A ballast water system is essential for the safe operation of a ship, but the operation of these systems causes significant threats to the environment and local economy.
What Is a Ballast Water System?
A ballast water system allows a ship to pump water in and out of very large tanks to compensate for a change in cargo load, shallow draft conditions, or weather.
The capacity of ballast water tanks might be millions of gallons on a large vessel. This allows vessels to carry a light or heavy load while maintaining ideal buoyancy and handling conditions in all situations.
A ship might discharge all ballast water tanks to pass a shallow area or forward tanks only to raise the bow in rough open seas.
Physical components of the system include; raw water intakes, large and small strainers, pumps, distribution pipes, ballast water tanks, treatment system, discharge system, and all the valves, sensors, and controls to run the equipment.
Invasive Species in Ballast Water
Invasive species are a significant threat to ecosystems and the economies of the affected areas. Researchers think that about one-third of all documented invasive plants and animals are able to travel in the ballast water tanks of ships.
Zebra Mussels were introduced into Lake Saint Clair in 1988 when a ship emptied ballast water into the Great Lakes System. The Great Lakes hold nearly twenty percent of the earth’s fresh surface water in a watershed system. The non-native mussels eliminated native varieties once used by industry and have caused an estimated 7 billion dollars (US) in damage by encrusting or clogging underwater equipment essential to industrial and recreational activities.
Sea Lamprey and Spiny Water Fleas are organisms which feed off of host fish or compete with young fish for food. Many species of fish impacted by these invasive species have significant commercial or sporting value. These animals and others can live in fresh or salt water and may spread into inland waterways from saline ports and harbors.
Plants can also travel long distances in ballast water. Eurasian Milfoil is a surface plant which can clog equipment and deter recreation where it forms thick mats. Eurasian Milfoil was introduced to the United States in the 1940s. Because the plant can produce large colonies from only one small fragment it is likely the plant was introduced in the ballast water of a ship.
Resolving Ballast Water Issues
For years amateurs and professional researchers have experimented with a huge array of weapons to combat invasive species in a ship’s ballast water. Most of the difficulty is due to the fact that huge volumes of water must be treated in a reasonably short period of time. Many land-based systems for treating public supplies takes many hours or days to pass water through their treatment systems.