Former
Pesticide Manufacturing
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 1). 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 2).
Fig. 1. Creation of DARAMEND and guar mixture. |
Fig. 2. DARAMEND® layer injected between
clay and weathered limestone. |
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.
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®.
Contact Adventus Group for more information about
soil remediation. |
