Description
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Project: Former Pesticide Manufacturing
Confidential Client Southeast USA
Summary
A pilot study was conducted to determine the
applicability of deep In Situ DARAMEND®. bioremediation* for treatment of
soil containing volatile organic compounds (VOCs) and organochlorine
pesticides (OCPs). A total of 43,590 lbs of DARAMEND was injected into
four injection points. The injections were conducted using hydraulic
fracturing. Sampling conducted 7 months after the injections showed a
decrease in Toxaphene and total OCP with over 90%.
Bench-Scale Treatability Study
Adventus conducted bench-scale tests to determine the applicability of deep in situ DARAMEND
bioremediation for treatment of soil containing VOCs and OCPs. A
pilot-scale demonstration project is currently proceeding on site.* The
bench-scale work evaluated several DARAMEND treatment scenarios, using a
number of DARAMEND. products, and compared straight anoxic conditions to a
cycled aerobic/anoxic protocol. The testing was performed in sealed
columns to simulate in situ conditions and prevent contact with the
atmosphere.
The most effective treatment consisted of the addition of DARAMEND.
product D2002/6390Fe20, which contains slow-release organic carbon,
nutrients, and micro-scale zero-valent iron. This treatment reduced the
total OCPs from 46.9 mg/g to 1.1 mg/g after 117 days of treatment,
representing greater than 97% reduction in total OCPs. During this same
period, the VOCs, primarily xylene and ethylbenzene, were reduced by over
99%.
Pilot Study Field Injection
Given the success of this
treatment technology at bench-scale, a pilot-scale demonstration project
was initiated in October of 2003. The goal of the project was to reduce
source zone soil concentrations of OCPs and VOCs through the deep in-situ
injection of DARAMEND into the source area. A series of four applications
of 1% DARAMEND by weight with respect to the mass of soil in the
treatment area was implemented. The applications were planned for
intervals of between 14 and 21 days. Soil in the treatment zone was a
highly weathered limestone at depths of 31' to 37'. The injection method
consisted of driving rods to these depths using a Geoprobe rig, followed
by hydraulic fracturing and injection of DARAMEND.
Four locations were chosen for injection, with two to three depths per
location. At each location a total of approximately 2,800 pounds of
DARAMEND was injected (i.e. 1,400 pounds per injection at locations with
2 depths and 930 pounds per injection at locations with 3 depths). The
DARAMEND product was delivered to the site in 25 kg bags for ease of
handling and the material was handled with negligible dust creation.
DARAMEND was placed in a hopper, and mixed in-line with a guar solution
for delivery to the subsurface treatment area (Figure 2
right). To enhance groundwater movement through the DARAMEND fractures,
sand was introduced, at ratios of 1:2 and 1:1 sand to DARAMEND by
mass.
The product was successfully injected in each of these scenarios.
Sampling of the treatment area to determine the aerial and vertical extend
of the DARAMEND injections was performed using Geoprobe sampling
equipment. The DARAMEND layers were easily visible in the cores, whether
the fracture was a hairline fracture near the tip of the fracture, or
whether it was a few inches in thickness closer to the injection location
(Figure 3 right).
Results
Soil concentrations of Toxaphene and total
OCPs were measured in June of 2004. Given the fact that OCPs bind strongly
to the soil, the concentrations vary widely from one location to the next.
For samples that were taken from as close to the same location and depth
as possible, and for samples that showed a decrease in concentration
between November 2003 and June 2004, the results are tabulated in
Table 1 (See Below).
Four out of twelve samples showed an increase between these sampling
dates, however the median concentrations of those increases were 9 µg/g
and 12 µg/g for Toxaphene and total OCPs respectively. These data show
that the soil concentrations of Toxaphene and total OCPs decreased
significantly between the dates shown. The decrease in the average
concentration of both Toxaphene and total OCPs was 93%.
Table 1. Influence of in-situ DARAMEND on average Toxaphene and total OCP concentrations between November 2003 and June 2004 for selected samples.
|
Toxaphene (µg/g) |
Total OCPs (µg/g) |
Average Nov 2003 Value |
127.7 |
169.1 |
Average June 2004 Value |
8.7 |
11.8 |
Decrease in Average Concentration |
93.2% |
93.0% |
*Prior to establishment of EHC., this product was referred to as Deep
In situ DARAMEND.
Companies On This Project
ADVENTUS GROUP
