Effect of different aeration methods on swine wastewater treated by <i>Oenanthe javanica</i> combined with microbes in winter

The aim of this research is to study the effect of different aeration methods on swine wastewater treated by Oenanthe javanica combined with microbes, and the change in the microbial community. Experiments were conducted by circulation, aeration, and standing (control) groups, and a sample was taken at 7-day intervals during the treatment period of 35 days. The water indices were analyzed by national standard methods. The microbial community characteristics were analyzed using a high-throughput sequencing technology (Illumina MiSeq sequencer). The dissolved oxygen values in the control, aeration, and circulation groups were 0.60, 10.38 mg·L-1 and 10.85 mg·L-1, respectively. The best growth of Oenanthe javanica was observed in the control group, where a relative growth rate of 0.03 g·g-1·d-1 was achieved. The water purification efficiency of the three treatments was significantly different, in this case, the circulation group showed superior results with the removal rates of chemical oxygen demand (COD), ammonium nitrogen, and total nitrogen at 89.89%, 69.40%, and 77.65%, respectively. The relative abundance of Flavobacterium decreased from 43.21% to 0.16%, while that of Christensenellaceae and Ruminococcaceae increased significantly. Oenanthe javanica grew well in the treated swine wastewater during winter. The purification efficiency can be obviously improved by supplementing oxygen through circulation or aeration. After 35 days of treatment, the microbial diversity in the water increased; Moreover, Flavobacteria and Pseudomonas were identified as the functional bacteria of denitrification. The proliferation of Clostridiales is also beneficial for the removal of COD