Oil Spills

Oil is the most common pollutant in the oceans.

More than 3 million metric tons of oil contaminate the sea every year.

The majority of oil pollution in the oceans comes from land.

Run off and waste from cities, industry, and rivers carries oil into the ocean.

Ships cause about a third of the oil pollution in the oceans when they wash out their tanks or dump their bilge water.

Human impact of oil spills

• An oil spill represents an immediate fire hazard.

• Spilled oil can also contaminate drinking water supplies.

• Contamination can have an economic impact on tourism and marine resource extraction industries.

Effects on Environment

• Oil floats on top of water, less light penetrates into the water, limiting the photosynthesis of marine plants and phytoplankton.

• Oil spills reduce oxygen absorption of the water, causing oxygen dissolution under oil spills to be even less than the deep sea levels.

• It causes sediments adherence to the sea floor, destabilizing plants.

• The oil penetrates and opens up the structure of the plumage of birds, reducing its insulating ability, and makes the birds more vulnerable to temperature fluctuations and less buoyant in the water.

• It also impairs birds' flight abilities, making it difficult or impossible to forage and escape from predators.

• Suspended oil can gain weight by bonding with minerals and settle on the sea floor and harm the ecosystem there.

• Algae and other local plants have been reported to be eradicated. Animals that come in touch with high concentrations of oil die of oil poisoning.

• Worms, microorganisms and young sea creatures are more sensitive. Humans and other animals living near the sea are also threatened.

•  Among these compounds, aromatic hydrocarbons that low boiling point are more dangerous, such as benzene, toluene and xylene. Naphthalene and Phenanthrene are more poisonous for fishes.

Effects on Marine Life

• Aromatic compounds are more soluble in water than saturated hydrocarbons; therefore creatures may become poisoned without direct contact with the oil by the polluted water.

• Fortunately these compounds are volatile; their harmful effects will decrease with time.

Density

• When oil leaks or spills into water it floats on the surface of both freshwater and saltwater.

• Oil floats because it is less dense than water.

• Oil has a density of 0.85 g/cm³ and seawater has a density of 1.02 g/cm³

• When these two liquids are mixed together, the denser seawater forms a layer underneath the less dense oil.

• It’s much easier to clean-up an oil spill because of oil’s lower density.

Clean-Up Methods

1. Chemical Methods:• Dispersants.

2. Physical Methods:• Burning

3. Biological Methods:• Bioremediation

4. Mechanical Methods:• Booms.• Sorbents.• Skimmers.

ChemicalMethods

Dispersants• Chemicals, such as detergents, break apart

floating oil into small particles or drops so that the oil is no longer in a layer on the water’s surface.

• These chemicals break up a layer of oil into small droplets.

• These small droplets of oil then disperse or mix with the water.

• The problem with this method is that dispersants often harm marine life and the dispersed oil remains in the body of water where it is toxic to marine life.

PhysicalMethods

Burning

• Burning of oil can actually remove up to 98% of an oil spill.

• The spill must be a minimum of three millimetres thick and it must be relatively fresh for this method to work.

• There has been some success with this technique in Canada.

• The burning of oil during the Gulf War was found not as large a problem as first thought because the amount of pollution in the atmosphere did not reach the expected high levels.

• Field-testing is needed to check the feasibility of this technology.

Biological Methods

Bioremediation

• There are bacteria and fungi that naturally break down oil.

• This process is usually very slow- it would take years for oil to be removed by microorganisms.

• Adding either fertilizer or microorganisms to the water where the spill is located can speed up the breakdown process.

• The fertilizer gives the bacteria and fungi the nutrients they need to grow and reproduce quicker.

• Adding microorganisms increases the population that is available to degrade the oil.

• A drawback to adding fertilizers is that it also increases the growth of algae.

• When the large numbers of algae die they use up much of the oxygen & hence there isn’t enough oxygen for animals like fish.

MechanicalMethods

Booms• It’s easier to clean-up oil if it’s all in one spot, so

equipment called containment booms act like a fence to keep the oil from spreading or floating away.

• Booms float on the surface and have three parts:

i. A ‘freeboard’ or part that rises above the water surface and contains the oil and prevents it from splashing over the top.

ii. A ‘skirt’ that rides below the surface and prevents the oil from being pushed under the booms and escaping.

iii. A cable or chain that connects, strengthens, and stabilizes the boom.

iv. Connected sections of boom are placed around the oil spill until it is totally surrounded and contained.

Sorbents• These are materials that soak up liquids by either absorption or adsorption.

• Oil will coat some materials by forming a liquid layer on their surface (adsorption).

• This property makes removing the oil from the water much easier.

• This is why hay is put on beaches near an oil spill or why materials like vermiculite are spread over spilled oil.

•One problem with using this method is that once the material is coated with oil, it may then be heavier than water.

•Then you have the problem of the oil-coated material sinking to the bottom where it could harm animals living there.

•Absorbent materials, very much like paper towels, are used to soak up oil from the water’s surface or even from rocks and animal life on shore that becomes coated with oil.

Mechanical Method-

Skimmers

• Once you’ve contained the oil, you need to remove it from the water surface.

• Skimmers are machines that suck the oil up like a vacuum cleaner, blot the oil from the surface with oil-attracting materials, or physically separate the oil from the water so that it spills over a dam into a tank.

• Much of the spilled oil can be recovered with skimmers

• The recovered oil has to be stored somewhere though, so storage tanks or barges have to be brought to the spill to hold the collected oil.

• Skimmers get clogged easily and don’t work well on large oil spills or when the water is rough.

Types of skimmers

• Oil skimmers are commonly found in three types:

1.Weir

2.Oleophilic

3.Non- Oleophilic

Weir skimmers• Weir skimmers function by allowing the oil floating on the surface of the water to flow over a weir. • The height of the weir may be adjustable. • These devices will collect water when oil is no longer present. • Weir skimmers are also available in floating, self-adjusting variations. • These models allow them to be effectively used even in changing water levels.

Weir Skimmer

Oleophilic skimmers • Oleophilic skimmers function by using a rotating

element such as a drum, to which the oil adheres. • The oil is wiped from the surface of the drum and

collected. • They are very efficient and do not pick up any

appreciable amounts of water even when oil is not present. 

• Oleophilic skimmers are distinguished not by their operation but by the component used to collect the oil.

• Ropes, discs, or drums are treated with a substance or otherwise manufactured to adhere to oil.

Non- Oleophilic skimmers

• Non-oleophilic skimmers are distinguished by the component used to collect the oil. • A metal disc, belt or drum is used in applications

where an oleophilic material is inappropriate, such as in a hot alkaline aqueous parts washer.• The skimmer is generally turned off whenever

there is no oil to skim thus minimizing the amount of water collected. • Metal skimming elements are nearly as efficient

as oleophilic skimmers when oil is present.

Thank-You

Project By:Shagun Ramola

Class: XI-AK.V. No.1, Harni road, Vadodara.