Numerical Simulation of Air Sparging for Enhanced Aerobic Biodegradation of Gasoline in the Subsurface

申请人建议扩展多相组分模型CompFlow BioF，以包括非平衡通量生物降解配方，并模拟脉冲空气喷射以增强汽油源区的好氧生物降解。该几何问题涉及一个可变饱和多孔介质含水层，其中多组分汽油混合物从位于渗流区内的地下储罐中泄漏。汽油形成轻非水相（LNAPL），随后在地下水位上被动员并变得浮力，随后汽油成分（基质）的传质和平流扩散运输进入原始地下水。由于汽油组分的质量传递发生在水相中，基于扩散通量的生物降解模型反应了电子从电子供体（汽油组分作为底物）到电子受体（氧用于好氧降解）的化学平衡，并在增加生物质浓度的同时去除溶解的底物。生物反应发生在各种限速条件下，包括电子供体限制、电子受体限制和微生物密度限制。基于扩散通量的质量传递方法允许水相和生物质相相对于另一相处于不平衡状态，并以高度瞬态的方式演变其组成。这是对传统的基于monod的方法的重大改进，该方法假设一个准稳态近似来确定生物反应速率。因此，本提案的目的是为在包括大气空气喷射和水相营养注入等技术的条件下进行多相多组分的好氧和厌氧生物降解模拟提供所需的知识库。结果将使模拟增强的生物降解技术能够设计、实施和潜在地优化污染物羽流修复系统。

The applicant proposes to contribute to extend the multi-phase compositional model CompFlow BioF to include a non-equilibrium flux-based biodegradation formulation and simulate pulsed air sparging for enhanced aerobic biodegradation of gasoline source zones. The problem geometry involves a variably saturated porous-media-only aquifer in which a multi-component gasoline mixture is leaked from an underground storage tank located within the vadose zone. The gasoline forms an light-non-aqueous phase (LNAPL) which subsequently mobilizes and becomes buoyant on the water table, with subsequent mass transfer and advective-diffusion transport of the gasoline components (substrate) into the pristine groundwater. As mass transport of the gasoline components occurs in the aqueous phase, the diffusive flux-based biodegradation model reacts a stochiometric balance of electrons from the electron donor (gasoline components as substrate) to the electron acceptor (oxygen for aerobic degradation) and removes dissolved substrate while increasing the biomass concentration. Bioreactions occur under various rate-limiting conditions including, electron donor-limiting, electron acceptor-limiting, and microbial density-limiting. The diffusive flux-based mass transport approach allows for the aqueous and biomass phases to be in disequilibrium with respect to another, and evolve their composition in a highly transient manner. This is a significant improvement over the conventional Monod-based approach which assumes a quasi-steady-state approximation for determining the bioreaction rate. The objective of this proposal is therefore to contribute to the knowledge base required for the multi-phase multi-component simulation of aerobic and anaerobic biodegradation under conditions that include technologies to enhance reactions such as atmospheric air sparging and aqueous phase nutrient injection. The outcome will be to enable simulation of enhanced biodegradation technologies to design, implement, and potentially optimize contaminant plume remediation systems.