Bioremediation of oil spills

Submitted by-Anchal Garg Environment Science2016

Oil spills• Oil spills occur frequently throughout the world. There are

both inland and oceanic spills. • Oil spills require quick action so that they cause as little

damage as possible. • According to the Environmental Protection Agency (EPA),

“oil releases threaten public health and safety by contaminating drinking water, causing fire and explosion hazards, diminishing air and water quality, compromising agriculture, destroying recreational areas, wasting nonrenewable resources, and costing the economy millions of dollars” (2006).

Methods• The methods chosen to clean up an oil spill are determined

based upon the type of oil spilled, the location and its proximity to sensitive environments, and other environmental factors.

Mechanical methods- booms, skimmers, and truck vacuums. Chemical methods- dispersants, surface washing agents, and

surface collecting agents. Biological methods -use of microbiological cultures, enzyme

additives, and nutrient additives to increase the rate of biodegradation of the contaminants.

Natural methods - another course of action. Simply allows the area to recover naturally and is cheaper than any other method.

Bioremediation• The use of microorganisms, fungi or bacteria, to decompose

pollutants into simpler compounds is called bioremediation. • Microbes breaking down different substances into water,

carbon dioxide, and other compounds .• The prime goal of bioremediation is to create an optimal

environment for the microbes to degrade pollutants. • Bioremediation is a cost effective alternative but is a very

slow process, sometimes taking weeks to months for results.• An advantage of bioremediation is that the microbes are able

to completely destroy the toxic hydrocarbon compounds and do not just transfer them to another area.

Enhancement of bioremediation

1. Addition of oxygen,2. Nutrient addition (Bio stimulation),3. Using alternative electron acceptor,4. Addition of surfactants,5. Addition of microorganisms (Bio

augmentation).

Bio augmentation• addition of microbes to supplement the current population to

degrade oil and other hydrocarbons.• This is usually not necessary, since these microbes are present in

nearly every location. • In order to utilize microbes, it is first essential to find which types

of microbes are capable of degrading oil and determine their nutrient and environmental requirements.

• There are 70 genera of microbes that are known to degrade hydrocarbons.

• The degradation of oil will only occur if the other requirements are met, such as available nutrients and the proper environment temperature.

Several genera of oil-degrading bacteria :- Flavobacterium and Cytophoga sp., Pseudomonas sp., Xanthomonas sp., Alcaligenes sp., and Arthrobacter sp.

Bacteria :- strains of Pseudomonas aeruginosa, Pseudomonas stutzeri, and Bacillus subtilis

Bio stimulation• addition of nutrients to aid in the growth of the indigenous

microbe population.• Major nutrients: carbon, nitrogen, phosphorous, oxygen,

and water.• Main concerns are oxygen supply and temperature.• Nutrients must be available and in contact with microbes.• 1 g hydrocarbon requires 150mg N and 30mg P.• C:N:P = 100:5:1• Commonly used water-soluble nutrient products include

mineral nutrient salts (e.g. KNO3, NaNO3, NH4NO3, K2HPO4)

• When a fertilizer is added to a contaminated area, following things should be checked-

1) Rate of release 2) Washout effect- “Washout” refers to tide that

carries water out to sea and takes some nutrients with it

3) Type of nutrients

Advantages • Less expensive,• Natural process, • Not disruptive to surrounding ecosystems ,• Does not require moving oil to another location, • Continues to improve conditions.

Disadvantages • Bio-augmentation not very effective,• Success depends on proper nutrients and environmental conditions, • Takes time to evaluate site, • Takes time to see results.

Exxon Valdez Oil Spill

• On March 24, 1989, the tanker Exxon Valdez grounded on Bligh Reef in Alaska's Prince William Sound, rupturing its hull and spilling nearly 11 million gallons of crude oil into a remote, scenic, and biologically productive body of water.

Techniques used to remove or clean oil

i. Controlled burning,ii. Chemical dispersants,iii. high pressure/hot water washing, iv. cold water washing, v. fertilizer enhanced bioremediation,vi. manual and mechanical removal of oil and oil

laden sediments.

Controlled Burns

• efficiently and rapidly reduce the volume of a threatening oil slick.

• Concerns over atmospheric emissions

Chemical Dispersants

• Dispersants used to break up the oil and speed up the natural biodegradation process. Example- Xylan gums.

• similar to emulsifying agents.• Dispersants are not appropriate for all oils and all

locations. If the oil is dispersed through the water column it can affect marine organisms like corals and sea grass.

• It can also affect organisms that are important in the seafood industry.

Manual/mechanical cleaningGenerally, the strategy to cleaning up a spill

begins with containment booms and skimming technologies.

contain the oil spill with booms and then collect the oil from the surface of the water by using skimmer equipment.

Large sponges called sorbents can also be used to absorb much of the oil.

References• Bragg, J. R., Prince, R. C., Wilkinson, J. B. & Atlas, R. M.

Bioremediation for Shoreline Cleanup Following the 1989 Alaskan Oil Spill

• EPA Website. (2006) http://www.epa.gov/oilspill/index.htm • Gordon, Ray. (1994) “Bioremediation and its Application to

Exxon Valdez Oil Spill in Alaska.”• Michel, J., S. Christopherson, and F. Whipple. (1994)

Mechanical Protection Guidelines. Columbia, South Carolina • R.C. Prince, R.R. Lessard and J.R. Clark; 2003, Bioremediation

of marine oil spills; Oil & Gas Science and Technology Vol. 58 (4), pp. 463-468

Thank you

Thank you