MARPOL Annex I - OWS Sizing (15 ppm Bilge Separator)
Required oily water separator capacity from machinery space bilge water generation rate and ship operational profile.
Formula, assumptions, limits
OWS capacity in m³/h sized so that the daily bilge water generation can be processed within the contingency hours available. Reserve factor 1.5 to 2.5 typical to allow for variability and equipment downtime. Type approval under MEPC.107(49) for new installations or MEPC.60(33) for older. The OWS must include 15 ppm alarm and three-way valve. Discharge through ship’s side only when oil content below 15 ppm with continuous monitoring; otherwise return to bilge tank or transfer to slop tank.
Symbol legend
SymbolMeaningUnitSource
Required OWS capacitym³/hcomputed Daily bilge waterm³/dayoperations Reserve factormultiplieroperator policy Available processing hours/dayh/daywatchkeeping
In short
Required oily water separator capacity from bilge water generation.