Abstract
Ammonia-oxidizing bacteria (AOB), ammonia oxidizing archaea (AOA) and N2O-reducing denitrifiers were measured by quantitative real-time PCR (qPCR) in activated sludge samples from four full-scale wastewater treatment plants (WWTPs) in South Spain, and their abundances were linked to the generation of N2O in the samples using multivariate analysis (Non-metric multidimensional scaling, MDS, and BIO-ENV). The average abundances of AOA remained in similar orders of magnitude in all WWTPs (106 copies amoA/L activated sludge mixed liquor), while significant differences were detected for AOB (105-109copies amoA/L) and N2O-reducers (107-1010copies nosZ/L). Average N2O emissions measured in activated sludge samples ranged from 0.10 ± 0.05 to 6.49 ± 8.89 mg N2O-N/h/L activated sludge, and were strongly correlated with increased abundances of AOB and lower counts of N2O-reducers. A significant contribution of AOA to N2O generation was unlikely, since their abundance correlated negatively to N2O emissions. AOB abundance was favoured by higher NO3− and NO2−concentrations in the activated sludge.
Published Version
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