Environmental Engineering Reference
In-Depth Information
Groundwater
observation well
Zone C
P7 P8
P9 P10
B4
P12
P13
Gas-sampling
port
P11
G3
G4-2
P3 P4
B5
G4-1
G5-1 G5-2
B2
P5 P6
G1
G2
P1 P2
B1
B3
Container with the
ozone generator
Distributor
Oxygen tank
Zone B
Zone A
N 2 -tank
NH 3 -tank
Input collector
60
Collector
Zone A
fence
50
G6-1
G6-2
40
Gas injection port
G7
P14
30
Groundwater
observation well
20
10
O 2 -injection
NH 3 -injection
0
0
100
200
300
400
500
600
Time in days
FIGURE 10.19
Left: map of the Schwarze Pumpe drain and gate test site with the reactive zones A to C; right:
evidence of iron removal by gas injection in zone A at the collector well.
oxidation (36%), or transferred and consumed in the vadose zone (51%)
without provoking a dominant stripping of VOC. With a 150-day lag time,
enhanced aerobic biodegradation of the complex organic and inorganic con-
taminant plume was initiated and reached up to 11% of consumption of the
total oxygen gas supply. Simultaneous heterotrophic and autotrophic bio-
degradation was found (Figure 10.20) and chemical oxidation from the initial
excess supply of oxygen gas was also found. However, nitrification in zone C
remained limited as the required chemical preoxidation of the hydrocarbon
mass by ozone in the gate reactor of zone B was not turned on during the
test period. Degradation rates were found to be 0.05-0.1/day for benzene and
short-chained alkyl phenols (Uhlig, 2010).
The Schwarze Pumpe site example demonstrated the suitability of gas
PRBs in treatment train applications, particularly when a complex con-
tamination situation is present. Often, site restoration and impact reduction
targets cannot be achieved or conducted economically by stand-alone appli-
cations of a main treatment technology (e.g., a pump and treat). The applica-
tion of gas PRBs offers a wide range of aerobic and anaerobic conditioning.
Posttreatment or polishing measures are required (e.g., for final degradation
of CHC, hydrophilic alcohols [in situ flushing] or phenols [MPPE] extraction).
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