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

• Published in: Environmental technology 2021-04, Vol.42 (9), p.1326-1335
• Main Authors: Han, Kyungjin, Hong, Uijeon, Park, Sunhwa, Kwon, Sooyoul, Kim, Young
• Format: Article
• Language: English
• Subjects: Anaerobic biodegradation; Anaerobic microorganisms; Aquifers; Benzene; Benzene Derivatives; Biodegradation; biodegradation fraction; Biodegradation, Environmental; Bioremediation; BTEX; Carbon dioxide; Denitrification; Dilution; dissimilative heterotrophic denitrification; Ethylbenzene; Evaluation; Groundwater; Heterotrophic microorganisms; Hydrocarbons; in situ zero-order rate coefficients; Isomers; Mathematical analysis; Microorganisms; Nitrogen dioxide; Nitrous oxide; Toluene; Well-to-well test; Xylene; Xylenes
• ISSN: 0959-3330; 1479-487X
• DOI: 10.1080/09593330.2019.1668482

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 NO 3 − 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 NO 3 − denitrification was confirmed by simultaneous detection of both NO 2 − and N 2 O and significant production of CO 2 during the NO 3 − degradation. The biodegradation fractions of NO 3 − 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.