AbstractA sequencing batch reactor was constructed to realize simultaneous nitrification and denitrification (SND) and denitrifying phosphorus removal (DPR). The influence of different carbon sources (acetate, acetate and propionate, and propionate) was explored. The total nitrogen (TN) removal efficiency reached the highest value of 66.4% with acetate. The total phosphorus (TP) removal efficiency was nearly the same (97.9%–96.1%) with different carbon sources. Propionate facilitates TP removal during the hypoxic stage to weaken glycogen metabolism in phosphorus-accumulating organisms (PAOs) and promote dehydrogenase and phosphorus removal–related enzyme activities. Propionate also facilitates the competitiveness of PAOs against glycogen-accumulating organisms (GAOs). TN removal during the SND process in the hypoxic stage was maintained at 38.2%–40.2%, which is explained by the relative amount of change in nitrifying and denitrifying microorganisms. However, acetate promoted TN (from 9.2% to 17.3%) and TP (from 18.1% to 22.7%) removal during the DPR stage, thus enhancing final TN removal and maintaining TP removal. Consequently, acetate may be a better choice for a SND-DPR–coupled system.

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