What is an Oil Spill at Sea: Drills, Prevention And Methods Of Cleanup

Contamination of seawater due to an oil pour, as a result of an accident or human error, is termed an oil spill.

Understanding Oil Spills

Oil is among the most important energy sources in the world and because of its uneven distribution, it is transported by ships across the oceans and by pipelines across the lands. This has resulted in several accidents in the past while transferring the oil to vessels, during transportation, breaking of pipelines, as well as while drilling in the earth’s crust.

While massive and catastrophic spills receive most of the attention, smaller and chronic ones occur on a regular basis. These spills contaminate the coasts and estuaries and can cause serious health problems to human beings.

Oil is a mixture of hydrocarbon compounds, which are the decayed remains of marine animals and plants, died and drifted to the bottom.

For the past 600 million years, under intense pressure and temperatures, these remains changed into complicated hydrocarbons called petroleum.

Crude oil is a mixture of gas, naphtha, kerosene, light gas, and residuals, which causes hazardous health effects if consumed by any life forms.

oil spill

The production of petroleum products rose from 500 million tons in 1950 to over 2,500 million tons in the mid-1990s, which resulted in massive transportation and associated oil spills.

The number has been increasing with the increasing rate of oil transportation, ageing of oil tankers, as well as an increase in the size of oil tankers. Oil accounts for over half the tonnage of all sea cargo.

It is estimated that approximately 706 million gallons of waste oil enter the ocean every year, with over half coming from land drainage and waste disposal; for example, from the improper disposal of used motor oil.

Offshore drilling and production operations and oil spills or leaks from ships or tankers typically contribute less than 8 percent of the total. The remainder comes from routine maintenance of ships (nearly 20 percent), hydrocarbon particles from onshore air pollution (about 13 percent) and natural seepage from the seafloor (over 8 percent).

Public health impacts include illnesses caused by toxic fumes or by eating contaminated fish or shellfish. However, there are other less obvious public health impacts, including losses and disruptions of commercial and recreational fisheries, seaweed harvesting, boating, and a variety of other uses of affected water.

Any nation or tourist destination close to oil drilling or shipping lanes is at high risk of experiencing economic collapse and the disastrous environmental effects of oil spills and needs to be properly prepared to clean up.

To prevent oil spills is the topmost priority; and the responsibility lies equally on individuals as well as on governments and industries because the sources of oil waste in the ocean is due to carelessness, rather than an accident.

Integration of preventive measures in an industrial process, operation, or product should be a part of the cost of daily operations.

Before starting any fueling, de-fueling or internal transfer operation, all machinery and piping systems should be properly checked for tightness and for signs of leaking glands, seals and gaskets.

While changing the oil or adding oil to machinery, proper care should be taken to avoid oil spills.

deepwater horizon
Image for representation purpose only

Largest Oil Spill

Dreadful oil spill results in great damage to the marine environment and sometimes ends up with destroying a complete species.

It is said that the largest known oil spill incident was not an accident but a result of a preplanned war. As per statistics, there was a recorded discharge of billions of gallons of oil from the largest oil spill.

We all are familiar with “the Gulf War” of 1991 in which the forces from Iraq quit their invasion of Kuwait. After that, for blocking the forces from the United States, the Iraqi forces left the oil pipelines and wells of oil open and set it to fire. The fire was so massive that it begins in January and ended after four months in April.

In this incident, as per reports, more than 200 million gallons of oil was thrown in “the Persian Gulf”. This oil spill incident not only harmed marine species but also destroyed major oil reserve in the world, thus diminishing oil availability.

This oil spill not only resulted in marine water pollution but also fouled the coastlines, damaged the fisheries, killed the aquatic life especially non-mobile life and ruined the aesthetics of the place and thus reduced the capital generation from tourism.

It had a long-lasting effect on the marine life of the area. The after-effects of this oil spill were even more terrific, as it even took months to clear the affected area and bring it back to its normal condition.

Due to such destruction caused by this oil spill, it became a burning issue and a matter of grave concern for almost all the countries around the globe.

On the basis of outcome and reasons for these incidents, maritime authorities are becoming more careful in handling oil with the latest technical advancements.

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Oil Spill Drills On Ship

It is generally referred to as fighting Oil Spill on Ship. The ship should be equipped with all required precautionary measures and the crew on the ship should be accustomed to oil spill safety drill prior to the voyage. These safety measures will help in catering accidents which break-in during the voyage without any prior warning.

Before making preparation for the prevention of oil spills or fighting with oil spillage it is essential to know about different types of oil spillage.

These accidents are of two types – in one oil does not go overboard and the other in which oil goes on board.

The later one causes maximum damage so it is considered a dreadful incident as compared to the former one.

