Description
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In-Situ Soil Bioremediation of Petroleum
Hydrocarbons
Using Aerobic DARAMEND - A Case Study from Taiwan
Soil Bioremediation Theory
Soil impacted with petroleum hydrocarbons (TPH) along with polynuclear
aromatic hydrocarbons (PAHs) and pentachlorophenol (PCP) were treated at
an inactive manufacturing site in Taiwan using DARAMEND® soil treatment
technology from ADVENTUS. DARAMEND promotes aerobic biodegradation of
these compounds by providing timed-release nutrients such as nitrogen,
organic carbon, phosphorus etc. as well as creating the right conditions
of pH, alkalinity etc. to enhance the microbial activity of indigenous
microorganisms. Oxygen for aerobic biodegradation is provided by tilling
the soils periodically and moisture is provided by simple irrigation
system. The benefit of in-situ bioremediation at this site allowed the
treatment to occur on site avoiding the need for the often expensive
off-site treatment and disposal option.
Bioremediation Operation:
There are several critical factors for effective bioremediation of
hydrocarbon contaminated soil, including soil moisture content (a function
of the water holding capacity (WHC)), pH, aeration of the soil via
tilling, and the application rate of DARAMEND based on the concentration
of contaminants. These variables must be controlled at optimum levels to
realize the highest effectiveness of treatment. At the beginning of this
study, baseline soil analysis was conducted to determine the
concentrations of target compounds. The soil was also analyzed for pH and
WHC. DARAMEND was applied at an application rate of 1% to soil mass
(approximately 52 kg of DARAMEND to 5,200 kg of soil to be treated).
Immediately after adding the DARAMEND, soil samples were collected and
analyzed for pH, soil moisture content and WHC for both the control soil
pile and the soil pile amended with DARAMEND (See Table 1). The soil pH
was in the neutral range and ideal for promoting bioremediation.
Both, the control and the treatment soil piles were aerated twice a
week using a tiller and irrigated to maintain moisture. Soil samples were
analyzed weekly for operational monitoring (pH and moisture). The target
moisture content was set at 70% of the WHC. The initial WHC of treatment
soil pile was at 44.2%.
Results and Conclusion
Analytical results indicate that there was a 68% reduction in TPH-D
during the first three weeks after DARAMEND was applied. No significant
reductions were observed over the next four weeks suggesting that another
dose of DARAMEND was required. However, soil samples collected on Dec 8,
2009 showed a sudden drop in TPH-G (almost 50% from that observed after
the first three weeks). This could be due to the fact that between week 4
and week 8, the high molecular weight and long-chain TPH were being broken
down to lighter intermediates but there was no net reduction in TPH. After
week 9, the lighter intermediates started to mineralize. It appears that
additional DARAMEND will be required to increase the removal efficiency.
The final results of soil analysis of this study were successful in
achieving the regulated soil TPH limits of 646 mg/kg
Cost
The overall treatment cost for this project was estimated at $ 32 per ton, all inclusive of material and labor.
Companies On This Project
ADVENTUS GROUP
Hazardous Material Removal
