Evaluation of Biosparging Performance and Process Fundamentals for Site Remediation

Principal Investigators
R.R. Dupont, D.L. Sorensen, and W.J. Doucette, Utah State University

Abstract

Goal: The goal of this project is to conduct a detailed investigation of air sparging systems operated in a pulsed mode to provide a fundamental framework from which to evaluate the applicability and effectiveness of biosparging technology for a given set of site, soil, and waste constraints.

Rationale: Air sparging represents a highly attractive remediation alternative for contaminants located below the ground water table. It has been shown through anecdotal evidence that contaminant emission rates increase and ground water concentrations are greatly reduced at ground water monitoring well points. Specific mechanisms of air sparging system performance are yet to be investigated, and adequate monitoring of field scale systems to quantitatively document their performance throughout affected areas of injection well influence are yet to be developed.

Approach: The proposed research project will involve two integrated components, companion field scale and laboratory scale studies. The field study will be utilized to provide mass transfer and contaminant biodegradation rates resulting from a field scale biosparging system, as affected by media property and heterogeneity limitations inherent at field sites. The laboratory component of the proposed research will provide detailed analysis of mass transfer and contaminant degradation rates under controlled conditions. Laboratory investigations will include an evaluation of the effect of bubble size, air injection rate, air injection depth, media properties, and contaminant properties on observed mass transfer and contaminant degradation rates. Air injection versus inert gas injection will allow the separate evaluation of mass transfer and degradation, while air injection in clean water systems will allow an evaluation of system mass transfer relationships independent of effects due to contaminant properties and/or contaminant/media interactions.

Status: Development of an expert system shell has been initiated. This expert system is being designed to provide technical assistance to the regulatory community in evaluating potential effectiveness and applicability of various technologies for management and remediation of contaminated soils and ground water resulting from petroleum releases. It will provide a standard approach for the site assessment process, guiding the user through source characterization, vadose zone and saturated zone contaminant mass estimations, contaminant plume delineation, and intrinsic biodegradation rate estimates, and with results of this study, suggestions for air injection-based design and predictions of system performance. Work is also being directed toward design of an instrumentation bundle for use in collecting in situ measurements in a three-dimensional sampling grid surrounding the injection point at the field site. Other work included use of an analytical model to design the sampling grid, surveying the site to locate the injection point and sampling points, and carrying out an economic evaluation of sampling procedures and instrumentation to identify the most feasible data collection scheme for use in field testing. This project is in its second year.

Clients/Users: Results from this project will be of interest to other researchers, the U.S. Department of Defense, private industry, and regulatory personnel.

Key words: biosparging, biodegradation, mass transfer.

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