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Membranes 2018, 8(3), 72; https://doi.org/10.3390/membranes8030072

Submerged Osmotic Processes: Design and Operation to Mitigate Mass Transfer Limitations

1
Laboratory of Chemical and Environmental Engineering (LEQUIA), Institute of the Environment, University of Girona, 17003 Girona, Spain
2
Catalan Institute for Water Research (ICRA), 17003 Girona, Spain
*
Author to whom correspondence should be addressed.
Received: 27 July 2018 / Revised: 15 August 2018 / Accepted: 23 August 2018 / Published: 1 September 2018
(This article belongs to the Special Issue Modeling and Design of Membrane Reactors)
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Abstract

Submerged forward osmosis (FO) is of high interest for bioreactors, such as osmotic membrane bioreactor, microalgae photobioreactor, food or bioproduct concentration where pumping through pressurized modules is a limitation due to viscosity or breakage of fragile components. However, so far, most FO efforts have been put towards cross flow configurations. This study provides, for the first time, insights on mass transfer limitations in the operation of submerged osmotic systems and offer recommendations for optimized design and operation. It is demonstrated that operation of the submerged plate and frame FO module requires draw circulation in the vacuum mode (vacuum assisted osmosis) that is in favor of the permeation flux. However, high pressure drops and dead zones occurring in classical U-shape FO draw channel strongly disadvantage this design; straight channel design proves to be more effective. External concentration polarization (ECP) is also a crucial element in the submerged FO process since mixing of the feed solution is not as optimized as in the cross flow module unless applying intense stirring. Among the mitigation techniques tested, air scouring proves to be more efficient than feed solution circulation. However, ECP mitigation methodology has to be adapted to application specificities with regards to combined/synergetic effects with fouling mitigation. View Full-Text
Keywords: membrane bioreactor; forward osmosis; water reuse; submerged membrane; concentration polarization; module design; vacuum assisted osmosis membrane bioreactor; forward osmosis; water reuse; submerged membrane; concentration polarization; module design; vacuum assisted osmosis
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).
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Blandin, G.; Rodriguez-Roda, I.; Comas, J. Submerged Osmotic Processes: Design and Operation to Mitigate Mass Transfer Limitations. Membranes 2018, 8, 72.

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