Parameterization of modeling subsurface hydrocarbon contamination and biosurfactant enhanced remediation processes

Subsurface hydrocarbon contamination caused by accidental spills or operational leakages of petroleum products is a global environmental concern. In order to cost-effectively and eco-friendly recover the contaminated sites, biosurfactant enhanced aquifer remediation (BSEAR) technologies have become a popular subject in both research and practice. However, the inherent uncertainties and complexities of the subsurface systems make it challenging in numerical simulation of the hydrocarbon transport and fate as well as remediation processes. Efforts in developing more efficient and robust parameterization approaches for such modeling purpose, therefore, are highly desired. This research aims to help fill the gap by developing a novel hybrid stochastic – design of experiment aided parameterization (HSDP) method for modeling BSEAR processes. The method was developed and tested based on an integrated physical and numerical modeling system comprised of a set of intermediate scale flow cells (ISFCs) and a numerical simulator named BioF&T 3D. Generally, the HSDP method was performed by: 1) building the design of experiment (DOE) models based on screened parameters and defined responses, which could reflect the goodness of fit between observed and simulated data; 2) identifying the and interactions among parameters and their significance; 3) optimizing the DOE predicted responses; 4) introducing stochastic data within reduced intervals based on the optimized parameters; 5) running Monte Carlo simulation to find the optimal responses with the corresponding combinations of parameters. The flow cell tests proved that the HSDP method could improve both efficiency and robustness of modeling parameterization and significantly reduce the computational demand without compromising the effectiveness in quantifying parameter interactions and uncertainties. Furthermore, a specific lab synthetized surfactin was applied in this study. The effect of dissolution enhancement was observed from parallel flow cell experiments especially during the first 12 hours following the initial hydrocarbon release. The HSDP method was demonstrated to be capable of advancing BioF&T 3D, which lacks the capacity of simulating surfactant. By incorporating the HSDP method, the BSEAR processes were effectively simulated with a satisfactory overall goodness of fit (R² = 0.76, 0.81, 0.83, and 0.81 for benzene, toluene, ethylbenzene, and xylene, respectively). The enhanced dissolution effect was also reflected in the modeling parameterization by increasing the first 12 hours hydrocarbon loading ratio (12LR) compared to non-biosurfactant processes. This research developed a new parameterization method HSDP, which is capable of revealing interactions of parameters, as well as quantifying their uncertainties, in a robust and efficient manner. Also, using this method, this study initiated the attempts to advance simpler numerical models in simulating complicated BSEAR processes, which is particularly attractive for the potential applications in practice

Laboratory directed research and development annual report. Fiscal year 1994

The Department of Energy Order DOE 5000.4A establishes DOE`s policy and guidelines regarding Laboratory Directed Research and Development (LDRD) at its multiprogram laboratories. This report represents Pacific Northwest Laboratory`s (PNL`s) LDRD report for FY 1994. During FY 1994, 161 LDRD projects were selected for support through PNL`s LDRD project selection process. Total funding allocated to these projects was $13.7 million. Consistent with the Mission Statement and Strategic Plan provided in PNL`s Institutional Plan, the LDRD investments are focused on developing new and innovative approaches in research related to our {open_quotes}core competencies.{close_quotes} Currently, PNL`s core competencies have been identified as integrated environmental research; process science and engineering; energy systems development. In this report, the individual summaries of LDRD projects (presented in Section 1.0) are organized according to these core competencies. The largest proportion of Laboratory-level LDRD funds is allocated to the core competency of integrated environmental research. Projects within the three core competency areas were approximately 91.4$35K or less. The projects described in this report represent PNL`s investment in its future and are vital to maintaining the ability to develop creative solutions for the scientific and technical challenges faced by DOE and the nation. The report provides an overview of PNL`s LDRD program, the management process used for the program, and project summaries for each LDRD project

The Evolution of Complex DNAPL Releases: Rates of Migration and Dissolution

A series of local and bench scale laboratory experiments and bench and field scale numerical simulations were conducted to develop a better understanding of the interrelationship between nonwetting phase (NWP) source zones and downgradient aqueous phase concentrations in saturated porous media contaminated by immiscible organic liquids. Specific emphasis was placed on the factors governing the rate of NWP source zone evolution and the factors governing the rate of mass transfer from the NWP to the aqueous phase. Hysteretic NWP relative permeability-saturation (krN-SW) relationships were measured at the local scale for six sands to examine the relationship between krN-SW functions and porous media type. Parameterization of the measured constitutive relationships revealed a strong correlation between mean grain diameter and the maximum value of NWP relative permeability. The measured krN-SW relationships, were validated through a bench scale experiment involving the infiltration, redistribution, and immobilisation of NWP in an initially water saturated heterogeneous porous medium. This match of simulation to experiment represents the first validation of a multiphase flow model for transient, fixed volume NWP releases. Multiphase flow simulations of the bench scale experiment were only able to reproduce the experimental observations, in both time and space, when the measured krN-SW relationships were employed. Two-dimensional field scale simulations of a fixed volume NWP release into a heterogeneous aquifer demonstrate the influence of spatially variable krN-S relationships correlated to porous media type. Both the volume of the NWP invaded porous media, and the length of time during which NWP is migrating, will be under predicted if variable (correlated) kr,N is not accounted for in the numerical model iv formulation. This under prediction is exacerbated as the mean intrinsic permeability of the release location decreases. A new, thermodynamically-based interfacial area (IFA) model was developed for use in the single-boundary layer expression of mass transfer as an alternative to existing empirical correlation expressions. The IFA model considers consistency and continuity of constitutive relationships, energy losses, effective specific interfacial area for mass transfer, and dissolution of residual NWP. A bench scale experiment involving the release and dissolution of a transient NWP source zone in heterogeneous porous media was conducted to evaluate the appropriateness of the developed IFA model when utilised to predict NWP dissolution rates. Comparison of measured downgradient dissolved phase concentrations and source zone NWP saturations in time and space with those from numerical simulations of the experiment reveal that the proposed IFA model is superior to both a local equilibrium assumption and existing empirical correlation expressions. This represents the first mass transfer model validated for the dissolution of a complex NWP source zone. Twodimensional simulations at the field scale of multiphase flow and dissolution suggest that employing existing mass transfer expressions instead of the IFA model lead to incorrect predictions of the life spans of NWP source zones, downgradient dissolved phase concentrations, and the rate of mass flux through a downgradient boundary. The practical implication of this research is that accurate numerical predictions of the evolution of a transient NWP source in porous media require consideration of krN-S relationships and NWP / aqueous phase IFA, as these factors dictate the rates of the key subsurface contaminant processes of migration and dissolution, respectively

