Why do ships carry ballast water?
Ships are designed and built to move through water carrying cargo, such as oil, grains, containers, machinery and people. If the ship is travelling without cargo, or has discharged some cargo in one port and is on route to its next port of call, ballast may be taken on board to achieve the required safe operating conditions. This includes keeping the ship deep enough in the water to ensure efficient propeller and rudder operation and to avoid the bow emerging from the water, especially in heavy seas. Water has a good weight-to-volume ratio and is carried in separate tanks used just for ballast, or in empty cargo tanks. When a vessel is departing a port, water and any sediment that may be stirred up, is pumped into the ballast tanks and released again when it takes on cargo at the next port. To prevent large foreign objects from entering the ship with the ballast water, ships’ sea chests are covered with grates. Safety, weather conditions, a ship’s load, and the route taken are the prim
