Ballast Water ManagementSaturday, 1st October 2016
Since the introduction of steel-hulled vessels around 120 years ago, water has been used as ballast to stabilize vessels at sea. Ballast water is pumped in to maintain safe operating conditions throughout a voyage. This practice reduces stress on the hull, provides transverse stability, improves propulsion and manoeuvrability, and compensates for weight changes in various cargo load levels and due to fuel and water consumption.
In ancient times, ships used to carry solid ballast for stability as the cargo was minimal or there was no cargo to be carried. However, as time passed difficulties were faced during loading and discharging of solid cargo. The process of transferring of solid cargo was also time-consuming and for this reason solid ballast was replaced by water ballast. As sea water was readily available and in huge amount, it was used for the ballasting and de-ballasting process.
Ballasting or de-ballasting is required when the ship is to enter a channel, cross any canal like Panama Canal and Suez Canal, during loading or unloading of cargo, and when a ship is going to berth.
When no cargo is carried by the ship, the latter becomes light in weight, which can affect its stability. For this reason, ballast water is taken in dedicated tanks in the ship to stabilize it. Tanks are filled with ballast water with the help of high capacity ballast pumps and this process is known as Ballasting.
However, when the ship is filled with cargo, the stability of the ship is maintained by the weight of the cargo itself and thus there is no requirement of ballast water. The process of taking out ballast water from the ballast tanks to make them empty is known as de-ballasting.
While ballast water is essential for safe and efficient modern shipping operations, it may pose serious ecological, economic and health problems due to the multitude of marine species carried in ships’ ballast water. These include bacteria, microbes, small invertebrates, eggs, cysts and larvae of various species. The transferred species may survive to establish a reproductive population in the host environment, becoming invasive, out-competing native species and multiplying into pest proportions.
Scientists first recognized the signs of an alien species introduction after a mass occurrence of the Asian phytoplankton algae Odontella (Biddulphia sinensis) in the North Sea in 1903. But it was not until the 1970s that the scientific community began reviewing the problem in detail. In the late 1980s, Canada and Australia were among countries experiencing particular problems with invasive species, and they brought their concerns to the attention of IMO’s Marine Environment Protection Committee (MEPC).
The problem increased as trade and traffic volume expanded over the last few decades, and in particular with the introduction of steel hulls, allowing vessels to use water instead of solid materials as ballast. The effects of the introduction of new species have in many areas of the world been devastating. Quantitative data show the rate of bio-invasions is continuing to increase at an alarming rate. As the volumes of seaborne trade continue overall to increase, the problem may not yet have reached its peak.
The spread of invasive species is now recognized as one of the greatest threats to the ecological and the economic well being of the planet. These species are causing enormous damage to biodiversity and the valuable natural riches of the earth upon which we depend. Direct and indirect health effects are becoming increasingly serious and the damage to the environment is often irreversible.
For some examples of aquatic bio-invasions causing major impact please click here. It should be noted, however, that there are hundreds of other serious invasions, which have been or are in the process of being recorded around the world.
BWM Convention status
The International Convention for the Control and Management of Ships’ Ballast Water and Sediments (BWM Convention) will enter into force on September 8, 2017, in an attempt to halt the spread of invasive aquatic species.
The Convention will require all ships to implement a ballast water management Plan. All ships will have to carry a Ballast Water Record Book and will be required to carry out ballast water management procedures to a given standard.