Microbial PCB dechlorination in dredged sediments and the effect of moisture

Area of Science:

• Environmental chemistry
• Microbiology
• Environmental science

Background:

• Polychlorinated biphenyls (PCBs) are persistent organic pollutants found in sediments.
• Reductive dechlorination is a key process for PCB degradation in anaerobic environments.
• Hudson River sediments have historically been contaminated with PCBs.

Purpose of the Study:

• To investigate PCB reductive dechlorination in dredged Hudson River sediments.
• To assess the impact of moisture content on dechlorination and dechlorinating microorganisms.
• To compare dechlorination in encapsulated versus in-situ sediments.

Main Methods:

• Analysis of PCB congener patterns in dredged and river sediments.
• Microbial inoculation experiments using sediments with varying moisture levels.
• Most probable number (MPN) technique to quantify dechlorinating microorganisms.

Main Results:

• Dechlorination in encapsulated sediments was less advanced than in river sediments.
• Encapsulated sediments harbored viable dechlorinating microorganisms, but they did not effectively degrade residual PCBs in dredged sediments.
• Simulated dewatering reduced both the extent of dechlorination and the population of dechlorinating microorganisms.
• A significant correlation was found between dechlorination extent and the death rate of dechlorinating populations.

Conclusions:

• Moisture content critically influences PCB reductive dechlorination by affecting the survival of dechlorinating microorganisms.
• Dewatering processes can significantly limit the effectiveness of bioremediation for PCB-contaminated sediments.
• The death rate of dechlorinating microbial populations is a key factor in moisture-dependent dechlorination limits.