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Oil SpillByDr.Amer Abdel RazikOil SpillMajor oil spills attract the attention of the public and the mediaGulf of Mexico oil spillExxon Valdez oil spillThis attention has created a global awareness of the risks of oil spills and the damage they do to the environment

260,000 barrels the Exxon Valdez spilled in Alaskas Prince William Sound in 19893Oil SpillOil spill is categorized as:Off shoreMore hazardous but relatively easier to cleanOnshore and land spillsLess hazardous but difficult to cleanThe average cost of cleanup worldwide ranges from $20 to $200 per liter, depending on the type of oil and where it is spilled

4The tanker Burmah Agate catches fires after colliding with another ship. (International Maritime Organization).

Properties of OilThe main physical properties which affect the behaviour and the persistence of an oil spilled at sea are:1- specific gravity, 2-distillation characteristics, 3- viscosity 4- and pour point. All are dependent on chemical composition (e.g. the amount of asphaltenes, resins and waxes which the oil contains).Weathering ProcessesThe processes included in weathering are evaporation, emulsification, natural

dispersion, dissolution, photooxidation, sedimentation, adhesion to materials, interactionwith mineral fines, biodegradation, and the formation of tar ballsBehaviour of Oil in the Environment

A schematic representation of the fate of a crude oil spill showing changes in the relative importance of weatheringprocesses with time - the width of each band indicates the importance of the processOil with a low specific gravity (high API) tend to contain a high proportion of volatile components and to be of low viscosity

When medium and light oils spread unhindered, the oil will eventually form very thin films. These appear as iridescent (rainbow) and silver sheens, which dissipate rapidly

Appearance, spreading, and evaporation loss of various oils spilled on an absorbent surface and in a beaker.Comparison of spreading of different oils and fuels.

When oil becomes mixed with sediment, the density canbecome sufficiently high for it to sink if it is washed off thebeach. In this photo, large patches of sunken oil are visible inshallow water close to the beach.

Oils spilled into the sea at temperatures below their pour pointform solid fragments. This photo shows Nile Blend crude, pourpoint +33o C, in sea water of 28o C. Such oils are highlypersistent and have the potential to travel great distances

EmulsificationThe dissipation of many oils is slowed by the formation ofhighly viscous water-in-oil emulsio

Water-in-oil emulsions often accumulate on shores in

Emulsified oil is very viscous and dense

A greatly magnified image (x1,000) of a water-in-oil emulsion showing individual water droplets surrounded by oil.

Typical rates of viscosity increase in moderate to rough seas. The viscosity of Group 1 oils never exceeds 100cSt and so is not shown.

The volume of oil and water-in-oil emulsion remaining on the sea surface shown as a percentage of the original spill volume(100%). The curves represent an estimated average behaviour for each group. The behaviour of a particular crude oil may differfrom the general pattern depending on its properties and environmental conditions at the time of the spill.Oil Spill CleanupThe average cost of cleanup ranges from $20 to $200 per literThe first response to oil spill is containment of the spill to avoid spread of the oilFor offshore oil spills, combination of the following methods are used for clean up:BoomsSkimmersChemical DispersantsIn-situ burningBioremediationThe effectiveness of any cleaning method depends on ocean currents and tides, as well as the weather22BoomsBooms are floating barriers used for the confining the spilled oil either to:Prevent it from spreading to a particular areaDivert it to another area where it can be recovered or treatedConcentrate the oil so it can be recovered, burned or otherwise treated.

23SkimmersSkimmers are mechanical devices designed to remove oil from the water surfaceSurface skimmersVacuum skimmersOil-sorbents

24DispersantsDispersing agents are surfactants used to promote formation of small oil droplets that disperse throughout the top layer of waterTheir effectiveness and environmental impact are controversial

25In-situ BurningControlled burning of oil at or near the spill siteRate of burning 3-4 mm/min 5000 Liter/m2/dayDisadvantagesRequires at least 2-3 mm thick oil slackToxic emissions

26BioremediationBiological methods involve microbiological biodegradation Addition of natural materials to contaminated environment to accelerate the natural biodegradation process

27Oil SorbentsSorbents are materials that recover oil through either absorption or adsorption Sorbents come in many different forms:Loose materials to pads or even boomsThey are used in the following ways:To clean up the final traces of oil spills on water or landAs a backup to other containment means, such as sorbent boomsAs a primary recovery means for very small spills

28Sorbents for Oil spill Removal29Sorption CapacitySorption capacity depends on: Sorbent Actual and bulk densityHydrophobicitySurface areaPore size distribution

Oil DensityViscosityCompositionTemperature

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