186 7 Pollution of Aquatic Systems: Pollution Through Eutrophication, Fecal Materials, and Oil Spills
can partially or completely degrade oil to water-soluble
compounds and eventually to carbon dioxide and
water. Two approaches are adopted in using micro-
organisms to remediate oil pollution: (i) biostimula-
tion, which seeks to increase the activity of oil-degrading
indigenous orga nisms and (ii) bioaugmentation,
which is the introduction of microorganisms, which
degrade oil into water (Smith and Osborn 2009 ).
(i) Biostimulation
Biostimulation of the indigenous microor-
ganisms involves the provision of materials,
which increase the activity of the oil-degrading
microorganisms. This includes providing
those nutrients known to be deficient in the
sea environment, or providing conditions,
which increase the efficiency of the micro-
organisms to utilize what is available.- Addition of nutrients:
Usually, the rate-limiting factor for oil
degradation in the marine environment is
inorganic nutrient concentration, and in
particular, nitrogen (N) and phosphorous
(P). Biostimulation through the addition
of nutrients containing these two ele-
ments has been the most widely used
bioremediation strategy. Oil degradation
is significantly enhanced by this method. - Addition of surfactancts:
The hydrocarbons present in crude oil are
mostly insoluble in water; furthermore,
being hydrophobic the microorganisms,
which degrade them need to be in contact
with the oil for the membrane-bound
enzymes, which breakdown the oil to act.
Many of the bacteria produce surfactants,
which reduce the surface tension of, and
emulsify, the oil and enable contact
between the microorga nisms and oil. For
this reason, the addition of surfactants
to supplement those produced naturally
is a widely used method to enhance
degradation of oil. Surfactants reduce
surface tension and increase the surface
area of hydrophobic compounds such as
oil, therefore, increa sing its bioavailability.
Biosurfactants produced by bacteria
have been used for bioremediation. They
have the advantage of nontoxicity when
compared with chemical surfactants.
In cases where the surfactants is mem-
brane bound the micro organism is added
directly to the oil spill (Maneerat 2005 ).
(ii) Bioaugmentation
The addition of oil degraders has been done
in many cases, especially in the early stages
of the spill (about 5 days). Several studies
have shown that bioaugmentation with
Alcanivorax leads to enhanced degradation
of the branched alkanes (pristane and
phytane). Similar observations have also
been made that bioaugmentation with
Thalassolituus, which causes increased
degradation of n-alkanes. There have also
been a few reports of failures.References
American Petroleum Institute (2010). http://www.petroleumhpv.
org/docs/crude_oil/111503_crude_robsumm_final.pdf.
Accessed 26 July 2010.
Anonymous. (2003). Robust Summary Information on Crude
Petroleum (CAS No 8002-05-9).
Anonymous. (2004). Indicators for waterborne pathogens.
Washington, DC: National Research Council.
Anonymous. (2005). Microbial source tracking guide document.
National Risk Management Research Laboratory Office of
Research and Development. Cincinnati: U.S. Environmental
Protection Agency. US EPA/600/R-05/064 June 2005.
Anonymous. (2006). Standard methods for the examination of
water and wastewater. Washington, DC: American Public
Health Association, American Water Works Association,
Water Environment Federation.
Anonymous. (2007). Total daily maximum loads. US EPA.
http://iaspub.epa.gov/waters/national_rept.control%23TOP_
IMP. Accessed 19 Sept 2007.
Anonymous. (2009). Overview of spills. http://www.temple.edu/
environment/review_oil_spills.htm. Accessed 10 April 2009.
Anonymous. (2010a). Harmful algal blooms. http://www.cdc.
gov/hab/cyanobacteria/facts.htm#cyanoform. Accessed 29
June 2010.
Anonymous. (2010b). The International Tanker Owners Pollution
Federation Ltd. http://www.itopf.com/information-services/
data-and-statistics/statistics/. Accessed 29 June 2010.
Anonymous. (2010c). List of oil spills. http://en.wikipedia.org/
wiki/List_of_oil_spills. Accessed 3 Jan 2011.
Bonde, G. (1966). Bacteriological methods for the estimation of
water pollution. Health Laboratory Science, 3, 124–128.
Callaghan, T. (2005). Microbial source tracking science or
scam? 2005 Beach closure workshops. New England
Interstate Water Pollution Control Commission. http://www.nei-
wpcc.org/beachworkshop/presentations.asp. Accessed 22
Sept 2007.