Environmental Engineering Reference
In-Depth Information
soil temperature averaged 12˚C. Microbial contaminant degradation also
continued at high levels during this time. The PAH-degrading bacteria
appear to remain active over a wide range of temperatures. The increase in
CO
2
production after tilling is evident in troughs 2 and 3 within 2 h (Figure
7.35).
7.4.4 Comparison of LTUs and troughs
Using normalized concentrations to account for addition of the bulking
agent, the results from land-farming PAHs are shown in Figure 7.36. Both
biostimulation and bioaugmentation improved the rate of PAH degradation
over that of traditional land farming and natural attenuation. Bioaugmenta-
tion showed the most rapid process initially, eliminating much of the bacte-
rial acclimation time. Efforts should be made to determine how to sustain
this initial rapid phase. Reapplication of the slow-release nitrogen and the
carrier bacteria element are two parameters that require further investiga-
tion. Table 7.19 summarizes the results of the pilot study conditions in terms
of overall removal, the speed of the process, and the microbial community
produced. Both supplementation and bioaugmentation used alone or in
conjunction with other treatments (chemical, physical, or biological) show
promise in the remediation of highly contaminated soils that have previously
been considered unsuitable for land farming.
25
8
20
6
15
Average O
2
4
Average CO
2
Tilling
10
2
5
0
0
300
400
500
600
700
800
900
1000
Time (hours)
Figure 7.35
The effect of tilling on microbial respiration in trough 2.