There are two most common reasons for oil spills which are as follows:

  • Oil can spill when oil is being transferred internally, that is when oil is passing through a sounding pipe or oil vents
  • Bunker operation is the second major event when oil can spill. It implies that there is more probability of oil spill while discharging sludge

If appropriate equipment is used and the personnel is trained in this concern, we can control marine pollution to a certain extent and for less dangerous events this marine pollution can be completely avoided

Basic training is given to the crew during any oil spill drill:

The basic actions to be followed and checked during any oil spill drill is summed up as below:

  1. The side scuppers of the ship should be shut down immediately when there is seen any oil on deck. Turn the alarm on and bring it to notice of duty officer
  2. The points such as the sounding point or vents where the spillage started should be located and must be looked for its solution. All the processes of oil transfer should also be put off from these points or tanks
  3. Muster list should be prepared in advance and all personnel should be trained for handling spillage. The shipmaster should call the emergency muster when they noticed any spill
  4. The ship should be equipped with SOPEP equipment which can contain the spill within the ship. After collecting all the spilt oil in SOPEP drums, clear the affected area at the earliest
  5. Tanks should be filled within permissible level so as to avoid spills
  6. Scupper plug should be properly tightened, and sometimes sawdust supplements the tightness of plug. This will not let the oil to rush overboard but act as an additional barrier.
  7. After fighting victoriously from the incident of an oil spill, a report should be prepared and discussed in a meeting and preventive measures should be detailed in the meeting to fight and prevent such an incident in future

Additional training on oil spill during sludge discharge or bunkering covers the below checks and actions to be taken:

  1. Bunkering manifold should have a supervising officer to check it for leakage intermittently on short regular intervals. There should be a remote switch which can send an alarm to STOP BUNKER SUPPLY. Put off the sludge transfer operation with immediate effect
  2. Bring oil spillage in the notice of Chief engineer and the officer on duty
  3. Drip tray should be checked regularly for overfilling
  4. Portable foam firefighters should be made available for any discrepancy in case it occurs

Solutions For Oil Spill

The biggest threat to the safe marine environment is “oil spill” from ships.

Every year the government of different countries spend dollars in billions and trillions in inspecting and clearing major oil spills from tanker ships.

Problems of an oil spill can be prevented at a preliminary stage by ensuring proper working of all active hoses and fuel lines, and also all the connections should be leak-proof or tight.

All the safety valves should be in proper working condition so that supply line which leaks can immediately be shut off when spill or leak encounters.

Oil tankers are not cleaned after every voyage, but they are cleaned once a decade or at the time when there is some clogging or other operational issues.

If there is noticed building up of sludge or deposition of water in tanker it should be cleaned immediately otherwise it may result in corrosion of tanker parts or body.

Prevention For Oil Spill

Sometimes, even oil spills of small ships add up to a huge quantity. These fishing vessels, ferries or recreational boats are comparatively smaller in size but are a major cause of pollution.

Spills in small vessels is mainly a result of refuelling activity or bilge discharging operation. During these operations, oil mounts up with water in the bottom part of the vessel and gets pumped out.

Oil spills can be prevented by the following measures:

  1. Engine crew should ensure engine bolts to be properly tight to avert the trickling of oil. When an engine is in use this causes vibration in bolts and results in loosening of bolts. The engine should be equipped with dripping pan or cookie sheet (or oil tray). There should be ample oil absorbent pads to soak discharge of oily water. Defected parts and fittings should be replaced before their complete failure. Lines can fail due to severe heat and water exposures
  2. Measures should be taken while refuelling the tank. The tank should not be overfilled and some clearance space should be left for fuel expansion. Bilge pump should be turned off properly after done with refuelling
  3. If spill transpires it should be maintained by the vessel master. He/she should collect the spilt oil and keep it within the ship and clear the affected area with absorbent pads. A record should be maintained regarding spill and all legal post-spill formalities should be cleared

Methods For Cleaning Sea After Oil Spill

Oil is a necessity and a major revenue-generating resource for many countries with vast oil reserves. Therefore, shipping of oil from the sea can never be put to an end rather we must look for safer expeditions. We must be ready for any emergency related to an oil spill and oil clean up from the sea.

As water is denser than oil, the latter floats when discharged in a water body. It forms a skimming layer over the water surface and therefore it is comparatively easier to decant oil from the sea than other chemical pollutants.

Different methods of cleaning sea after an oil spill are briefed as under:

1. Oil Booms

Oil Booms are the most common and popular equipment used in oil clean-up due to their simpler design and easier execution. These are also called “Containment Booms” which encloses the oil to a smaller area and not let it spread further.

oil boom oil spill
Image for representation purpose only

They have three parts namely: Freeboard; Skirt and Cable or Chain.

Freeboard is the portion which is extended beyond the water surface and thwarts splashing oil above the top.

