A Transport-Rate-Limited Numerical Model for Simulating Cell Growth and Biodegradation Rates in Porous Soil and Rock

申请人建议研究水文地质系统中增强生物修复的数值模拟主题。这将涉及扩展多相组分数值模型CompFlow BioF，以包括传输和反应速率有限的方法来模拟电子从基质到生物质，最后到土壤空隙空间内的受体的化学计量交换。这种生物降解配方的目的是能够模拟脉冲空气喷射的高度瞬态过程，以刺激汽油源区的有氧生物降解。该几何问题涉及可变饱和多孔介质或离散裂缝的多孔岩石含水层，其中多组分汽油混合物从位于渗透区的地下储罐中泄漏。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。由于汽油组分在地下水中发生含水层尺度的质量传递，因此KLA推导出了电子供体和受体在多孔介质空隙空间内从水相到附着在多孔介质上的生物质的质量传递系数。然后，该模型将电子从电子供体（作为底物的汽油成分）到电子受体（用于有氧降解的氧气）的化学计量平衡进行反应，并在增加生物质浓度的同时去除溶解的底物。生物反应发生在各种限速条件下，包括由于以下三个过程：电子供体限制质量传递，电子受体限制质量传递，以及由于生物质促进电子传递过程的能力而限制微生物密度。转运和反应速率限制方法允许连续过渡到限制生物反应过程的三个过程中的任何一个，并最终限制羽状尺度生物降解的时空演变。该方法还支持牛顿迭代的二次收敛，使CompFlow BioF多相成分模型能够模拟真实规模的含水层问题。因此，该提案的结果有助于在包括大气空气喷射和水相营养物注射等增强反应的技术的条件下进行多相多组分有氧和厌氧生物降解模拟所需的知识库。这一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 examine the topic of the numerical simulation of enhanced bioremediation in hydrogeological systems. This will involve extending the multi-phase compositional numerical model CompFlow BioF to include a transport and reaction rate limited approach to simulate the stoichiometric exchange of electrons from the substrate, to the biomass, and finally to the acceptor within the void space of the soil. The objective of this biodegradation formulation is to be able to simulate the highly transient processes of pulsed air sparging to stimulate aerobic biodegradation of gasoline source zones. The problem geometry involves a variably saturated porous media or discretely fractured porous rock aquifer in which a multi-component gasoline mixture is leaked from an underground storage tank located within the vadose zone. The gasoline forms a 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 aquifer-scale mass transport of the gasoline components occurs in the groundwater, a KLA derived mass transfer coefficient for the mass transport of electron donor and acceptor from the aqueous phase within the void space of the porous media onto the biomass that is attached to the porous media. The model then reacts a stoichiometric 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 due to the following three process: electron donor-limiting mass transfer, electron acceptor-limiting mass transfer, and microbial density-limiting due to the capacity of the biomass to facilitate the electron transfer process. The transport and reaction rate limited approach allow for a continuous transition to whichever of the three processes is limiting the bioreaction process and ultimately the spatial-temporal evolution of the plume-scale biodegradation. This approach also supports quadratic converge of the Newton iteration allowing the CompFlow BioF multi-phase compositional model to simulate real-world scale aquifer issues. The outcome 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. This outcome will enable simulation of enhanced biodegradation technologies to design, implement, and potentially optimize contaminant plume remediation systems.