Oily Water Separator (marine)

An oily water separator (OWS) (marine) is a piece of equipment specific to the shipping or marine industry. It is used to separate oil and water mixtures into their separate components. This page deals exclusively oily water separators aboard marine vessels. They are found on board ships where they are used to separate oil from oily waste water such as bilge water before the waste water is discharged into the environment. These discharges of waste water must comply with the requirements laid out in Marpol 73/78. For information on more general oil water separators Oily Water Separators (general).

Bilge water is a near-unavoidable product of shipboard operations. Oil leaks from running machinery such as diesel generators, air compressors, and the main propulsion engine. Modern OWSs have alarms and automatic closure devices which are activated when the oil storage content of the waste water exceeds a certain limit.

The primary purpose of a shipboard oily water separator (OWS) is to separate oil and other contaminants that could be harmful for the oceans. The International Maritime Organization (IMO) publishes regulations through the Marine Environment Protection Committee (MEPC). On July 18, 2003, the MEPC issued new regulations that each vessel built after this date had to follow. This document is known as MEPC 107(49) and it details revised guidelines and specifications for pollution prevention equipment for machinery space bilges of ships. Each OWS must be able to achieve clean bilge water under 15 ppm of type C oil or heavily emulsified oil, and any other contaminates that may be found. All oil content monitors (OCM) must be tamper-proof. Also whenever the OWS is being cleaned out the OCM must be active. An OWS must be able to clear out contaminants as well as oil. Some of these contaminating agents include lubricating oil, cleaning product, soot from combustion, fuel oil, rust, sewage, and several other things that can be harmful to the ocean environment.

The bilge area is the lowest area on a ship. The bilge water that collects here include drain water or leftover water from the boilers, water collecting tanks, drinking water and other places where water can not overflow. However, bilge water doesn't just include water drainage. Another system that drains into the Bilge system comes from the propulsion area of the ship. Here fuels, lubricants, hydraulic fluid, antifreeze, solvents, and cleaning chemicals drain into the engine room bilges in small quantities. The OWS is intended to remove a large proportion of these contaminants before discharge to the environment (overboard to the sea).

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