Date of Award

3-2004

Document Type

Thesis

Degree Name

Master of Science in Engineering Management

Department

Department of Systems Engineering and Management

First Advisor

Charles A. Bleckmann, PhD

Abstract

Groundwater contamination problems caused by methyl-tertiary butyl ether (MTBE) in subsurface waters have prompted the search for a gasoline oxygenate replacement. In order to avoid the problems encountered with MTBE, it is prudent to evaluate the fate and transport in the subsurface of proposed replacements, such as ethanol. In this study, ethanol transport and degradation in unsaturated soil was investigated using a series of eight soil columns. This preliminary study was to see if the soil column system components functioned properly, how similarly the eight soil columns performed, and if soil oxygen concentration affected degradation of ethanol. Tracer tests, using sodium chloride, determined the hydraulic characteristics of the soil columns. Oxygen sensors measured microbial activity in the soil columns when ethanol was added to the columns. The sensors were part of a control system that stabilized oxygen concentration at two levels (8% in four columns and 16% in four columns) to see the effect of oxygen concentration on ethanol degradation. A gas chromatograph (GC) was used to quantify column influent and effluent ethanol concentrations. The tracer tests showed an average retention time, pore volume, and mass balance error of 13.3 hr (± 1.4), 18.9 L (± 2.0), and 1.3% (± 3.8), respectively. The oxygen sensor data, which indicated a drop in oxygen concentration over time when ethanol was added, suggested that microbial activity was occurring. The microbial aerobic metabolism of ethanol caused the oxygen concentrations to drop to the set points of 8% and 16%, at which they stabilized. The GC analysis also showed ethanol degradation. Influent ethanol concentrations were ~ 1000 ppm, column effluent concentrations were at or near the method detection limit (MDL) of 1 ppm for both oxygen concentrations.

AFIT Designator

AFIT-GEM-ENV-04M-13

DTIC Accession Number

ADA422919

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