THE “PRESTIGE” ACCIDENT
Miguel Ángel Prieto Lage
Jonathan Albo Sánnhez
Emrrique León
Bach. Environmental Sciences and Technology
Year Fourth
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SUMMARY
SUMMARY
CHPATER I: THE “PRESTIGE” ACCIDENT ____________________________________ 7
1.
The "PRESTIGE" accident ___________________________________________________ 9
1.1.
The Accident ___________________________________________________________________ 9
1.2.
The oil spill ___________________________________________________________________ 12
1.3.
Clean up operation _____________________________________________________________ 12
1.4.
Looking for governaments _______________________________________________________ 14
1.5.
The consequences ______________________________________________________________ 20
CHPATER II: BIOREMEDIATION CONCEPTS ________________________________ 22
2.
Bioremedition Concepts _____________________________________________________ 24
2.1.
What is bioremediation? _________________________________________________________ 24
2.2.
Microbes _____________________________________________________________________ 26
2.3.
Nutritional Requirements ________________________________________________________ 28
2.3.1.
Carbon ____________________________________________________________________ 28
2.3.2.
Nitrogen ___________________________________________________________________ 28
2.3.3.
Phosphorous ________________________________________________________________ 29
2.4.
Environmental Requirements for Microbial Growth ___________________________________ 29
2.4.1.
Oxygen ____________________________________________________________________ 29
2.4.2.
Water _____________________________________________________________________ 30
2.4.3.
Variables __________________________________________________________________ 30
2.4.4.
Concentration _______________________________________________________________ 31
2.5.
Metabolic Pathways for Oil Decomposition __________________________________________ 31
2.5.1.
Aromatics __________________________________________________________________ 32
2.5.2.
Aliphatic ___________________________________________________________________ 33
2.5.3.
Asphaltenes ________________________________________________________________ 35
CHPATER III PRACTICAL APPLICATION ______________ Error! Bookmark not defined.
3.
Practical Application __________________________________ Error! Bookmark not defined.
3.1.
Area of Work _________________________________________ Error! Bookmark not defined.
3.2.
Evaluation of bioremediation processes and discussion of some usual problems Error! Bookmark
not defined.
3.3.
Materials and methods __________________________________ Error! Bookmark not defined.
3.4.
Results and discussion __________________________________ Error! Bookmark not defined.
4.
Summaries of major tanker spills from 1967 to the present day. _____ Error! Bookmark not
defined.
5.
E.S.4
Future of Bioremediation ______________________________ Error! Bookmark not defined.
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SUMMARY
REFERENCES: __________________________________________ Error! Bookmark not defined.
E.S.4
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PICTURES
PICTURES
Picture 1 Instituto de Investigaciones Marinas (IIM): _______________________ Error! Bookmark not defined.
Picture 2 Galicia Region on the European map. __________________________________________________ 10
Picture 3 Disaster in the making. Satellite image of the slick on 17 November, before the Prestige sank. ______ 12
Picture 8 _________________________________________________________________________________ 13
Picture 9 _________________________________________________________________________________ 14
Picture 4 _________________________________________________________________________________ 20
Picture 5 _________________________________________________________________________________ 21
Picture 6 __________________________________________________________ Error! Bookmark not defined.
Picture 7 __________________________________________________________ Error! Bookmark not defined.
Picture 10 Schematic Diagram of Aerobic Biodegradation in Soil. ____________________________________ 25
Picture 11 Aspect of the contrast tiles corresponding to control and the three more effective treatments, after a
200 days period. The states in which these tiles are shown correspond with a very good approximation to those
quantitatively described as the final points of the figure 5. Notice the appearance, practically unaltered, of the
control tiles (the most whitish areas that can be appreciated in some cases are excremental residues from gulls).
_________________________________________________________________ Error! Bookmark not defined.
Picture 12 Effect of the S-200 treatment on some rocks after a 200 days period ___ Error! Bookmark not defined.
Picture 13 _________________________________________________________ Error! Bookmark not defined.
Picture 14 _________________________________________________________ Error! Bookmark not defined.
Picture 15 _________________________________________________________ Error! Bookmark not defined.
Picture 16 _________________________________________________________ Error! Bookmark not defined.
Picture 17 _________________________________________________________ Error! Bookmark not defined.
Picture 18 _________________________________________________________ Error! Bookmark not defined.
Picture 19 _________________________________________________________ Error! Bookmark not defined.
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PICTURES
Picture 20 _________________________________________________________ Error! Bookmark not defined.
Picture 21 _________________________________________________________ Error! Bookmark not defined.
Picture 22 _________________________________________________________ Error! Bookmark not defined.
