ArticlePublished: 17 September 2025Hao Sheng ORCID: orcid.org/0009-0007-0028-45671,Jiawei Liu1 &Yayi Wang ORCID: orcid.org/0000-0001-5886-09411 Nature Sustainability (2025)Cite this articleSubjectsElement cyclesEnvironmental biotechnologyMicrobiology techniquesWater microbiologyAbstractSewage sludge, an unavoidable by-product of biological sewage treatment processes, is a growing environmental burden. If handled properly, it can also be a crucial secondary resource, as it contains many functional microbiomes and useful nutrients. Here we propose an in situ nitrate-driven oxidation approach to upcycle sewage sludge into valuable (>US$4,000 m−3) anaerobic ammonium oxidation (anammox) seeds, which are a key ingredient to achieve a fast start-up of the anammox process—a low-carbon nitrogen removal process—in biological sewage treatment facilities. The approach can effectively upcycle sewage sludge rich in endogenous reductants, such as organics and sulfur-based compounds, but poor in oxidative substances. Specifically, this approach employs nitrate-containing wastewater as an oxidant source and utilizes nitrate to oxidize reductants in sewage sludge to provide nitrite for anammox bacterial growth. This approach can initiate anammox seeds within 45 days and form anammox seeds with biomarkers within 90 days. This work reveals the potential of sewage sludge as a source of functional microbiomes and opens a new avenue to sustainable sewage management.This is a preview of subscription content, access via your institutionAccess optionsAccess Nature and 54 other Nature Portfolio journalsGet Nature+, our best-value online-access subscription27,99 € / 30 dayscancel any timeLearn moreSubscribe to this journalReceive 12 digital issues and online access to articles118,99 € per yearonly 9,92 € per issueLearn moreBuy this articlePurchase on SpringerLinkInstant access to full article PDFBuy nowPrices may be subject to local taxes which are calculated during checkoutFig. 1: Variations in physicochemical parameters during the anammox seed cultivation phase (1–37 days) and enrichment phase (38–102 days).Fig. 2: Variations in physicochemical parameters during the anammox seed maturing phase (103–210 days) and a 72-h in situ batch test (207–210 days).Fig. 3: Performance of the in situ nitrate-driven oxidation system.Fig. 4: 16S rRNA amplicon high-throughput sequencing and gene chip analysis.Data availabilityThe data generated in this study are included within the article and its Supplementary Information. 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China Life Sci. 61, 1451–1462 (2018).Article CAS Google Scholar Download referencesAcknowledgementsThis work was supported by the National Science Fund for Distinguished Young Scholars (grant no. 52225001) and the National Natural Science Foundation of China Joint Project (grant number U24A20185).Author informationAuthors and AffiliationsState Key Laboratory of Water Pollution Control and Green Resource Recycling, College of Environmental Science and Engineering, Tongji University, Shanghai, P. R. ChinaHao Sheng, Jiawei Liu & Yayi WangAuthorsHao ShengView author publicationsSearch author on:PubMed Google ScholarJiawei LiuView author publicationsSearch author on:PubMed Google ScholarYayi WangView author publicationsSearch author on:PubMed Google ScholarContributionsH.S. performed project planning, experimental work, data analysis, figure drawing and writing of the paper. J.L. performed figure drawing and polishing. Y.W. performed project planning and revision of the paper.Corresponding authorCorrespondence to Yayi Wang.Ethics declarationsCompeting interestsThe authors declare no competing interests.Peer reviewPeer review informationNature Sustainability thanks the anonymous reviewer(s) for their contribution to the peer review of this work.Additional informationPublisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.Extended dataExtended Data Fig. 1 Variations in physicochemical parameters associated with the anammox performance.a, Influent and effluent NO3−-N concentrations in the experimental reactor (1 − 37 days). b, TIN removal efficiencies for the control and experimental reactors (1 − 37 days). c, Influent and effluent NH4+-N concentrations for the experimental reactor. d, Influent and effluent NO2−-N concentrations for the experimental reactor. e, Anammox stoichiometric ratios for the experimental reactor. f, Influent and effluent pH values for the experimental reactor. g, Influent and effluent NH4+-N concentrations for the control (1 − 37 days). h, Influent and effluent NO2−-N concentrations for the control (1 − 37 days). i, Influent and effluent NH4+-N concentrations for the control. j, Influent and effluent NO2−-N concentrations for the control. k, Anammox stoichiometric ratios for the control. l, Influent and effluent pH values for the control.Source DataExtended Data Fig. 2 Variations in free ammonia concentrations and anammox hzsB gene abundance.a, Effluent free ammonia concentrations in the control and experimental reactors. b, Absolute abundance values for anammox hzsB genes. S0 indicates the original sample, CK indicates the control, and bars labeled 1 − 5 g/L indicate the experimental reactors, where the values represent the concentration of Ca(NO3)2·4H2O. Data in b are presented as mean values ± SD. All the samples were performed in triplicate (n = 3, technical replicates). Significant differences between the CK and experimental reactors were derived by a two-tailed t-test (p