Operational Guide · Registers & Logbooks

# Integrated Bilge Water Treatment System: the New Regulation 12A

Instead of two separate systems to coordinate (separator and 15ppm alarm), MEPC 84 opens the way to a single integrated system for bilge water treatment: a change in architecture, not just in threshold.

bilge water MARPOL Annex I Regulation 12A MEPC 84

## Operational Explanation

MEPC 84 approved a new Regulation 12A under MARPOL Annex I permitting the installation of an integrated bilge water treatment system, together with related supporting guidance. Unlike the traditional architecture, based on a separate oil separator (OWS) and a separate 15ppm alarm/monitoring system, the integrated system unifies treatment and monitoring in a single certified unit.

For the crew and the Chief Engineer, this is not just a technical update: it changes how operational compliance is verified, the maintenance required, and the training needed, since a fault or anomaly in the integrated system can have a different impact than the logic of the two separate systems the crew is historically used to.

## Regulatory Reference

MARPOL Annex I, new Regulation 12A (approved at MEPC 84, 2026): permits the installation of an integrated bilge water treatment system that unifies oil separation and 15ppm monitoring/alarm functions in a single certified unit, together with related supporting guidance.

## Scope of Application

Ships installing, as an alternative to the traditional separator + alarm architecture, an integrated bilge water treatment system compliant with the new Regulation 12A.

## Procedure / How to Complete It

1. For new installations, assess whether to adopt the integrated system under the new Regulation 12A or retain the traditional separator + alarm architecture.
2. If the integrated system is adopted, verify the single unit's certification against the supporting guidance associated with Regulation 12A.
3. Update planned maintenance procedures to reflect the integrated system's architecture, distinct from that of the two separate systems.
4. Train the Chief Engineer and engine room personnel on the integrated system's operating logic, including anomaly and alarm management.
5. Keep onboard documentation updated on the installed system's architecture (integrated or traditional), for reference in the event of an inspection.

## Practical Example

Example: a shipyard fitting out a newbuilding assesses, at the design stage, the adoption of the integrated bilge water treatment system under the new Regulation 12A, simplifying the plant architecture compared with the traditional two-system solution.

## Real Cases

The introduction of an integrated system option reflects the technological evolution of bilge water treatment systems, which over the years has seen increasingly sophisticated monitoring systems; the new Regulation 12A formalises this evolution at IMO level, offering an alternative certification path to the traditional one.

## Common Mistakes Mistake Library

Mistake | Consequence | How to avoid it
--- | --- | ---
Engine room personnel trained only on the traditional separator + alarm architecture, without updated training for the integrated system installed | Inadequate handling of anomalies or alarms specific to the integrated system | Always train personnel on the operating logic specific to the architecture actually installed on board
Onboard documentation not updated to reflect the integrated system's architecture after a retrofit | Documentary confusion in the event of an inspection or survey | Always update onboard documentation after every installation or retrofit of bilge water treatment systems

## PSC Observations

After the introduction of Regulation 12A, PSCOs will need to familiarise themselves with the new architecture of any integrated systems installed; in the meantime, verifying compliance of the bilge water treatment system remains a standard inspection check, regardless of the architecture installed.

## Operational Tips

- If you are considering a retrofit or a newbuilding, compare the costs/benefits of the integrated system against the traditional architecture before deciding.
- Do not assume that generic bilge water treatment system training automatically covers the specifics of the integrated system.
- Always update onboard documentation after any change to the bilge water treatment system's architecture.

## Checklist

- Bilge water treatment system architecture (integrated or traditional) clearly documented on board
- Integrated system's certification verified against the Regulation 12A supporting guidance, if applicable
- Planned maintenance updated for the specific architecture installed
- Engine room personnel trained on the actual system's operating logic
- Documentation updated after every retrofit or new installation

## FAQ

What does the new MARPOL Annex I Regulation 12A introduce?
The option of installing an integrated bilge water treatment system, which unifies oil separation and 15ppm monitoring/alarm functions in a single certified unit, as an alternative to the traditional two-system architecture.
Is the integrated system mandatory?
No, Regulation 12A introduces an alternative option to the traditional separator + alarm architecture, not an obligation to replace existing systems.
What changes for the crew with an integrated system?
The operating logic for handling anomalies and alarms differs from that of the traditional two separate systems, requiring specific training on the architecture actually installed.
🎬 Additional photos, videos and interactive diagrams for this topic will be available in a future version of the platform.

## Related Topics

Bilge Water Management MARPOL Annex VI

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