According to MARPOL, what is the maximum allowed oil content in ballast water?

Under MARPOL Annex I, the maximum allowable oil content in the discharge of ballast water is set at 15 parts per million (ppm). This regulation is a part of international efforts to combat marine pollution from ships, specifically concerning oil discharges. The limit is designed to protect marine environments from potential harmful effects caused by oily water discharges, which can severely impact aquatic ecosystems.

Ballast water is often mixed with oil residues due to the operation of ship machinery and equipment. Therefore, ensuring that the oil content in discharged ballast water does not exceed 15 ppm significantly helps to minimize pollution. Ships are required to have oil filtering equipment to ensure compliance with this regulation, thereby promoting safer environmental practices in shipping operations.

The other options represent levels that do not align with the MARPOL standards. While some may seem to be reasonable limits, only the 15 ppm threshold is officially recognized and enforced under MARPOL guidelines for the discharge of oil-contaminated water from ships.