Environmental Engineering Reference
In-Depth Information
Figure 6.28
Medium solids reactor 1.
oval-shaped iron pan with an open top. The top is covered with an airtight
Plexiglas lid. The total volume of this reactor is 360 L, with dimensions of
122 m × 0.61 m × 0.61 m. Contaminated soil at field moisture content was
treated in this high solids reactor. The reactor was equipped with a leachate
collection system at the bottom, consisting of a 10 cm gravel layer covered
with a geomembrane. A perforated aluminum sheet covered the geomem-
brane for uniform distribution of soil in the reactor. The process needs
minimal maintenance; however, the treatment efficiency is low, with pro-
longed treatment times. The major advantage of this bioremediation option
is that the treated material does not require any postremediation dewatering
for disposal/reuse. During the aerobic phase, soil was aerated by tilling/
mixing the soil with a low-power rotary cultivator.
Each treatment system underwent a two-phase cycle: an anaerobic
dechlorination phase followed by an aerobic degradation phase. The anaer-
obic phase trigger was 6 to 8 months or a predetermined percent dechlori-
nation, whichever comes first. The aerobic phase followed the anaerobic
phase and lasted for about 2 to 4 months.
All three reactors in each bioremediation process were seeded with
anaerobic inoculum obtained from Hudson River sediment. Anaerobic inoc-
ulum was applied at 0.8% w/w (dry solid:dry soil). In two of the reactors
for each bioremediation process (Table 6.9), iron (20 m
M
FeSO
4
in pore water)
