Association of nitrogen micro-cycle functional genes in subsurface wastewater infiltration systems

The distribution patterns of amoA, nxrA, narG, napA, nirK, qnorB, nosZ, nas, nifH, and 16S rRNA of anammox bacteria (ANO) were quantitatively studied in four subsurface wastewater infiltration systems (SWIS). Furthermore, the ecological groups of nitrogen transformation functional genes and key nitrogen transformation pathways were investigated. The results indicated that ANO, qnorB, nifH, and other dominant genes were mainly enriched in the up-flow area of the SWIS; amoA, nxrA, nirK, narG, napA, and other rare genes together with the nosZ dominant gene community were mainly enriched in the infiltration area. The key mechanism of denitrification in the up-flow area was the coupled collaboration between anammox and reduction of NO to N2O catalyzed by the qnorB gene codase, while the key mechanisms of denitrification in the infiltration area included: anammox, nitrification, and the coupled collaboration between aerobic denitrification and reduction of N2O to N2 catalyzed by the nosZ gene codase.