Description
T.H. Agriculture & Nutrition (THAN) Superfund Site
Montgomery, Alabama, USA
Project: Bioremediation of Pesticide Impacted Soil/Sediment
Summary
Soil and sediment (~4,500 tons) impacted with Toxaphene, DDT, DDD and
DDE were excavated from impacted areas on the site, including a surface
water drainage way. Impacted soils were placed in a prepared bed on site
and a cycled, anaerobic /aerobic bioremediation treatment protocol was
administered. Following the application of 3 to 12 treatment cycles,
Toxaphene, DDT, DDE, and DDD concentrations were reduced by 95%, 89%, 71%,
and 76%, respectively.
The Challenge
Toxaphene, DDT, and DDD exceeded remedial objectives in most areas of
the site. Toxaphene and DDD concentrations, in particular, were highly
elevated in some areas. We believe that Toxaphene and DDD concentrations
in this range have never been successfully remediated using a biological
treatment technology.
The Solution
Application of DARAMEND, a proprietary organic amendment, and powdered
iron through repeated and sequential application generate anaerobic and
aerobic conditions. Amendments are incorporated to a depth of two feet
using a specialized deep rotary tiller. Water is then applied to bring
soil moisture content up to 90% of the soil water holding capacity (WHC).
These steps are repeated for each treatment cycle.
The Result
The remedial goals (i.e., Toxaphene = 29 mg/kg, DDT = 94 mg/kg, DDD =
132 mg/kg, and DDE = 94 mg/kg) were reached in all areas of the treatment
cell following the application of 3 to 12 treatment cycles. The number of
treatment cycles required to reach the remedial goal was primarily
dependent on the initial concentrations. Analytical results indicate that
mean Toxaphene, DDT, DDD, and DDE concentrations were reduced from 189
mg/kg, 81 mg/kg, 180 mg/kg, and 25 mg/kg to 10 mg/kg, 9 mg/kg, 52 mg/kg,
and 6 mg/kg, respectively.
This corresponds to removal and destruction efficiencies (RDE) of 95%,
89%, 71%, and 76%. In some sampling zones, initial pesticide
concentrations were much higher than the mean concentrations, and
performance in these zones was correspondingly more effective. For
example, Toxaphene, DDT, DDD, and DDE concentrations were reduced from 720
mg/kg, 227 mg/kg, 590 mg/kg, and 65 mg/kg to 10.5 mg/kg, 15 mg/kg, 87
mg/kg, and 8.6 mg/kg, respectively, in heavily impacted regions of the
site. This corresponds to RDEs of 99%, 94%, 85%, and 87%.
The Cost
The treatment cost per ton varied according to the initial
concentration and ranged between $29/ton and $63/ton. The average unit
cost for the treatment of approximately 4,500 tons of soils was
approximately $55/ton.
The Timeline
As indicated above, variable contaminant concentrations resulted in
variable treatment time requirements. Remedial goals were reached after
three treatment cycles (6 weeks) in less heavily impacted regions on the
site, while the most heavily impacted areas required 12 treatment cycles
(24 weeks). On average, remedial goals were achieved following the
application of approximately 8 treatment cycles (16 weeks).
Companies On This Project
ADVENTUS GROUP
