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 (NO) emission. In the nitrifying sequencing batch reactor (SBR), the removal percentage of ammonium nitrogen reached to 99.98% with a high nitritation efficiency of 93.24%, and the NO emission factor was 0.88%. In the denitrifying sequencing batch reactor (SBR), there was almost no nitrate nitrogen and nitrite nitrogen in the effluent, and the maximum NO emission was 0.078 mg N/L. The dominant ammonia oxidizing bacteria was in SBR (13.6%), and the main potential denitrifiers in SBR were (14.6%), an uncultured genus in the family (4.0%), an uncultured genus in family (2.4%) and (1.1%). Metagenomic analysis revealed that mainly distributed in (38.3%), (27.1%), sp. GH22 (20.5%) and sp. TK794 (15.0%), and had the NO reduction potential in SBR.