{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,31]],"date-time":"2026-01-31T05:48:11Z","timestamp":1769838491542,"version":"3.49.0"},"reference-count":44,"publisher":"MDPI AG","issue":"4","license":[{"start":{"date-parts":[[2021,2,18]],"date-time":"2021-02-18T00:00:00Z","timestamp":1613606400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100003593","name":"Conselho Nacional de Desenvolvimento Cient\u00edfico e Tecnol\u00f3gico","doi-asserted-by":"publisher","award":["GDE 201469\/2014-6"],"award-info":[{"award-number":["GDE 201469\/2014-6"]}],"id":[{"id":"10.13039\/501100003593","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sustainability"],"abstract":"<jats:p>The present study aimed to optimize the struvite chemical precipitation process in nitrogen-rich anaerobic co-digestion systems. Struvite precipitation experiments were carried out using a mixture of cattle slurry liquid fraction and sewage sludge, with and without ultrasound pretreatment. Marine salt or MgCl2 were used as magnesium source in NH4+:Mg2+ stoichiometric proportions of 1:1.5 and 1:3. Under the tested conditions, ammonium nitrogen and orthophosphate were removed from the mixed liquor with a maximum observed efficiency of 43% and 92%, respectively, when the ultrasound treatment was applied prior to struvite precipitation, using MgCl2 as source of magnesium (NH4+:Mg2+ of 1:3). The operating time was 40 min. Different pretreatments were tested prior to the biomethanization experiments, struvite precipitation, ultrasound and a combination of both pretreatments. The application of ultrasound (with an energy input of 218 kJ L\u22121) and struvite precipitation (NH4+:Mg2+ of 1:3) increased the methane content in the biogas by 82% and reduced hydraulic retention time by 28%, when compared to the anaerobic co-digestion assays without pretreatment. The hydrolytic pretreatment increased the bioavailability of nitrogen by 5%, thus enhancing the removal efficiency of ammonium nitrogen by 20%. Consequently, an increase in the carbon to nitrogen ratio was observed, favoring the methanogenesis process.<\/jats:p>","DOI":"10.3390\/su13042175","type":"journal-article","created":{"date-parts":[[2021,2,18]],"date-time":"2021-02-18T21:59:58Z","timestamp":1613685598000},"page":"2175","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":5,"title":["Combined Pretreatment by Ultrasound and Struvite Precipitation of Raw Substrates: A Strategy to Overcome C\/N Ratio Unbalance in Nitrogen-Rich Anaerobic Co-Digestion Systems"],"prefix":"10.3390","volume":"13","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-3312-2242","authenticated-orcid":false,"given":"Renata D\u2019arc","family":"Coura","sequence":"first","affiliation":[{"name":"LEAF\u2014Linking Landscape, Environment, Agriculture and Food, Instituto Superior de Agronomia, Universidade de Lisboa, 1349-017 Lisboa, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4082-1762","authenticated-orcid":false,"given":"Ana Cristina","family":"Rodrigues","sequence":"additional","affiliation":[{"name":"ProMetheus-Research Unit in Materials, Energy and Environment for Sustainability, Instituto Polit\u00e9cnico de Viana do Castelo, 4900-347 Viana do Castelo, Portugal"},{"name":"CEB\u2014Centre of Biological Engineering, Campus de Gualtar, Universidade do Minho, 4710-057 Braga, Portugal"}]},{"given":"Joaquim Mamede","family":"Alonso","sequence":"additional","affiliation":[{"name":"ProMetheus-Research Unit in Materials, Energy and Environment for Sustainability, Instituto Polit\u00e9cnico de Viana do Castelo, 4900-347 Viana do Castelo, Portugal"},{"name":"CIBIO-InBIO\u2014Research Centre in Biodiversity and Genetic Resources, Campus de Vair\u00e3o Rua Padre Armando Quintas, Universidade do Porto, 7, 4485-661 Vair\u00e3o, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6004-6869","authenticated-orcid":false,"given":"Ana Isabel","family":"Ferraz","sequence":"additional","affiliation":[{"name":"ProMetheus-Research Unit in Materials, Energy and Environment for Sustainability, Instituto Polit\u00e9cnico de Viana do Castelo, 4900-347 Viana do Castelo, Portugal"},{"name":"CEB\u2014Centre of Biological Engineering, Campus de Gualtar, Universidade do Minho, 4710-057 Braga, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6606-2963","authenticated-orcid":false,"given":"Luis Miguel","family":"Brito","sequence":"additional","affiliation":[{"name":"CIMO\u2014Mountain Research Center, Escola Superior Agr\u00e1ria, Instituto Polit\u00e9cnico de Viana do Castelo, 4990-706 Ponte de Lima, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4595-3641","authenticated-orcid":false,"given":"Jo\u00e3o