Step feed mode synergistic mixed carbon source to improve sequencing batch reactor simultaneous nitrification and denitrification efficiency of domestic wastewater treatment

The limited efficiency of nitrogen removal has traditionally hindered wide application of simultaneous nitrification and denitrification (SND) technology. Here, the nitrogen removal characteristics of a sequencing batch reactor were studied by adopting a strategy of a step-feeding mode, synergistic regional oxygen limitation, and a mixed carbon source. The changes of the microbial population succession and nitrogen metabolism functional genes were analyzed. This strategy provided a favorable level of dissolved oxygen and continuous carbon sources for driving the denitrification process. The total nitrogen removal efficiency and SND rate reached 92.60% and 96.49%, respectively, by regulating the ratio of sodium acetate to starch in the step feed to 5:1. This procedure increased the relative abundance of denitrifying functional genes and induced the growth of a variety of traditional denitrifying bacteria and aerobic denitrifying bacteria participating in the process of nitrogen removal. Overall, this work offers a new strategy for achieving efficient SND.