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TABLES
TABLES
Table 1 Composición química global dunha mostra de fuel envellecido do Prestige, recollida o 18/11/02 polo
Ailette nunha mancha no mar. ________________________________________________________________ 12
Table 2 Some Petrolitic Micro-organisms. _______________________________________________________ 27
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FIGURES
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FIGURES
Figure 1 Basic Structures of Aromatics _________________________________________________________ 32
Figure 2 Basic Structures of Aliphatics _________________________________________________________ 34
Figure 3Relationships between the time-course of total fuel Tt (continuous line) and Rt index (dotted line),
supposing a first order kinetics for degradation of de-asphalted fraction, and zero order kinetics for asphaltenes
(see also text). ______________________________________________________ Error! Bookmark not defined.
Figure 4 Treatment of the tiles and fractionation of total fuel extracts in the four main groups of components:
aliphatic hydrocarbons and cycloalkanes, polyaromatic hydrocarbons, resins and asphaltenes. Raw extracts were
obtained by submerging complete tiles in closed glass recipients with dichloromethane:methanol (2:1), under
rotary agitation (60 rpm) during 24 hours at 20ºC. The redundant pathways (as silica-gel column
chromatography and isooctane/dimethyl sulfoxide/water partition) have only used as confirmatory expedients. In
S-200 treatments, the saponification pathway (A1) was necessary to eliminate the formulation residue that, in A2
pathway, contaminates both the asphaltenes and de-asphalted fraction. _________ Error! Bookmark not defined.
Figure 5 Remaining total fuel (% of the initial level) in tiles subjected to the different treatments assayed (0:
control without treatment), at indicated times. Error bars refer to confidence intervals (n=4; =0.05). ___ Error!
Bookmark not defined.
Figure 6 Time-course of remaining total fuel (%) in control tiles (0) and those treated with the three more
effective formulations (F, I, J) after 2-3 months. Error bars refer to confidence intervals (n=3; =0.05). _ Error!
Bookmark not defined.
E.S.4
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EQUATIONS
EQUATIONS
Equation 1
Error! Bookmark not defined.
Equation 3
Error! Bookmark not defined.
Equation 4
Error! Bookmark not defined.
Equation 5
Error! Bookmark not defined.
Equation 6
Error! Bookmark not defined.
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CHPATER I:
THE “PRESTIGE” ACCIDENT
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CHAPTER I: The “PRESTIGE” accident
1. THE "PRESTIGE" ACCIDENT
1.1.
THE ACCIDENT
The Galician coast is located in the northwest of Spain, between 41º and 45º
N and 9º and 6º W (Picture 2). The climate of the region is typical of the
Atlantic, with wet winters and fresh summers and is very influenced by the
position of the Azores high. The wind therefore is predominantly SW in winter
and NE in summer. Due to these configurations and its location as a west
coast, this area is located close to the northern boundary of the CanariesPortuguese up welling system. In late spring and summer, up welling
favourable winds are typical and ENACW (Eastern North Atlantic Central
Water) is up welled (Fraga, 1981), renewing nutrients.
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CHAPTER I: The “PRESTIGE” accident
Picture 1 Galicia Region on the European map.
This feature and the complex coast with a lot of inlets named rias make
Galicia one of the most productive fishing and aquaculture areas in the world
(Blanton et al., 1984). This coast is also a prime tourist destination and is
known for its ecological value. The small islands located in the mouths of the
rias form the National Park of the Atlantic Islands. Despite this, this area has
intense maritime traffic and has already experienced several significant oil
spills in the last several decades, e.g., Urquiola in 1976 and Aegean Sea in
1992.
At 14:00 UTC on November 13, 2002, coincidental with the passage of a
severe squall line, the old tank-steamer named Prestige carrying about
77.000 tons of fuel oil began to leak approximately 30 nautical miles off the
Galician coast (Le Cedre, 2002). Between November 13 and 14, the vessel was
practically adrift about 4 miles from the coast of Cape Fisterra. Considering
an eventual risk of severe damage, the vessel was moved away from the coast.
It then travelled north-westward until November 15 when it was 60 miles
from the coast. From this point, it was carried south-westward, spreading the
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CHAPTER I: The “PRESTIGE” accident
oil spill into a long “fuel front” exactly to the west, exposing the Atlantic
coastline of Galicia.
While the first fuel spilled had already beached on November19 at 7:00 UTC,
the tanker split in half about 100 miles off the Galician coast and about
20,000 tons of fuel were spilled. At around noon, the ship sunk at a depth of
about 3500 m. The fuel oil travelled toward the east driven by westerly winds
and arrived at the Galician coast in the next few days. Afterwards, the main
spill remained off the Galician and Portuguese coasts and then it continued
moving to the Cantatrice Sea. After the vessel sank, the fuel in the tanks was
still leaking out through the breaches in the hull. Initially a flow of 125
tons/day was measured. This amount began to decrease as the French
submarine Nautile blocked the holes up. By December 26, however, more
than 4000 tons of oil had leaked out of the vessel and gave rise to a large
slick behind the main head of the second spill. This tail was formed by a lot of
tar balls that could not be seen from the aircraft. This third oil spill flow
diminished to 2 tons/day by February 29.
