Enhanced phosphorus removal in aerobic granular sludge system seeded with dewatered sludge pre-granules: Performance and mechanism

YANG Hao-sheng; LI Hui-ping; WANG Xing-bo; CHEN Guang; WANG Li-hua; LV Yan; PANG Wei-hai; XIE Li; YANG Dian-hai

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China Environmental Science ›› 2026, Vol. 46 ›› Issue (3) : 1331-1343.

Enhanced phosphorus removal in aerobic granular sludge system seeded with dewatered sludge pre-granules: Performance and mechanism

YANG Hao-sheng¹, LI Hui-ping¹, WANG Xing-bo¹, CHEN Guang², WANG Li-hua², LV Yan², PANG Wei-hai¹, XIE Li¹, YANG Dian-hai¹

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Abstract

In this study, dewatered sludge pre-granules were used as seed sludge to cultivate aerobic granular sludge (AGS) with high phosphorus removal capabilities over a 120-day operation. Inoculation with pre-granules allowed the system to bypass the initial granulation phase, establishing stable biological phosphorus removal by day 42. During the stable period, the experimental group achieved an average total phosphorus removal efficiency of (94.4±3.7)%, outperforming the control group (85.9±5.1)%. The pre-granulated AGS exhibited a particle size of 1100~1300μm, a sludge volume index of 50~80mL/g, and average removal efficiencies for chemical oxygen demand and total nitrogen of (94.5±2.9)% and (79.3±6.4)%, respectively. Scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS) revealed a notably higher iron content in the pre-granulated AGS (3.87% vs. 0.24% in the control), with iron uniformly distributed inside the granules. High-throughput sequencing further indicated enrichment of extracellular polymeric substance (EPS) secretion microorganisms, such as Candidatus_Competibacter (10.9% vs. 5.0% in the control). The results demonstrated that, unlike the primarily biological phosphorus removal mode in the control, the pre-granulated AGS developed a synergistic chemical-biological removal mechanism. Initially, EPS complexed with residual ferric iron from the dewatered sludge pre-granules, enhancing chemical phosphorus adsorption and providing a structural skeleton that improved granule stability. Subsequently, this stable structure facilitated microbial retention, yielding a higher mixed liquor volatile suspended solids concentration (4.3g/L vs.3.1g/L). Although the relative abundance of polyphosphate-accumulating organisms (PAOs) was similar between groups (0.48% vs. 0.47%), the absolute abundance of PAOs was elevated in the pre-granulated system. Moreover, the stable granular structure likely supported higher metabolic activity PAOs, as reflected by an increase in the relative abundance of key functional genes, such as polyphosphate kinase (ppk1, 0.42‰ vs. 0.34‰).

Key words

aerobic granular sludge / dewatered sludge / pre-granulation / polyphosphate-accumulating organism / biological phosphorus removal

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YANG Hao-sheng, LI Hui-ping, WANG Xing-bo, CHEN Guang, WANG Li-hua, LV Yan, PANG Wei-hai, XIE Li, YANG Dian-hai. Enhanced phosphorus removal in aerobic granular sludge system seeded with dewatered sludge pre-granules: Performance and mechanism[J]. China Environmental Science. 2026, 46(3): 1331-1343

