Microbial Perchlorate Reduction Driven by Ethane and Propane

Area of Science:

• Environmental Microbiology
• Bioremediation
• Groundwater Contamination

Background:

• Methane is a known electron donor for microbially removing oxidized groundwater contaminants.
• Natural gas, a cheaper alternative to methane, contains ethane and propane, which need utilization to prevent emissions.
• Perchlorate is a common groundwater contaminant requiring effective remediation strategies.

Purpose of the Study:

• To investigate the microbial reduction of perchlorate using ethane (C2H6) and propane (C3H8) as electron donors.
• To assess the feasibility of using natural gas components for in situ groundwater remediation.
• To identify microorganisms and genes involved in ethane/propane-driven perchlorate reduction.

Main Methods:

• Operation of two membrane biofilm reactors (MBfRs) with ethane and propane, respectively, for perchlorate removal.
• Batch tests to confirm ethane/propane consumption and perchlorate reduction.
• Polyhydroxyalkanoate (PHA) synthesis and utilization studies.
• Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) to analyze gene expression (bmoX, pcrA).
• High-throughput sequencing for microbial community analysis (16S rRNA, bmoX, pcrA).

Main Results:

• Continuous perchlorate removal was achieved in MBfRs supplied with ethane and propane.
• Perchlorate reduction was directly linked to ethane and propane oxidation.
• Microbial synthesis and subsequent utilization of PHAs for perchlorate reduction were observed.
• Gene expression analysis showed positive correlations between bmoX and C2H6/C3H8 consumption, and pcrA and perchlorate consumption.
• Mycobacterium species were identified as dominant ethane/propane oxidizers, and Dechloromonas as potential perchlorate reducers.

Conclusions:

• Ethane and propane can effectively drive microbial perchlorate reduction in groundwater under oxygen-limiting conditions.
• This process utilizes readily available natural gas components, offering a cost-effective remediation strategy.
• The study identifies key microorganisms and genes involved, paving the way for optimized bioremediation approaches.