Bilge Water on board ships
The bilge of a vessel is the lowest compartment on a vessel. This is where bilge water collects. It may result from condensate, rough seas, rain, leaks in the hull or stuffing box, or other interior spillage. The collected water may contain various contaminants including oil and lubricants and must be pumped out periodically when the bilge holding tank gets filled.
Discharge of bilge liquids may be restricted and for commercial vessels is regulated in international waters under jurisdiction of the International Maritime Organization (IMO) through the regulation Marpol Annex I. IMO Resolution MEPC.107 (49) requires for treated bilge water overboard discharge that it does contains no more than 15 parts per million (ppm) oil content .
Other regulations require even stricter discharge standards like e.g. the voluntary DNV-GL Clean Design that stipulates a maximum 5 ppm of oil content remaining in the water after treatment, prior to pumping overboard.
Bilge Water treatment on board ships
There are a number of process technologies available to treat bilge water, each with its own advantages and disadvantages. The most commonly used process technology is based on gravity and filtration, such as our OWS-COM. The technology is based on a strictly physical/mechanical process and therefore does not require the use of chemicals. Gravity & filter systems are therefore relatively straight-forward to use and maintain. The advantage of these systems is the minimal effort required for start up, annual maintenance is realtively small and the technology is suitable for a wide range of vessels.