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CHAPTER I: The “PRESTIGE” accident
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Picture 2 Disaster in the making. Satellite image of the slick on 17 November, before the
Prestige sank.
1.2.
THE OIL SPILL
The type of oil carried by the "PRESTIGE” is very persistent and difficult to
clean and is similar to the oil that was carried by Erika. But Erika was a
smaller ship carrying 35,000 tonnes, of which 20,000 tonnes were spilled.
Hence, the "PRESTIGE" carries a lot more of this dangerous cargo. The
estimations by experts indicate that are around 20,000 tonnes spilled.
Hidrocarburos
Hidrocarburos
Resinas
Asfaltanos
saturados (%)
aromáticos (%)
(%)
(%)
Prestige
48.5 ± 1.0
37.6 ± 1.9
8.3 ± 0.8
5.6 ± 0.6
Erika
22.2
55.6
15.6
6.6
40.9
37.9
11.5
9.7
Baltic
Carrier
Table 1 Composición química global dunha mostra de fuel envellecido do Prestige, recollida o
18/11/02 polo Ailette nunha mancha no mar.
1.3.
CLEAN UP OPERATION
A major offshore cleanup operation was carried out using vessels from Spain
and nine other European countries. The response, which was probably the
largest international effort of its kind ever mounted, was hampered by severe
weather and by the inability of those vessels that lacked cargo heating
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CHAPTER I: The “PRESTIGE” accident
capability to discharge recovered oil. Over a thousand fishing vessels also
participated in the cleanup in sheltered coastal waters and during favourable
weather. As some of the oil moved into French waters, control of a reduced atsea recovery operation passed to the French authorities.
Picture 3
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CHAPTER I: The “PRESTIGE” accident
Picture 4
The open-sea recovery operation off Spain reportedly removed almost 50,000
tonnes of oil-water mixture. However this, and the extensive booming of
estuaries and sensitive areas by the deployment of over 20km of boom, failed
to prevent extensive coastal contamination. Altogether approximately 1,900
km of shoreline were affected. The shorelines of Spain were largely cleaned
manually by a workforce of over 5,000 military and local government
personnel, contactors and volunteers. The process was slow, especially in
rocky areas where access was difficult. A further problem was re-oiling of
previously cleaned areas by re-mobilised oil. On the French Atlantic coast the
beach contamination took the form of numerous tar balls. In total, some
141,000 tonnes of oily waste was collected in Spain and 18,300 tonnes in
France.
1.4.
LOOKING FOR GOVERNAMENTS
TURNING ON THE BLACK TIDE BY TOM LAPPIN
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CHAPTER I: The “PRESTIGE” accident
Revolutions start in the aftermath of wars. War might appear to be a
melodramatic word to use to describe the clean-up operation in northwestern Spain after the black tide of fuel spilled from the wreck of the tanker
Prestige two months ago, but it can seem like the most appropriate analogy
for Galician communities fighting every day to preserve their future
livelihoods.
In the fishing villages along the stretch of coastline whose name, Costa Da
Morte, the coast of death, has never seemed more appropriate, each morning
presents a fresh challenge. The fishing fleets, used to sailing at dawn to go in
search of Atlantic catches, still set out in regular flotillas.
They are forbidden to catch potentially contaminated fish so their quarry is
the thick tar that is floating a few miles offshore. Armed in many cases with
little more than poles, nets and buckets, the fishermen haul in as much of
the tar as they can find. "Chapapote", as it is called in Galician, has become
the most familiar word bandied about in Spain. The view of the fishermen is
that any tar that can be hauled out of the sea is a little less that will wash
ashore on the Galician beaches.
A couple of miles east of the fishing port of Camelle last week, 40 or so
volunteers were cleaning up rocks and sand, equipped with buckets and a
pressurised water-hose. They were grinning in the face of an icy wind blowing
in off the Atlantic, their white protective suits soaked by the incessant rain,
and blackened by oil. They had arrived on a bus the previous day from
Alicante, pretty much the furthest point on mainland Spain from Galicia. "We
had to come," said Martin Barrondo Vazquez, whose usual experience of
beaches is serving drinks on the Costa Blanca. "We know the government will
do next to nothing, so it’s up to Spanish people to clean up the mess. When
we asked around in Alicante for volunteers we had more people wanting to
come than we could fit in the bus. They were all thinking, ‘what if it happened
on our coast’. We’ll be here for a week, and we’ll do what we can. It might not
be much, but at least we’ll know we helped."