References

[1] de Sousa Rollemberg S L, Barros A R M, Firmino P I M, et al. Aerobic granular sludge: Cultivation parameters and removal mechanisms [J]. Bioresource Technology, 2018,270:678-688.
[2] Nancharaiah Y V, Reddy G K K. Aerobic granular sludge technology: Mechanisms of granulation and biotechnological applications [J]. Bioresource Technology, 2018,247:1128-1143.
[3] Vydehi P, Ravindran G, Shyamala G, et al. Aerobic granular-based wastewater treatment: Current trends, formation, applications, granulation, efficiency, and bottlenecks [J]. Journal of Water Process Engineering, 2025,70:107075.
[4] Zhou K, Wu B R, Su L H, et al. Enhanced phosphate removal using nanostructure hydrated ferric-zirconium binary oxide confined in a polymeric anion exchanger [J]. Chemical Engineering Journal, 2018, 345:640-647.
[5] Han X S, Jin Y, Yu J G. Rapid formation of aerobic granular sludge by bioaugmentation technology: A review [J]. Chemical Engineering Journal, 2022,437(Part 1):134971.
[6] Wang L, Zhan H H, Wang Q Q, et al. Enhanced aerobic granulation by inoculating dewatered activated sludge under short settling time in a sequencing batch reactor [J]. Bioresource Technology, 2019,286: 121386.
[7] 刘文如,宋家俊,王建芳,等.硝化微颗粒污泥快速培养及其亚硝化功能快速实现 [J]. 环境科学, 2020,41(1):353-359. Liu W R, Song J J, Wang J F, et al. Rapid achievement of nitrifying micro-granular sludge and its nitritation function [J]. Environmental Science, 2020,41(1):353-359.
[8] Xu D, Liu J, Ma T, et al. Rapid granulation of aerobic sludge in a continuous-flow reactor with a two-zone sedimentation tank by the addition of dewatered sludge [J]. Journal of Water Process Engineering, 2021,41:101941.
[9] Sun Z, Zhang J M, Wang J, et al. Direct start-up of aerobic granular sludge system with dewatered sludge granular particles as inoculants [J]. Journal of Environmental Management, 2023,326(Part A):116540.
[10] Li H P, Xie L, Zhou B Q, et al. Insightful evaluation and validation of the performance and structural characteristics of pre-granulated aerobic granular sludge [J]. Journal of Environmental Chemical Engineering, 2025,13(3):116523.
[11] Li H P, Li Y X, Zhou T, et al. The rapid start-up of AGS by inoculating seed granular sludge in treatment of industrial park wastewater: performance evaluation and structural characterization [J]. Environmental Science: Water Research & Technology, 2025,11: 2308-2325.
[12] 张翔宇,范业弘,朱晗彬,等.城镇中小规模污水处理厂碳排放分析及碳削减对策 [J]. 环境科学, 2025,46(1):107-117. Zhang X Y, Fan Y H, Zhu H B, et al. Carbon emission analysis and carbon reduction strategy of small and medium-scale municipal wastewater treatment plants in cities and towns [J]. Environmental Science, 2025,46(1):107-117.
[13] 何秋来.厌氧/好氧/缺氧同步硝化反硝化除磷颗粒污泥系统构建及强化策略研究 [D]. 武汉:武汉大学, 2019. He Q L. Start-up and enhancement of simultaneous nitrification, denitrification and phosphorus removal system based on aerobic granular sludge in the anaerobic/oxic/anoxic mode [D]. Wuhan: Wuhan University, 2019.
[14] Wang C, Qi W K, Zhang S J, et al. Innovation for continuous aerobic granular sludge process in actual municipal sewage treatment: Self- circulating up-flow fluidized bed process [J]. Water Research, 2024, 260:121862.
[15] Ma J W, Chen L, Ji Y N, et al. Aerobic sludge granulation and simultaneous partial nitrification, denitrification, and phosphorus removal in an AOA-SBR with low dissolved oxygen [J]. ACS ES&T Water, 2024,4(11):5065-5076.
[16] Cassidy D P, Belia E. Nitrogen and phosphorus removal from an abattoir wastewater in a SBR with aerobic granular sludge [J]. Water Research, 2005,39(19):4817-4823.
[17] Li Y M, Zou J T, Zhang L L, et al. Aerobic granular sludge for simultaneous accumulation of mineral phosphorus and removal of nitrogen via nitrite in wastewater [J]. Bioresource Technology, 2014, 154:178-184.
[18] Franca R, Pinheiro H M, Van Loosdrecht M C M, et al. Stability of aerobic during long-term bioreactor operation [J]. Biotechnology Advances, 2018,36(1):228-246.
