Environmental BioTechnologies, Inc.

Soil Flushing

Taken from the Laboratory to the Field

A company in Canada experienced a diesel fuel spill of approximately 1,800 to 2,700 liters which seeped into the gravel pad under the diesel generator building, and off site into an area of trees and brush. The sand/gravel material underneath the building had a TPH concentration of 24,800 ppm and the TPH levels in the tree and brush area ranged from 41,000 to 325,000 ppm. Diesel fuel was observed running out of the rock face along the edge of the gravel pad.

Environmental BioTechnologies, Inc. (EBT) was contracted to conduct a bench-scale treatability study designed to determine if in situ soil washing and bioremediation would be an effective method for removing the diesel fuel from the sand/gravel material (Figure 1). Based on EBT’s previous experience with various surfactants, the efficiency of soil washing was tested using water only, and three different surfactants.

Figure 1. Representation of a soil flushing program

Laboratory results demonstrated that the most promising treatment was with the use of a surfactant in which the diesel concentration was reduced from 9,710 mg/kg to 3,780 mg/kg soil, a 61% reduction.

Previous studies conducted by EBT have demonstrated that in situ microbial processes are capable of quickly reducing residual concentrations of diesel fuel. Therefore, for this project EBT designed a two phase soil flushing and bioremediation process. In the first stage, the site was flushed with several volumes of the surfactant solution. In the second stage, a water rinse containing the proper mixture of inorganic nutrients was applied to support bioremediation of the residual petroleum hydrocarbons.

Implementation of the field remediation process followed the laboratory predictions perfectly. During the flushing operation, diesel contaminated flush water was observed running into the absorbent packed trenches. The flush water reached a peak TPH concentration of 51,000 ppm at the start of the second day of flushing, and declined to 3,000 ppm TPH at the end of the second day. The last volume of flush water contained fertilizers (nitrogen and phosphorus) to promote biodegradation of the residual diesel contamination. It is anticipated that biodegradation will continue in the spring and summer months. Future work will involve monitoring of the site to maintain the proper soil nutrient concentrations, and to follow the biodegradation of the residual TPH.

Technology Application

Environmental BioTechnologies, Inc. (EBT) conducts laboratory and field studies which involve an assessment of the physical, chemical and biological parameters of a contaminated material. Bench-scale soil washing studies provide a relative index on the removal rates of petroleum hydrocarbons upon the addition of various surfactants. EBT provides technical and field support for the design and operation of soil washing projects in the field.

For more information concerning this technology, please feel free to contact Environmental BioTechnologies, Inc.

 

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Environmental BioTechnologies, Inc.
255C S. Guild Ave.
Lodi, CA 95240
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