Ballast water treatment operation in muddy waters

It is quite common to encounter problems during the operation of Ballast Water Treatment Systems (BWTS) in muddy waters, especially in Chinese ports.
In many cases, especially for BWTS with filters it is safer for the system to bypass it in order not to cause serious damages on the filters and render the entire BTWS out of order.
What is the regulatory aspect of this matter? Are operators allowed to do this?


Even though this is a known issue, at present none of current IMO statutory instruments addresses such issue.

If the BWTS cannot be operated at disports with brakish water, then it can be by-passed. But Ballast water exchange will then be needed once the vessel is clear of the port.
A respectively worded record under code 3.6 should be entered to the Ballast Record Book.
Flag must be promptly informed. Company’s SMS should be consulted too.



We have been informed that Intertanko is currently collecting data from various ports, pertaining to muddy/brackish waters and perhaps there is going to be a discussion in IMO, in order to examine the matter. However, the above is not confirmed and as described by Kostas, the vessel’s operators will need to approach Flag/RO for approval to by-pass the system and most probably Port Authorities will need to be consulted, in case the system trips due to high differential pressure across the filters. The latter, may have disastrous impact to the vessel, as she may be ordered by Port Authorities to carry out ballasting OPL, with significant delays/costs to ship owners’.

I would suggest when the vessel is to ballast in muddy waters, filters to be mechanically/chemically cleaned (always following makers’ recommendation) prior arrival to port. Additionally, I would also suggest to clean electrolyzers, as quite often the sediments may accumulate on the units. Furthermore, minimum throughput through the filter, operating the Flow Control valve manually, shall be established. Should the flow is kept to minimum, Chief Officer should start ballasting operation as quickly as practically possible (keeping in mind SFs/BMs are in allowable limits) to avoid or minimise delays (discharging rate is also a key factor). Last but not least, manual back-flushing, using the systems’ pump (where fitted) to ensure that the system will not trip should be carried out. The above recommendations can be effective and we have managed to perform ballast operation in muddy waters, following the above guidance.


Fully agree with Kostas’ and Andreas’ replies.
For ease of reference I am attaching the IMO Circular BWM.2 / Circ.62 as well.
BWM.2_Circ.62.pdf (69.9 KB)


It seems that the above subject will be further discussed at MEPC79 in Dec 22. “Challenging Waters” will be the new term in our work life :slight_smile:

Below from DNV


At MEPC 79, the Committee was unable to determine whether to address these situations through contingency measures or new operational guidance.

The Committee invited concrete proposals for MEPC 80 about guidance to ships dealing with challenging uptake water, with a reminder that BWMS bypass should only be used as a last resort.

Awaiting updates from MEPC 80 scheduled for June 2023.