Description
Site: Former Pesticide Manufacturing Facility
Project: Pilot-Scale Deep In Situ DARAMEND Injection for Source
Zone Reduction of Chlorinated Pesticides
Client: Confidential
BACKGROUND
ADVENTUS conducted a laboratory study to demonstrate the effectiveness
of deep in situ DARAMEND® bioremediation of soil contaminated with
volatile organic compounds (VOCs) and organochlorine pesticides (OCPs). A
pilot-scale demonstration project is also currently proceeding on site.
The bench-scale work evaluated many DARAMEND treatment scenarios, using
numerous DARAMEND products, as well as straight anoxic conditions, versus
aerobic-anoxic cycling. The studies were performed in sealed columns to
simulate in-situ conditions and prevent contact with the atmosphere.
The best treatment consisted of the addition of DARAMEND 2002/6390Fe20,
which seamlessly integrates fibrous organic matter with 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-SCALE DEMONSTRATION
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 contaminated area was designed for. The
applications were to occur at intervals of 14 to 21 days. The targeted
zone of contamination 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
were 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 was
delivered to the site in 25 kg bags for ease of handling, and the material
was handled with negligible dust creation (Figure 1).
The DARAMEND product can be delivered in any size of bag required for
the project. To inject the product, it was placed in a hopper, and mixed
in-line with a guar solution for delivery to the subsurface
(Figure 2). To enhance groundwater movement through the
DARAMEND fractures, sand was introduced in some fractures, at ratios of
1:2 and 1:1 sand to DARAMEND by mass.
The product was successfully injected in each of the se scenarios.
Sampling of the subsurface to determine the aerial and vertical extend of
the DARAMEND injections was performed using Geoprobe sampling equipment.
The DARAMEND layers were easily visible from 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). 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.
Four 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/kg
and 12 µg/kg 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%.
Companies On This Project
ADVENTUS GROUP