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CHAPTER I: The “PRESTIGE” accident
Comparisons are being made with the individual response of volunteers, not
just from Spain but from all over the world, and with the continued failure of
the Spanish government to give a proper response to the situation. In Galicia
there is disbelief at the government’s refusal to acknowledge the scale of the
disaster
Mariano Rajoy is vice-president in the government, and regarded as one of the
favourites to succeed Jose-Maria Aznar as leader of the Partido Popular, and
de facto as the Spanish premier. He is also a Galician, but it was apparent
from the outset that he was aligning himself with the Madrid government
rather than his homeland. "It is not a black tide, just a few localised slicks,"
Rajoy said on 23 November. The black tide was already on the verge of
coating the Galician coasts and becoming the worst ecological disaster ever to
hit Spain. By 5 December he was assuring the population that the bulk of the
fuel in the stricken Prestige would solidify. By then 150 tons a day were
flowing out of of the prow of the wreck.
Those who took their information from abroad could read in the Washington
Post that the disaster was "more serious than the Exxon Valdez". In Spain, it
was difficult to get away from the suspicion that the government wanted to
bury their heads in the (oil-drenched) sand. Juan Lopez Uralde, director of
Greenpeace in Spain, said "the State has abandoned Galicia."
The president of the Galician Xunta - the provincial government - is Manuel
Fraga Iribarne, an octogenarian, the founder of the Partido Popular, and
Spain’s greatest political survior. As a former minister of information during
Franco’s dictatorship, he should be adept in the black arts of propaganda.
When the Prestige went down though, Fraga was on a hunting holiday down
south in Aranjuez, and has found it difficult to take control of the situation
ever since. The indications are that Fraga, who had hitherto exercised a kind
of hypnotic control over Galician politics, might be foundering.
Compounding the frantic cover-up and disinformation after the sinking of the
Prestige was the belated realisation that the authorities had handled the
problem about as wrong-headedly as possible. Their decision to force the
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CHAPTER I: The “PRESTIGE” accident
tanker out into open seas made it inevitable that any subsequent spillage
would cover a far greater area of coastline than if the vessel had been brought
in to port. "The worst danger is over now," Fraga said on 15 November. "At 60
miles, the risk is not that high," said Enrique Lopez Viega, the Fisheries
minister on 16 November. Neither of them had a clue what they were talking
about.
The lies and panicky concealments continued. Early figures from the
government suggested that the Prestige had spilled a total of around 3,000
tons. Local newspapers immediately queried this figure and suggested that
19,000 was a more accurate estimation. As more information has come to
light, it became apparent that the true figure is closer to 30,000 tons. The
initial government estimate of the cost of the clean-up was 42 million. Latest
figures suggest 1,000 million might get close to covering it.
A mordant cartoon in the Vox De Galicia showed the various machinery
provided by European nations to combat the oil. France had sent a
submarine, Britain and Italy had sent a couple of salvage ships apiece, the
Belgians had sent a navy vessel and the Spanish had provided ... a bucket.
In the face of government impotence, Galicians had to act for themselves.
Perhaps the most heroic example came from the fishermen of the Ria De
Arousa to the south. There, in the first week of December, 15 mussel boats
set out to the mouth of the estuary, and the fishermen, lacking proper
equipment, battled with buckets, skimming spoons, garden tools and their
bare hands against the tide of oil, preventing the fuel from reaching shore. By
11 January tests showed that the Ria was free of contamination, and the
mussel crops had been saved. The Arousa experience served as a rallying
point for Galician resistance.
When the oil started to wash ashore, Galicians stopped listening to what the
government was saying, and started to believe the evidence of their eyes. In
the fishing port of Muxia, one of the worst affected regions, Ana Veira, a local
shellfish-gatherer in her fifties, said the situation took her back 30 years.
"This is like Franco’s time. Every day the government tells us another lie, and
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CHAPTER I: The “PRESTIGE” accident
every day we can see for ourselves that they are lying. I look at the young
people and they are shocked that they cannot trust the rulers. For the older
ones it is all the same. We have seen this before. The only true reports are
from abroad. We have to find out from France and Portugal what is
happening in our own lands." And with a little race-memory paranoia left over
from the dictatorship, Ana Veira was reluctant to offer her full name.
It’s difficult to disagree with the argument that the story of the aftermath of
the Prestige disaster has been a polarised tale of the Madrid government’s
incompetence and mendacity, contrasting with the impressive community
action and courage in Galicia. While the politicians prevaricated, the
Galicians were hauling tar off the rocks. Of such images popular revolutions
are made.
Unsurprisingly this has provided a fillip to the already strong nationalist
movement within Galicia. Nationalist politicians have hardly been slow to
exploit the failings of Madrid to make their own political capital. Leading the
way is the protest "platform" group Nunca Mais (Never Again), whose
evocative banner is the blue diagonal stripe of Galicia, edged by black on both
sides to represent the wave of fuel.
