Three-dimensional stratification of bacterial biofilm populations in a moving bed biofilm reactor for nitritation-anammox.
Moving bed biofilm reactors (MBBRs) are increasingly used for nitrogen removal with nitritation-anaerobic ammonium oxidation (anammox) processes in wastewater treatment. Carriers provide protected surfaces where ammonia oxidizing bacteria (AOB) and anammox bacteria form complex biofilms. However, the knowledge about the organization of microbial communities in MBBR biofilms is sparse. We used new cryosectioning and imaging methods for fluorescence in situ hybridization (FISH) to study the structure of biofilms retrieved from carriers in a nitritation-anammox MBBR. The dimensions of the carrier compartments and the biofilm cryosections after FISH showed good correlation, indicating little disturbance of biofilm samples by the treatment. FISH showed that Nitrosomonas europaea/eutropha-related cells dominated the AOB and Candidatus Brocadia fulgida-related cells dominated the anammox guild. New carriers were initially colonized by AOB, followed by anammox bacteria proliferating in the deeper biofilm layers, probably in anaerobic microhabitats created by AOB activity. Mature biofilms showed a pronounced three-dimensional stratification where AOB dominated closer to the biofilm-water interface, whereas anammox were dominant deeper into the carrier space and towards the walls. Our results suggest that current mathematical models may be oversimplifying these three-dimensional systems and unless the multidimensionality of these systems is considered, models may result in suboptimal design of MBBR carriers.
Department of Chemistry & Molecular Biology, Microbiology, University of Gothenburg, Box 462, Göteborg SE-405 30, Sweden. ralmstra@mines.edu.
Robert
R
Almstrand
Water Environment Technology, Department of Civil and Environmental Engineering, Chalmers University of Technology, Göteborg SE-412 96, Sweden. Frank.Persson@chalmers.se.
Frank
F
Persson
Division of Microbial Ecology, Department of Microbiology and Ecosystem Science, University of Vienna, Vienna 1090, Austria. daims@microbial-ecology.net.
Holger
H
Daims
AnoxKaldnes AB, Klosterängsvägen 11A, Lund SE-226 47, Sweden. maria.ekenberg@anoxkaldnes.com.
Maria
M
Ekenberg
AnoxKaldnes AB, Klosterängsvägen 11A, Lund SE-226 47, Sweden. magnus.christensson@anoxkaldnes.com.
Magnus
M
Christensson
Water Environment Technology, Department of Civil and Environmental Engineering, Chalmers University of Technology, Göteborg SE-412 96, Sweden. Britt-Marie.Wilen@chalmers.se.
Britt-Marie
BM
Wilén
Department of Chemistry & Molecular Biology, Microbiology, University of Gothenburg, Box 462, Göteborg SE-405 30, Sweden. fred.sorensson@cmb.gu.se.
Fred
F
Sörensson
Department of Chemistry & Molecular Biology, Microbiology, University of Gothenburg, Box 462, Göteborg SE-405 30, Sweden. malte.hermansson@cmb.gu.se.
Malte
M
Hermansson
D000693:Anaerobiosis; D018407:Bacterial Physiological Phenomena; D018441:Biofilms; D019149:Bioreactors; D017404:In Situ Hybridization, Fluorescence; D058465:Nitrification; D062065:Wastewater / Q000382:microbiology
D062065:Wastewater