Accession Number:

ADA422919

Title:

Aerobic Biodegradation of Alternative Fuel Oxygenates in Unsaturated Soil Columns

Descriptive Note:

Corporate Author:

AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING AND MANAGEMENT

Personal Author(s):

Report Date:

2004-03-01

Pagination or Media Count:

135.0

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.

Subject Categories:

  • Fuels
  • Water Pollution and Control

Distribution Statement:

APPROVED FOR PUBLIC RELEASE