[19] Liu Y Q, Tay J H. Characteristics and stability of aerobic granules cultivated with different starvation time [J]. Applied Microbiology and Biotechnology, 2007,75:205-210.
[20] Mu Z B, Wang X, Wang H G, et al. Aeration-phase calcium addition for stabilizing aerobic granular sludge in treating municipal wastewater with low-strength municipal wastewater [J]. ACS ES&T Water, 2025,5(8):4701-4714.
[21] GB 18918-2002 城镇污水处理厂污染物排放标准 [S]. GB 18918-2002 Discharge standard of pollutants for municipal wastewater treatment plants [S].
[22] Liang D B, Guo W, Li D Y, et al. Enhanced aerobic granulation for treating low-strength wastewater in an anaerobic-aerobic-anoxic sequencing batch reactor by selecting slow-growing organisms and adding carriers [J]. Environmental Research, 2022,205:112547.
[23] Mino T, Van Loosdrecht M C M, Heijnen J J. Microbiology and biochemistry of the enhanced biological phosphate removal process [J]. Water Research, 1998,32(11):3193-3207.
[24] Liu W T, Nakamura K, Matsuo T, et al. Internal energy-based competition between polyphosphate- and glycogen- accumulating bacteria in biological phosphorus removal reactors—Effect of PC feeding ratio [J]. Water Research, 1997,31(6):1430-1438.
[25] Long B, Yang C Z, Pu W H, et al. Rapid cultivation of aerobic granular sludge in a pilot scale sequencing batch reactor [J]. Bioresource Technology, 2014,166:57-63.
[26] Layer M, Garcia Villodres M, Hernandez A, et al. Limited simultaneous nitrification-denitrification (SND) in aerobic granular sludge systems treating municipal wastewater: Mechanisms and practical implications [J]. Water Research X, 2020,7:100048.
[27] Wang L, Liu X, Li Z W, et al. Filamentous aerobic granular sludge: A critical review on its cause, impact, control and reuse [J]. Journal of Environmental Chemical Engineering, 2023,11(3):110039.
[28] Angela M, Béatrice B, Mathieu S. Biologically induced phosphorus precipitation in aerobic granular sludge process [J]. Water Research, 2011,45:3776-3786.
[29] Li W W, Zhang H L, Sheng G P, et al. Roles of extracellular polymeric substances in enhanced biological phosphorus removal process [J]. Water Research, 2015,86:85-95.
[30] Yin C Q, Meng F G, Meng Y B, et al. Differential ultraviolet-visible absorbance spectra for characterizing metal ions binding onto extracellular polymeric substances in different mixed microbial cultures [J]. Chemosphere, 2016,159:267-274.
[31] Felz S, Kleikamp H, Zlopasa J, et al. Impact of metal ions on structural EPS hydrogels from aerobic granular sludge [J]. Biofilm, 2020,2: 100011.
[32] Wang B D, Ni M C, Zeng Y, et al. Transforming behavior and removal mechanism of phosphorus from municipal wastewater in a continuous flow aerobic granular sludge-membrane bioreactor: Unveiling the functional genes associated with phosphorus metabolism [J]. Chemical Engineering Journal, 2025,507:160578.
[33] Guardado I, Urrutia O, Garcia-Mina J M. Methodological approach to the study of the formation and physicochemical properties of phosphate-metal-humic complexes in solution [J]. Journal of Agricultural and Food Chemistry, 2005,53(22):8673-8678.
[34] 毕贞,宋歌,黄勇.胞外聚合物在吸磷/释磷过程中的作用机制 [J]. 中国环境科学, 2025,45(12):6602-6616. Bi Z, Song G, Huang Y. The role of extracellular polymeric substances in phosphorus adsorption processes [J]. China Environmental Science, 2025,45(12):6602-6616.
[35] Li D X, Xi H L. Layered extraction and adsorption performance of extracellular polymeric substances from activated sludge in the enhanced biological phosphorus removal process [J]. Molecules, 2019,24(18):3358.
[36] Liu Y, Lin Y M, Tay J H. The elemental compositions of P-accumulating microbial granules developed in sequencing batch reactors [J]. Process Chemistry, 2005,40(10):3258-3262.
[37] Pan K, Qian Z, Chen Y X, et al. Two-way role of iron-carbon in biochemical reactions: Microelectrolysis and enhanced activity of aerobic granular sludge for efficient refractory wastewater treatment [J]. Water Research, 2024,264:122222.
