with petroleum. Photographical surveys, comparing EAP22treated and EAP22-untreated beach sections, showed a very
important petroleum disappearance on contaminated sites.
But the efficiency of this treatment was objected by some
observers for whom the Inipol EAP22 action was limited to a
“washing” of contaminated beaches (in line with the surfactant properties of the additive), the microorganisms having
used not petroleum but oleic acid as carbon and energy
source. However, the monitoring of petroleum biodegradation
in different plots by using 17α (H)21β (H) hopane (Fig. 16.33)
as internal conserved standard showed that the biodegradation
rates were two to seven times higher than that in untreated
plots, according to the treated zones (Pritchard et al. 1992;
Bragg et al. 1994; Prince et al. 1994).
16.8.3.2 Bioremediation of Soils
and Groundwaters
Petroleum product pollutions have a number of causes:
emission from the production sites, often linked to the
plant dilapidation, during transportation from the production
site to refineries (oil pipeline network, rail and road transport), and contamination of oil processing and storage places
(storage in refineries, petrol stations, storage tanks of
individuals). All these pollution can be chronic or accidental.
For instance, during the Gulf war, 400 km
2 soil were
contaminated by fallouts from 800 set ablaze oil wells, and
50 millions m
3 crude oil were discharged by burning well
eruptions. Once in contact with soil, hydrocarbon will penetrate more or less quickly and deeply depending on the
soil structure, its texture, its clay and organic matter
composition, hydrological conditions, and pollutant nature
(log kow*, hydrophobicity, etc.); in some cases, hydrocarbons may reach the groundwater level.
In soils, hydrocarbons are submitted to a set of physicochemical (dissolving, evaporation, adsorption, dispersal, etc.)
and biological (biodegradation) (Vandecasteele 2008) processes, similar to those taking place in marine ecosystems.
Though a natural hydrocarbon disappearance occurs
in these biotopes, treatments based on microorganism
biodegradation capacities through microbiological means
(biostimulation, bioincrease, rhizostimulation (Box 16.6))
were developed in addition to physicochemical treatments
(burning, thermal desorption), to comply with increasingly
constraining regulations.
Treatments implemented in situ and ex situ will be
separately considered:
(i) In situ treatments are implemented when polluted areas
represent large surfaces and/or are deeply located; under
these conditions, digging cannot be considered. In situ
biostimulation of hydrocarbonoclastic community
activity can be achieved through bioventilation or biobubbling: injection of air for aerobic biodegradation and
electron acceptors other than dioxygen if the site
is under anoxic conditions (supply of nitrate, sulfate,
iron). For instance, nitrate (15–125 mg dm
À3 ) and
sulfate (15–100 mg dm
À3 ) were injected over a
15-month period in groundwaters contaminated by
BTEX (Cunningham et al. 2001). The set of compounds
was degraded at the end of the treatment, particularly
xylenes whose biodegradation seems to be linked to the
use of sulfate by the sulfate-reducing community.
Bioincrease can also be considered. Introduction of a
genetically modified microorganism was undertaken
to treat a soil artificially contaminated with HAPs (naphthalene, anthracene, phenanthrene). The strain Pseudomonas fluorescens HK44 that is able to degrade these
hydrocarbons survived 22 months after inoculation. The
efficiency of this bioincrease treatment in terms of remediation was difficult to establish because of the heterogeneous contaminant distribution in the soil, but their
concentration significantly decreased within zones
occupied by the microorganisms (Ripp et al. 2000).
(ii) Ex situ treatments can be applied when the polluted
zone is limited and shallow (a few meters); in such a
case, soil is transferred out and treated. This operational
mode enables a better control of bioincrease and/or
biostimulation treatments that will be applied. A first
solution involves one fermenter (of variable size, with a
volume up to 1,000 m
3 ) to treat the collected material
introduced as sludge; it is thus kept in suspension in the
aqueous phase. This technique enables the establishment of biodegradation optimal conditions and makes
easier supplementation, if necessary, of nutrients
(biostimulation) and microorganisms adapted to the
biodegradation of the related pollution source
(bioincrease). This technology allows the treatment of
highly contaminated soils (up to 250 g kg
À1 ), but the
equipment and energetic costs induced by ventilation
limit its development.
A second approach consists of treating polluted soils in
biopiles (cf. Sect. 16.2.2). To stimulate biodegradation, soil
can be enriched with nutrients (nitrogen, phosphorus). Structuring agents, in particular organic debris (straw, wood
chips, etc.), can also be added. Stimulation of aerobic biodegradation is insured by two ways:
(i) Through regular reversal of the contaminated soil with
mechanical machines that homogenize and ventilate the
biopile (dynamic biopile)
(ii) By insufling or pumping out air through a tubing
network spread inside the structure
The biopile treatment proved to be efficient to treat sludges
from urban STEPs contaminated by PAH. Oleszczuk (2007)
treated STEP sludges from different origins, faintly
contaminated by one PAH mixture with 3, 4, 5, and 6 aromatic rings. Sludges were piled up and their ventilation was
insured by insufling air and by mechanical reversal (every 15
16 Applied Microbial Ecology and Bioremediation
737
important petroleum disappearance on contaminated sites.
