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

Carbon source, operation mode and microbial species have great effects on the synthesis of poly-beta-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 CH3COONa and CH3CH2CH2COONa, 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 CH3CH2CH2COONa was applied under anoxic/oxic mode; (3) in case of CH3COONa as the carbon source, the concentrations of NO and N2O in the bulk liquid were similar to 0.4 mg/L and similar to 0.02 mg/L, respectively, while in case of CH3CH2CH2COONa, N2O of similar to 0.2 mg/L and NO of similar to 2.5 mg/L were recorded and the latter was decreased to similar to 1.0 mg/L at the end of the cycle; (4) no obvious dominant genus in case of using CH3COONa, while Plasticicutruilans sp. being the major microbial community when using CH3CH2CH2COONa. 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. CH3COONa is a better carbon source for aerobic denitrification compared with CH3CH2CH2COONa.