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

申请人建议有助于扩展多相组成模型CompFlow BioF，以包括基于非平衡通量的生物降解制剂，并模拟脉冲空气喷射以增强汽油源区的好氧生物降解。问题的几何形状涉及一个饱和的多孔介质只有含水层中的多组分汽油混合物是从位于渗流区的地下储罐泄漏。汽油形成轻的非水相（LNAPL），其随后在地下水位上流动并变得漂浮，随后汽油组分（基质）发生传质和平流扩散运输到原始地下水中。由于汽油组分的传质发生在水相中，基于扩散通量的生物降解模型使来自电子供体（汽油组分作为底物）的电子的化学计量平衡与电子受体（用于好氧降解的氧）反应，并在增加生物质浓度的同时去除溶解的底物。生物反应在各种限速条件下发生，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输方法允许水相和生物质相相对于另一相处于不平衡状态，并且以高度瞬时的方式发展它们的组成。这是一个显着的改进，传统的莫诺为基础的方法，假设一个准稳态近似确定的生物反应速率。因此，本提案的目的是为在包括大气喷射和水相营养物注入等增强反应技术的条件下进行有氧和厌氧生物降解的多相多组分模拟所需的知识库做出贡献。其结果将使模拟增强生物降解技术的设计，实施，并可能优化污染物羽补救系统。

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.