[38] Yilmaz G, Lemaire R, Keller J, et al. Simultaneous nitrification, denitrification, and phosphorus removal from nutrient-rich industrial wastewater using granular sludge [J]. Biotechnology and Bioengineering, 2008,100:529-541.
[39] Lin Y M, Bassin J P, Van Loosdrecht M C M. The contribution of exopolysaccharide induced struvites accumulation to ammonium adsorption in aerobic granular sludge [J]. Water Research, 2012,46(4): 986-992.
[40] Doyle J D, Parsons S A. Struvite formation, control and recovery [J]. Water Research, 2002,36(16):3925-3940.
[41] Huang W L, Huang W W, Li H F, et al. Species and distribution of inorganic and organic phosphorus in enhanced phosphorus removal aerobic granular sludge [J]. Bioresource Technology, 2015,193:549- 552.
[42] Liu Y Q, Lan G H, Zeng P. Size-dependent calcium carbonate precipitation induced microbiologically in aerobic granules [J]. Chemical Engineering Journal, 2016,285:341-348.
[43] Shyamala G, Ravindran G, Karri R R, et al. Microbial ecology in aerobic granular sludge biofilm technology and its impact on treatment efficiency - A critical review [J]. Journal of Water Process Engineering, 2025,76:108112.
[44] Liu P X, Yang Y, Ge M, et al. Morphology and community structure characteristics of aerobic granular sludge: A review [J]. Journal of Environmental Chemical Engineering, 2025,13(5):118659.
[45] Mei Z H, Wang J L, Luo J H, et al. Unraveling the mechanism of dissolved organic matter in enhancing nitrogen removal from leachate wastewater treatment via aerobic granular sludge process [J]. Water Research, 2025,287(Part A):124407.
[46] Oehmen A, Lemos P C, Carvalho G, et al. Advances in enhanced biological phosphorus removal: From micro to macro scale [J]. Water Research, 2007,41(11): 2271-2300.
[47] Seviour T W, Lambert L K, Pijuan M, et al. Selectively inducing the synthesis of a key structural exopolysaccharide in aerobic granules by enriching for Candidatus “Competibacter phosphatis” [J]. Applied Microbiology and Biotechnology, 2011,92:1297-1305.
[48] 李军,魏鑫,邓永春,等.污泥生物炭对低C/N废水好氧颗粒污泥长期运行稳定性的影响 [J]. 中国环境科学, 2024,44(4):2032-2043. Li J, Wei X, Deng Y C, et al. Effects of sludge biochar on the long-term stability of aerobic granular sludge in low C/N wastewater [J]. China Environmental Science, 2024,44(4):2032-2043.
[49] He Q L, Li J F, Wang M, et al. A novel AOA-SNDPRr process for simultaneous wastewater treatment, phosphorus recovery, and in situ sludge reduction with ultralong sludge retention time [J]. ACS ES&T Engineering, 2025,5(4):855–863.
[50] Kang D, Yuan Z H, Li G Y, et al. Toward integrating EBPR and the short-cut nitrogen removal process in a one-stage system for treating high-strength wastewater [J]. Environmental Science & Technology, 2023,57(35):13247-13257.
[51] Wang D Q, Tooker N B, Srinivasan V, et al. Side-stream enhanced biological phosphorus removal (S2EBPR) process improves system performance – A full-scale comparative study [J]. Water Research, 2019,167:115109.
[52] Xiong W, Wang S J, Jin Y, et al. Insights into nitrogen and phosphorus metabolic mechanisms of algal-bacterial aerobic granular sludge via metagenomics: Performance, microbial community and functional genes [J]. Bioresource Technology, 2023,369:128442.
[53] Zhang L X, Guan Y T, Jiang S C. Investigations of soil autotrophic ammonia oxidizers in farmlands through genetics and big data analysis [J]. Science of The Total Environment, 2021,777:146091.
[54] Halm H, Musat N, Lam P, et al. Co-occurrence of denitrification and nitrogen fixation in a meromictic lake, Lake Cadagno (Switzerland) [J]. Environmental Microbiology, 2009,11:1945-1958.
[55] 秦璐.侧流强化生物除磷工艺机理与性能优化研究 [D]. 西安:西安理工大学, 2023. Qin L. Study on the mechanism and performance optimization of side-stream enhance biological phosphorus removal process [D]. Xi’an: Xi’an University of Technology, 2023.
[56] 陈丽萍.城市污水厂中聚磷菌的富集及其碳源摄取与物质代谢特征研究 [D]. 广州:华南理工大学, 2023. Chen L P. Carbon uptake and metabolic characteristics of enriched polyphosphate accumulating organisms from municipal wastewater treatment plants [D]. Guangzhou: South China University of Technology, 2023.