Temporary storage of treated sewage and grey water in ballast water tanks

Notice to: Ship Owners / Managers/ Operators / Surveyors / Auditors :

C24034 | 17th July 2024

The IMO has issued Circular BWM.2/Circ.82 which advises that the ‘Guidance for the temporary storage of treated sewage and/or grey water in ballast water tanks’ has been approved at MEPC.81. The Guidance is included as an Annex to the Circular and establishes a uniform procedure for minimizing the impact on the environment while ensuring practicability on ships

The Guidance notes that there are exceptional situations where, to comply with coastal State regulations or inadequate reception facilities at ports, dry-docks, and terminals, it may become necessary to store treated sewage and/or grey water in ballast water tanks.

The Guidance consists of:

• Definitions,
• General matters for application and
• General Guidance

Key points to note are:

Temporary storage of treated sewage/grey water (TS/GW) in ballast tanks should only be considered in specific ports and areas that restrict the discharge of TS/GW and where the ship does not have dedicated tanks with adequate storage capacity.

Mixing ballast water and TS/GW in a ballast tank should be avoided.

Where a ship stores TS/GW temporarily in its ballast tanks:

• periodic inspections should be made of those tanks’ coatings and measures taken to prevent impacts.
• appropriate measures should be taken to prevent contamination of the ballast system by TS/GW and to prevent accidental discharge of TS/GW within restricted waters, e.g.:
  • closing the valves or using blanks, spectacle flanges, and pipeline blinds
  • or using an isolated pump and pipeline, dedicated portable hose, and/or
  • using a lockout/tagout).
• The tank should be fully emptied, including removal of any residual ballast water, as far as practicable, through the BWMS. The removal and disposal of sediments should be carried out as far as practicable and in line with paragraph 1.3 of part A of Guidelines (G4) (resolution MEPC.127(53) as amended).

Where a tank changes its use back to ballast water storage after being used for TS/GW storage, the following procedures should be followed:

• After discharge of TS/GW BW the tank, pipes, and dual-purpose pumps should be flushed with the normal maximum volume of the tank.
• Water used to flush the tanks should not be discharged through the BWMS.
• After the discharge and flushing, the ballast water tank should be reconnected to the ballast system and the tank should be flushed once more with treated ballast water to replace the residual water.

It should be ascertained that the non-availability of a BW tank due to storage of TS/GW does not impact the hull strength and stability of the ship, including ship safety and operational performance.

The discharge of ballast water and TS/GW should comply with:

• the BWM Convention;
• MARPOL Annex IV; and
• any local TS/GW discharge requirements

The ship’s Ballast Water Management Plan (BWMP) should include a ship-specific change-over procedure, from ballast water storage to TS/GW storage and back to ballast water storage, including pump and piping associated with the dual-purpose BW tanks, with specific details on how the flushing is conducted. The BW tanks to be used for temporary storage of TS/GW should be identified in the BWMP.

The Ballast Water Record Book (BWRB) should have an entry made under the appropriate code related to additional operational procedures and general remarks containing the details as mentioned in examples 22 and 23 in BWM.2/Circ.80.

Act now

Ship Owners/ Managers/ Operators/ Surveyors/ Auditors should ensure that:

• Masters and Officers of ships with temporary storage of treated sewage and/or grey water in ballast water tanks are aware of this Guidance and
• That the procedures are properly implemented.

Surveyors when attending onboard such ships should check the Ballast Water Management Plan, and Ballast Water Record Book, for evidence of proper implementation and recording of the procedures.