Tow, Emily W.Rencken, Martin M.Lienhard V, John H.2016-10-122016-12Tow, EW, Rencken, MM & Lienhard V, JH 2016, 'In situ visualization of organic fouling and cleaning mechanisms in reverse osmosis and forward osmosis', Desalination, vol. 399, pp.138-147.0011-9164 (print)1873-4464 (online)10.1016/j.desal.2016.08.024http://hdl.handle.net/2263/57120Fouling models rely on knowledge of foulant accumulation and removal mechanisms. In this study, a fouling visualization apparatus is developed to elucidate centimeter-scalemechanisms of organic fouling and cleaning in reverse osmosis (RO) and forward osmosis (FO). Alginate is used as a model organic foulant and dyed with methylene blue, which is shown not to affect fouling or cleaning, and to sufficiently highlight the gel for visualization at low salinity (up to 1% NaCl). When cleaning by increasing the cross-flow velocity, with or without reverse permeation, foulant peels off the membrane in discrete pieces in both RO and FO. Videos of cleaning show that foulant cake swelling and wrinkling can facilitate gel detachment and removal. Despite their effectiveness in slowing fouling, spacers can hinder removal of detached foulant pieces by obstructing their path. Finally, photographs point to a new mechanism of internal fouling in FO: vapor formation due to sub-atmospheric pressure within the membrane. Awareness of these mechanisms allows for better modeling of fouling and motivates optimization of swelling-inducing cleaning procedures.en© 2016 Elsevier B.V. All rights reserved. Notice : this is the author’s version of a work that was accepted for publication in Desalination. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. A definitive version was subsequently published in Desalination, vol. 399, pp. 138-147, 2016. doi :10.1016/j.desal.2016.08.024.AlginateDesalinationFoulingReverse osmosis (RO)Forward osmosis (FO)Engineering, built environment and information technology articles SDG-06SDG-06: Clean water and sanitationEngineering, built environment and information technology articles SDG-09SDG-09: Industry, innovation and infrastructureEngineering, built environment and information technology articles SDG-12SDG-12: Responsible consumption and productionPostprint Article