Environmental Engineering Reference
In-Depth Information
100
80
60
40
20
0
0
10
15
30
Days
Non-inoculated control
10
4
cells . g
−1
of sediment
10
6
cells . g
−1
of sediment
Figure 6.19
PCB degradation in 50% slurry microreactors.
In our trials, two cell densities were used, a low density of ~10
4
cells/g
and a high density of ~10
6
cells/g. Rifampicin-resistant cells were grown in
liquid K1 mineral salt media with 20 m
M
biphenyl and then transferred to
K1 with 2 m
M
2-CBA (LB400(
ohb
)) or 4-CBA (RHA1(
fcb
)) to log phase. Cells
were then added to fine-grade vermiculite. We used vermiculite at a rate of
3% w/w vermiculite to soil. We diluted our inoculum with nonsterile tap
water so that we added a total volume of 1 ml of dilute inoculum to 1 ml
of vermiculite. We homogenized the inoculum/vermiculite mixture and then
added it to soil. In the nonvermiculite treatment, we diluted the inoculum
to a volume that would adjust the soil water potential to -0.5 bars. This
volume is dependent on the water potential of the soil and must be adjusted
for each new case.
Prior to the addition of the inoculum, 2-CBP or 4-CBP was added from
a 1
M
stock to 4 ml of acetone, which was dribbled into the soil with constant
stirring. The soil was then vigorously mixed in a sealed metal container for
30 min and allowed to stand overnight at room temperature for volatilization
of acetone from the soil. Two grams of inoculated, chlorobiphenyl-contam-
inated soil was dispensed into each of 24 10-ml serum vials per treatment,
and these were then sealed with a Teflon-coated rubber septum and crimp
top. Samples were taken at random, in triplicate over the course of the
experiment. Microcosms were incubated at 25˚C and sampled on days 0, 2,
5, 10, 15, 20, 30, and 60. Sampling was done by injecting 5 ml of 10 m
M
