Sewage treatment effect of AOA-SBR under different C/P value and its mechanism of nitrogen and phosphorus removal

Aiming at the practical problem of difficulty in nitrogen and phosphorus removal in WWTPs due to low influent C/P value, five groups of AOA-SBR were used to carry out the experiment on the treatment of sewage with different C/P values (120, 40, 24, 17, 13). The results showed that when the C/P value decreased from 120 to 40, the average removal rates of TN and TP in the AOA-SBR system increased from 70.36% and 90.90% to 79.31% and 99.22%. The analysis showed that the difference in denitrification of each system mainly occurred in the anoxic period, and the reduction of TN in the anoxic period reached the maximum when the C/P value was 40. Moreover, the concentration of orthophosphate entered the anoxic period was more suitable at this time, which promoted the DPR of the system. Phosphorus forms analysis showed that when the influent C/P value was further reduced (24, 17, 13), the accumulation of AP content in the activated sludge inhibited the activity of PAOs (including DPAOs), and finally decreased the denitrification and phosphorus removal effects. Based on metabolic composition and pathway analysis, the enrichment of DPAOs (Dechloromonas, Pseudomonas, Rhodobacter) and higher relative abundances of nas+nap and phbC/phaC+phaZ were the key to improve the nitrogen and phosphorus removal efficiency of AOA-SBR system at low C/P value.