Project Description:

Bioremediation, a promising technology, utilizes microbes to break down, transform, and ultimately eliminate specific pollutants such as petroleum hydrocarbons from contaminated soil. This process can be carried out in-situ, directly within the affected environment. However, in-situ bioremediation faces challenges due to varying soil types, moisture levels, heterogeneities, and resident microorganisms. Despite these complexities, it offers significant economic and environmental benefits. Research in the literature has shown that increasing temperature accelerates microbial activity. In-situ thermal treatment for contaminated soil is gaining popularity as hazards posed by light nonaqueous phase liquids continue to grow. While numerous remediation methods are available, there is a particular emphasis on technologies capable of swiftly addressing soil contamination by diverse petroleum hydrocarbons. Thermal treatment (see Figure 1) offers rapid and efficient remediation, often achieving removal rates exceeding 99% across a broad spectrum of hydrocarbon fractions.

The overall objectives of the current project are to: (1) provide a comprehensive review of the microbial organisms present in soil and their ideal temperature requirements for activity, (2) explore thermally-enhanced bioremediation techniques utilizing a solar-underground borehole system as a renewable energy source to augment the remediation of contaminated sites, (3) develop a finite element model for analyzing the thermal treatment method, and (4) investigate the efficacy of the thermal treatment method in remediating hydrocarbon-contaminated soils.

US DOT Priorities:

This project directly supports the US DOT strategic goal related to climate and sustainability:
“Tackle the climate crisis by ensuring that transportation plays a central role in the solution. Substantially reduce greenhouse gas emissions and transportation-related pollution and build more resilient and sustainable transportation systems to benefit and protect communities.”

More than fifty percent of the US population depends on groundwater as its primary source of drinking water. Consequently, the introduction of contaminants from transportation sectors, such as leaks from aboveground storage tanks, spills from gas stations, and the use of road salts and chemical deicers, poses a significant public health risk to groundwater. Contaminants originating from diverse sources have the potential to impact drinking water wells and other receptors. Once these contaminants infiltrate the groundwater, they can migrate toward water wells and drinking water supplies. The proposed project aims to evaluate the effectiveness of thermal treatment methods for remediating contaminated soil and groundwater and to investigate the feasibility of implementing solar-underground thermal systems to enhance bioremediation techniques.

Outputs:

This study will provide a robust fully coupled finite element model that can be used to model if solar-underground systems can be used for enhancing bioremediation. 

The developed model can be used to understand the efficacy of thermal treatment under various conditions, including different subsurface geologies (homogeneous and layered), and temperature conditions (maximum subsurface temperature).  Additionally, the role of buoyant flow (natural convection and forced convection) on thermal treatment will be predicted.

The model developed in this study can be used to identify which parameters will have the most significant impact on bioremediation and thermal treatment. Additionally, by understanding the subsurface conditions that lead to buoyant flow and the influence of buoyant flow on contaminant transport, this research can inform the design and implementation of thermal treatment. The research findings will help us to better select the thermal treatment method and ideal temperature needed for bioremediation.

The model that will be developed in this project can be used to analyze the efficiency of thermally enhanced bioremediation and thermal treatment on contaminant removal. If promising the method can be used by local DOTs and federal agencies to treat the areas that are subjected to contamination from transportation sectors.

Outcomes/Impacts:

• a. The application of the research output will lead to significant changes in soil and groundwater contaminant removal. The developed model will be useful for local Departments of Transportation and federal-level agencies to predict the efficacy of thermal treatment methods depending on the types of soil and contaminant. This will inform regulatory bodies and policymakers in developing effective strategies to remediate pollution and protect soil and the environment. This project helps prevent issues raised by soil and groundwater contamination. The proposed research can model subsurface contamination removal and perform necessary remediation actions to prevent pollution risks in groundwater and drinking water.
• b. The outputs and technology developed in this research can be transferred to practice through collaboration with local Department of Transportations and federal agencies. By sharing the predictive model and findings, transportation authorities can incorporate them into their decision-making processes and remediation efforts. This will lead to changes in practice by improving the monitoring and management of soil and groundwater pollution, thereby informing policy decisions related to environmental protection and public health.
• c. The research outputs will positively impact the transportation system in several ways. By accurately predicting contamination levels and identifying subsurface contaminated zones, the transportation sector can implement targeted remediation efforts, enhancing safety and reliability. Additionally, by preventing pollution from reaching drinking water supplies, the research contributes to the durability and sustainability of the transportation infrastructure. 

The proposed project provides an excellent opportunity to train undergraduate and graduate students in performing geoenvironmental modeling. One undergraduate and one graduate student will be hired to conduct hydro-thermal-chemical modeling and explore the flow of subsurface contaminants in the ground. The outcomes of the project will be presented at national and international conferences, including the American Society of Civil Engineering – Geo-congress (GI), American Geophysical Union (AGU), and Transportation Research Board (TRB) meetings. The results will be disseminated through journal and conference proceedings. By training undergraduate and graduate students in geoenvironmental modeling, the project ensures a sustainable workforce capable of addressing future challenges in soil and groundwater remediation. The dissemination of research outcomes through conferences and publications ensures that the knowledge generated from the project reaches a wide audience and informs future research and practice in the transportation sector.