(45b) Investigation of Fate and Transport of Organic Contaminants in Soil Columns Packed with Different Soil Textures

Leaking underground storage tanks and accidental spills have contaminated our subsurface solid matrices. Although great strides have been made in underground storage tank (UST) design and release prevention technology in hopes of reducing hydrocarbon spills statewide, understanding interactions between hydrocarbons and soil is critical to selecting remediation methods needed to protect the state's water resources. This project ties in with the areas of fate and transport of contaminants for groundwater and improved methods for groundwater remediation and hydrologic and hydraulic modeling processes. This project seeks: (i) to conduct adsorption isotherm experiments to characterize the adsorption of various contaminants (e.g., petroleum hydrocarbons, chlorinated organics, and heavy metals) onto various types/textures of soil, (ii) to conduct continuous flow experiments through packed soil columns to determine the breakthrough characteristics and retardation coefficients; (iii) to model the results from the batch experiments using various isotherm models (e.g., Langmuir and Freundlich isotherms), and (iv) to model the results from the continuous flow packed bed experiments using the bed depth-service time model and the 1-D and 2-D advective dispersion models describing flow through columns.

The project objectives are: (1) to quantify the adsorption characteristics obtained for the Langmuir and Freundlich isotherm models as a function of the soil texture/soil type; (2) to compare and contrast the adsorption characteristics for adsorption of selected common contaminants (e.g., petroleum hydrocarbons, benzene, toluene, ethylbenzene, xylenes, chlorinated organics, and heavy metals) to observe the effect of contaminant molecular structure (e.g., chain length, aliphatic vs. aromatic compounds, saturated vs. unsaturated organic structures, etc.) on the adsorption characteristics of these compounds on various types of soils; (3) to determine the retardation coefficients of the various contaminants in continuous flow experiments in soil columns packed with soils of different texture; (4) to determine whether the hydraulic conductivity/permeability changes over time for different contaminants and treatment conditions; (5) to determine whether the soil columns can be effectively treated by injecting microorganisms or by introducing in-situ oxidation chemical agents in the injection fluids; and (6) model the performance of the flow through the packed bed/soil columns using the bed depth-service time relationship and the 1-D and 2-D advective dispersion transport models.

The general approach for the packed column experiments involves performing both batch and continuous flow operation in order to generate sufficient data to pursue follow-on funding to perform the research in pilot-scale demonstrations. Eight tasks are being performed on this project: (1) Collection of appropriate contaminated soils for use in the continuous flow soil column experiments; (2) Perform bench-scale batch adsorption/desorption tests of various concentrations of contaminants in contact with various soil matrices to determine the uptake of contaminant; (3) Model the adsorption uptake using Langmuir and Freundlich isotherm models; (4) Perform continuous flow processing of contaminant solutions (single contaminant systems) through packed bed reactors containing different soil types; (5) Perform continuous flow processing with injection of microorganisms through packed soil columns containing different soil types contaminated with various organic contaminants; (6) Perform continuous flow processing with injection of advanced oxidants through packed soil columns containing different soil types contaminated with various organic contaminants; (7) Modeling the desorption/treatment performance of the continuous flow experiments using the bed depth-service time and advective dispersion model; and (8) Prepare project reports. This paper reports on the results of Tasks 2 and 3.