More than 100,000 people marched through the streets of the Galician capital
Santiago De Compostela on 1 December, their protest lent a sedate dignity by
the fact that they all had to carry umbrellas against a traditional Galician
downpour. The polite chants were addressed to Aznar "O de bigote, que limpie
o chapapote" (you with the moustache, come and clear up the tar). The
following day, there was no sign of the premier, but King Juan Carlos, whose
three decades on the throne have given him finely-tuned political antennae,
arrived in Muxia and Laxe on the Costa da Morte. He walked the stricken
beaches, and called for unity in the face of disaster.
The king had spotted the potential for political upheaval in the the black
wake of the Prestige. In Santiago the Nunca Mais banner was at the head of
the march. The writer Manuel Rivas addressed the throng, demanding the
declaration of a disaster zone, an emergency plan, international legislation
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CHAPTER I: The “PRESTIGE” accident
against "capitalist criminals" and the resignation of the authorities who had
allowed the accident to result in the worst of all possible consequences.
This being Spain, there are already attempts to discredit Nunca Mais. A legal
vigilante group Manos Limpias (Clean Hands) has issued a court action
against them, alleging that funds destined to aid coastal communities have
been used for political agitation, and that Nunca Mais has close links with the
nationalist BNG party. Galicians are cynical enough not to be surprised by
that, but for now, every other window, even in the relatively affluent capital
Santiago, bears the black and blue flag of Nunca Mais. This was a popular
movement waiting to happen.
The government is running scared. On 24 January Aznar arrived at the coast,
in A Coruña, bearing sackloads of cash. The "Galicia Plan" for recovery has a
budget of 12,500 million, with Aznar offering his personal guarantee that all
the money will be spent to regenerate the region.
The Prestige accident was "an extraordinarily tough blow", the premier
belatedly acknowledged, but "The image of an isolated, resigned, backward
region, of a ‘black Galicia’ is a falsehood. It doesn’t exist". Aznar waxed all
Blairite about his vision of kick-starting a Galicia of economic dynamism,
with more and better communications, new technology, more cultural and
rural tourism …
For many locals, the money might be welcome, if the figures are not another
piece of government equivocation, but Aznar’s voice was the sound of Nero
fiddling, while locals and volunteers slave every day to save their land. While
the premier was announcing his largesse, outside thousands of Galicians,
assembled by Nunca Mais, gathered in the Praza Maria Pita to how their
demands for Aznar’s resignation. At the centre of the square, beside a flame
representing Galician liberty, stands the statue of Maria, a Corunese heroine
who led the locals in repelling an English attack in 1589. Her strapping
fishwife’s arms, skewering one of Drake’s sailors with her spear, send out a
historic message that Aznar would be wise to heed. Don’t mess with Galicia.
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1.5.
CHAPTER I: The “PRESTIGE” accident
THE CONSEQUENCES
The consequences of this oil-spill incise directly on thousands of local sailors,
shellfish gatherers and other workers and companies bound to the sea, but
indirectly all of us are affected.
The Prestige oil tanker sank near northern Spain on 19 November 2002,
polluting about 3,000 km (1,800 miles) of coastline.
Picture 5
The spill is estimated to have killed 300,000 seabirds, making it one of
Europe's worst wildlife disasters.
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CHAPTER I: The “PRESTIGE” accident
Picture 6
The economic cost of the accident to fishing and tourism has been put at
about 5bn euros (£3.4bn).
The polluting effects of the Prestige oil spill could still be an issue today.
Although a clean-up operation has removed most of the oil on coastal land,
there are concerns about the large quantity which sank to the sea bed.
Owing to the highly persistent nature of Prestige’s cargo, the released oil
drifted for extended periods with winds and currents, travelling great
distances. Oil first came ashore in Galicia, where the predominantly rocky
coastline was heavily contaminated. Remobilisation of stranded oil and fresh
strandings of increasingly fragmented weathered oil continued over the
ensuing weeks, gradually moving the oil into the Bay of Biscay and affecting
the north coast of Spain and the Atlantic coast of France, as far north as
Brittany. Some light and intermittent contamination was also experienced on
the French and English coasts of the English Channel. Although oil entered
Portuguese waters, there was no contamination of the coastline.
Fisheries exclusion zones were put in place in Galicia shortly after the
incident, banning virtually all fishing along about 90% of the coastline. All
bans had been lifted by October 2003. The impact on fisheries in France was
less extensive. In both countries, an impact on tourism was reported for
2003.
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CHPATER II:
BIOREMEDIATION CONCEPTS
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CHAPTER II: Bioremediation concepts
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2. BIOREMEDITION CONCEPTS
Knowledge on bioremediation acquired since 1942 allows us to manipulate
environmental factors to enhance natural biodegradation. This knowledge
includes:
 Identification
of
microbes
capable
of
degrading
petroleum
hydrocarbons.
 Nutrient requirements of these microbes, such as carbon, nitrogen and
phosphorous.
 Environmental requirements such as oxygen, water and temperature.