Carlos Castro","family":"Abrantes","sequence":"additional","affiliation":[{"name":"ProMetheus-Research Unit in Materials, Energy and Environment for Sustainability, Instituto Polit\u00e9cnico de Viana do Castelo, 4900-347 Viana do Castelo, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1356-3358","authenticated-orcid":false,"given":"Ant\u00f3nio Guerreiro","family":"Brito","sequence":"additional","affiliation":[{"name":"LEAF\u2014Linking Landscape, Environment, Agriculture and Food, Instituto Superior de Agronomia, Universidade de Lisboa, 1349-017 Lisboa, Portugal"}]}],"member":"1968","published-online":{"date-parts":[[2021,2,18]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"901","DOI":"10.1016\/j.procbio.2013.04.012","article-title":"Ammonia inhibition in anaerobic digestion: A review","volume":"48","author":"Yenigun","year":"2013","journal-title":"Process Biochem."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"383","DOI":"10.1016\/j.rser.2014.05.038","article-title":"Reviewing the anaerobic digestion of food waste for biogas production","volume":"38","author":"Zhang","year":"2014","journal-title":"Renew. Sustain. Energy Rev."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"65","DOI":"10.1016\/S1389-1723(04)70167-X","article-title":"Effect of ammonium adition on methanogenic community in a fluidized bed anaerobic digestion","volume":"97","author":"Sawayama","year":"2004","journal-title":"J. Biosci. Bioeng."},{"key":"ref_4","first-page":"4861","article-title":"Counteracting ammonia inhibition in anaerobic digestion by removal with a hollow fiber membrane contactor","volume":"46","author":"Lauterbpcl","year":"2012","journal-title":"Water Resour."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"163","DOI":"10.1016\/j.biortech.2012.07.116","article-title":"Feasibility of anaerobic co-digestion of pig waste and paper sludge","volume":"124","author":"Parameswaran","year":"2012","journal-title":"Bioresour. Technol."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"127","DOI":"10.1016\/j.watres.2018.06.021","article-title":"Characterizing and modelling free ammonia and ammonium inhibition inanaerobic systems","volume":"143","author":"Astals","year":"2018","journal-title":"Water Res."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"4044","DOI":"10.1016\/j.biortech.2007.01.057","article-title":"Inhibition of anaerobic digestion process: A review","volume":"99","author":"Chen","year":"2008","journal-title":"Bioresour. Technol."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"79","DOI":"10.1016\/j.biortech.2008.06.029","article-title":"Increased biogas production at wastewater treatment plants through co-digestion of sewage sludge with grease trap sludge rom a meat processing plant","volume":"100","author":"Luostarinen","year":"2009","journal-title":"Bioresour. Technol."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"191","DOI":"10.1016\/j.ibiod.2016.10.037","article-title":"Synergistic effect from anaerobic co-digestion of sewage sludge andorganic wastes","volume":"116","author":"Xie","year":"2017","journal-title":"Int. Biodeterior. Biodegrad."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"29","DOI":"10.1038\/478029a","article-title":"Phosphorus cycle: A broken biogeochemical cycle","volume":"478","author":"Elser","year":"2011","journal-title":"Nature"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"4191","DOI":"10.1016\/S0043-1354(01)00143-9","article-title":"Conditions influencing the precipitation of magnesium ammonium phosphate","volume":"35","author":"Stratful","year":"2001","journal-title":"Water Res."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"542","DOI":"10.1016\/j.cej.2015.02.057","article-title":"Feasibility of coupling anaerobic digestion and struvite precipitation in the same reactor: Evaluation of different magnesium sources","volume":"270","author":"Astals","year":"2015","journal-title":"Chem. Eng. J."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"1043","DOI":"10.1016\/j.jclepro.2019.06.007","article-title":"Integrating wet oxidation and struvit precipitation for sewage sludge treatment and phosphorus recovery","volume":"232","author":"Munir","year":"2019","journal-title":"J. Clean. Prod."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"171","DOI":"10.2166\/wst.2003.0045","article-title":"Removal and recovery of phosphate and ammonium as struvite from supernatant in anaerobic digestion","volume":"48","author":"Yoshino","year":"2003","journal-title":"Water Sci. Technol."