22.6 Pilot- and Field-Scale Mycoremediation
As reported so far, a number of studies at laboratory scale dealing with the
mycoremediation of contaminated matrices was carried out. In contrast, there are
only few reports concerning the use of fungi at field scale, which demonstrate the
effectiveness and economic viability of the fungal technology application at pilot
and full scale. For instance, despite its great effectiveness in degrading organic
pollutants in laboratory-scale experiments, the model white-rot fungus
P. chrysosporium has never been so effective in any field-scale tests.
One of the first trials was reported in the 1990s: the white-rot fungus
P. chrysosporium was used in the treatment of a trinitrotoluene (TNT)-contaminated
soil from a former Naval Submarine Base Bangor (Washington, USA) at pilot scale.
The initial TNT content of 1844 ppm was reduced up to 41% in 4 months. However,
the final concentration was still significantly above the target level and thus the test
was considered a failure (US EPA 1993).
A decade later, a field-scale trial for the remediation of crude oil-contaminated
soil was performed. In this case, the efficiency of two biological approaches was
compared: composting biopiles technology where the soil was aerated and amended
with bulking agents vs. fungal bioaugmentation (Li et al. 2004). Three fungal strains
characterized by high lipase activities (Mucor sp., Cunninghamella sp., and Fusarium sp.) and previously isolated, were reintroduced into the contaminated matrices
either with or without P. chrysosporium. The results showed that the introduction of
the allochthonous fungus did not improve the efficiency of total petroleum hydrocarbons (TPH) removal process.
A similar outcome was also achieved a few years later in a pilot-scale experiment
for the treatment of soil contaminated by TNT, PAHs, PCDDs, and PCDFs
(Tuomela et al. 2012). In this case, the litter-decomposing fungus P. velutina
inoculum was firstly prepared using pine bark as growth substrate. Once the inoculum was prepared, the allochthonous fungus was inoculated into soil and the extent
of degradation of the target pollutants was evaluated. P. velutina growth was
completely inhibited when introduced into highly affected soil (PAHs and TNT
concentrations of 5000 mg/kg and > 10 g/kg, respectively) and no degradation
occurred. Furthermore, P. velutina growth was limited by the presence of molds
such as Trichoderma. Contrarily, the degradation process significantly enhanced
when PAH- and TNT-contaminated soil was diluted with garden compost. However,
the role of the litter-decomposing soil fungus in the removal of PAHs and TNT could
not be clarified since also the growth of indigenous microorganisms was clearly
stimulated under such conditions. These results were also confirmed 2 years later
when a field-scale experiment (2 t) for the treatment of a PAH-contaminated soil was
carried out (Winquist et al. 2014). At first, a laboratory-scale experiment was
performed to compare the extent of PAH degradation in soil mixed with green
compost and incubated with or without P. velutina. A higher degradation (up to
96% for 4-ring PAHs and 39% for 5- and 6-ring PAHs) was achieved in microcosms
inoculated with the fungus than in the biostimulated ones after 3 months. Secondly, a
454
T. Stella
As reported so far, a number of studies at laboratory scale dealing with the
mycoremediation of contaminated matrices was carried out. In contrast, there are
only few reports concerning the use of fungi at field scale, which demonstrate the
effectiveness and economic viability of the fungal technology application at pilot
and full scale. For instance, despite its great effectiveness in degrading organic
pollutants in laboratory-scale experiments, the model white-rot fungus
P. chrysosporium has never been so effective in any field-scale tests.
One of the first trials was reported in the 1990s: the white-rot fungus
P. chrysosporium was used in the treatment of a trinitrotoluene (TNT)-contaminated
soil from a former Naval Submarine Base Bangor (Washington, USA) at pilot scale.
The initial TNT content of 1844 ppm was reduced up to 41% in 4 months. However,
the final concentration was still significantly above the target level and thus the test
was considered a failure (US EPA 1993).
A decade later, a field-scale trial for the remediation of crude oil-contaminated
soil was performed. In this case, the efficiency of two biological approaches was
compared: composting biopiles technology where the soil was aerated and amended
with bulking agents vs. fungal bioaugmentation (Li et al. 2004). Three fungal strains
characterized by high lipase activities (Mucor sp., Cunninghamella sp., and Fusarium sp.) and previously isolated, were reintroduced into the contaminated matrices
either with or without P. chrysosporium. The results showed that the introduction of
the allochthonous fungus did not improve the efficiency of total petroleum hydrocarbons (TPH) removal process.
A similar outcome was also achieved a few years later in a pilot-scale experiment
for the treatment of soil contaminated by TNT, PAHs, PCDDs, and PCDFs
(Tuomela et al. 2012). In this case, the litter-decomposing fungus P. velutina
inoculum was firstly prepared using pine bark as growth substrate. Once the inoculum was prepared, the allochthonous fungus was inoculated into soil and the extent
of degradation of the target pollutants was evaluated. P. velutina growth was
completely inhibited when introduced into highly affected soil (PAHs and TNT
concentrations of 5000 mg/kg and > 10 g/kg, respectively) and no degradation
occurred. Furthermore, P. velutina growth was limited by the presence of molds
such as Trichoderma. Contrarily, the degradation process significantly enhanced
when PAH- and TNT-contaminated soil was diluted with garden compost. However,
the role of the litter-decomposing soil fungus in the removal of PAHs and TNT could
not be clarified since also the growth of indigenous microorganisms was clearly
stimulated under such conditions. These results were also confirmed 2 years later
when a field-scale experiment (2 t) for the treatment of a PAH-contaminated soil was
carried out (Winquist et al. 2014). At first, a laboratory-scale experiment was
performed to compare the extent of PAH degradation in soil mixed with green
compost and incubated with or without P. velutina. A higher degradation (up to
96% for 4-ring PAHs and 39% for 5- and 6-ring PAHs) was achieved in microcosms
inoculated with the fungus than in the biostimulated ones after 3 months. Secondly, a
454
T. Stella