 Metabolic pathways of decomposition for oil fractions. These oil
fractions include the aromatics, aliphatics and asphaltenes.
2.1.
WHAT IS BIOREMEDIATION?
Bioremediation is a treatment process that uses naturally occurring micro
organisms (yeast, fungi, or bacteria) to break down, or degrade, hazardous
substances into less toxic or no toxic substances. Micro organisms, just like
humans eat and digest organic substances for nutrients and energy. In
chemical terms, “organic” compounds are those that contain carbon and
hydrogen atoms. Certain micro organisms can digest organic substances
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CHAPTER II: Bioremediation concepts
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such as fuels or solvents that are hazardous to humans. The micro organisms
break down the organic contaminants into harmless products—mainly
carbon dioxide and water.
Picture 7 Schematic Diagram of Aerobic Biodegradation in Soil.
In the simplest terms, bioremediation is the use of micro organisms to
decompose toxic pollutants into less harmful compounds. In this paper, the
term bioremediation is used in the context of promoting the degradation of
petroleum hydrocarbons (oil).
To fully understand bioremediation we must discuss the term biodegradation.
Biodegradation is a natural process by which microbes alter and break down
petroleum hydrocarbons into other substances. The resulting products can be
carbon dioxide, water, and partially oxidized biologically inert by-products
(Bragg et al. 1992, p6). Bacteria that consume petroleum are known as
“hydrocarbon oxidizers”: because they oxidize compounds to bring about
degradation (Chianelli et al. 1991).
Bioremediation is the optimization of biodegradation. This acceleration can be
accomplished by two forms of technology: (1) fertilizing (adding nutrients)
and/or (2) seeding (adding microbes). These additions are necessary to
overcome
certain
environmental
factors
that
may
limit
or
prevent
biodegradation.
Bioremediation is not limited to marine oil spills or land oil spills; it has
potential to help clean up pesticides and hazardous waste. There are also
benefits to bioremediation such as saving money, being ecologically sound,
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CHAPTER II: Bioremediation concepts
destroying contaminates (not moving them form one place to another) and
treating waste on site.
Once the contaminants are degraded, the micro organism population is
reduced because they have used their entire food source. Dead micro
organisms or small populations in the absence of food pose no contamination
risk.
The application of bioremediation will be an important aspect of waste
management now and into the future as more is learned about this
technology.
2.2.
MICROBES
Certain enzymes produced by microbes attack hydrocarbons molecules,
causing degradation. The degradation of oil relies on having sufficient
microbes to degrade the oil through the microbes’ metabolic pathways (series
of steps by which degradation occurs). Fortunately, nature has evolved many
microbes to do this job. Throughout the world there are over 70 genera of
microbes that are known to degrade hydrocarbons (See table 2) (U.S.
Congress 1991a, p.9). These microbes usually account for less than 1% of
natural populations of microbes, but can account for more than 10% of the
population in polluted ecosystems (U.S. Congress 1991a, p.9).
If microbes are not present in a system they can be added to help promote
bioremediation. The added microbes can be cultures grown from other
contaminated areas or they can be microbes genetically engineered to degrade
oil. However, even when these microbes are present, degradation of
hydrocarbons can take place only if all other basic requirements of the
microbes are met.
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CHAPTER II: Bioremediation concepts
Table 2 Some Petrolitic Micro-organisms.
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2.3.
CHAPTER II: Bioremediation concepts
NUTRITIONAL REQUIREMENTS
Microbes are dependent on nutrients for survival. These nutrients are the
basic building blocks of life and allow microbes to create the necessary
enzymes to break down hydrocarbons. Although nutritional requirements
vary among micro organisms (Atlas 1984, p. 333) all of them will need
nitrogen, phosphorous and carbon. The survival of a micro organism depends
on whether or not it can meet its nutritional needs.
2.3.1.
Carbon
Carbon is the most basic structural element of all living forms and is needed
in greater quantities than other elements. The nutritional requirements of
carbon to nitrogen are 10:1 and carbon to phosphorus 30:1 (Atlas and Bartha
1981, p.70). Reduced organic carbon is a source of energy for microbes
because it has high energy yielding bonds in many compounds. In the
decomposition of oil, there is plenty of carbon for the micro organism due to
the structure of the oil molecule.
2.3.2.
Nitrogen
Nitrogen is found in the proteins, enzymes, cell wall components, and nucleic
acids of micro organisms (Atlas and Bartha 1981, p.70). "Micro organisms
must be supplied nitrogen in some form" (Wistreich and Lechtman 1988,
p.90) because without it, the microbial metabolism will be altered (Atlas and
Bartha 1981, p.70).
"Because molecular nitrogen can be used by only a few micro organisms,
most micro organisms require fixed forms of nitrogen, such as organic amino
nitrogen, ammonium ions, or nitrate ions" (Atlas 1984, p.333). These other
forms of nitrogen can be scarce in certain environments, causing nitrogen to
become a limiting factor in the growth of microbial populations.