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"1601","DOI":"10.1016\/S0043-1354(02)00526-2","article-title":"Removal of ammonium and phosphates from wastewater resulting from the process of cochineal extraction using MgO-containing by-product","volume":"37","author":"Chimenos","year":"2003","journal-title":"Water Res."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"229","DOI":"10.1016\/S0960-8524(03)00076-2","article-title":"Struvite precipitation in anaerobic swine lagoon liquid: Effect of pH and Mg:P ratio and determination of rate constant","volume":"89","author":"Nelson","year":"2003","journal-title":"Bioresour. Technol."},{"key":"ref_17","unstructured":"Pullammanappallil, P., and Mohan, G. (2016). Recovery of Nutrients from Water and Wastewater by Precipitation as Struvite. (US20160185633A1), U.S. Patent."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"14","DOI":"10.1016\/j.cej.2014.06.036","article-title":"Effect of ultrasound, thermal and alkali treatments on the rheological profile and water distribution of waste activated sludge","volume":"255","author":"Simyn","year":"2014","journal-title":"Chem. Eng. J."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"128","DOI":"10.1016\/j.ibiod.2014.07.004","article-title":"Short chain fatty acids accumulation and microbial community succession during ultrasonic-Pretreated sludge anaerobic fermentation process: Effect of alkaline adjustment","volume":"94","author":"Liu","year":"2014","journal-title":"Int. Biodeterior. Biodegrad. J."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"1200","DOI":"10.1080\/10643389.2013.763587","article-title":"Ultrasonic Treatment of Waste Sludge: A Review on Mechanisms and Applications","volume":"44","author":"Tyagi","year":"2014","journal-title":"Crit. Rev. Environ. Sci. Technol."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"289","DOI":"10.1007\/s00449-011-0588-x","article-title":"Ultrasonic sludge disintegration for enhanced methane production","volume":"35","author":"Kim","year":"2012","journal-title":"Bioprecess Biosyst. Eng."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"26522","DOI":"10.1016\/j.ijhydene.2017.06.178","article-title":"Effect of substrate pretreatment on biogas production through anaerobic digestion offood waste","volume":"42","author":"Deepanraj","year":"2017","journal-title":"Int. J. Hydrogen Energy"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"248","DOI":"10.1016\/j.jhazmat.2010.05.004","article-title":"The determination of fertilizer quality of the formed struvite from effluentof a sewage sludge anaerobic digester","volume":"181","author":"Uysal","year":"2010","journal-title":"J. Hazard. Mater."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"350","DOI":"10.1016\/j.watres.2014.07.040","article-title":"Impacts of microalgae pretreatments for improved anaerobic digestion: Thermal treatment, thermal hydrolysis, ultrasound and enzymatic hydrolysis","volume":"65","author":"Ometto","year":"2014","journal-title":"Water Res."},{"key":"ref_25","unstructured":"APHA (1992). Standard Methods for Examination of Water and Wastewater, American Public Health Association. [18th ed.]."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"7495","DOI":"10.1016\/j.biortech.2008.02.020","article-title":"Nitrogen loss in chicken litter compost as affected by carbon to nitrogen ratio and turning frequency","volume":"99","author":"Ogunwande","year":"2008","journal-title":"Bioresour. Technol."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"9313","DOI":"10.1016\/j.biortech.2011.07.022","article-title":"Characterization of organic matter microstructure dynamics during co-composting of sewage sludge, barks and green waste","volume":"102","author":"Watteau","year":"2011","journal-title":"Bioresour. Technol."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"445","DOI":"10.1002\/jctb.280361003","article-title":"Characteristics of the pH-influenced adaptation of methanogenic sludge to ammonium toxicity","volume":"36","author":"Koster","year":"1986","journal-title":"J. Chem. Technol. Biotechnol."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"433","DOI":"10.1080\/10643380701640573","article-title":"Phosphorus Recovery from Wastewater by Struvite Crystallization: A Review","volume":"39","author":"Hobbs","year":"2009","journal-title":"Crit. Rev. Environ. Sci. Technol."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"2167","DOI":"10.1016\/S0043-1354(00)00498-X","article-title":"Phosphorus removal from a real anaerobic supernatant by struvite crystallization","volume":"35","author":"Battistoni","year":"2001","journal-title":"Water Res."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"165","DOI":"10.1016\/S0960-8524(00)00187-5","article-title":"Stable performance of anaerobic digestion in the presence of a high concentration of propionic acid","volume":"78","author":"Pullmmanappallil","year":"2001","journal-title":"Bioresour. Technol."