Session: Innovation in Remediation Strategies & their Impact on Superfund Contaminants:

Experiments were conducted to measure biodegradation of polychlorinated biphenyl (PCB) congeners contained in mixture Aroclor 1248 and congeners present in wastewater lagoon sediment contaminated decades earlier at Altavista, Virginia. A well-characterized strain of aerobic PCB-degrading bacteria, Paraburkholderia xenovorans LB400, was incubated in laboratory bioreactors with PCB-contaminated sediment collected at the site and a plant-derived biosurfactant called ‘saponin’. GC/MS-MS triple quadrupole spectrometry was used to screen for all 209 PCB congeners. The experiments evaluated strain LB400’s ability to degrade PCBs in absence of sediment and in PCB-contaminated sediment slurry both with and without saponin. In absence of sediment and saponin, LB400 transformed 76% of Aroclor 1248 within seven days, spanning all homolog groups present in the mixture. In sediment bioreactors without saponin, only 7% of PCBs were transformed. In bioreactors with sediment and saponin, biodegradation of di-, tri-, and tetrachlorobiphenyls was significantly enhanced relative to the treatments without saponin. These findings show that LB400 is capable of rapidly biodegrading most PCB congeners when they are freely dissolved in liquid but cannot degrade PCB congeners having four or more chlorine substituents in sediment slurry unless saponin is present. Although, the results suggest that saponin significantly enhances biodegradation of PCBs from contaminated sediment. These findings are important because they may help to inform strategies for bioaugmentation/biostimulation of legacy-contaminated sediments.

Keri Hornbuckle

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