Operational Guide · Registers & Logbooks

# Sludge Management

Storage and disposal of the oily residues generated by purifiers and separators: the point environmental inspectors scrutinise most closely.

sludge MARPOL Annex I oily residues magic pipe

## Operational Explanation

"Sludge" is the oily residue produced mainly by fuel and lubricating oil purifiers, and to a lesser extent by drainage and leakage in the machinery space. It must be collected in dedicated tanks, recorded in the Oil Record Book (code C) and disposed of only through a port reception facility or compliant on-board incineration.

## Regulatory Reference

MARPOL Annex I, Regulation 17 (ORB entry code C — collection and disposal of oily residues). Linked to Annex VI Regulation 16 for the incineration of the resulting ash.

## Scope of Application

All ships fitted with combustion machinery that generates oily residues (main and auxiliary engines, HFO/MDO/LO purifiers).

## Procedure / How to Complete It

1. Record daily the estimated volume of sludge produced by the purifiers.
2. Transfer sludge to the dedicated tank; never mix it with untreated bilge water.
3. For disposal in port: contact the reception facility, confirm availability, obtain the Waste Delivery Receipt.
4. For on-board incineration: verify that the incinerator is approved and that the operation is permitted in the zone (not in port, not in an ECA where prohibited).
5. Record the operation in the Oil Record Book (code C) with quantity and destination.
6. Carry out a monthly mass balance (sludge balance): estimated production vs. recorded disposal.

### Diagramma: bilancio sludge (input/output)

## Practical Example

Example of a monthly balance: estimated production 2.4 m³ (historical purifier data) — disposed of: 1.6 m³ at a Rotterdam reception facility + 0.7 m³ incinerated on board = 2.3 m³. A 0.1 m³ variance is justified by a tank level change: acceptable and documented.

## Real Cases

The most recurrent case worldwide (with fines that have exceeded USD 10-40 million in USCG proceedings) involves the installation of a "magic pipe": a bypass that discharges sludge or bilge water directly into the sea, circumventing the separator. Investigations almost always start from a sludge balance that "doesn't add up".

## Common Mistakes Mistake Library

Mistake | Consequence | How to avoid it
--- | --- | ---
Sludge balance with a large, unexplained variance | Suspicion of illegal discharge, in-depth investigation | Documented monthly balance, cross-checked against fuel consumption
Internal tank-to-tank transfers not recorded | Inconsistency in ORB volumes | Record every internal transfer as a code C entry
Disposal without a Waste Delivery Receipt | Unable to prove proper disposal | Always keep the reception facility's receipt

## PSC Observations

PSC and USCG inspectors regard the sludge balance as one of the most reliable indicators of a possible illegal discharge: estimated production systematically exceeding recorded disposal is almost always grounds for further investigation, often including inspection of piping and valves.

## Operational Tips

- Keep a separate sludge balance log, updated monthly and cross-checked against fuel consumption.
- Never mix sludge with bilge water before it is recorded.
- Always keep Waste Delivery Receipts together with the ORB.

## Checklist

- Monthly sludge balance updated and consistent
- Waste Delivery Receipts kept for every disposal in port
- No unrecorded internal transfer
- Incinerator used only in permitted zones

## FAQ

Can sludge always be incinerated on board?
No: incineration is prohibited in port and in certain ECA/Special Areas; it must be checked case by case under MARPOL Annex VI Regulation 16.
What should be done if the sludge balance doesn't add up?
Investigate the cause immediately (leaks, estimation error, tank not correctly sounded) and document it: an unexplained variance is the main red flag for a PSCO.
🎬 Additional photos, videos and interactive diagrams for this topic will be available in a future version of the platform.

## Related Topics

Oil Record Book Incinerator Operations Bilge Water Management Decision Tree: Sludge (IT)

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