},{"key":"ref_32","first-page":"1391","article-title":"Nitrogen removal by free ammonia stripping from high pH ponds","volume":"53","author":"Idelovitch","year":"1981","journal-title":"J. Water Pollut. Control Fed."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"241","DOI":"10.2166\/wst.1993.0504","article-title":"Biological phosphorus removal from wastewater by anaerobic-anoxic sequencing batch reactor","volume":"27","author":"Kuba","year":"1993","journal-title":"Water Sci. Technol."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"136514","DOI":"10.1016\/j.scitotenv.2020.136514","article-title":"Product and cost perspectives of phosphorus recovery from human urine using solid waste ash and sea salt addition\u2014A case of Thailand","volume":"713","author":"Pinatha","year":"2020","journal-title":"Sci. Total Environ."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"163","DOI":"10.1016\/j.cej.2004.11.013","article-title":"Solubilization of waste-activated sludge by ultrasonic treatment","volume":"106","author":"Bougrier","year":"2005","journal-title":"Chem. Eng. J."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"327","DOI":"10.1016\/j.cej.2008.09.003","article-title":"Pretreatment of activated sludge: Effect of sonication on aerobic and anaerobic digestibility","volume":"148","author":"Salsabil","year":"2009","journal-title":"Chem. Eng. J."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"2626","DOI":"10.1080\/19443994.2014.1001794","article-title":"Resource recovery from anaerobic digestate: Struvite crystallisation versus ammonia stripping","volume":"57","author":"Hidalgo","year":"2013","journal-title":"Desalination Water Treat."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"297","DOI":"10.1016\/j.jclepro.2017.01.116","article-title":"Applying a chemical equilibrium model for optimizing struvite precipitation for ammonium recovery from anaerobic digester effluent","volume":"147","author":"Jia","year":"2017","journal-title":"J. Clean. Prod."},{"key":"ref_39","first-page":"3106","article-title":"Optimization of struvite crystallization to recover nutrients from raw swine wastewater","volume":"56","author":"Lin","year":"2015","journal-title":"Desalination Water Treat."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"590","DOI":"10.1016\/j.rser.2014.10.055","article-title":"A review on current aspects and diverse prospects for enhancing biogas production in sustainable means","volume":"42","author":"Divya","year":"2015","journal-title":"Renew. Sustain. Energy Rev."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"9379","DOI":"10.1038\/s41598-017-09977-6","article-title":"Process performance and methane production optimizing of anaerobic co-digestion of swine manure and corn straw","volume":"7","author":"Mao","year":"2017","journal-title":"Sci. Rep."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"5123","DOI":"10.1007\/s12649-019-00838-z","article-title":"Improved Methane Production Using Lignocellulolytic Enzymes from Trichoderma koningiopsis TM3 through Co-digestion of Palm Oil Mill Effluent and Oil Palm Trunk Residues","volume":"11","author":"Nutongkaew","year":"2020","journal-title":"Waste Biomass Valorization"},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"2371","DOI":"10.1016\/j.watres.2009.12.043","article-title":"Phosphorus recovery by struvite crystallization in WWTPs: Influence of the sludge treatment line operation","volume":"44","author":"Marti","year":"2010","journal-title":"Water Res."},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"143","DOI":"10.1016\/j.resconrec.2015.12.009","article-title":"Phosphorus recovery as struvite: Recent concerns for use of seed, alternative Mg source, nitrogen conservation and fertilizer potential","volume":"107","author":"Kataki","year":"2016","journal-title":"Resour. Conserv. Recycl."}],"container-title":["Sustainability"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2071-1050\/13\/4\/2175\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T05:25:35Z","timestamp":1760160335000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2071-1050\/13\/4\/2175"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2021,2,18]]},"references-count":44,"journal-issue":{"issue":"4","published-online":{"date-parts":[[2021,2]]}},"alternative-id":["su13042175"],"URL":"https:\/\/doi.org\/10.3390\/su13042175","relation":{},"ISSN":["2071-1050"],"issn-type":[{"value":"2071-1050","type":"electronic"}],"subject":[],"published":{"date-parts":[[2021,2,18]]}}}