Operating a BWMS: Records, Malfunctions, Contingencies

Certificates do not discharge ballast; crews do. A ship can carry a perfectly approved system and still collect a deficiency on the quay, because what inspections actually examine is the daily discipline: the record book, the response to malfunctions, and what the crew did on the day the water was too dirty to treat. This lesson is that discipline.

The record book

Every uptake, every treatment or circulation, every exchange, every discharge, to sea or to a reception facility, and every accidental or exceptional discharge goes into the ballast water record book, with dates, positions, volumes and tanks. The officer in charge signs each operation; the master signs each completed page. Treat it with the seriousness of the Oil Record Book, because inspectors do: entries are read against the GPS track, the sounding log and the plan, and an entry that cannot have happened where and when it claims is worse than a missing one.

The bookkeeping rules were tightened after years of inconsistent practice. From 1 February 2025 the record book must follow an amended, far more prescriptive format, with structured entries and codified operations; from 1 October 2025 an electronic record book may be approved in its place, carrying a declaration that it meets the IMO's electronic record book requirements. Lloyd's Register's class news on the change sets out both dates and the approval procedure. If your ship still runs a pre-amendment book, that is a finding waiting to be written.

When the system misbehaves

Treatment systems fail in predictable ways, and it pays to know the catalogue before an alarm teaches it to you. ClassNK's guidance on typical BWMS malfunctions is the best free tour: filters clogging in silty water until the unit does nothing but backflush and the ballast rate collapses; TRO sensors drifting or failing outright, often nothing more exotic than expired reagent; UV lamps failing or low-transmittance alarms tripping in turbid harbours; electrochlorination units refusing to run in water too fresh or too cold for their chemistry; and the quiet underworld of stuck valve actuators and misreading flow meters.

The countermeasures are correspondingly unglamorous: slow the ballast operation to a rate the filter can live with, clean and calibrate on schedule, and carry the spares that actually fail, sensor reagents, lamps, seals, rather than the ones the brochure lists. A malfunction is not a crisis. An undocumented one is: log it, tell the master, and let the office and the flag know while options still exist.

When compliance is not possible

Sometimes the system is down, or the port's water is beyond it, and the ship still has to work cargo. The Convention's answer is contingency measures: worked out in advance in the plan, and agreed with the port state before any non-compliant discharge. The recognised menu includes discharging to another ship or a reception facility, carrying out a ballast water exchange where geography allows, repairing and retreating the water, or simply not discharging at all in that port. The one option that does not exist is the quiet bypass: modern systems log bypass valve movements, and a port state that finds one unexplained treats it exactly as you would expect. Early notification is the whole game: a port state told before arrival can usually agree something; one that discovers the problem at the sample point cannot.

A related route exists for a specific, recurring headache: ports whose water quality challenges the system itself: sediment so heavy or algal loads so dense that filters choke and UV cannot penetrate. Interim guidance adopted as resolution MEPC.387(81) addresses exactly this. It treats a bypass as the last resort, to be considered only once the system has been run as far as practicable, and where a bypass has happened it expects ballast water exchange plus treatment before discharge, with every step entered in the record book; the revised management plan guidelines adopted at MEPC 84 in 2026 fold these procedures into the plan itself. Lloyd's Register's summary of the adoption is a readable starting point before the resolution itself.

The thread through all of it is the same: the Convention forgives hardware that fails and water that cannot be treated, and it does not forgive silence. The record book entry you are hesitating to write is almost certainly the one that would have saved the ship trouble.