Ballast water management in ships

Ballast water systems of ships are used for receiving and pumping out water in order to equalise the heel and trim, as well as to increase or decrease the draft, thus ensuring the required seaworthiness of the ship. The ballast water tanks carry various species of marine organisms through the oceans every day, some of which survive, causing the spread of invasive species. According to the IMO BWM (Ballast Water Management) Convention, which came into effect in September 2017, all ships are required to have ballast water treatment devices and systems installed in in order to prevent the spread of such microorganisms.

Cruise ships, large tankers, and bulkers need large quantities of ballast water, which is usually supplied to a ship from the coastal waters of a region after it has discharged wastewater or unloaded cargo and is then released in the region where the cargo is loaded. Ballast water discharges typically contain a wide range of biological material, from plants, animals, viruses, and bacteria. This material often holds non-native, invasive species that can cause significant ecological and economic damage to aquatic ecosystems, as well as posing serious human health problems, therefore, to protect against such dangers, ballast water treatment systems need to be installed on ships.

By 2024, the ballast water management (discharge and/or intake) systems of all existing and newly built ships must comply with the D2 standard of the Ballast Water Management Convention. This means that the maximum permissible limit of living organisms discharged with the water, including certain indicator microorganisms harmful to human health, is regulated and as a result, all ships have to be equipped with ballast water management systems.

It has been found that ozone (O3) is one of the most powerful and fastest-acting oxidizers for oxidizing bacteria present in water, including moulds, yeasts, organic material, and viruses. Ozone is a colourless oxidizing biocide that has a distinct odour and occurs naturally in the earth’s atmosphere. It has very unstable properties and decomposes rapidly when injected into water.