Challenging water quality conditions MEPC.387(81) aims to address operational challenges encountered by a vessel fitted with a type-approved, properly installed and maintained ballast water management system (BWMS) when the ship is operating in challenging water quality (CWQ) conditions*. The guidance includes: Recommended steps to identify when a BWMS is inoperable owing to CWQ Actions to avoid bypass of the BWMS Steps to recover from bypass, including actions to return to compliance with the D-2 discharge standard Planning, record-keeping and communication principles. *Challenging water quality (CWQ) refers to ambient uptake water having quality parameters (including but not limited to high total suspended solids, or turbidity) that cause a properly installed, maintained and operated type-approved BWMS to be temporarily inoperable due to an operational limitation or an inability to meet operational demand. However, temperature and salinity are not parameters that define CWQ.
https://www.lr.org/en/knowledge/class-news/14-24/