Which vessels must be equipped with an Oily Water Separator (OWS)?

Oily Water Separators (OWS) are essential equipment on vessels to manage bilge water that may contain oil. The correct requirement pertains to vessels over 400 gross tonnage, as mandated by various international conventions, including MARPOL Annex I. This standard is set to ensure that larger vessels, which may produce significant amounts of oily bilge water due to their size and operations, are equipped with effective means to treat the water before discharge, thus minimizing pollution.

Vessels over 150 gross tonnage are indeed subject to regulations; however, the specific requirement for OWS primarily applies to those over 400 gross tonnage to account for the environmental risk associated with larger vessels. Tankers and fishing vessels have additional regulations but do not specifically dictate that an OWS must be installed solely based on their gross tonnage. Thus, the stipulation clearly indicates that it is the larger vessels, beyond 400 gross tonnage, that need this particular equipment to comply with international regulations aimed at protecting marine environments.