DNV provides guidance on oily water separators

An oily water separator (OWS), bilge separator or oil filtering equipment is required by MARPOL Annex I, Regulation 14 to be installed on any ship above 400 GT. The equipment shall be of a design approved by the administration and tested and installed according to guidelines in MEPC.107(49) as amended by MEPC.285(70).

There are two different sampling points mentioned in MEPC.107(49):

• For future inspections
• For the bilge alarm

Sampling points for future inspection:

As mentioned in Technical and Regulatory News No. 15/2023, paragraph 6.1.1 of MEPC.107(49) requires that “for future inspection purposes on board ship, a sampling point should be provided in a vertical section of the water effluent piping as close as is practicable to the 15ppm Bilge Separator outlet”.

Sampling points for the bilge alarm:

For the sampling point for extracting samples to the bilge alarm, paragraph 6.2.2 of MEPC.107(49) requires that “the arrangement on board ship for the extraction of samples from the 15 ppm Bilge Separator discharge line to the 15 ppm Bilge Alarm should give a truly representative sample of the effluent with an adequate pressure and flow”.

Hence, the requirement to install the sampling point in a vertical section of the effluent pipe applies to the sampling point for inspection only and does not apply to the sampling point for extracting samples to the bilge alarm. For the latter sampling point, the applicable installation requirements by the manufacturer of the oily water separator / bilge separator shall be followed to ensure a representative sample of the effluent with adequate pressure and flow.

Possible locations of these two sampling points are shown below as adapted from Figure 1 of MEPC.107(49). A loop may be installed at the bilge separator outlet to comply with the requirement stating that the sampling point for inspection purposes should be a vertical section of the effluent pipe.