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Open AccessFeature PaperArticle

Hybrid Forward Osmosis–Nanofiltration for Wastewater Reuse: System Design

1
Department of Environment, Land and Infrastructure Engineering (DIATI), Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Turin, Italy
2
Decarbonisation and Environmental Laboratories, Eni S.p.A., Via F. Maritano 26, 20097 San Donato M.se, Italy
3
Syndial S.p.A., Piazza M. Boldrini 1, 20097 San Donato M.se, Italy
4
[email protected], Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Turin, Italy
*
Author to whom correspondence should be addressed.
The two authors contributed equally to this manuscript.
Membranes 2019, 9(5), 61; https://doi.org/10.3390/membranes9050061
Received: 12 April 2019 / Revised: 29 April 2019 / Accepted: 2 May 2019 / Published: 6 May 2019
(This article belongs to the Special Issue Forward Osmosis: Modelling and Applications)
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Abstract

The design of a hybrid forward osmosis–nanofiltration (FO–NF) system for the extraction of high-quality water from wastewater is presented here. Simulations were performed based on experimental results obtained in a previous study using real wastewater as the feed solution. A sensitivity analysis, conducted to evaluate the influence of different process parameters, showed that an optimum configuration can be designed with (i) an influent draw solution osmotic pressure equal to 15 bar and (ii) a ratio of influent draw solution to feed solution flow rate equal to 1.5:1. With this configuration, the simulations suggested that the overall FO–NF system can achieve up to 85% water recovery using Na2SO4 or MgCl2 as the draw solute. The modular configuration and the size of the NF stage, accommodating approximately 7000 m2 of active membrane area, was a function of the properties of the membranes selected to separate the draw solutes and water, while detailed simulations indicated that the size of the FO unit might be reduced by adopting a counter-current configuration. Experimental tests with samples of the relevant wastewater showed that Cl- and Mg2+-based draw solutes would be associated with larger membrane fouling, possibly due to their interaction with the other substances present in the feed solution. However, the results suggest that fouling would not significantly decrease the performance of the designed system. This study contributes to the further evaluation and potential implementation of FO in water reuse systems. View Full-Text
Keywords: forward osmosis; nanofiltration; wastewater reuse; system design; fouling forward osmosis; nanofiltration; wastewater reuse; system design; fouling
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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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Giagnorio, M.; Ricceri, F.; Tagliabue, M.; Zaninetta, L.; Tiraferri, A. Hybrid Forward Osmosis–Nanofiltration for Wastewater Reuse: System Design. Membranes 2019, 9, 61.

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