The anammox process at typical feast-famine states: Reactor performance, sludge activity and microbial community

Anaerobic ammonium oxidation (Anammox) is a chemolithotrophic bioprocess which has been widely applied in the treatment of different concentrations of ammonium-containing wastewaters. However, there is less attention on the problem that the instantaneous growth rate (or metabolic rate) and equilibrium growth rate were un-synchronous for anammox bacteria due to their long generation time and self-immobilization of the granular sludge which could lead to the inaccurate estimation. In this study, the anammox process was firstly divided to four typical feast-famine (starvation, satiation, tolerance and poison) states based on the combination of both off-site and in-situ anammox reaction kinetics. Then, four respective lab-scale bioreactors were operated at each state for over a year to achieve stable anammox performance. The results showed that the nitrogen removal rates of bioreactors were 0.53, 2.24, 9.30 and 12.96 kg N/(m(3).d); and the specific anammox activities of granular sludge were 188.94 (48%), 313.29 (79%), 397.50 (100%) and 198.60 (50%) mg N/(g VSS.d) which could reflect the reactivity of each feast-famine state. The stable microbial communities of bioreactors were cultured and analyzed, whose species diversity went down with the decrease of Shannon and ACE index. The relative abundance of anammox bacteria increased from 11% to 57% from starvation to poison state. Candidatus Brocadia/Nitrospira, Candidatus Kuenenia and Brocadiaceae unclassified were revealed to be the distinctive functional bacteria, which could serve as the indicator of each state. The setting up of the typical feast-famine states could be regarded as the landmark to help the design, control and optimization of anammox process.