Environmental Engineering Reference
In-Depth Information
of the specific homologue by its toxic equivalent (TEQ)
factor. To calculate
the magnitude of reduction and the rate of degradation of these contami-
nants, the initial and final concentration values were used. Zero-order (con-
centration-independent) removal rates were assumed to be due to the high
concentrations of the contaminants. Statistical significance of all chemical
and respiration data was established at a 95% confidence interval using n =
7 (LTUs) or n = 5 (troughs). Statistical differences between LTUs 1 and 2 and
between troughs 1, 2, and 3 were determined using the two-tailed critical
t-test.
The microbiological data of the LTUs were subjected to a Tukey HSD to
determine if there was significance to the differences between the data for
the two LTUs, taking into account that more than two samples were taken
(Ringelberg et al., 1989). An evaluation of similarities between single PLFA
profiles was accomplished by application of a hierarchial cluster analysis
(Wards method). PLFA concentrations, expressed as a molar percentage,
were arcsin transformed prior to the analysis. Correlations between PLFA
and other study variables were assessed by Spearman rank order correlation
statistics. Both cluster and correlation analyses were performed using the
Statistica software package, version 5.0 (Statsoft, Inc., Tulsa, OK).
Gas analysis was performed using an LMSx Multigas Analyzer
®
equipped with an infrared detector and oxygen cell (Columbus Instruments,
Columbus, OH). Oxygen, carbon dioxide, and methane concentrations in
the soil were monitored. This unit operates effectively across a temperature
range of -10 to 40˚C. The CO
2
detection range is from 0 to 40%, with an
accuracy of ±0.1%. The O
2
detection range is 0 to 25%, with an accuracy of
±0.5%. The aspiration rate is 100 ml/min. The response times are 20 and 30
sec for CO
2
and O
2
, respectively.
7.4 Accomplishments
7.4.1 Flask studies
7.4.1.1 PAH removal
Figure 7.1
6
shows the gas chromatographs of solvent extracts of POPILE
soil after the 11-month microcosm study. Panel A illustrates the untreated
soil. Some degradation was observed for some of the PAHs when the soil
was amended with bulking agent (ground rice hulls) and dried-blood fer-
tilizer (panel B). There was a dramatic decrease for many of the PAHs in the
microcosms amended with bulking agent, dried-blood fertilizer, and
P. aerug-
inosa
strain 64 on the vermiculite carrier (panel C). Although
S. paucimobilis
strain EPA 505 was previously shown to be able to degrade HMW PAHs in
pure culture, it did not increase PAH removal in the study reported here.
The high concentrations of PCP (approximately 2300 mg/kg) did not inhibit
PAH biodegradation in this soil. Table 7.13 shows the percent decrease rel-
ative to initial concentrations for PAHs in the POPILE microcosms. The
decrease in concentration is calculated as
1
/
2
absorbance from October 1999
