Advanced Treatment of Effluents Loaded with Sulfide from Unhairing-Liming Tannery Unit:A Combination of Chemical and Biological Processes

Advanced Treatment of Effluents Loaded with Sulfide from Unhairing-Liming Tannery Unit:A Combination of Chemical and Biological Processes | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Advanced Treatment of Effluents Loaded with Sulfide from Unhairing-Liming Tannery Unit:A Combination of Chemical and Biological Processes Anass OMOR, Omar Laidi, Marwa El Jai, Zakia Rais, Karima Elkarrach This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8086826/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 4 You are reading this latest preprint version Abstract This study investigates a hybrid treatment process for highly polluted tannery effluents from the unhairing-liming stage, which are characterized by elevated sulfide and Chemical Oxygen Demand (COD) levels, posing significant risks to human health and the environment. The process integrates chemical precipitation with Ferric Chloride (FeCl₃) and biological treatment in a Sequencing Batch Reactor (SBR). At an optimal FeCl₃ concentration of 1.2 mol.L⁻¹ and pH 8.5, the chemical stage achieved 90.11% sulfide removal and 88.33% COD removal through sulfide precipitation and organic matter coagulation but failed to meet Moroccan discharge standards. Subsequent SBR treatment, operating at a high organic load (1.5 kg COD.d⁻¹.m⁻³), improved removal efficiencies to 99.97% for sulfides and 99.60% for COD, ensuring full regulatory compliance. One-way ANOVA confirmed the statistical significance of the combined process (p < 0.001). XRD and SEM analyses identified gypsum (CaSO₄.2H₂O) as the primary precipitate, which exhibited favorable morphology for sludge management. The FeCl₃–SBR system provides a robust, sustainable solution for small- and medium-scale tanneries, particularly in developing countries. Tannery effluents Coupled treatment Precipitation Ferric chloride Sequencing batch reactor Full Text Cite Share Download PDF Status: Under Review Version 1 posted Reviewers agreed at journal 16 Dec, 2025 Reviewers invited by journal 02 Dec, 2025 Editor assigned by journal 24 Nov, 2025 First submitted to journal 22 Nov, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8086826","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":553976005,"identity":"1afc39b4-6655-4e99-9c88-ff299204dd9d","order_by":0,"name":"Anass 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Processes","fulltext":[],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":true,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":true,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"environmental-science-and-pollution-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"espr","sideBox":"Learn more about [Environmental Science and Pollution Research](https://www.springer.com/journal/11356)","snPcode":"11356","submissionUrl":"https://submission.nature.com/new-submission/11356/3","title":"Environmental Science and Pollution Research","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Tannery effluents, Coupled treatment, Precipitation, Ferric chloride, Sequencing batch reactor","lastPublishedDoi":"10.21203/rs.3.rs-8086826/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8086826/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThis study investigates a hybrid treatment process for highly polluted tannery effluents from the unhairing-liming stage, which are characterized by elevated sulfide and Chemical Oxygen Demand (COD) levels, posing significant risks to human health and the environment. The process integrates chemical precipitation with Ferric Chloride (FeCl₃) and biological treatment in a Sequencing Batch Reactor (SBR). At an optimal FeCl₃ concentration of 1.2 mol.L⁻\u0026sup1; and pH 8.5, the chemical stage achieved 90.11% sulfide removal and 88.33% COD removal through sulfide precipitation and organic matter coagulation but failed to meet Moroccan discharge standards. Subsequent SBR treatment, operating at a high organic load (1.5 kg COD.d⁻\u0026sup1;.m⁻\u0026sup3;), improved removal efficiencies to 99.97% for sulfides and 99.60% for COD, ensuring full regulatory compliance. One-way ANOVA confirmed the statistical significance of the combined process (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). XRD and SEM analyses identified gypsum (CaSO₄.2H₂O) as the primary precipitate, which exhibited favorable morphology for sludge management. The FeCl₃\u0026ndash;SBR system provides a robust, sustainable solution for small- and medium-scale tanneries, particularly in developing countries.\u003c/p\u003e","manuscriptTitle":"Advanced Treatment of Effluents Loaded with Sulfide from Unhairing-Liming Tannery Unit:A Combination of Chemical and Biological Processes","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-12-04 14:36:05","doi":"10.21203/rs.3.rs-8086826/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewerAgreed","content":"","date":"2025-12-17T02:39:44+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-12-02T10:14:00+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-11-25T04:54:55+00:00","index":"","fulltext":""},{"type":"submitted","content":"Environmental Science and Pollution Research","date":"2025-11-22T12:06:33+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"environmental-science-and-pollution-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"espr","sideBox":"Learn more about [Environmental Science and Pollution Research](https://www.springer.com/journal/11356)","snPcode":"11356","submissionUrl":"https://submission.nature.com/new-submission/11356/3","title":"Environmental Science and Pollution Research","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"78da4141-4306-4724-bba2-472d1469dc3a","owner":[],"postedDate":"December 4th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2025-12-04T14:36:05+00:00","versionOfRecord":[],"versionCreatedAt":"2025-12-04 14:36:05","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8086826","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8086826","identity":"rs-8086826","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}