Proliferation characteristics of nitrifiers during enrichment culture of Anammox biofilm
The proliferation characteristics of nitrifiers during enrichment culture of anaerobic ammonium oxidation(anammox)biofilm by increasing TN loading rate were investigated in an unsealed up-flow anaerobic fixed-bed biofilm(UAFB)reactor.The results showed that with the increasing surface ammonium loading rate(SALR),the ratio of ANO3/ANH4+ in UAFB reactor gradually decreased from 0.76±0.11 to 0.42±0.10,indicating that high substrate concentration is more conducive to the culture of Anammox biofilm and not conducive to the proliferation of nitrite oxidizing bacteria(NOB).Moreover,the ammonia oxidation rate(AUR)and nitrite oxidation rate(NUR)of Anammox biofilm significantly increased during the culture of Anammox biofilm but eventually tend to stabilize.The results of fluorescence in-situ hybridization(FISH)and Illumina MiSeq further confirmed that the abundance of Ca.Brocadia and Ca.Jettenia was up to 33.51%and 3.02%,and the total abundance of ammonia oxidizing bacteria(AOB)-Nitrosomonas was just 0.78%.However,the relative abundance of Nitrospira was up to 2.32%,which might negatively affect the stable operation of PN/Anammox system.