Microbial community shifts on an anammox reactor after a temperature shock using 454-pyrosequencing analysis

•Pyrosequencing was used to assess microbial community shifts in an anammox reactor.•Microbial diversity decreased as anammox reactor recovered from temperature shock.•N-removal results were consistent with 454-pyrosequencing results.•Anammox population shifted from Candidatus Kuenenia to Brocadia anammoxidans.

To explore the changes in the microbial community structure during the recovery process of an anammox reactor after a temperature shock, the 454-pyrosequencing technique was used. The temperature shock reduced the nitrogen removal rate up to 92% compared to that just before the temperature shock, and it took 70 days to recover a similar nitrogen removal rate to that before the temperature shock (ca. 0.30 g N L−1 d−1). Pyrosequencing results indicated that microbial diversity in the reactor decreased as the reactor progressively recovered from the temperature shock. Anammox bacteria were accounted as 6%, 35% and 46% of total sequence reads in samples taken 13, 45 and 166 days after the temperature shock. These results were in agreement with N-removal performance results and anammox activity measured in the reactor during the recovery process. An anammox specific primer was used to precisely determine the anammox species in the biomass samples.