The skirt is positioned at a place down the water surface and squeezes the oil under the boom and not let it escape or spread.

For stabilization and strengthening of a boom, a cable or chain is provided, until it is completely filled.

Other features of oil booms are as follows:

  • This method is employed when the area of spill is comparatively smaller
  • It is used where the containment booms are locally available because if the boom is to be transported from a faraway site, the spill can expand to a larger area and become difficult to manage
  • Also, it is used in the water where wave velocity is constant because fluctuating tides make it difficult for an oil boom to perform clean up properly

2. Skimmers

Once the oil is bounded by oil booms, it can be extracted or skimmed easily with the help of skimmers or oil scoops. These skimmers are fitted onto boats and remove the floating oil or greasy contaminants.

These are the mechanical equipment that works on the same principle as a vacuum cleaner. It sucks all the oil which is spread over the confined surface of the water in oil booms.

These use physical separation of oil and water and make it available for further use. Other main features of skimmers are as follows:

  • It is an economical method of oil cleanup because the equipment used for skimming oil are relatively cheaper.
  • There is a major loophole in the use of skimmer in oil decantation is that if debris is present in the confined region it can choke or clog the skimmer easily.

3. Sorbents:

The materials which can adsorb or absorb the liquid are termed sorbents. It is an easy process of oil cleanup. The most common sort of sorbents we all are familiar with is peat moss, vermiculite (straw) and hay.

Some other features of sorbents are as follows:

  • These are the materials which result in the least wastage and prevent the progression of pollution
  • These are highly useful for the small spills with the highest efficiency
  • These are also used to remove the small tints of large spill cleanups
  • There is also a difficulty in working with sorbents that are sorbents become denser than water after absorbing oil and may possibly sink to the bottom of the sea

4. Burning:

It is similar to burning rice husk after yielding rice crop. In this method, the floating oil is set to fire by igniting it safely. It is the most proficient method of oil clean up as it can efficiently remove 98% of total spilt oil.

Other features of burning in-situ the spilt oil are briefed as under:

  • It works safely and efficiently for the oil spread with a thickness of 3 millimetres and larger spread
  • This method is not eco-friendly as it releases toxic gases from the burning of oils to the environment

5. Dispersants:

When oil cannot be confined with booms then we are left with the last option of oil disintegration. Dispersals are the chemicals which are spread over spilt oil to initiate disintegration of oil.

After disintegration, the surface area of oil molecules increases and it becomes easier for them to form a bond with water. This will take the bonded molecules deeper in water and make them available for microbes which degrade them later on.

Some additional features of removal of oil from the sea by dispersants are as follows:

  • They can efficiently remove the large oil spills easily. Dispersants convert the oil in tarballs when oil gets bonded chemically with water. But sometimes these tarballs become larger in size and get to the seashore
  • Sometimes these chemical dispersants adversely affect non-mobile marine species

6. Other Methods

Some other methods employed for safer oil spill cleanups from the sea are hot water washing or washing with high-pressure water; manual labour; bioremediation and natural recovery.

Hot water washing is used when it is quite impossible to remove oil from mechanical or manual methods.

With high-pressure sprayers, water at about 170-degree Celsius is sprayed and this hot water at high pressure flush the oil to the water surface and make it available for mechanical equipment such as booms, shovels and skimmers.

In manual labour oil cleanup method, hand-held tools or mechanical equipment are used for oil cleanups. It is a time consuming but an economical method of decanting oil from sea shoreline. Also, the places where other methods seem inaccessible, this method serve victoriously.

Bioremediation method involves removal of oils by application of specific microorganisms. These microorganisms disintegrate the oil complex into simpler molecules whose decomposition and cleaning is easier.

Sometimes fertilizers are used for degrading the oil which may result in other harms to the marine ecosystem. Natural recovery is the simplest as well as no negative effect method of oil spill cleanups.

The major principle underlying this method is the principle of self-cleansing action of rivers which lead to auto removal of oil by evaporation or natural disintegration by aerobic or anaerobic biological organisms.

It is the most eco-friendly and cheaper method amongst all. It is a time-consuming process and employed usually for small oil spills.

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Disclaimer: The authors’ views expressed in this article do not necessarily reflect the views of Marine Insight. Data and charts, if used, in the article have been sourced from available information and have not been authenticated by any statutory authority. The author and Marine Insight do not claim it to be accurate nor accept any responsibility for the same. The views constitute only the opinions and do not constitute any guidelines or recommendation on any course of action to be followed by the reader.

The article or images cannot be reproduced, copied, shared or used in any form without the permission of the author and Marine Insight. 


  1. The article explains the oil clean up procedure, but doe’s not explain the steps to clean up a large Bitumen spill in a ocean environment, I would like to see this question answered in some depth.

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