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Experimental Study of Water Flow on Migration of DNAPL in Fracture Network: Distribution, Transport and Remediation using Density Modification of Surfactant

Shirzadi, Vahid | 2025

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 58020 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Ghazanfari, Mohammad Hossein
  7. Abstract:
  8. Groundwater is one of the vital sources of drinking water worldwide, yet it faces the risk of contamination from organic and inorganic substances. These pollutants can persist in the environment for extended periods, leading to continuous contamination. One of the key factors in the rapid transport of these contaminants is the presence of fracture networks within porous media. These fractures play a crucial role in facilitating the movement of pollutants to deeper layers of groundwater aquifers. The fracture networks enable contaminants to migrate more rapidly and penetrate various regions, complicating pollution management. Additionally, the natural flow of groundwater acts as a driving force for the displacement of these pollutants. To address these threats, accurate data obtained through laboratory studies on pollutant distribution and behavior is essential.In this study, two porous media models were designed and constructed: the first model contains a fracture network, while the second represents a heterogeneous porous medium. The fractured flow model was designed to include both horizontal and vertical fractures to precisely investigate their effects on the transport and dissolution of trichloroethylene (TCE). A flushing fluid was injected into these porous media at a controlled flow rate to examine the impact of flow rate variations on contaminant transport and dissolution. Due to its higher density, TCE migrates to the lower sections of the medium, requiring the flushing fluid to overcome gravitational forces. Therefore, a specialized remediation technique must be employed for subsurface cleanup.The investigation of TCE transport and remediation in fractured and heterogeneous porous media revealed significant differences in contaminant entrapment within different regions of the two models. In fractured systems, fractures pose significant challenges for remediation and require a more detailed examination. Horizontal fractures facilitate the easier migration of TCE, while vertical fractures act as reservoirs for contaminant storage. The remediation of these vertical zones was one of the main challenges of this study. By applying surfactant density modification, which reduces surface tension and overcomes gravitational forces, a significant reduction in TCE saturation was observed, confirming the effectiveness of this approach.Furthermore, mass transfer of the non-aqueous phase under different flow rates and flushing solutions was analyzed, leading to the development of new empirical correlations for the modified dimensionless Sherwood number as a function of the Reynolds number and saturation level. This research contributes to the advancement of scientific knowledge regarding mass transfer in fractured porous media and aids in the development of more effective strategies for groundwater remediation
  9. Keywords:
  10. Dense Non-Aqueous Phase Liquids (DNAPL) ; Densifier ; Fracture Network Modeling ; Surfactant Density Modification ; Groundwater ; Trichloroethylene

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