In partial nitritation/anammox systems, aerobic and anoxic ammonium-oxidizing bacteria (AerAOB and AnAOB) remove ammonium from wastewater. In this process, large granular microbial aggregates enhance the performance, but little is known about this type of granulation so far. In this study, aggregates of three reactors (A, B, C) with different inoculation and operation were studied. The test objectives were to quantify the AerAOB and AnAOB abundance and the activity balance for the different aggregate sizes, and to relate aggregate morphology, size distribution, and architecture putatively to the inoculation and operation of the reactors. Fluorescent in-situ hybridization (FISH) was applied on aggregate sections to quantify AerAOB and AnAOB, as well as to visualize the aggregate architecture. The activity balance of the aggregates was calculated as the nitrite accumulation rate ratio (NARR), i.e. the net aerobic nitrite production rate divided by the anoxic nitrite consumption rate, with all rates determined in aerobic and anoxic batch tests. The space occupied by extracellular polymeric substances (EPS) was calculated from transmission electron micrographs. All smallest aggregates were flocs and nitrite sources (NARR, > 1.7). Large A and C aggregates were granules capable of autonomous nitrogen removal (NARR, 0.6 to 1.1) with internal AnAOB zones surrounded by an AerAOB rim. Around 50% of the autotrophic space in these granules consisted of AerAOB- and AnAOB-specific EPS. Large B aggregates were thin film-like nitrite sinks (NARR, <0.5) in which AnAOB were not shielded by an AerAOB layer. Voids and channels occupied 13 to 17% of the anoxic zone of AnAOB-rich aggregates (B and C). Inoculation and operation of an OLAND reactor influences the aggregate size distribution, activity balance, morphology and architecture. Hypothesized granulation pathways include granule replication by division and budding.
|Title of host publication||Proceedings of the 13th International Symposium on Microbial Ecology|
|Publisher||International Society for Microbiology|
|Publication status||Published - 2010|
|Event||13th International Symposium on Microbial Ecology - Seattle, WA, United States|
Duration: 22 Aug 2010 → 27 Aug 2010
Conference number: 13
|Conference||13th International Symposium on Microbial Ecology|
|Period||22/08/2010 → 27/08/2010|
Vlaeminck, S., Terada, A., Smets, B. F., De Clippeleir, H., Carballa, M., & Verstraete, W. (2010). Aggregate size and architecture determine biomass activity for one-stage partial nitritation and anammox. In Proceedings of the 13th International Symposium on Microbial Ecology (Vol. CT31.008). International Society for Microbiology.