Laboratory directed research and development. Annual report, fiscal year 1995

This document is a compilation of the several research and development programs having been performed at the Pacific Northwest National Laboratory for the fiscal year 1995

Tracing back the source of contamination

From the time a contaminant is detected in an observation well, the question of where and when the contaminant was introduced in the aquifer needs an answer. Many techniques have been proposed to answer this question, but virtually all of them assume that the aquifer and its dynamics are perfectly known. This work discusses a new approach for the simultaneous identification of the contaminant source location and the spatial variability of hydraulic conductivity in an aquifer which has been validated on synthetic and laboratory experiments and which is in the process of being validated on a real aquifer

Projecting the Hydrological and Geochemical Evolution of a Constructed Fen Watershed in the Athabasca Oil Sands Region, Alberta, Canada

Ongoing commercial bitumen surface mining operations have fundamentally altered large areas of forested uplands and fen peatlands in the Athabasca Oil Sands Region (AOSR), Alberta, Canada. Returning fen peatland functions that are representative of the pre-disturbance state has become a matter of increasing public interest, and has been adopted into the regulatory framework. Prompted by the prevalence of fens on the undisturbed landscape, this regulatory framework has recently mandated the trial of fen peatland reclamation at the pilot-scale to assess the viability of including these ecosystems in mine closure planning. It was hypothesized that the creation of a surrogate fen that exhibited many of the same functional traits as a natural system could be accomplished by providing a reasonable approximation of the hydrogeologic setting of peatlands characteristic to the region. This principle guided the conceptual design of the Nikanotee Fen Watershed, one of the pioneering experimental watersheds built on the post-mined landscape. The design of this pilot project incorporated an upland aquifer capable of supplying the peatland with a consistent source of water. Construction of the site was completed in January 2013, and used a combination of salvaged, process-affected, and engineered materials. Residual concentrations of sodium and other solutes imparted to the coarse tailings sand aquifer material during the bitumen extraction process, introduced the potential for rooting zone salinization that could negatively impact fen vegetation. Initial assessments of the Nikanotee Fen Watershed demonstrated that in the early post-construction period the site was functioning in accordance with the design. However, meaningful changes in the function of the system will occur as the site matures due to soil evolution, vegetation development, and the progressive transport of solutes from the upland to the fen. The timeline that these processes will evolve on preclude purely observational research and require the use of techniques that can project hydrologic behaviour into the future as the site matures. Generating information on the future efficacy of the Nikanotee Fen Watershed will be crucial to informing mine operators and reclamation planners of the viability of fen reclamation. Assessing the probable trajectory of the upland and fen was accomplished using field data, laboratory experiments, and numerical modelling. The impact of the evolving upland in the short-term (due to soil weathering) and the long-term (due to vegetation development) was investigated with soil moisture dynamics modelling. Next, a thorough characterization of the hydraulic properties that influence the fate and transport of sodium from the tailings sand aquifer was conducted with a field-scale tracer test, and laboratory experiments. Finally, the likely developmental pathway of the fen was evaluated by integrating information from the previous research into a groundwater flow and solute transport model of the watershed. These studies have (1) illustrated the impact of weathering on the soil hydraulic properties and water balance fluxes of cover soils in the early post-construction period; (2) demonstrated the value of snowmelt for recharging groundwater in the reclaimed uplands and improved the understanding of the relationship between cover soil systems and vegetation growth; (3) identified the hydraulic and transport properties of coarse tailings sand – a material that will be ubiquitous on the closure landscape; and (4) provided a novel evaluation of the hydrochemical trajectory of a constructed peatland watershed with respect to water availability and sodium concentrations, which upheld the original conceptual design, and strongly suggested that the system will continue to support fen ecohydrological function. This research represents one of the first comprehensive attempts to illuminate the probable developmental pathway of a fen reclamation pilot project in a post-mined landscape. The Nikanotee Fen Watershed has accomplished many of its epistemic goals associated with the generation of research and operational knowledge, and ultimately, appears poised to replicate fen ecohydrological function into the future by successfully regulating the limited available moisture, and managing the salinity from process-affected materials

Environmental Sciences Division: Summaries of research in FY 1996

This document describes the Fiscal Year 1996 activities and products of the Environmental Sciences Division, Office of Biological and Environmental Research, Office of Energy Research. The report is organized into four main sections. The introduction identifies the basic program structure, describes the programs of the Environmental Sciences Division, and provides the level of effort for each program area. The research areas and project descriptions section gives program contact information, and provides descriptions of individual research projects including: three-year funding history, research objective and approach used in each project, and results to date. Appendixes provide postal and e-mail addresses for principal investigators and define acronyms used in the text. The indexes provide indexes of principal investigators, research institutions, and keywords for easy reference. Research projects are related to climatic change and remedial action