The effects of organic carbon, ammoniacal-nitrogen, and oxygen partial pressure on the stratification of membrane-aerated biofilms |
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Authors: | Timothy M LaPara Alina C Cole John W Shanahan Michael J Semmens |
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Institution: | (1) Department of Civil Engineering, University of Minnesota, 122 Civil Engineering, 500 Pillsbury Drive SE, Minneapolis, MN 55455, USA |
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Abstract: | The purpose of this study was to examine the effects of different nutrient (carbon, nitrogen, oxygen) concentrations on the
microbial activity and community structure in membrane-aerated biofilms (MABs). MABs were grown under well-defined conditions
of fluid flow, substrate concentration, and membrane oxygen partial pressure. Biofilms were then removed and thin-sliced using
a cryostat/microtome parallel to the membrane. Individual slices were analyzed for changes with depth in biomass density,
respiratory activity, and the population densities of ammonia-oxidizing and denitrifying bacteria populations. Oxygen-sensing
microelectrodes were used to determine the depth of oxygen penetration into each biofilm. Our results demonstrated that ammonia-oxidizing
bacteria grow near the membrane, while denitrifying bacteria grow a substantial distance from the membrane. However, nitrifying
and denitrifying bacteria did not grow simultaneously when organic concentrations became too high or ammonia concentrations
became too low. In conclusion, membrane-aerated biofilms exhibit substantial stratification with respect to community structure
and activity. A fundamental understanding of the factors that control this stratification will help optimize the performance
of full-scale membrane-aerated biofilm reactors for wastewater treatment. |
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Keywords: | Biofilms Hybrid bioreactor MABR Membrane aeration Nutrient removal |
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