Handbook of Solvents - George Wypych - ChemTech - Ventech!

23.1 Natural attenuation of chlorinated solvents 1609
Figure 23.1.10. Centerline output. Cape Canaveral Air Force Base,
Florida. [From references 109].
ygen readings at the site were less
than 0.7 mg/L at all monitoring
points. The rate coefficients were
calculated by calibrating the
model to the 1997 field data. The
source zone was simulated as a
spatially-variable source and the
source concentrations ranged
from 0.001 to 98.5 mg/L for the
various compounds as shown in
Table 23.1.12. The source thickness
was estimated by using the
deepest point in the aquifer where
chlorinated solvents were detected.
Centerline concentrations
for all five species (PCE, TCE,
c-DCE, VC and ETH) predicted by the model are shown in Figure 23.1.10. Figure 23.1.10
shows the centerline predictions for each chlorinated solvent and a no degradation curve for
all of the chlorinated solvents as well as field data. The data in Figure 23.1.10 indicate that
TCE concentrations discharging into the ocean will be less than 0.001 mg/L.
23.1.6.3 RT3D numerical model
RT3D (Reactive Transport in 3 Dimensions) 111 is a FORTRAN 90-based model for simulating
3D multi-species, reactive transport in groundwater. This model is based on the 1997
version of MT3D (DOD Version 1.5), but has several extended reaction capabilities. RT3D
can accommodate multiple sorbed and aqueous phase species with any reaction framework
that the user needs to define. RT3D can simulate different scenarios, since a variety of
pre-programmed reaction packages are already provided and the user has the ability to specify
their own reaction kinetic expressions. This allows, for example, natural attenuation processes
or an active remediation to be evaluated. Simulations can be applied to modeling
contaminants such as heavy metals, explosives, petroleum hydrocarbons, and/or chlorinated
solvents.
RT3D’s pre-programmed reaction packages include:
1 Two species instantaneous reaction (hydrocarbon and oxygen).
2 Instantaneous hydrocarbon biodegradation using multiple electron acceptors
- 2+ 2-
(O2,NO3,Fe ,SO4,CH4). 3 Kinetically limited hydrocarbon biodegradation using multiple electron acceptors
- 2+ 2-
(O2,NO3,Fe ,SO4,CH4). 4 Kinetically limited reaction with bacterial transport (hydrocarbon, oxygen, and
bacteria).
5 Non-equilibrium sorption/desorption. Can also be used for non-aqueous phase
liquid dissolution).
6 Reductive, anaerobic biodegradation of PCE, TCE, DCE, and VC.
7 Reductive, anaerobic biodegradation of PCE, TCE, DCE, and VC combined with
aerobic biodegradation of DCE and VC.
8 Combination of #3 and #7.