Environmental Engineering Reference
In-Depth Information
Trials were next done to determine the viability of vermiculite-immobi-
lized
P. aeruginosa
strain 64 in the soils with intact autochthonous commu-
nities and to compare survival of immobilized cultures to that of cultures
added directly to the soil.
7.3.5.6 Microcosm preparation
Microcosms were established in triplicate in sterile plastic specimen cups
with tight-fitting snap lids. PAH-contaminated soil (100 g) from the POPILE
site was added to each cup. The distribution of amendments to the contam-
inated soil is shown in Table 7.11. The soil was mixed with an equal volume
of ground rice hulls as a bulking agent. The dried blood was added at a rate
of 2% of the wet weight of the soil. Vermiculite inoculated with
P. aeruginosa
strain 64 or with
S. paucimobilis
strain EPA 505 was added at 2% by weight
of soil. Bacteria in broth were added to 2 g of vermiculite and allowed to
soak for approximately 20 min. Deionized water was added to all micro-
cosms as needed to maintain a water content of 30 to 40% by weight, and
cup contents were stirred thoroughly each week to simulate tilling of land
treatment units.
7.3.5.7 Microbial analysis
The microcosms were sampled by adding 1 g of soil to 10 ml of saline (0.75%
NaCl). The tubes were shaken vigorously. Appropriate dilutions were made
and aliquots were plated on LB agar with 0.3% glycerol. The plates were
incubated 24 to 72 h at 30˚C, and colony-forming units were counted.
7.3.5.8 Chemical analysis
PAHs were extracted from soil microcosm samples by mixing 10 g of soil
with 5 g of diatomaceous earth, which had been baked at 450˚C for 4 h to
remove moisture. Diatomaceous earth was used to be sure the soil sample
was completely dry before solvent extraction, as per the manufacturer's
recommendations. This mixture was allowed to dry on the bench overnight,
packed into an extraction cell, and extracted with a methylene chloride:ace-
tone (50:50) mixture in an ASE 200 (Dionex) solvent extractor at 1500 psi and
Table 7.11
Experimental Design of the Flask (Microcosm) Study
Variable
Control
Test A
Test B
Test C
Contaminated soil (100 g)
X
X
X
X
Bulking agent; rice hulls (1:1)
X
X
X
Fertilizer; dried blood (2%)
X
X
X
Biosurfactant producer;
P. aeruginosa
strain
64 (2%)
X
X
HMW PAH degrader;
S. paucimobilis
strain
EPA 505 (2%)
X
