Globally, it is estimated that about 10 billion tonnes of ballast water is transferred each year. The water taken onboard for ballasting may contain aquatic organisms, including dormant stages of microscopic toxic aquatic plants, which can cause harmful algal blooms upon release. Additionally, pathogens such as bacteria have been transported with ballast water.
As ships now travel faster, the survival rate of species carried in ballast tanks has increased. Studies show that many species of bacteria, plants, and animals can survive in ballast water even after journeys lasting several months.
As a result, non-indigenous organisms have often been introduced into new environments, sometimes with disastrous consequences for the local ecosystem, including the destruction of important fish stocks or rare species.
Thus, ballast water treatment is essential and necessary to prevent ecological damage and protect marine biodiversity.
The International Maritime Organization (IMO) has introduced regulations guiding Ballast Water Treatment (BWT) under the Ballast Water Management Convention, which was adopted on 13 February 2004 and entered into force 12 months later.
Currently, more than 20 Ballast Water Management Systems (BWMS) have been approved by flag administrations. These systems use various treatment methods, including:
- Filtration and UV radiation
- Chemical disinfection
- Deoxygenation
- Heat treatment
- Electrolysis and ozone treatment
These methods are selected based on ship type, trade route, and compliance with IMO type-approval standards.
- Flag State Responsibilities:
- Ensure that ships flying its flag comply with the Ballast Water Management Convention.
- Verify that ships are equipped with approved BWMS.
- Issue the necessary certificates and conduct inspections for compliance.
- Port State Responsibilities:
- Monitor and inspect foreign ships calling at their ports for compliance with ballast water management procedures.
- Enforce the convention through sampling, testing, and detaining non-compliant vessels.
- May also impose penalties for violations.