The effect of aquifer heterogeneity on natural attenuation rate of BTEX |
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| Authors: | Tuba Uçanku? Kahraman Ünlü |
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| Institution: | (1) Department of Environmental Engineering, Middle East Technical University, Inonu Bulvari, 06531 Ankara, Turkey |
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| Abstract: | Monitored natural attenuation can be a viable option for remediation of groundwater contamination by BTEX compounds. Under
the field conditions, the rate of contaminant mass attenuation through natural processes, such as biodegradation, to a large
extent affected by the groundwater flow regime, which is primarily controlled by the aquifer heterogeneity. Numerical simulation
techniques were used to describe quantitatively the relationship between biodegradation rate of BTEX and aquifer heterogeneity.
Different levels of aquifer heterogeneity were described by random hydraulic conductivity fields (K) having different statistical
parameters, the coefficient of variation (CV) and the correlation length (h). The Turning Bands Algorithm was used to generate
such K fields. Visual MODFLOW/RT3D was used to simulate the fate and transport of dissolved BTEX plume within heterogeneous
aquifers. The multispecies reactive transport approach described BTEX degradation using multiple terminal electron-accepting
processes. First-order biodegradation rate constants were calculated from simulated BTEX plumes in heterogeneous flow fields.
The results showed that aquifer heterogeneity significantly affected biodegradation rate; it decreased with increasing CV
when h was in the range of up to 12 m, whereas it increased with increasing CV when h was greater than about 12 m. For well characterized aquifers, this finding could be of great value in assessing the effectiveness
of natural attenuation during feasibility studies at BTEX contaminated sites. |
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| Keywords: | Monitored natural attenuation BTEX Aquifer heterogeneity Random hydraulic conductivity fields Numerical simulation |
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