Abstract
Coagulation is widely regarded as an indispensable pretreatment process in reverse osmosis (RO) systems of zero liquid discharge applications. Yet in practical applications, coagulation pretreatment often causes perplexing impact on membrane fouling and even deteriorates the RO performance with ambiguous mechanisms, thereby seriously disrupting the progress of RO-based applications. This study systematically reveals the RO performance devolution caused by Fe- or Al-based coagulation pretreatment, and elucidates the fundamental mechanism of membrane fouling deterioration due to residual coagulants. The Al-based coagulation predominantly triggers inorganic fouling, with the disruption of microbial ecological interaction networks within the biofilm exacerbated by copper-induced oxidative stresses. The Fe residues dramatically enhance the production of extracellular polymeric substances and facilitate robust fouling layer development, exacerbating membrane fouling and diminishing RO performance. These findings not only provide essential engineering guidance for optimizing practical operations but also deepen the understanding of the coagulation–RO interactions, establishing a refined framework for enhancing the efficiency and sustainability of advanced water treatment systems.
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Data availability
The sequencing data are available in the NCBI database named BioProject PRJNA1059279. Source data supporting the findings of this study are provided with this paper. Source data are provided in this paper.
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Acknowledgements
This work was supported by the Major Program of MOST of China (No. 2022YFC3203103 to X.H.), Beijing Natural Science Foundation (No. JQ22027 to K.X.), Fundamental Research Funds for the Central Universities (QNTD202506 to S.L.), Huaneng Group science and technology research project (HNKJ22-H105 to X.H. and S.L.), and China Postdoctoral Science Foundation (2025M781191 to H.D.).
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X.H., S.L., and H.D. conceived the idea and designed the research. H.D. carried out the experiments. R.G. and Y.L. contributed to data collection. H.D., W.L., and C.C. analyzed and integrated the data. H.D. wrote the initial draft. Y.F.L. contributed to experimental design and manuscript review. H.D. and S.L. iterated multiple versions. X.H., S.L., K.X., and H.D. made the final revision of the manuscript.
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Ding, H., Liang, S., Lin, W. et al. Coagulation pretreatment could deteriorate reverse osmosis membrane fouling. Nat Commun (2026). https://doi.org/10.1038/s41467-026-70892-4
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DOI: https://doi.org/10.1038/s41467-026-70892-4


