Temperature effects on bioremediation of PAHs and PCP contaminated south Louisiana soils: A laboratory mesocosm study |
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| Authors: | Javed Iqbal Caroline Metosh-Dickey Ralph J Portier |
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| Institution: | (1) Department of Environmental Studies, Louisiana State University, Baton Rouge, LA 70803, USA;(2) W. A. Callegari Environmental Center, LSU AgCenter, Dean Lee Dr., Baton Rouge, LA 70820, USA |
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| Abstract: | Goal, Scope and Background Temperature and soil moisture content are important environmental variables in bioremediation technologies. Optimizing these
variables in-situ would enhance and maintain remediation of hazardous wastes during cold winter seasons or in cold regions and may lead to
reduced maintenance and/or cost. The effect of elevated temperature and soil moisture on bioremediation efficiency was investigated
using a laboratory mesocosm approach. Selected polycyclic aromatic hydrocarbons (PAHs) and phenols degradation in contaminated
flooded soils, commonly found in Superfund sites situated in coastal plains sediments/soils, were evaluated in the mesocosms.
Material and Methods Four laboratory mesocosm treatments in triplicate simulating in-situ bioremediation of contaminated site soils using an immobilized microbe bioreactor system, i.e., bioplug, were established
to evaluate temperature effects. Elevated temperature treatments of site soils with and without contaminant-specific microorganisms
were established at a temperature of 42±2°C. Similarly, treatment of site soils with and without contaminant-specific microorganisms
were established at an ambient temperature of 21±1°C. Composite samples were analyzed for selected PAHs and chlorinated phenols
to determine rates of mineralization and overall remediation efficiency for different temperature regimes.
Results Mesocosm studies indicated that the high temperature inoculated treatment demonstrated a significant reduction in mean total
PAHs and total phenols with a kinetic rate (KR) of 76±13 ng g−1 d−1 in 49 days (approximately 84% reduction; p<0.01) The KR for low temperature inoculated treatment was 54±1 ng g−1 d−1 in 49 days (approximately 66% reduction; p<0.01). High temperature non-inoculated mesocosms exhibited significant mineralization
of all constituents with KR of 15±6 ng g−1 d−1 (approximately 65% reduction; p<0.01) in 49d compared to 54% reduction for low temperature non-inoculated treatment with
KR of 12±3 ng g−1 d−1 (p=0.1794). Phenol compounds in inoculated treatments were also significantly reduced (65%, p<0.01) at elevated temperatures
compared to ambient (52%, p<0.01).
Discussion Increased bioavailability and desorption were noted for elevated temperature and moisture in the soil laboratory mesocosms
simulating a field in situ remediation protocol. This protocol employing the application of immobilized microflora indicated that in situ systems provide an economical advantage if optimal elevated temperature and moisture are controlled properly. Results also
suggested that temperature and moisture optimization needs to be combined with efficient nutrients delivery systems for impacted
soils/sediments.
Conclusions The study demonstrated that temperature and soil moisture contents are important factors in the success of in-situ bioremediation techniques at hazardous waste sites situated in a coastal zone. Kinetic rates were significantly enhanced
to remediate known recalcitrant compounds (PAHs and phenols) in aged soil.
Recommendations and Perspectives The placement of a preferred microbial consortia such as an immobilized microbial population in an entrained bioreactor, i.e.,
bioplug, can significantly reduce constituents of concern in a timely manner for contaminated soils/sediments. However, frequent
monitoring of the soil temperature, moisture content, nutrient level, and dissolved oxygen is necessary to achieve predictable
kinetic rates of mineralization.
ESS-Submission Editor: Dr. Teresa Cutright (tcutright@uakron.edu) |
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| Keywords: | Bioremediation immobilized microbe bioreactor kinetic rates mesocosm phenols polycyclic aromatic hydrocarbons Superfund temperature |
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