Ballast Water & BWMS
Ballast Water is water a ship takes into dedicated tanks to maintain stability, trim and safe draft when it is lightly loaded or has discharged cargo, and pumps out again as it loads. Managing ballast is essential to keeping the vessel safe and correctly trimmed.
Because ballast water taken on in one port and discharged in another can carry invasive marine species and pathogens, the IMO's Ballast Water Management Convention now requires ships to treat their ballast using an approved Ballast Water Management System (BWMS) — using filtration and UV or chemical treatment — before discharge. Compliance involves the BWMS itself, a ballast water management plan, and record-keeping that is checked at survey and by port state control.
Ballast keeps a ship safe when it isn't full of cargo — but unmanaged, it has moved invasive species around the world for decades. The BWM Convention made treatment mandatory, so operators now run and maintain a BWMS and keep the records to prove compliance. It is both a safety fundamental and a live regulatory obligation.
Why do ships carry ballast water?
To maintain stability, trim and safe draft when lightly loaded or after discharging cargo.
What is a BWMS?
A Ballast Water Management System — approved equipment (filtration plus UV or chemical treatment) that treats ballast water before discharge to meet the BWM Convention.