Accepted Manusc pt Variations in microbiome composition of sewer biofilms due to ferrous and ferric iron dosing Bruno Kiilerich, Asker Daniel Brejnrod, Jes Vollertsen and Pia Kiilerich Accepted Manuscript Version This is the unedited version of the article as it appeared upon acceptance by the journal. A final edited version of the article in the journal format will be made available soon. As a service to authors and researchers we publish this version of the accepted manuscript (AM) as soon as possible after acceptance. Copyediting, typesetting, and review of the resulting proof will be undertaken on this manuscript before final publication of the Version of Record (VoR). Please note that during production and pre-press, errors may be discovered which could affect the content. © 2019 The Author(s). This open access article is distributed under a Creative Commons Attribution (CC-BY) 4.0 license. Publisher: Cogent OA Journal: Cogent Environmental Science DOI: http://dx.doi.org/10.1080/23311843.2019.1595293