Enhanced shortcut nitrogen removal and metagenomic analysis of functional microbial communities in a double sludge system treating ammonium-rich wastewater.

Biological nitrogen removal processes based on partial nitrification are promising for ammonium-rich wastewater treatment. In this study, a partial nitrification-denitrification double sludge system was applied to treat synthetic ammonium-rich wastewater. Metagenomic analysis of functional genes and metabolic pathways was conducted, also with the evaluation of system performance and nitrous oxide (N2O) emission. In the nitrifying sequencing batch reactor (SBRPN), the removal percentage of ammonium nitrogen reached to 99.98% with a high nitritation efficiency of 93.24%, and the N2O emission factor was 0.88%. In the denitrifying sequencing batch reactor (SBRDN), there was almost no nitrate nitrogen and nitrite nitrogen in the effluent, and the maximum N2O emission was 0.078 mg N/L. The dominant ammonia oxidizing bacteria was Nitrosomonas in SBRPN (13.6%), and the main potential denitrifiers in SBRDN were Thauera (14.6%), an uncultured genus in the Comamonadaceae family (4.0%), an uncultured genus in Rhodocyclaceae family (2.4%) and Comamonas (1.1%). Metagenomic analysis revealed that amo mainly distributed in Nitrosomonas eutropha (38.3%), Nitrosomonas europaea (27.1%), Nitrosomonas sp. GH22 (20.5%) and Nitrosomonas sp. TK794 (15.0%), and Bacteroidetes had the N2O reduction potential in SBRPN.