Effects of carbon sources and operation modes on the performances of aerobic denitrification process and its microbial community shifts

Abstract

Carbon source, operation mode and microbial species have great effects on the synthesis of poly-β-hydroxybutyrate (PHB) which has been identified as the key issue for aerobic denitrification process. In this study, an aerobic denitrification SBR was operated under anoxic/oxic mode and completely oxic mode with the carbon source of CH₃COON_a and CH₃CH₂CH₂COON_a, respectively. Total nitrogen (TN) removal efficiencies, PHB content in activated sludge, production of nitric oxide (NO) and nitrous oxide (N₂O) of the process were investigated in great detail. The main results obtained from the trial were: (1) the average TN removal was in the range of 86.11%-90.05%; (2) the maximum TN removal efficiency and the maximum PHB content of the process being achieved when the carbon source of CH₃CH₂CH₂COON_a was applied under anoxic/oxic mode; (3) in case of CH₃COON_a as the carbon source, the concentrations of NO and N₂O in the bulk liquid were ∼0.4 mg/L and ∼0.02 mg/L, respectively, while in case of CH₃CH₂CH₂COON_a, N₂O of ∼0.2 mg/L and NO of ∼2.5 mg/L were recorded and the latter was decreased to ∼1.0 mg/L at the end of the cycle; (4) no obvious dominant genus in case of using CH₃COON_a, while Plasticicumulans sp. being the major microbial community when using CH₃CH₂CH₂COON_a. Overall, the effect of carbon source on microbial community is obvious. Nevertheless, operation mode affects the PHB synthesis, while PHB plays an important role in aerobic denitrification process for achieving a relatively high TN nitrogen removal efficiency. CH₃COON_a is a better carbon source for aerobic denitrification compared with CH₃CH₂CH₂COON_a.

Keywords: Aerobic denitrification process; Carbon source; Microbial community; Operation mode; Shift.