Environmental Engineering Reference
In-Depth Information
7.4.3.3 Microbial characterization
The dried blood used in the troughs to provide a slow-release source of
nitrogen was a complicating factor in phospholipid analysis, which was
overcome by looking for lipopolysaccharide fatty acids unique to
P. aerugi-
nosa
strain 64. These are 3OH10:0 and 3OH12:0. They were found in the
initial samples and at month 3. The change in biomass over the course of
the study is shown in Figure 7.32. The first month of the study saw large
increases in biomass in troughs 2 and 3, particularly in trough 3. This was
presumably due to the bioaugmentation. The addition of dried blood
enhanced microbial abundance by a factor of 4 to 15 times. However, the
significant early differences had disappeared by month 3. Trough 3 then
demonstrated a rapid recovery until 10 months, when biomass values were
again similar between troughs 2 and 3.
The early increases in microbial abundance in trough 3 were associated
with a clearly defined shift in microbial community composition from that
apparent in trough 1 (control) but not trough 2 (biostimulation). The relative
abundance of PLFAs detected in troughs 2 and 3 is clearly distinct from those
detected in trough 1, regardless of the time sampled (Figure 7.33). In trough
1, Gram-positive PLFA biomarkers averaged between 15 and 25% through-
out the 41-week time trial. In troughs 2 and 3, the relative abundance never
exceeded 9%, and it averaged 6%.
The low relative abundance of Gram-positive bacterial biomarkers in
troughs 2 and 3 was offset by increases in the relative abundances of
Gram-negative bacterial biomarkers. The PLFA pattern detected in both of
these troughs strongly suggests the enhancement of a Gram-negative
pseudomonad community.
14000
12000
10000
8000
6000
4000
Pan1 - control
Pan2 - biostimulation
Pan3 - bioaugmentation
2000
0
0
2
4
6
8
10
12
Time (months)
Figure 7.32
Effect of different amendments on biomass in trough pilot study.
