Microbiology of a nitrite-oxidizing bioreactor

Area of Science:

• Environmental Microbiology
• Wastewater Treatment
• Microbial Ecology

Background:

• Nitrite oxidation is a key process in wastewater treatment.
• The microbial communities responsible for nitrite oxidation in sequencing batch reactors are not fully understood.
• This study investigates the microbiology of a lab-scale nitrite-oxidizing sequencing batch reactor (NOSBR).

Purpose of the Study:

• To characterize the microbial community structure of a NOSBR.
• To identify the dominant bacteria responsible for nitrite oxidation.
• To investigate the phylogenetic diversity of the microbial communities in the NOSBR and its seed sludge.

Main Methods:

• Microscopy
• Culture-dependent methods (micromanipulation, dilution and spread plate inoculation)
• Molecular biological methods (16S ribosomal DNA clone libraries, phylogenetic analysis)

Main Results:

• The NOSBR sludge contained a complex microbial community, including heterotrophs but no isolated autotrophs.
• Seed sludge was dominated by Proteobacteria and high G+C gram-positive bacteria.
• NOSBR sludge was overwhelmingly dominated by bacteria closely related to Nitrospira moscoviensis (89%).
• Bacteria from the Nitrospira phylum were identified in a wastewater treatment system for the first time.

Conclusions:

• Bacteria closely related to Nitrospira moscoviensis are the dominant nitrite oxidizers in the studied NOSBR.
• This finding suggests that Nitrospira species play a significant role in nitrite oxidation in wastewater treatment systems.
• This is the first report of Nitrospira bacteria in wastewater treatment systems.