[Nitrogen and Phosphorus Removal from Low C/N Municipal Wastewater Treated by a SPNDPR System with Different Aeration...

An anaerobic (180 min)/aerobic operated sequencing batch reactor (SBR) fed with urban sewage was optimized by regulating the aeration quantity to investigate the deep-level nitrogen (N) and phosphorus (P) removal. The amount of aeration was regulated by adjusting the volume of gas per unit volume of reactor passed in unit time, when the unit is L·(min·L)^-1, from 0.125 L·(min·L)^-1 gradually to 0.025 L·(min·L)^-1, and aerobic times from 3 h to 6 h. The experimental results show that the effluent NH₄⁺-N, NO₂^--N, NO₃^--N, and PO₄^3--P concentrations of the optimized SPNDPR system were 0, 8.62, 0.06, and 0.03 mg·L^-1. The effluent TN concentration was about 9.22 mg·L^-1, and the TN removal efficiency was up to 87.08%. When the aeration quantity was decreased from 0.125 L·(min·L)^-1 to 0.100 L·(min·L)^-1; then decreased to 0.075 L·(min·L)^-1, the nitrification rate of the system recovered and stabilized at 0.16 mg·(L·min)^-1. However, when the aeration quantity continuously decreased to 0.050 L·(min·L)^-1 and then to 0.025 L·(min·L)^-1, the nitrification rate decreased to 0.09 mg·(L·min)^-1 and 0.06 mg·(L·min)^-1. With reduction of the aeration quantity[from 0.125 L·(min·L)^-1 to 0.100, 0.075, 0.050 and 0.025 L·(min·L)^-1] and extension of aerobic time (from 3 h to 6 h), the TN removal efficiency increased gradually from 62.82% to 87.08%, and the SND efficiency increased from 19.57% to 72.11%. It was proven that reducing the aeration quantity can enhance the SPND function and deep denitrification by the system was realized. By enhancing the anaerobic intracellular carbon storage and aerobic phosphorus uptake, denitrifying phosphorus removal, partial nitrification, and endogenous nitrification were achieved. The SPNDPR system, after reducing aeration and prolonging aerobic time, was able to realize deep-level denitrification and dephosphorization using low C/N urban sewage.