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Lab-Scale Biodegradation Study of BTEX under the Unsaturated Condition and Its Effect on Soil Matric Potential

S, Karthick., CJ, Sangeetha., T, Shashidhar.
Soil & sediment contamination 2019 v.28 no.2 pp. 171-183
BTEX (benzene, toluene, ethylbenzene, xylene), bacterial growth, benzene, biodegradation, ethylbenzene, polluted soils, pollution, soil matric potential, toluene, unsaturated flow, xylene
Benzene, toluene, ethylbenzene, and xylene are collectively known as BTEX which contributes to volatile environmental contaminants. This present study investigates the microbial degradation of BTEX in batch and continuous soil column experiments and its effects on soil matric potential. Batch degradation experiments were performed with different initial concentrations of BTEX using the BTEX tolerant culture isolated from petroleum-contaminated soil. In batch study, the degradation pattern for single substrate showed that xylene was degraded much faster than other compounds followed by ethylbenzene, toluene, and benzene with the highest μₘₐₓ = 0.140 h⁻¹ during initial substrate concentration of 100 mg L⁻¹. Continuous degradation experiments were performed in a soil column with an inlet concentration of BTEX of about 2000 mg L⁻¹ under unsaturated flow in anaerobic condition. BTEX degradation pattern was studied with time and the matric potential of the soil at different parts along the length of the column were determined at the end of the experiment. In continuous degradation study, BTEX compounds were degraded with different degradation pattern and an increase in soil matric potential was observed with an increase in depth from top to bottom in the column with applied suction head. It was found that column biodegradation contributed to 69.5% of BTEX reduction and the bacterial growth increased the soil matric potential of about 34% on an average along the column height. Therefore, this study proves that it is significant to consider soil matric potential in modeling fate and transport of BTEX in unsaturated soils.