Successful hydraulic strategies to start up OLAND sequencing batch reactors at lab scale
Article first published online: 11 JAN 2012
© 2012 The Authors. Microbial Biotechnology © 2012 Society for Applied Microbiology and Blackwell Publishing Ltd
Special Issue: Microbial Resource Management. Guest Editors: Nico Boon and Willy Verstraete
Volume 5, Issue 3, pages 403–414, May 2012
How to Cite
Schaubroeck, T., Bagchi, S., De Clippeleir, H., Carballa, M., Verstraete, W. and Vlaeminck, S. E. (2012), Successful hydraulic strategies to start up OLAND sequencing batch reactors at lab scale. Microbial Biotechnology, 5: 403–414. doi: 10.1111/j.1751-7915.2011.00326.x
- Issue published online: 16 APR 2012
- Article first published online: 11 JAN 2012
- Received 31 August, 2011; accepted 7 December, 2011.
Oxygen-limited autotrophic nitrification/denitrification (OLAND) is a one-stage combination of partial nitritation and anammox, which can have a challenging process start-up. In this study, start-up strategies were tested for sequencing batch reactors (SBR), varying hydraulic parameters, i.e. volumetric exchange ratio (VER) and feeding regime, and salinity. Two sequential tests with two parallel SBR were performed, and stable removal rates > 0.4 g N l−1 day−1 with minimal nitrite and nitrate accumulation were considered a successful start-up. SBR A and B were operated at 50% VER with 3 g NaCl l−1 in the influent, and the influent was fed over 8% and 82% of the cycle time respectively. SBR B started up in 24 days, but SBR A achieved no start-up in 39 days. SBR C and D were fed over 65% of the cycle time at 25% VER, and salt was added only to the influent of SBR D (5 g NaCl l−1). Start-up of both SBR C and D was successful in 9 and 32 days respectively. Reactor D developed a higher proportion of small aggregates (0.10–0.25 mm), with a high nitritation to anammox rate ratio, likely the cause of the observed nitrite accumulation. The latter was overcome by temporarily including an anoxic period at the end of the reaction phase. All systems achieved granulation and similar biomass-specific nitrogen removal rates (141–220 mg N g−1 VSS day−1). FISH revealed a close juxtapositioning of aerobic and anoxic ammonium-oxidizing bacteria (AerAOB and AnAOB), also in small aggregates. DGGE showed that AerAOB communities had a lower evenness than Planctomycetes communities. A higher richness of the latter seemed to be correlated with better reactor performance. Overall, the fast start-up of SBR B, C and D suggests that stable hydraulic conditions are beneficial for OLAND while increased salinity at the tested levels is not needed for good reactor performance.