Comments on BWM.2/Circ.82

Referencing BWM.2/Circ.82: Guidance for the Temporary Storage of Treated Sewage and/or Grey Water in Ballast Water Tanks, the transition of a ballast water (BW) tank from temporary sewage/grey water (TS/GW) storage back to ballast water storage necessitates precise procedures:

1.????The contents of the BW tank(s) should be discharged. The BW tank, pipes, and dual-purpose pumps should be flushed with the normal maximum volume of the tank.

2.????Water used to flush the tanks should not be discharged through the BWMS to avoid residue from the TS/GW entering the BWMS as this could potentially harm the BWMS.

3.????Subsequent to 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 thus ensuring the tank is ready to return to ballast operations in accordance with the BWM Convention.

However, it's crucial to recognize that these procedures may not suffice to guarantee compliance with the D-2 Standard in most cases, as evidenced by practical experience and testing.

Challenges and Considerations:

Quality of Treated Sewage: Despite the label "treated sewage," the actual treatment efficacy varies widely among vessels, often falling short of regulatory thresholds. Consequently, treated sewage entering ballast tanks should be treated as raw sewage due to potential contamination.

Untreated Water Residue: Flushing the ballast tank with untreated water is appropriate, but operators must address the residual untreated water, which can amount to significant volumes and may contain high concentrations of organisms, especially if flushing occurs nearshore.

Effectiveness of BWMS: Testing experiences reveal that vessels employing UV systems may require multiple ballast/deballast cycles to sufficiently dilute untreated water to meet organism concentration limits. Chlorine/chlorine dioxide systems offer easier treatment of residual untreated water but may necessitate specific holding times longer than the TA ones to achieve compliance.

Recommendations for Compliance:

To ensure compliance when transitioning TS/GW holding tanks back to ballast tanks, consider the following:

A) Location of Procedures: Conduct exchange and changeover procedures as far from shore as possible, preferably outside the 200-nautical-mile mark, where organism concentrations are minimal or even nonexistent.

B) Thorough Flushing and Stripping: Fully discharge BW tank contents and thoroughly flush tanks, pipes, and pumps with tank volume. If feasible, overflow the tank for approximately 30 minutes. Deballast this water and strip to remove unpumpable water.

C1) UV System Users: Conduct at least two flushings with treated ballast water, if you are near shore, more will be required.

C2) Chlorine/Chlorine Dioxide Systems: Opt for either two flushings with treated water and ensure a holding time of 1-2 hours before discharge or a single flush with a 24-hour holding time of treated water before ballasting again.

By adhering to these comprehensive procedures, the risk of non-compliance will be eliminated.

Contact us Saron Marine Environmental Services to make sure you are indeed in compliance and not just on paper.

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