Hydrogenotrophic denitrification in a microporous membrane bioreactor

Area of Science:

• Environmental microbiology
• Water treatment technologies
• Bioreactor engineering

Background:

• Groundwater contamination by nitrates poses a significant environmental and health risk.
• Traditional denitrification methods often require organic substrates, increasing treatment complexity and cost.
• Microporous membrane bioreactors offer a potential solution for efficient and contained biological water treatment.

Purpose of the Study:

• To investigate the efficacy of hydrogenotrophic denitrification for nitrate removal from contaminated groundwater.
• To evaluate the performance of a bench-scale microporous membrane bioreactor in a continuous flow system.
• To identify the microbial community responsible for denitrification in the bioreactor.

Main Methods:

• Utilized a bench-scale microporous membrane bioreactor (0.02 microm pore diameter) for groundwater denitrification.
• Employed a hydrogenotrophic denitrification culture, eliminating the need for organic substrates.
• Maintained equal pressure across the membrane to facilitate nitrate diffusion and removal.
• Analyzed the microbial community using 16S and 23S rRNA-targeted oligonucleotide probes.

Main Results:

• Achieved high nitrate removal efficiencies, ranging from 96% to 92% for influent concentrations of 20-40 mg/L NO3(-)-N.
• Observed flux values between 2.7-5.3 g NO3-N m(-2)d(-1).
• The membrane effectively prevented microbial contamination, with effluent heterotrophic plate counts of 9 (+/- 3.5) CFU/mL.
• Identified the denitrifying culture as belonging to the beta subclass of Proteobacteria, potentially within the beta-3 subgroup.

Conclusions:

• Hydrogenotrophic denitrification in a microporous membrane bioreactor is a highly effective method for removing nitrate from contaminated groundwater.
• The membrane bioreactor system successfully prevented microbial contamination of the treated water.
• The study identified a novel microbial community, likely beta-3 Proteobacteria, capable of hydrogenotrophic denitrification, warranting further identification.