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CHAPTER II: Bioremediation concepts
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2.3.3.
Phosphorous
Phosphorous is needed in the membranes (composed of phospholipids), ATP
(energy source of cell) and to link together nucleic acids (Atlas and Bartha
1981, p.70).
2.4.
ENVIRONMENTAL REQUIREMENTS FOR MICROBIAL GROWTH
Along with nutrients, microbes need certain conditions to live. Because
microbial growth and enzymatic activity are affected by stress from the
following factors, the rates of biodegradation will also be affected. As the
stress increases (less favourable conditions occur) the microbes have a harder
time living in their environment. Just as humans need certain conditions to
live (like oxygen) so microbes need it. There is a certain range of conditions in
which microbes can live. As conditions reach the extremes microbial growth
slows down, but when conditions are perfect the microbial community can
thrive.
2.4.1.
Oxygen
Biodegradation is predominantly an oxidation process. "Bacteria enzymes will
catalyze the insertion of oxygen into the hydrocarbon so that the molecule
can subsequently be consumed by cellular metabolism" (Bragg et al. 1991,
p.6). Because of this, oxygen is one of the most important requirements for
the biodegradation of oil. There is usually enough oxygen to prevent a lack of
it
from
limiting
biodegradation.
The
primary
source
of
oxygen
for
biodegradation is atmospheric oxygen.
When oxygen is limiting, the water can be aerated to allow biodegradation to
take place. An example of this is in wastewater treatment plants when oxygen
is added in the aeration basin. Oxygen is important in hydrocarbon
degradation because the major pathways for both saturate and aromatic
hydrocarbons involve molecular oxygen or oxygenases (Atlas 1981, p.195).
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CHAPTER II: Bioremediation concepts
Theoretical calculations show that 3.5g of oil can be oxidized for every gram of
oxygen present (Atlas 1981, p.195).
The current evidence for anaerobic degradation of hydrocarbons is not
considered of ecological importance because the rate is so negligible, even
though some microbes have been found to degrade alkanes under anaerobic
conditions, when isolated (Atlas 1981, p.194). There have not been many
reports of hydrocarbons being anaerobically degraded in natural ecosystems
(Atlas 1981, p.194). However, "nitrate of sulphate could serve as an
alternative electron acceptor" (Atlas 1981, p.194) instead of oxygen during
anaerobic microbial degradation of petroleum hydrocarbons.
2.4.2.
Water
Water is needed by micro organisms since it makes up a large proportion of
the cell’s cytoplasm. Water is also important because most enzymatic
reactions take place in solution. Water is also needed for transport of most
materials into and out of the cell (Atlas and Bartha 1981, p.70).
Water is not a limiting factor in the case that we are discussing (marine oil
spill), but for example, in bioremediation of oil spilled on land it may be an
important factor which needs to be controlled.
2.4.3.
Variables
"Several variables, including pressure, salinity, and pH, may also have
important effects on biodegradation rates" (U.S. Congress 1991a, p.11). In the
natural environment, these factors are not a major problem where
populations of micro organisms naturally exist, which is good since these
variables are not easily controlled in the environment.
Although hydrocarbon degradation has been found to occur at a wide range
of temperatures (as low as below 0°C to as high as 70°C) it is an important
factor on the rate of biodegradation (Atlas 1981, p.190).
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CHAPTER II: Bioremediation concepts
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The temperature is so important because "at low temperatures, molecules
move relatively slowly, and colliding molecules do not always bring about a
reaction" (Atlas 1984, p.339). Raising the temperature will increase the
possibility of reactions taking place and increase the rate of diffusion.
Without reactions and diffusion life cannot exist. In general the rate of
enzymatic reactions can be doubled for every 10°C rise in temperature as long
as the enzymes are not denatured (Atlas 1984, p.339). The more enzymatic
reactions the faster the biodegradation will occur.
Even
though
temperature
plays
an
important
part
in
the
rate
of
biodegradation, it does not act alone. The composition of the microbial
community and the quality of the oil can affect the rates of biodegradation
just as much.
2.4.4.
Concentration
The concentration of pollutants is an important factor. If the concentration of
petroleum hydrocarbons is too high then it will reduce the amount of oxygen,
water and nutrients that are available to the microbes. This will create an
environment where the microbes are stressed reducing their ability to break
down the oil.
Once the necessary requirements are present either naturally or by addition,
the oil can begin to be broken down by the microbes. Favourable conditions
for the microbes will help optimize the degradation of the oil. The degradation
of these hydrocarbons occurs in certain steps and can be represented by
metabolic pathways.
2.5.
