Seasonal and spatial changes of N-transforming microbial communities in sequential sedimentation-biofiltration systems - Influence of system design and environmental conditions

The microbial activity in nitrogen (N) and phosphorus (P) transformation is an important parameter ensuring proper functioning of innovative biotechnological solutions involved in urban water treatment - sequential sedimentation-biofiltration systems (SSBSs). The study focused on metabolic activity, seasonal variability, and construction differences of microbial communities in three SSBSs. Carbon source utilization indicated that microbial metabolic potential was higher in spring and summer as compared to autumn. Bacterial gene abundances in nitrification (amoA) and denitrification (nosZ) indicated that nitrifiers were higher in spring (14.2 ± 2.5 °C) and denitrifiers in summer (21.9 ± 1.9 °C). Brown coal biofilm (denitrification zone) presented the highest nosZ (2.02 × 1010 copies g−1). Bacterial community analysis using 16S rRNA and correlations with TN, NO3-N, and NH4-N concentration, suggested that the Comamonadaceae (Limnohabitants), Flavobacteriaceae (Flavobacterium), Crenotrichaceae (Crenothrix), and Rhodobacter were important communities involved in N transformations. Limestone biofilm (geochemical zone) presented the highest amoA (8.95 × 107 copies g−1), and the Comamonadaceae, Rhodocyclaceae (Dechloromonas), Rhodobacter, and Crenothrix were suggested to be involved in nutrient transformation processes. Metabolic activity and abundance of microbial communities increased when the temperature was higher than 10 °C, and it consequently helped to improve the removal efficiency of nutrients in SSBSs.