Denitrifying phosphorus removal performance optimizationand stable operation of A2N2 system
WANG Mei-xiang, ZHAO Wei-hua, WANG Shu-ying, HUANG Yu, PAN Cong, PENG Yong-zhen
Key Laboratory of Beijing for Water Quality Science and Water Environment Recovery Engineering, Engineering Research Center of Beijing, National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Beijing University of Technology, Beijing 100124, China
The two-sludge denitrifying phosphorus removal system (A2N2) with "anaerobic/nitrification/anoxic/ nitrification" operation mode was used to treat low C/N ratio real domestic wastewater in sequencing batch reactors (SBR). Through the operating condition optimization of A2/O-SBR and N-SBR unit, the system achieved efficient denitrifying phosphorus removal performance with the low carbon source sewage and solved the problem of high NH4+-N in A2N-SBR process. Experimental results showed that post-aeration was essential to the efficient nutrient removal performance and long-term stable operation of the A2N2-SBR. Complete denitrifying phosphorus uptake without aerobic phosphorus uptake at the anoxic stage of the A2N2-SBR was disadvantageous to the growth and reproduction of denitrifying phosphorus accumulating organisms (DPAOs). Anaerobic duration of 1.5h in the A2/O-SBR was ensured the complete oxidation of biodegradable COD, and nitrification duration of 5h in the N-SBR provided sufficient time for NH4+-N oxidation. With anaerobic phosphorus release of 1.5h, denitrifying phosphorus uptake of 2h, and aerobic phosphorus uptake of 0.5h in the A2/O-SBR unit, and the first nitrification of 5h and second nitrification of 1h in the N-SBR unit, the average effluent COD, NH4+-N, TN and PO43--P concentrations in the A2N2-SBR system was 46.2, 0.82, 13.63 and 0.82mg/L, respectively. Simultaneous nitrogen and phosphorus removal was achieved in the novel A2N2-SBR system.
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