Fig. 3From: Application of hierarchical oligonucleotide primer extension (HOPE) to assess relative abundances of ammonia- and nitrite-oxidizing bacteriaPrincipal component analysis (PCA) of the measured water quality parameters in the effluent stream throughout the operational phases. The PCA plot suggests that there was high ammonium NH4 + oxidation during Phases B and C but an accumulation of nitrite and an increase in the chemical oxygen demand (COD) during the late operational phases D2 and EBack to article page