In situ field method for evaluating biodegradation potential of BTEX by indigenous heterotrophic denitrifying microorganisms in a BTEX-contaminated fractured-rock aquifer

ABSTRACT

Generally different anaerobic degradation potentials for benzene, toluene, ethylbenzene and xylene isomers (BTEX) has been reported due to site specific conditions, such as the indigenous microbial population, electron acceptors (EA) available and concentrations of each BTEX compound. It was of interest to estimate relative biodegradation potential of each BTEX compound during enhanced anaerobic bioremediation of a BTEX-contaminated aquifer. In this study, an in situ method for assessing the degradation potentials of each BTEX compound present as a mixture under NO₃⁻injecting conditions by performing a series of single-well push-pull tests and well-to-well tests (WWTs) was developed. During the 1st and 2nd WWTs, biological heterotrophic dissimilative NO₃⁻ denitrification was confirmed by simultaneous detection of both NO₂⁻ and N₂O and significant production of CO₂ during the NO₃⁻ degradation. The biodegradation fractions of NO₃⁻ injected during the 1st and 2nd WWTs were 1.7% and 5.0%, respectively, with 7.18 and 8.85 mmol N/L/day of in situ zero-order denitrification rate coefficients. The concentrations of benzene, ethylbenzene, and xylenes measured were similar to values calculated when considering only dilution, but the measured concentrations of toluene were significantly lower than the values calculated were. These results indicate that in situ method presented in the study successfully evaluate anaerobic biodegradation potential of individual BTEX compounds by indigenous heterotrophic denitrifying microorganisms.

GRAPHICAL ABSTRACT

KEYWORDS:

• Well-to-well test
• BTEX
• dissimilative heterotrophic denitrification
• in situ zero-order rate coefficients
• biodegradation fraction

Acknowledgements

This research was supported by a Korea University grant. This article has not been reviewed by these agencies, and no official endorsement should be inferred.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This research was supported by a Korea University grant.