High-throughput sequencing-based microbial characterization of size fractionated biomass in an anoxic anammox reactor for low-strength wastewater at low temperatures.

The microbial characterization of three size-fractionated sludge obtained from a suspended-growth anoxic anammox reactor treating low-strength wastewater at low temperatures were investigated by using high-throughput sequencing. Particularly, the spatial variability in relative abundance of microorganisms involved in nitrogen metabolism were analyzed in detail. Results showed that population segregation did occur in the reactor. It was found, for the first time, that the genus Nitrotoga was enriched only in large granules (>400μm). Three anammox genus including Candidatus Jettenia, Brocadia and Kuenenia were detected. Among them, Candidatus Brocadia and Kuenenia preferred to grow in large-sized granules (>400μm), whereas Candidatus Jettenia dominated in small- and moderate-sized sludge (<400μm). The members of genus Candidatus Jettenia appeared to play the vital role in nitrogen removal, since sludge with diameters smaller than 400μm accounted for 81.55% of the total biomass. However, further studies are required to identify the activity of different-size sludge.