retains the fundamental safeguards of the existing guidance: bypass remains a last resort, and ships remain responsible for meeting the Convention’s discharge standard. It also calls for further scientific evidence and operational experience on identifying challenging water quality and on the effectiveness and practicability of decontamination, particularly tank flushing. BIMCO will continue to engage with members and bring their operational experience into these discussions to help inform practical improvements to the guidance.
It remains for MEPC 85 to decide whether to take forward a revision of the guidance. Through this submission, the co-sponsors are making the case for further work, drawing on operational experience, with a clear aim of better support for decisions on board, greater predictability between ports and guidance that reflects the conditions ships encounter.
The submission, MEPC 85/4/1, is available to all members through the public IMODOCS (you will need to create an account). Alternatively, members wishing to obtain a copy, discuss the proposals or share relevant operational experience are welcome to contact us.
