Video: How is Waste Oil Treated Onboard Ships?

A vast amount of waste oil is generated by ships, which use different oils for machinery operations. The waste oil can come from various sources, such as engine lubrication, fuel consumption, and other mechanical processes.

However, the ship has limited tanks to store it.

Ships don't throw or pump the oil overboard. It is unlawful to do so and could lead to hefty fines and imprisonment of the crew members.

Instead, the waste oil is segregated in sludge and bilge, as ships have dedicated sludge and bilge tanks.

Bilge and Sludge are a mixture of oil and water, the only difference being that bilge has less quantity of oil while sludge has more oil in it.

Many tanks on ships carry different types and grades of oil. They are usually provided with a heating arrangement to keep the oil's viscosity at a limit and separate water from it.

These tanks have drains from where the heavy water, which settles in the bottom, can be drained, separated and sent to bilge tanks.

The fuel is further treated in the centrifugal separator, where additional impurities in the form of sludge and water are separated and sent to the sludge tank.

Similarly, all machinery leakages are sent to the bilge or sludge tank, depending upon the quantity of oil the leakage mixture contains.

The bilge water can be treated in onboard equipment called an oily water separator (OWS). It filters the water as it passes through different stages of filtration.

These stages are designed to separate the oil and water based on their densities.

The second stage is again provided with a fine filter to remove more oil from the output of the first stage so that the output from this unit should be less than 15 ppm to fulfil legal discharge criteria.

The separated oil is collected and properly disposed of, while the clean water is released into the environment. This process ensures that the ship's waste oil is appropriately managed and does not harm the ecosystem.

Thus, managing waste oil onboard is a complex yet important process that must be carried out periodically to protect the oceans and seas from being polluted.

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Zahra is an alumna of Miranda House, University of Delhi. She is an avid writer, possessing immaculate research and editing skills. Author of several academic papers, she has also worked as a freelance writer, producing many technical, creative and marketing pieces. A true aesthete at heart, she loves books a little more than anything else.