But the efficiency of this treatment was objected by some
observers for whom the Inipol EAP22 action was limited to a
“washing” of contaminated beaches (in line with the surfactant properties of the additive), the microorganisms having
used not petroleum but oleic acid as carbon and energy
source. However, the monitoring of petroleum biodegradation
in different plots by using 17α (H)21β (H) hopane (Fig. 16.33)
as internal conserved standard showed that the biodegradation
rates were two to seven times higher than that in untreated
plots, according to the treated zones (Pritchard et al. 1992;
Bragg et al. 1994; Prince et al. 1994).
16.8.3.2 Bioremediation of Soils
and Groundwaters
Petroleum product pollutions have a number of causes:
emission from the production sites, often linked to the
plant dilapidation, during transportation from the production
site to refineries (oil pipeline network, rail and road transport), and contamination of oil processing and storage places
(storage in refineries, petrol stations, storage tanks of
individuals). All these pollution can be chronic or accidental.
For instance, during the Gulf war, 400 km
2 soil were
contaminated by fallouts from 800 set ablaze oil wells, and
50 millions m
3 crude oil were discharged by burning well
eruptions. Once in contact with soil, hydrocarbon will penetrate more or less quickly and deeply depending on the
soil structure, its texture, its clay and organic matter
composition, hydrological conditions, and pollutant nature
(log kow*, hydrophobicity, etc.); in some cases, hydrocarbons may reach the groundwater level.
In soils, hydrocarbons are submitted to a set of physicochemical (dissolving, evaporation, adsorption, dispersal, etc.)
and biological (biodegradation) (Vandecasteele 2008) processes, similar to those taking place in marine ecosystems.
Though a natural hydrocarbon disappearance occurs
in these biotopes, treatments based on microorganism
biodegradation capacities through microbiological means
(biostimulation, bioincrease, rhizostimulation (Box 16.6))
were developed in addition to physicochemical treatments
(burning, thermal desorption), to comply with increasingly
constraining regulations.
Treatments implemented in situ and ex situ will be
separately considered:
(i) In situ treatments are implemented when polluted areas
represent large surfaces and/or are deeply located; under
these conditions, digging cannot be considered. In situ
biostimulation of hydrocarbonoclastic community
activity can be achieved through bioventilation or biobubbling: injection of air for aerobic biodegradation and
electron acceptors other than dioxygen if the site
is under anoxic conditions (supply of nitrate, sulfate,
iron). For instance, nitrate (15–125 mg dm
À3 ) and
sulfate (15–100 mg dm
À3 ) were injected over a
15-month period in groundwaters contaminated by
BTEX (Cunningham et al. 2001). The set of compounds
was degraded at the end of the treatment, particularly
xylenes whose biodegradation seems to be linked to the
use of sulfate by the sulfate-reducing community.
Bioincrease can also be considered. Introduction of a
genetically modified microorganism was undertaken
to treat a soil artificially contaminated with HAPs (naphthalene, anthracene, phenanthrene). The strain Pseudomonas fluorescens HK44 that is able to degrade these
hydrocarbons survived 22 months after inoculation. The
efficiency of this bioincrease treatment in terms of remediation was difficult to establish because of the heterogeneous contaminant distribution in the soil, but their
concentration significantly decreased within zones
occupied by the microorganisms (Ripp et al. 2000).
(ii) Ex situ treatments can be applied when the polluted
zone is limited and shallow (a few meters); in such a
case, soil is transferred out and treated. This operational
mode enables a better control of bioincrease and/or
biostimulation treatments that will be applied. A first
solution involves one fermenter (of variable size, with a
volume up to 1,000 m
3 ) to treat the collected material
introduced as sludge; it is thus kept in suspension in the
aqueous phase. This technique enables the establishment of biodegradation optimal conditions and makes
easier supplementation, if necessary, of nutrients
(biostimulation) and microorganisms adapted to the
biodegradation of the related pollution source
(bioincrease). This technology allows the treatment of
highly contaminated soils (up to 250 g kg
À1 ), but the
equipment and energetic costs induced by ventilation
limit its development.
A second approach consists of treating polluted soils in
biopiles (cf. Sect. 16.2.2). To stimulate biodegradation, soil
can be enriched with nutrients (nitrogen, phosphorus). Structuring agents, in particular organic debris (straw, wood
chips, etc.), can also be added. Stimulation of aerobic biodegradation is insured by two ways:
(i) Through regular reversal of the contaminated soil with
mechanical machines that homogenize and ventilate the
biopile (dynamic biopile)
(ii) By insufling or pumping out air through a tubing
network spread inside the structure
The biopile treatment proved to be efficient to treat sludges
from urban STEPs contaminated by PAH. Oleszczuk (2007)
treated STEP sludges from different origins, faintly
contaminated by one PAH mixture with 3, 4, 5, and 6 aromatic rings. Sludges were piled up and their ventilation was
insured by insufling air and by mechanical reversal (every 15
16 Applied Microbial Ecology and Bioremediation
737