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Modeling the effects of exogenous bacteria in bioaugmentations on the fate and transport of subsurface organic contaminants.

机译：模拟生物强化中外源细菌对地下有机污染物的命运和运输的影响。

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This dissertation develops three mathematical models that represent one-dimensional contaminant transport in the presence of colloids in dual-porosity soils, two-dimensional contaminant bioaugmentation in single-porosity soils, and two-dimensional contaminant bioaugmentation in dual-porosity soils. Bioaugmentation is considered as a technique for improving inherent biodegradation processes by injecting exogenous bacteria and nutrients. The effects of the injection of bacteria and of their migration during the operation of bioaugmentation on the contaminant biodegradation processes are investigated by applying both single- and dual-porosity models to case studies. A biomodal approach is adopted to investigate the effects of the hydrogeologically ineffective region in dual-porosity soils on the contaminant transport and biodegradation. Biodegradation by bacteria in both the solid and aqueous phases is incorporated into the models, and the microcolony concept is used to represent solid phase bacteria. The models also consider permeability reduction caused by biomass accumulation.; Having proposed mathematical models to represent the fate and transport of a subsurface organic contaminant during in situ bioaugmentations, this dissertation conducts numerical experiments by applying the models to case studies. Simulation results demonstrate that the proposed models can successfully represent the fate and transport of the subsurface organic contaminant in the presence of colloids or bacteria in single- and dual-porosity soils. The presence of the immobile region in dual-porosity soils is observed to serve as a solute reservoir and to further enhance the contaminant transport in the presence of colloids. The immobile region also serves to reduce the bioavailability of contaminants and the efficiency of biodegradation processes by keeping contaminants from being utilized by bacterial metabolism. Model results indicate that, in operations of bioaugmentation, the injection of exogenous bacteria and nutrients required to accelerate bacterial metabolism clearly improves the performances of the contaminant transport. The success of in situ bioaugmentation involving the injection of bacteria and nutrients depends on controlling the contact of biodegrading microorganisms with target contaminants and supplying enough nutrients and electron acceptors to stimulate microbial activities into a contaminated zone.
机译：本文建立了三种数学模型，分别代表了在双孔隙土壤中胶体存在时的一维污染物运移，在单孔隙土壤中的二维污染物生物强化和在双孔隙土壤中的二维污染物生物强化。生物强化被认为是通过注入外源细菌和营养物来改善固有生物降解过程的技术。通过将单孔和双孔模型应用于案例研究，研究了生物强化操作过程中细菌注入及其迁移对污染物生物降解过程的影响。采用生物模式方法研究了双孔隙土壤中水文地质无效区域对污染物迁移和生物降解的影响。固相和水相中细菌的生物降解都被纳入模型中，而小殖民地概念被用来代表固相细菌。这些模型还考虑了由生物质积累引起的渗透率降低。提出了数学模型来表示就地生物强化过程中​​地下有机污染物的命运和转移，本文通过将模型应用于案例研究进行了数值实验。仿真结果表明，所提出的模型可以成功地描述在单孔和双孔土壤中胶体或细菌存在下地下有机污染物的命运和迁移。观察到在双孔隙土壤中存在固定区域，可以作为溶质储集层，并在胶体存在的情况下进一步增强污染物的迁移。不可移动区域还用于通过防止污染物被细菌代谢利用来降低污染物的生物利用度和生物降解过程的效率。模型结果表明，在生物强化操作中，注入外源细菌和加速细菌代谢所需的营养素可以明显改善污染物转运的性能。涉及细菌和养分注入的“原位”（italic）生物强化的成功取决于控制生物降解微生物与目标污染物的接触，并提供足够的养分和电子受体以刺激微生物进入污染区。

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