Environmental Engineering Reference
In-Depth Information
Table 7.2
A list of treatments used in the experiment. Those treatments not receiving bacterial
inoculum received 75 ml of sterile distilled water
Treatment
Petroleum
conc. (ppm)
Arte-
misia
Alfalfa
Basal salt
mixture
(BSM)
a
Bacterial
inoculum
Biosurfactant
1. Plant control
0
Ye s
Ye s
Ye s
No
No
2. Petroleum control
10,000
Ye s
Ye s
Ye s
No
No
3. Plant only
10,000
Ye s
Ye s
Ye s
No
No
4. Bacteria only
10,000
Ye s
No
No
Yes—75 ml
No
5. Plant + Bacteria
10,000
Ye s
Ye s
Ye s
Yes—75 ml
No
6. Plant +
Biosurfactant
10,000
Ye s
Ye s
Ye s
No
Yes—30 ml
7. Plant + Bacteria +
Biosurfactant
10,000
Ye s
Ye s
Ye s
Yes—75 ml
Yes—30 ml
a
75 ml per pot
bacteria and pure biosurfactant were tested on a degradation of 10,000 ppm petro-
leum spiked into sterilized Absheron soil. These factors alone, and in combination,
were studied together with petroleum degradation data, plant biomass and microbial
analysis with the intention to understand the complex interactions present in the
petroleum contaminated soil.
In Table
7.2
different treatments examined are mentioned. Samples from control
plant with no petroleum content demonstrated distinguished amount TPH/g dry soil
at zero time; taking into account that the chromatogram did not show the character-
istic peaks for used petroleum samples, so we considered it as a zero point.
Twenty eight days after the start of the experiments, less than 20 % of TPH re-
mained in all treatments (Fig.
7.1
). After 56 days, this value stabilized at about 10 %
with no further observable degradation. Although the difference among treatments
was not significant, it did appear that variants 6 (with bacterial inoculum) and 7
(bacterial inoculum + biosurfactant) had more rapid degradation of petroleum in
the rhizosphere of all plants but more in wormwood. TPH was found to be 15 ± 6 %
and 9 ± 5 % after 14 days as compared to about 40 % under treatment with petroleum
control. The sample from our petroleum control showed about 14 % decrease in
TPH content by the end of the experiment, which could have been due to evapora-
tion of light petroleum fraction (Gremoin et al.
2004
).
Another trend revealed in the course of this study was the increase in number
of bacteria over 70 days of incubation in treatments 5 and 7 compared to that in 4.
Presence of all plants affected the increase of bacterial population by 70th day of in-
cubation with some advantage of wormwood and alfalfa versus ryegrass (Fig.
7.2
).
Such an effect can be explained that nutrition from root exudates may influence
the structure and activity of a soil microbial community (Burgmann et al.
2005
).
The samples with biosurfactant addition demonstrated a sharp increase in bacterial
amount sooner, than without it, and at 28th and 56th day of incubation respectively.
It might be due to turning on by facilitation of hydrocarbons by biosurfactant for
bio- and phyto-degradation (Huang et al.
2004
).
