Ballast water treatment systems are being rendered inoperable in some ports where the local water quality is challenging.

Documents submitted to the International Maritime Organization show that the systems are facing problems primarily in ports, where the water has heavy sedimentation that gums up filters or hampers ultraviolet light treatment.

The situation comes as the global fleet is midway through a phased schedule in which shipowners are required to install ballast water systems in a bid to protect marine ecosystems from invasive species.