Nitrifying biomass characterization and monitoring during bioaugmentation in a membrane bioreactor

Abstract

A membrane bioreactor (MBR), fed with domestic wastewater, was bioaugmented with nitrifying biomass selected in a side-stream MBR fed with a synthetic high nitrogen-loaded influent. Microbial communities evolution was monitored and comparatively analysed through an extensive bio-molecular investigation (16S rRNA gene library construction and terminal-restriction fragment length polymorphism techniques) followed by statistical analyses. As expected, a highly specialized nitrifying biomass was selected in the side-stream reactor fed with high-strength ammonia synthetic wastewater. The bioaugmentation process caused an increase of nitrifying bacteria of the genera Nitrosomonas (up to more than 30%) and Nitrobacter in the inoculated MBR reactor. The overall structure of the microbial community changed in the mainstream MBR as a result of bioaugmentation. The effect of bioaugmentation in the shift of the microbial community was also verified through statistical analysis.

Keywords:

• activated sludge modelling
• wastewater treatment
• nitrifiers
• ammonia-oxidizing bacteria
• nitrite-oxidizing bacteria

Acknowledgements

This work was supported by the Tuscany Region (BACON project, prot. no. AOOGRT/261197/S-80.10) and by the EU Marie Curie programme (project Carbala IRSES 2011-295176). We thank S. Donati and C. Martinelli for their support to experimental work. S. Gabrielli is acknowledged for his technical assistance with graphic artwork.

Disclosure statement

No potential conflict of interest was reported by the authors.