Abstract

Groundwater at many existing and former industrial sites and disposal areas is contaminated by organic compounds (e.g., halogenated compounds, petroleum hydrocarbons) that were released into the environment. At many organic-compound spill sites, residual amounts of non-aqueous-phase liquids (NAPLs) persist within pore spaces or fractures. The slow dissolution of residual NAPLs results in a contaminated plume of groundwater. Because it is a lengthy and costly process to remove the residual NAPLs, remediation can focus on preventing further migration of the dissolved contamination. Thus, the plume control must be maintained for a long period of time. Therefore, more economic approaches are desirable for groundwater remediation to provide for a long-term control of contaminated groundwater. One cost-effective approach for remediation of contaminated aquifers that is attracting increased attention is the installation of permeable bioreactive zones or biobarriers within aquifers. The passive biobarrier concept has several advantages over other physical-chemical remedial technologies including environmental friendly, lower maintenance costs, treatment in situ, absence of above ground facilities, and no groundwater reinjection. The biobarrier concept typically involves the construction of a barrier containing substrates (e.g., nutrients, electron acceptors) or inoculated microbial consortia, which can enhance the in situ bioremediation of organic contaminants. A biobarrier can be used as a stand-alone system, when biodegradable materials are the only contaminants. In the field application, the biobarrier technology can be integrated with other established technologies and applied as the treatment train concept. Development of a biologically active passive barrier would be a feasible alternative to enhance in situ bioremediation cost-effectively.