Aerobic Cometabolism of Halogenated Aliphatic Hydrocarbons: A Technology Overview
of chlorinated solvents has been moving from an innovative to mainstream technology
for environmental applications. Cometabolism of chlorinated solvents by monooxygenase
has been demonstrated for trichloroethylene (TCE) and dichloroethylene (DCE).
Cl-out microbes combine the
dehalogenation of PCE with the monooxygenase destruction of TCE and DCE to complete the PCE breakdown pathway. Under the right conditions, cometabolic bioremediation can be cost effective, fast and complete. Aerobic bioremediation can augment mass transfer technologies such as pump and treat or sparging/vapor extraction to improve their efficiency.
Bioremediation of chlorinated solvents, especially trichloroethylene (TCE) and tetrachloroethylene (PCE), has been successful under anaerobic conditions. However, there has been limited success in the anaerobic degradation of the breakdown products dichloroethylene (DCE) and vinyl chloride. In addition, the need to maintain anaerobic conditions can be a limiting factor in the success of anaerobic degradation. Aerobic bioremediation is an emerging technology in which enhanced microbial cometabolism degrades PCE, TCE, and related breakdown products through to inorganic constituents. This article describes the process of aerobic cometabolism using a commercially available proprietary blend of microbes (Cl-out), explains the benefits and limits of the process, and presents field application results. Cl-out is a blend of microbial strains that will degrade chlorinated solvents, such as PCE, TCE, 1,2,- chloroethylene (1,2-DCE), vinyl chloride, methylene chloride, and chlorobenzene. The microbes were isolated from contaminated soils where the naturally occurring microbes had adapted and developed the ability to cometabolize the contaminants. Laboratory tests have shown that Cl-out will cometabolize chlorinated solvents into harmless by-products without toxic by-product accumulation.