SOLAS-International Convention for the Safety of Life at Sea, 1974

The operational and construction regulations introduced by MARPOL, which entered into force in 1983, have been a success, with statistics from reputable industry and independent bodies showing that these regulations, along with other safety-related regulations such as the introduction of mandatory traffic separation schemes and international standards for seafarer training, have been instrumental in the continuous decline of accidental oil pollution that has taken place over the last 30 years.

The MARPOL convention, in 1983, introduced a number of radical new concepts, such as a requirement for new oil tankers to be fitted with segregated ballast tanks, so as to obviate the need to carry ballast water in cargo tanks. This was superseded by the requirement for oil tankers delivered from 1996 onwards to be fitted with a double hull. The protection of the marine environment was thus greatly enhanced.

As far as operational oil pollution is concerned, the many innovations introduced by MARPOL on allowable discharges of bilge water through the oily water separator (with the well-known 15ppm standard), or oily waters from the cargo tanks, through the oil discharge and monitoring system, have contributed greatly to a noticeable decrease in the pollution of the world’s seas, though it is fair to recognise that a greater effort to impose compliance must be carried out.

Regulation 15 - Control of discharge of oil 
A Discharges outside special areas

Any discharge into the sea of oil or oily mixtures from ships of 400 gross tonnage and above shall be prohibited except when all the following conditions are satisfied:

1. the ship is proceeding en route;
2. the oily mixture is processed through an oil filtering equipment meeting the requirements of regulation 14 of this Annex;
3. the oil content of the effluent without dilution does not exceed 15 parts per million;
4. the oily mixture does not originate from cargo pump-room bilges on oil tankers; and
5. the oily mixture, in case of oil tankers, is not mixed with oil cargo residues.

B Discharges in special areas

Any discharge into the sea of oil or oily mixtures from ships of 400 gross tonnage and above shall be prohibited except when all of the following conditions are satisfied:

1. the ship is proceeding en route;
2. the oily mixture is processed through an oil filtering equipment meeting the requirements of regulation 14.7 of this Annex;
3. the oil content of the effluent without dilution does not exceed 15 parts per million;
4. the oily mixture does not originate from cargo pump-room bilges on oil tankers; and
5. the oily mixture, in case of oil tankers, is not mixed with oil cargo residues.
6. In respect of the Antarctic area, any discharge into the sea of oil or oily mixtures from any ship shall be prohibited.

Nothing in this regulation shall prohibit a ship on a voyage only part of which is in a special area from discharging outside a special area in accordance with paragraph 2 of this regulation.

C Requirements for ships of less than 400 gross tonnage in all areas except the Antarctic area

In the case of a ship of less than 400 gross tonnage, oil and all oily mixtures shall either be retained on board for subsequent discharge to reception facilities or discharged into the sea in accordance with the following provisions:

1. the ship is proceeding en route
2.  the ship has in operation equipment of a design approved by the Administration that ensures that the oil content of the effluent without dilution does not exceed 15 parts per million;
3. the oily mixture does not originate from cargo pump-room bilges on oil tankers; and.4the oily mixture, in case of oil tankers, is not mixed with oil cargo residues.

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SOLAS-International Convention for the Safety of Life at Sea, 1974