title: The effects of organic carbon, ammoniacal-nitrogen, and oxygen partial pressure on the stratification of membrane-aerated biofilms.
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.
authors.affiliation: Department of Civil Engineering, University of Minnesota, 122 Civil Engineering, 500 Pillsbury Drive SE, Minneapolis, MN 55455, USA. lapar001@umn.edu
authors.forename: Timothy M
authors.initials: TM
authors.lastname: LaPara
authors.forename: Alina C
authors.initials: AC
authors.lastname: Cole
authors.forename: John W
authors.initials: JW
authors.lastname: Shanahan
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Semmens
mesh_terms: D000641:Ammonia / Q000378:metabolism / Q000494:pharmacology*; D001419:Bacteria / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D001431:Bacteriological Techniques / Q000295:instrumentation / Q000379:methods; D018441:Biofilms / Q000187:drug effects* / Q000254:growth & development; D002244:Carbon / Q000378:metabolism / Q000494:pharmacology*; D009584:Nitrogen / Q000378:metabolism / Q000494:pharmacology; D010100:Oxygen / Q000378:metabolism / Q000494:pharmacology*; D010313:Partial Pressure
chemical_list: D002244:Carbon; D000641:Ammonia; D009584:Nitrogen; D010100:Oxygen