The BioTrol methanotrophic bioreactor system is an aboveground remedial technology for water contaminated with halogenated hydrocarbons. Trichloroethene (TCE) and related compounds pose a difficult challenge to biological treatment. Unlike aromatic hydrocarbons, for example, TCE cannot serve as a primary substrate for bacterial growth. Degradation depends on cometabolism (see figure below), which is attributed to the broad substrate specificity of certain bacterial enzyme systems. Although many aerobic enzyme systems reportedly cooxidize TCE and related compounds, BioTrol claims that the methane monooxygenase (MMO) produced by methanotrophic bacteria is the most promising.
Methanotrophs are bacteria that can use methane as a sole source of carbon and energy. Although certain methanotrophs can express MMO in either a soluble or particulate (membrane-bound) form, BioTrol has discovered that the soluble form used in the BioTrol process induces extremely rapid TCE degradation rates. Two patents have been obtained, and an additional patent on the process is pending. Results from experiments with Methylosinus trichosporium strain OB3b indicate that the maximum specific TCE degradation rate is 1.3 grams of TCE per gram of cells (dry weight) per hour. This rate is 100 to 1,000 times faster than reported TCE degradation rates for nonmethanotrophs. This species of methanotrophic bacteria reportedly removes various chlorinated aliphatic compounds by more than 99.9 percent.
BioTrol has also developed a colorimetric assay that verifies the presence of MMO in the bioreactor culture.
The bioreactor system can treat water contaminated with halogenated aliphatic hydrocarbons, including TCE, dichloroethene isomers, vinyl chloride, dichloroethane isomers, chloroform, dichloromethane (methylene chloride), and others. In the case of groundwater treatment, bioreactor effluent can either be reinjected or discharged to a sanitary sewer or a National Pollutant Discharge Elimination System.
This technology was accepted into the SITE Emerging Technology Program in July 1990. Both bench- and pilot-scale tests were conducted using a continuous-flow, dispersed-growth system. As shown in the figure below, the pilot-scale reactor displayed first-order TCE degradation kinetics. The final report on the demonstration appears in the Journal of the Air and Waste Management Association, Volume 45, No. 1, January 1995. The Emerging Technology Bulletin (EPA/540/F-93/506) and the Emerging Technology Summary (EPA/540/SR-93/505) are available from EPA.
EPA PROJECT MANAGER:
David Smith
U.S. EPA
Region 8
999 18th Street
Denver, CO 80202
303-293-1475
Fax: 303-294-1198
TECHNOLOGY DEVELOPER CONTACT:
Durell Dobbins
BioTrol®
10300 Valley View Road, Suite 107
Eden Prairie, MN 55344-3546
612-942-8032
Fax: 612-942-8526