METABOLIC PATHWAYS FOR OIL DECOMPOSITION
Over the last 20 years complex chemical equations have been derived to
describe the metabolic pathways in which oil is broken down. "The general
outline bioremediation pathways for aliphatic and aromatic hydrocarbons
have been formulated and continue to be developed in greater detail with
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CHAPTER II: Bioremediation concepts
-
time" (Glaser, Venosa and Opatken 1991, p.559). All of these pathways will
result in the oxidation of at least part of the original hydrocarbon molecule
(Bragg et al., p7). The content of a particular petroleum mixture will also
influence how each hydrocarbon will degrade (Atlas 1981, p.182) and the type
and size of each hydrocarbon molecule will determine the susceptibility to
biodegradation (Atlas and Bartha 1993, p.394).
"There are several hundred individual components in every [type of] crude oil,
and the composition of each crude oil varies with its origin" (Atlas and Bartha
1993, p.394). The difference in composition determines the quality of any
particular oil. Petroleum is a complex mixture of hydrocarbons, but it can be
fractionated into aromatic, aliphatic, asphaltic and a small portion of nonhydrocarbon compounds (Atlas and Bartha 1993, p.394; Atlas 1981, p180).
2.5.1.
Aromatics
Aromatic hydrocarbons are made up of at least one benzene ring or
substituted benzene ring (see figure 1 for basic aromatics). These compounds
can be degradable when they are simple and have a low molecular weight.
However, as they increase in complexity and molecular weight they are their
difficulty to be degraded (U.S. Congress 1991a, p.8). "Aromatics with five or
more rings are not easily attacked and may persist in the environment for
long periods of time" (U.S. Congress 1991a, p.8).
Figure 1 Basic Structures of Aromatics
The microbial metabolism of aromatic hydrocarbons is shown in figure 2. This
figure shows the degradation of benzene as an example of how a member
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CHAPTER II: Bioremediation concepts
from this group of compounds is broken down. Orth of meta cleavage starts
the process by opening up the aromatic ring, and the process ends with
acetyl-CoA or Pyruvic acid (Atlas and Bartha 1993, p. 396).
Condensed aromatic rings are attacked one ring at a time if they are
degradable (See Figure 3). The first ring is opened and reduced to pyruvic acid
and CO2, and then the next ring is attacked in the same manner (Atlas and
Bartha 1993, p396).
2.5.2.
Aliphatic
Also known as the saturates, this group includes compound such as nparaffins, iso-paraffins and alicyclic hydrocarbons (cycloparaffins) (See Figure
2).
The type and size of the hydrocarbon molecule will affect its ability to be
metabolized by micro organism (Atlas and Bartha 1993, p396). The straightchain alkane (n-paraffin) compounds with 10 to 24 carbon atoms are
degraded the fastest because they are easiest to metabolize (U.S. Congress
1991a, p.7). The shorter chains "are toxic for many micro organisms, but they
generally evaporate from oil slicks rapidly" (Atlas and Bartha 1981, p424). As
the length of a chain increases, it becomes resistant to biodegradation, and
those compounds with molecular weights of 500 to 600 are no longer able to
serve as a carbon source due to its length (Atlas and Bartha 1981, p.424).
Branching of alkenes will reduce the biodegradability (U.S. Congress 1991a,
p.8).
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CHAPTER II: Bioremediation concepts
-
Figure 2 Basic Structures of Aliphatics
For more detailed information on the order of degradation see Atlas and
Bartha (1993) "Microbial Ecology".
"Some micro organisms attack alkenes subterminaly; that is, oxygen is
inserted on a carbon atom within the chain instead of at it’s end" (figure 5)
(Atlas and Bartha 1993, p. 394).
Alicyclic hydrocarbons with no terminal methyl groups are biodegraded in a
manner similar to the subterminal oxidation. Cyclohexane, an alicycliic
hydrocarbon, is degraded as shown in figure 6. (Atlas and Bartha 1991)
once fatty acids (molecules with the general formula CnH2n+1COOH) are
formed, the process of beta-oxidation will continue the catabolism. Betaoxidation will form acetate and a new fatty acid, containing two less carbons
then the original (Atlas and Bartha 1993 p.395). This process will repeat itself
until the compound is completely broken down. The hydrocarbon will
eventually be degraded to CO2 and H2O through the process of hydrocarbon
mineralization (Atlas and Bartha 1993 p.395). "The beta-oxidation sequence
does not necessarily require the presence of molecular oxygen; fatty acid
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CHAPTER II: Bioremediation concepts
biodegradation may proceed under anerobic conditions" (Atlas and Bartha
1993 p.395).
2.5.3.
Asphaltenes
Difficult to analyze with current methodology because of their complexity,
these compounds are not well understood (Atlas 1981 p.182). "No uniform
degradative pathway, comparable to the pathways established for aliphatic
and aromatic hydrocarbons, has yet emerged for the asphaltic petroleum
components" (Atlas 1981p.182). These compounds do not or are slow to
biodegrade (U.S. congress 1991a, p.8).
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