{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,22]],"date-time":"2026-06-22T22:57:23Z","timestamp":1782169043569,"version":"3.54.5"},"reference-count":23,"publisher":"Wiley","issue":"4","license":[{"start":{"date-parts":[[2007,4,1]],"date-time":"2007-04-01T00:00:00Z","timestamp":1175385600000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"}],"funder":[{"name":"U.S. Department of Education (Washington, D.C.)"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Water Environment Research"],"published-print":{"date-parts":[[2007,4]]},"abstract":"<jats:p>Diffusion of dissolved oxygen through activated sludge flocs was studied, as it represents a potential mechanism for simultaneous nitrification and denitrification in activated sludge systems. Dissolved oxygen profiles through six floc particles collected at different times from a full\u2010scale activated sludge plant demonstrated that that the dissolved oxygen concentration declines through all floc particles. For larger floc particles (2\u2010mm diameter and greater), the dissolved oxygen concentration reached near\u2010zero values at depths depending on process operating conditions. A mathematical model based on diffusion of dissolved oxygen, organic substrate (methanol), ammonia, nitrite, and nitrate through a spherical floc and consumption of dissolved oxygen by heterotrophs and autotrophs accurately predicted the dissolved oxygen profile and required adjustment of only one model parameter\u2014the concentration of heterotrophs. A different dissolved oxygen decline pattern was exhibited for the smaller floc particles characterized, with the dissolved oxygen reaching a non\u2010zero plateau toward the center of the floc. This pattern was not reproduced with the mathematical model developed and suggests that additional mechanisms are responsible for the transport of dissolved oxygen into the center of these flocs. Implications of these results regarding the occurrence of simultaneous nitrification and denitrification include consideration of the factors that affect floc size and distribution (simultaneous nitrification and denitrification is maximized with larger floc particles), coupling of the International Water Association (London) activated models to predict activated sludge composition with diffusion models to consider intrafloc effects, and the effects of substrate diffusion on the apparent half\u2010saturation constant for various substrates in activated sludge systems.<\/jats:p>","DOI":"10.2175\/106143006x111835","type":"journal-article","created":{"date-parts":[[2007,4,4]],"date-time":"2007-04-04T23:39:32Z","timestamp":1175729972000},"page":"375-387","source":"Crossref","is-referenced-by-count":46,"title":["Diffusion of Oxygen Through Activated Sludge Flocs: Experimental Measurement, Modeling, and Implications for Simultaneous Nitrification and Denitrification"],"prefix":"10.1002","volume":"79","author":[{"given":"Glen T.","family":"Daigger","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Craig D.","family":"Adams","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Holley Kaempfer","family":"Steller","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"311","published-online":{"date-parts":[[2007,4]]},"reference":[{"key":"e_1_2_7_2_1","volume-title":"Standard Methods for the Examination of Water and Wastewater","author":"American Public Health Association; American Water Works Association; Water Environment Federation","year":"1998"},{"issue":"2","key":"e_1_2_7_3_1","first-page":"248","article-title":"The Overall Rate of Substate Uptake (Reaction) by Microbial Films\u2014Part 1: A Biological Rate Equation","volume":"52","author":"Atkinson B.","year":"1974","journal-title":"Chem. 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K.(2003)Simultaneous Nitrification and Denitrification in Activated Sludge Floc.Dissertation Presented to the Faculty of the Graduate School of the University of Missouri\u2010Rolla in partial fulfillment of the requirements for the Doctor of Philosophy in Civil Engineering."},{"key":"e_1_2_7_24_1","volume-title":"Dissertation for Department of Sanitary Engineering","author":"Wilen B\u2010M.","year":"1999"}],"container-title":["Water Environment Research"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/api.wiley.com\/onlinelibrary\/tdm\/v1\/articles\/10.2175%2F106143006X111835","content-type":"application\/pdf","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/onlinelibrary.wiley.com\/doi\/pdf\/10.2175\/106143006X111835","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2023,9,15]],"date-time":"2023-09-15T20:46:46Z","timestamp":1694810806000},"score":1,"resource":{"primary":{"URL":"https:\/\/onlinelibrary.wiley.com\/doi\/10.2175\/106143006X111835"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2007,4]]},"references-count":23,"journal-issue":{"issue":"4","published-print":{"date-parts":[[2007,4]]}},"alternative-id":["10.2175\/106143006X111835"],"URL":"https:\/\/doi.org\/10.2175\/106143006x111835","archive":["Portico"],"relation":{},"ISSN":["1061-4303","1554-7531"],"issn-type":[{"value":"1061-4303","type":"print"},{"value":"1554-7531","type":"electronic"}],"subject":[],"published":{"date-parts":[[2007,4]]}}}