Field scale modeling of BTEX released from multiple source zones

Abstract

A field-scale three-dimensional numerical flow and transport model was applied to simulate the fate and transport of benzene, toluene, ethylbenzene, and xylenes (BTEX) from six source zones of light non-aqueous-phase liquids (LNAPLs). A number of scenarios were defined to evaluate the effect of natural attenuation and enhanced remediation methods on the fate of BTEX. Two strategies were defined for cleaning up the site: (1) reduction of BTEX over the entire site down to the maximum concentration limit (MCL), and (2) remediation of the site to a level that reduces BTEX below MCLs only at the nearest discharge wells. The results show that under natural attenuation alone, the remediation time for benzene (time needed to decrease concentrations to a specified level) is more than 60 years, whereas that of TEX is longer, but only benzene will reach the receptors. LNAPL removal and enhanced bioremediation techniques could decrease this time to about 30 years for benzene. A cost-effective two-stage enhanced remediation operation should be applied. In the first stage, the entire dissolved BTEX plume should be treated, whereas in the second stage, after the remediation of benzene, the operation area should be limited to the remaining TEX plume areas. In the second strategy, air injection will be sufficient to prevent the BTEX plume from reaching the receptors. Addition of oxygen and hydrogen peroxide is likely too expensive.