Description
Wood Treatment Site
Confidential Client
Project: Biotreatment of Sludge Impacted by Organic Wood
Preservatives
Summary
Adventus conducted laboratory and field-scale pilot
studies to demonstrate the effectiveness of aerobic DARAMEND®
bioremediation technology to treat soil (lightly impacted) and sludge
(heavily impacted) by organic wood preservatives (creosote [polycyclic
aromatic hydrocarbons; PAHs] and pentachlorophenol [PCP]). Laboratory
studies conducted to support field-scale designs included a control (i.e.,
sludge only) and a number of aerobic treatments, each consisting of one or
a combination of the following parameters; (i) soil moisture content
adjustment, (ii) addition of DARAMEND bioremediation products, and (iii)
addition of inorganic nutrients (i.e., phosphorus and nitrogen). Soil
treatment consisted of biweekly monitoring of pH and soil moisture content
plus manual mixing of the soil/sludge to promote oxic conditions.
The Challenge
Treat soil lightly impacted and sludge heavily impacted by organic wood
preservatives (PAHs and PCPs).
The Solution
Substantial removal of CPs was achieved after 150 days of DARAMEND
treatment (Table 1 right). The highest removal efficiency
(>99%) occurred with the 10% sludge/90% soil mixture. Here, total CP
concentrations were reduced from 392 mg/kg to 1.97 mg/kg (n=2). Effective
removal of CPs was also achieved in treatments with higher sludge content.
For example, a 91% reduction (from 1,126 mg/kg to 101 mg/kg total CPs) was
achieved with a 40% sludge content. Substantial removal of PAHs was also
achieved after 150 days of DARAMEND® treatment (Table 2
right).
The highest removal efficiency (>95%) also occurred with the 10%
sludge/90% soil mixture, which supported a reduction in total PAHs from an
initial concentration of 219 mg/kg to 10.14 mg/kg (n=2) following 150 days
of treatment. Leachability studies have shown these patterns of removal to
support the position of using alternative end-points because the residual
PAH constituents are not bioavailable (i.e., biostabilization).
The Result
The biological processes required at least 60 days of acclimation (lag
time) before biodegradation of PCP commenced (Figure 1). The treatment
regimes with a higher percentage of sludge required a slightly longer lead
time. Ultimately, the treatment regimes with the lower proportion of the
heavily impacted sludge (10 or 20%) mineralized 35 to 50% of the added
radiotracer; mixtures containing 40% sludge mineralized approximately 30%
of the 14C-PCP within the first 150 days of treatment. Removal of both CPs
and PAHs continued with extended incubation time, which suggests that
treatment beyond 150 days would result in even lower residual
concentrations of monitored organic constituents. Depending on material
end use, the site-specific remedial objectives range from 3 to 20 mg/kg
for PCP and from 10 to 100 mg/kg for total PAHs.
These data proved that the various soil/sludge mixtures could be
effectively bioremediated using the aerobic DARAMEND® technology.
Field-scale pilot studie sare scheduled to begin in early 2004 using
approximately 25 yd³ of three soil/sludge mixtures (9:1, 4:6 and 2:8
ratios).
The Cost/Timeline
The estimated cost of treatment for the 4:6 materials ratio is
approximately $100/yd³, assuming a 12-month treatment time to reach the
industrial standards and 15-months of treatment time to reach the lower
residential standards.
Companies On This Project
ADVENTUS GROUP
