Recently, researchers from Biogas Institute of Ministry of Agriculture and Rural Affairs, Chinese Academy of Agricultural Sciences (BIOMA, CAAS) have revealed the performance differences between A/O and SBR processes in treating digested effluent of swine wastewater and its mechanisms. The results are published on Journal of Cleaner Production with the title of “Sequencing batch reactor (SBR) and anoxic and oxic process (A/O) display opposite performance for pollutant removal in treating digested effluent of swine wastewater with low and high COD/N ratios”.

The anaerobic-aerobic combined process is a mainstream approach for the treatment of swine wastewater. And anaerobic digestion is becoming increasingly attractive as a

way to treat swine wastewater since it can not only remove most of the biodegradable organic matters, but also produces renewable energy (methane). However, the disadvantage of the anaerobic digestion is that it is difficult to remove NH4+-N and the effluent may even present higher concentrations of NH4+-N than the influent. Meanwhile, the discharge standards of pollutants from the livestock industry have become increasingly stricter. Therefore, an efficient post-treatment for digested effluent of swine wastewater is necessary. Anoxic/oxic process (A/O) and sequencing batch reactor (SBR) are popular aerobic biological processes for treating digested effluent of swine wastewater. However, it is still not clear which of the two has better performance.

A previous study has proposed aerobic processes the anaerobic-addition of raw wastewater-intermittent aeration process (ANARWIA), and on this basis, the researchers further explored the differences between A/O and SBR processes in treating digested effluent of swine wastewater and its mechanisms. The study found that higher nitrogen removal capacity was observed for A/O in the treatment of wastewater with low C/N ratio, whereas for SBR in the treatment of wastewater with high C/N ratio. The substrate BOD5 concentrations and mixed liquor recycle ratio (R) are some of the main factors influencing performance differences between A/O and SBR processes in treating digested effluent of swine wastewater. And it also leads to higher ammonia-oxidizing and anammox activity in SBR, whereas higher denitrifying activity in A/O process.

The research was supported by the Chinese Agriculture Research System [CARS-36-06 B] and the Sichuan Science and Technology program [2021ZDZX0012].