DUAL-BIOFILM REACTIVE BARRIER FOR TREATMENT OF CHLORINATED BENZENES AT ANAEROBIC-AEROBIC INTERFACES IN CONTAMINATED GROUNDWATER AND SEDIMENTS

Through an ongoing collaborative study funded by the National Institute for Environmental Health Sciences, a novel technology is being developed for the treatment of chlorobenzenes and benzene contaminants in the subsurface using a flow-through barrier containing granular activated carbon coated with anaerobic and aerobic microorganisms. Laboratory and field tests are being conducted at the Standard Chlorine of Delaware, Inc. Superfund site where dense non-aqueous phase liquid (DNAPL) chlorobenzene contamination is present in wetland sediments and groundwater. Granular activated carbon (GAC) seeded with anaerobic and aerobic microbial cultures and mixed with sand or directly into the wetland sediment is proposed to form a surface reactive barrier that not only sequesters the chlorinated benzenes to reduce their bioavailability, but also facilitates their transformation to innocuous end products over short groundwater flowpaths. We seek to understand the environmental processes and conditions that influence interactions among contaminants and the barrier to improve its effectiveness for the treatment of contaminated groundwater.

Study objectives include determining sorption/desorption interactions between biofilms, GAC, and site sediment and defining degradation processes and rates for the dual-biofilm barrier in laboratory and field tests. Genetic sequencing verified biofilm attachment to GAC with no loss of major microbial species. In GAC-biofilm microcosms, about 85% of added chlorobenzenes were removed in 24 hours, and comparison to controls indicated removal by biodegradation in addition to sorption. Sorption isotherms determined for 1 to 3 substituted chlorobenzenes on GAC will be compared to those in the presence of biofilms and site water constituents. Initial column experiments are underway to evaluate the dual-biofilm barrier designs with site sediment and water. Interaction with EPA allows direct application of research to an effective remediation design for protection of the surrounding environments and communities at this Superfund site.