Search

Partial nitritation and anammox (PN/A) was applied in a lab-scale membrane bioreactor (MBR) to investigate its technical feasibility for treating ammonium-rich wastewater with low C/N ratio. The bacterial community was analyzed by molecular cloning and 16S rRNA sequence analysis. Partial nitritation (PN) was first realized in MBR by seeding aerobic activated sludge. With dissolved oxygen control, a steady effluent mixture with NO-N/NH-N ratio of 1.13 ± 0.08 was generated from the PN process. Subsequently, the MBR was seeded with anammox biomass on day 59. After running 300 days, the one-stage PN/A achieved a maximum nitrogen removal rate of 1.45 kg N/m/day at the nitrogen removal efficiency of 89.5 %. Microbial community analysis revealed that Nitrosomonas sp. HKU and Nitrosospira sp. YKU corresponded to nitritation; meanwhile, Candidatus Brocadia TKU sp. accounted for nitrogen removal of the PN/A system. Specifically, Nitrosomonas sp. were enriched in the reactor at the PN/A phase and then conquered Nitrosospira sp. to be the predominant ammonia oxidizers. Nitrite oxidizers and denitrifiers were detected in symbiosis with aforementioned microbes. Denitrification promised potential plus nitrogen depletion. The present one-stage PN/A process allows a significant decrease in operational costs compared with classical nitrification/denitrification. [ABSTRACT FROM AUTHOR]

Anaerobic ammonium oxidation (anammox) is an innovative pathway for biological nitrogen removal. The raw nitrogenous wastewater is ill-suited for direct depletion by anammox due to lack of sufficient nitrite. Partial nitritation (PN) was operated in a membrane bioreactor (MBR) to generate suitable feed for anammox, and functional microbes were analysed by 16S rRNA sequence analysis. The dissolved oxygen was adopted as the key selection factor to realize partial nitritation. The PN was realized in the MBR within 19 days. From day 26 and onwards, partial nitritation was stable and operated with an effluent NO 2 － -N/NH 4 ＋ -N ratio of 1.15 ± 0.09, which was a suitable mixture to feed subsequent anammox. The free ammonia overwhelmingly restrained the activity of nitrite oxidizers. High nitrite accumulation efficiency of 94.6 ± 3.1% was achieved throughout the experiment. The optimal dissolved oxygen of the bioreactor to create suitable media was 0.8–0.9 mg L −1 . The molecular cloning and phylogenetic analysis revealed that Nitrosospira sp. was the predominant ammonium-oxidizing bacteria corresponding to implement nitritation in the MBR. Sequences with original name of Nitrosospira sp. YKU were deposited in GenBank. The MBR promised potential merit to implement one-stage partial nitritation and anammox. [ABSTRACT FROM AUTHOR]