Development and Evaluation of Semicontinuous Slurry Microcosms to Simulate in Situ Biodegradation of Trichloroethylene in Contaminated Aquifers

Abstract

Trichloroethylene (TCE) was efficiently biodegraded in situ by aerobic cometabolism at the Moffett Federal Airfield test site, in the presence of phenol or toluene (Hopkins et al. Appl. Environ. Microbiol. 1993, 59, 2277; Hopkins et al. Environ. Sci. Technol. 1993, 27, 2542; Hopkins, G. D.; McCarty, P. L. Environ. Sci. Technol. 1995, 29, 1628). Using uncontaminated soil from this site as an inoculum, a semicontinuous slurry microcosm method was developed that reproduced in situ TCE degradation rates. The slurry method was then applied to evaluate the in situ TCE biodegradation potential at Edwards Air Force Base where full-scale application was contemplated. With 0.66 mg/L TCE and either 9.7 mg/L toluene or 13.4 mg/L phenol in the exchange fluid, steady state TCE removals varied between 87 and 99%, depending upon sample depth. Toluene and phenol growth yields based upon oxygen to substrate ratios were 0.77 and 0.59 g/g during the start-up phase and 0.52 and 0.36 g/g during steady state TCE removal, respectively. The TCE degradation rate constant ratio, k c/K c, was similar for the two substrates. Steady state TCE removals varied little in a given microcosm over 1 year of operation. In the Moffett and Edwards microcosms as well as at Moffett Federal Airfield (Fries et al. Appl. Environ. Technol. 1997, 63, 1523), toluene o-monooxygenase was the dominant TCE-oxidizing enzyme present.

Degradation kinetics of chlorinated aliphatic hydrocarbons by methane oxidizers naturally-associated with wetland plant roots

“…The ratio of initial [CH 4 ] to initial [TCE] in the study was~104, in comparison to 0.34-12 found in previous studies (Jenal-Wanner and McCarty, 1997). In 1,1,1TCA treatments, its concentrations were not significantly different between the live microcosms and killed controls in cycles C1 through C4 with CH 4 (one-way RM ANOVAs, treatment effect, time effect, P N 0.05, Fig.…”

“…The biomass yield, Y, reported here (Table 2) is slightly greater than literature values possibly because Jenal-Wanner and McCarty (1997) compared the ratio of stoichiometric O 2 to CH 4 loss with actual values in the experiment. The same study (Jenal-Wanner and McCarty, 1997) further indicated that the biomass estimate by their method can be higher because of losses in both soluble and particulate biomolecules, which in this study may have occurred as the supernatant was discarded after each cycle.…”

Semicontinuous microcosm study of aerobic cometabolism of trichloroethylene using toluene

“…Kuo). [10,11], phenol [12][13][14][15], and toluene [6,7,[14][15][16]. The toluenegrown TCE-degrading bacteria such as, Pseudomonas putida [17], Burkholderia cepacia G4, Ralstonia pickettii PKO1, and Pseudomonas mendocina KR1 [18], are reported in the literature.…”

A study on cometabolic bioventing for the in situ remediation of trichloroethylene

“…Jenal-Wanner and McCarty (1997) which the high TCE concentrations would have impaired the effectiveness of the microorganisms. The numbers of methane oxidizing bacteria increased substantially during cometabolic bioventing, with about 10 7 cells mL )1 at the end of the experiment.…”