Enhance nitrogen removal via endogenous denitrification in a sludge double recirculation-anaerobic/aerobic/anoxic process

doi:10.11949/0438-1157.20221008

Abstract

Abstract:

At present, how to economically and effectively realize the deep denitrification of low C/N domestic sewage is still a major challenge faced by sewage treatment plants. Theoretically, the endogenous denitrification in post anoxic zone can achieve advanced nitrogen removal. However,due to lacking external carbon source, it was often difficult to meet the discharge standard and saving-energy at the same time. In this study, a novel sludge double recirculation-anaerobic/aerobic/anoxic (AOA) process was set up. This process was conducive to the enrichment and cultivation of denitrifying glycogen accumulating organisms (DGAOs) and dominated by Candidatus Competibacte, which could develop and utilize of intracellular carbon sources. The TIN removal efficiency of 91.81% and the TIN concentration in effluent was 4.36mg·L^-1 in the long-term treatment of low C/N ratio (3.2) real municipal wastewater. In addition, the specific endogenous denitrification rate was increased with a higher MLSS in the anoxic zone after setting secondary sludge recirculation. This was the mainly reason for achieving advanced nitrogen removal. With the improvement of the nitrogen removal efficiency, the sufficient intracellular carbon sources storage in anaerobic zone was increase, and the endogenous denitrification enhanced. The nitrogen removal performance showed a positive cycle. Finally, the additional carbon source generation, which was from the bottom of the secondary sedimentation tank and introduced to the system through the secondary sludge recirculation, further enhanced the nitrogen removal. This study clarified the mechanisms and key factors for advanced nitrogen removal in sludge double recirculation-AOA system, and provided feasibility for the increased nitrogen removal efficiency in low C/N municipal wastewater treatment.

Key words: anaerobic, aeration, waste water, endogenous denitrification, low C/N ratio, enhanced nitrogen removal

摘要：

目前，如何经济有效地实现低C/N生活污水深度脱氮仍是污水处理厂面临的一个重大挑战。理论上后置反硝化可以实现深度脱氮效果，但往往由于缺乏外碳源难以同时满足经济高效脱氮。本研究建立的新型污泥双回流-厌氧/好氧/缺氧(AOA)工艺有利于富集培养以Candidatus Competibacter为主的反硝化聚糖菌(DGAOs)，能够开发与利用内碳源脱氮。该系统长期处理低C/N (3.2)实际城市生活污水，TIN去除率达91.81%，出水TIN浓度为4.36 mg·L^-1。此外，提高第二污泥回流量增加了缺氧区的MLSS同时提升了比内源反硝化速率，是深度氮去除的主要原因。随着去除效果的提升，充分的厌氧环境使得内碳源贮存量升高，脱氮效果呈现正向循环。二沉池底部产生的额外碳源随第二回流引入系统进一步强化脱氮。本研究阐明了污泥双回流-AOA系统节碳脱氮的原理与关键，为低C/N城市污水的脱氮效率提供了一种可行性。

关键词: 厌氧, 曝气, 污水, 内源反硝化, 低C/N, 强化脱氮

CLC Number:

X 703.1

Xinjie GAO, Zaizhou XU, Yongzhen PENG, Yuwei HUANG, Jing DING, Zeming AN, Chuanxin WANG. Enhance nitrogen removal via endogenous denitrification in a sludge double recirculation-anaerobic/aerobic/anoxic process[J]. CIESC Journal, 2022, 73(11): 5098-5105.

高歆婕, 许载周, 彭永臻, 黄雨薇, 丁静, 安泽铭, 汪传新. 污泥双回流-厌氧/好氧/缺氧强化内源反硝化深度脱氮[J]. 化工学报, 2022, 73(11): 5098-5105.

Figures/Tables 7

Fig.1 Schematic diagram of the AOA system

Fig.2 Long-term nitrogen removal performances in the AOA system

Fig.3 The variations of pollutant concentration in different zones of AOA system

Fig.4 Functional microorganisms in AOA system

Fig.5 The TIN loss and the TIN concentration in effluent in the AOA system with different R2

Fig.6 The effect of MLSS on nitrogen removal

Fig.7 The difference of COD and NH4+-N concentration between the effluent and the bottom of the secondary sedimentation tank during the long-term operation

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