An improved sharp interface model for characterizing the transport and extraction of subsurface LNAPL

Abstract

Multiphase extraction (MPE) is widely used as an in situ method for the remediation of groundwater contaminated by light non-aqueous liquid (LNAPL). For the purpose of achieving the best performance of MPE remediation, it is critical to accurately characterize the LNAPL transport processes above the groundwater table with an easy-to-use model. In this study, we developed an improved sharp interface model considering constant head at the well screen and shark-fin distribution of LNAPL saturation above groundwater table. The model was successfully validated using the test data of Lari et al. (2018). The results indicate, the LNAPL extraction rate is most sensitive to the properties of fluid and media. Also, this improved model was used to analyze the effects of technical parameters such as submersible position of oil pump and water extraction rate on remediation performance, we observed that in the case of a single-pump MPE, even after changing the hydraulic conductivity and porosity of the media, the optimized location of the submersible LNAPL pump is halfway inside the well. Similarly, in the case of dual-pump MPE, an increasing pump rate of water (Qw) promotes the LNAPL extraction rate, and an empirical relationship between the optimized LNAPL pump position (ms) varies with the Qw exhibiting a certain pattern. Overall, the improved sharp interface model better interprets the field MPE data compared to the interphase mass-transport model proposed by Lari et al. (2018). Therefore, the proposed model characterizes LANPL transport during LNAPL extraction better and can also be utilized to optimize the MPE more comprehensively.