The introduction of invasive marine species into new environments by ships' ballast water has been identified as one of the four greatest threats to the world's oceans. In 2004, IMO adopted the International Convention for the Control and Management of Ships' Ballast Water and Sediments. The Convention will enter into force 12 months after it has been ratified by 30 states representing 35 percent of the world's merchant shipping tonnage. DNV has wide knowledge of and expertise in ballast water management and treatment technologies. As advisors to the shipping industry, DNV has developed decision-support services to help shipowners select the right systems for their ships.
Requirements
The Convention will apply to all ships and offshore structures that carry ballast water and are engaged in international voyages.
The Ballast Water Management (BWM) Convention requires:
- A ship-specific Ballast Water Management Plan approved by the Administration on board
- A Ballast Water Record Book on board
- Ballast water exchange (Regulation D-1)
- An approved ballast water treatment system (Regulation D-2)
- An International Ballast Water Management Certificate.
The Convention stipulates two standards for discharged ballast water. The D-1 standard covers ballast water exchange while the D-2 standard covers ballast water treatment. Depending on the ship's date of construction and ballast water capacity, D-1 will be phased out and replaced by D-2 as shown in the table.
Many treatment systems are now available in the market and, with ratification of the Convention awaiting, shipowners have an excellent opportunity to evaluate how these systems perform before the Convention enters into force. The minimum treatment efficiency required by IMO is outlined in the D-2 standard and type approval is necessary to demonstrate compliance.
However, such approval is no guarantee that the treatment system will perform well in the areas where the ship will trade. A treatment system that is optimal for one vessel may not be the best solution for another. Several countries have also established local restrictions on ships calling into their ports or sailing in waters under their jurisdiction - causing confusion and concern in the market.
The careful selection of a treatment system is also important in order to ensure that the system meets the ship-specific requirements, such as ballast water capacity, power limitations, the integration of control systems, etc. Another important aspect is also to gain insight into the manufacturer's commercial reliability, support network and quality of supply capabilities.
DNV has wide knowledge of and expertise in ballast water management and treatment technologies. As advisors to the shipping industry, DNV has developed decision-support services to help shipowners select the right systems for their ships.
| Solution | Pros | Cons |
| Filters | Self cleaning | Reduced efficiency in high sediments waters Flow rate reduction Pressure drop |
| UV | Efficient | Reduced efficiency in high sediments waters |
| Electrolysts | Onboard disinfection Efficient One-way treatment | Reduced efficiency in water with low salinity |
| Cavitation | Efficient Independent of salinity | Pressure drop |
| Chemical injection | Low cost | Safety Storage Corrosion |
| Ozonation | Efficient Independent of salinity One-way treatment | Corrosion Safety |
| De-oxygenation | Corrosion Easy installation | Lower efficiency Maintenance of IG system Holding time High fuel cost of producing IG |
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