Anammox Bacterial Abundance, Biodiversity and Activity in a Constructed Wetland

An integrated approach to document high anammox activity and biodiversity in a constructed wetland (CW) was performed and showed that substantial anammox activity could mitigate undesirable N2O emission. The enhanced anammox bacterial abundance, biodiversity and activity were achieved by supplementing activated sludge to the CW. Up to 3.38 × 107 gene copies g–1 dry soil of anammox bacteria were enriched in the CW. The activity measured by isotope pairing technique increased from 1.6 nmol N g–1 sludge h–1 in the original activated sludge to 18 nmol N g–1 soil h–1 in the CW, with the specific cellular activity increased from 5.1 to 12.8 fmol cell–1 d–1. Up to 33% of produced N2 could be attributed to anammox process in the CW, with the remainder being due to denitrification. Phylogenetic analysis of anammox bacterial 16S rRNA genes indicated a shift of community from single Candidatus “Brocadia fulgida” in sludge to multiple “Jettenia”, “Brocadia”, and “Anammoxoglobus” species in the CW. With static chambers and control experiments, the CW with supplemented sludge had a 30% reduced N2O emission flux compared with the tests without adding biomass during an 8 month testing period.