Abstract
Byline: Carles Pellicer-Nacher, Stephanie Franck, Arda Gulay, Mael Ruscalleda, Akihiko Terada, Waleed Abu Al-Soud, Martin Asser Hansen, Soren J. Sorensen, Barth F. Smets Summary Membrane-aerated biofilm reactors performing autotrophic nitrogen removal can be successfully applied to treat concentrated nitrogen streams. However, their process performance is seriously hampered by the growth of nitrite oxidizing bacteria (NOB). In this work we document how sequential aeration can bring the rapid and long-term suppression of NOB and the onset of the activity of anaerobic ammonium oxidizing bacteria (AnAOB). Real-time quantitative polymerase chain reaction analyses confirmed that such shift in performance was mirrored by a change in population densities, with a very drastic reduction of the NOBaNitrospira and Nitrobacter and a 10-fold increase in AnAOB numbers. The study of biofilm sections with relevant 16S rRNA fluorescent probes revealed strongly stratified biofilm structures fostering aerobic ammonium oxidizing bacteria (AOB) in biofilm areas close to the membrane surface (rich in oxygen) and AnAOB in regions neighbouring the liquid phase. Both communities were separated by a transition region potentially populated by denitrifying heterotrophic bacteria. AOB and AnAOB bacterial groups were more abundant and diverse than NOB, and dominated by the r-strategists Nitrosomonas europaea and Ca. Brocadia anammoxidans, respectively. Taken together, the present work presents tools to better engineer, monitor and control the microbial communities that support robust, sustainable and efficient nitrogen removal. Article Note: Funding Information Veolia Water and the Danish Agency for Science Technology and Innovation (FTP-ReSCoBiR) funded the present study. Mael Ruscalleda was supported by the FI and BE (BE-2009-385) grant programmes from the Catalan Government (AGAUR). Supporting information: Additional Supporting Information may be found in the online version of this article CAPTION(S): TableS1. Probes used for the detection of target organisms by in-situ fluorescent hybridization. TableS2. Index of related taxonomy for each functional guild. Fig.S1. Reactor performance and microbial community abundances during reactor operation (qPCR performed with primers targeting functional genes). Fig.S2. Typical O2-mircoprofiles during aeration periods within an aeration cycle. Fig.S3. Rarefaction curves of denoised sequences and shared and unique OTUs between triplicate samples. Fig.S4. Phylogenic tree constructed with all the identified AOB, NOB and AnAOB sequences.