Ballast Water Management System (BWMS)

A ballast water management system treats ballast water to meet the D-2 discharge standard of the Ballast Water Management Convention, which caps the concentration of viable organisms in defined size classes to limit the spread of invasive species. Systems use combinations of filtration with ultraviolet irradiation or electrochlorination and must be type-approved under the BWMS Code, IMO Resolution MEPC.300(72), including testing against the more demanding US Coast Guard requirements for ships trading to US waters. Each ship carries a ballast water management plan and a record book.