Forward osmosis pretreatment of seawater for thermal desalination

Altaee, A; Sharif, A; Zaragoza, G

Forward osmosis pretreatment of seawater for thermal desalination

Altaee, A

Sharif, A Zaragoza, G

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Publication Type:: Chapter
Citation:: Water Filtration Systems: Processes, Uses and Importance, 2016, pp. 1 - 26
Issue Date:: 2016-01-01

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Field	Value	Language
dc.contributor.author	Altaee, A https://orcid.org/0000-0001-9764-3974	en_US
dc.contributor.author	Sharif, A	en_US
dc.contributor.author	Zaragoza, G	en_US
dc.date.issued	2016-01-01	en_US
dc.identifier.citation	Water Filtration Systems: Processes, Uses and Importance, 2016, pp. 1 - 26	en_US
dc.identifier.isbn	9781634840392	en_US
dc.identifier.uri	http://hdl.handle.net/10453/124813
dc.description.abstract	© 2016 Nova Science Publishers, Inc. Thermal desalination technologies are still widely used for seawater desalination. The main advantages of these technologies is that the capability to treat high salinity seawater and product water TDS is not affected by the feed salinity. Nevertheless, thermal desalination suffers from a number of drawbacks including limited feed conversion ratio and high energy consumption. The latter issue is further aggravated by scale development and deposition on the heat exchangers. Scaling problems can be alleviated by dosing antiscalants in the feed water, though this wouldn't prevent the scaling issue over time. Furthermore, Nanofiltration (NF) filtration of seawater is sometimes carried out for the removal of scaling ions from seawater. NF coupling with thermal desalination may prevent scaling problems, but the cost of NF pretreatment was unjustifiably expensive. Alternatively, Forward Osmosis (FO) pretreatment of seawater was proposed for the removal of scaling ions from the seawater feed to the thermal desalination plants. FO operates by natural osmosis energy created across a semipermeable membrane separating two solutions having different osmotic pressure. Therefore, the cost of seawater pretreatment can be reduced significantly. FO process is relatively new technique and requires more evaluation and investigation before field application. The main challenges of FO application in seawater desalination and pretreatment, in particular, are the draw solution type and FO membrane. Important requirements the selection of the most optimal draw solution is to be inexpensive, easy to regenerate, and non-toxic material. Recent studies proposed brine reject to be the draw solution of FO process; however, brine reject osmotic pressure would induce a limited membrane flux due to its moderately low osmotic pressure. Higher membrane flux can be achieved by manipulating the operating parameters and/or using FO membrane of high water permeability. Applying positive pressure on the feed side of the FO membrane, Pressure Assisted FO (PAFO), promotes water flux across the membrane. The combination of PAFO process and high permeability membrane would enhance the performance of FO process for seawater pretreatment. Additionally, the impact of increasing the feed flow rate, Enhanced Flow FO (EFFO), on the performance of FO process should be investigated and compared with that of the PAFO process. Finally, power consumption associated with PAFO and EFFO would ultimately decide the cost-effectiveness of the pretreatment process.	en_US
dc.relation.ispartof	Water Filtration Systems: Processes, Uses and Importance	en_US
dc.title	Forward osmosis pretreatment of seawater for thermal desalination	en_US
dc.type	Chapter
pubs.embargo.period	Not known	en_US
pubs.organisational-group	/University of Technology Sydney
pubs.organisational-group	/University of Technology Sydney/Faculty of Engineering and Information Technology
pubs.organisational-group	/University of Technology Sydney/Faculty of Engineering and Information Technology/School of Civil and Environmental Engineering
pubs.organisational-group	/University of Technology Sydney/Strength - CTWW - Centre for Technology in Water and Wastewater Treatment
utslib.copyright.status	closed_access
pubs.publication-status	Published	en_US

Abstract:

© 2016 Nova Science Publishers, Inc. Thermal desalination technologies are still widely used for seawater desalination. The main advantages of these technologies is that the capability to treat high salinity seawater and product water TDS is not affected by the feed salinity. Nevertheless, thermal desalination suffers from a number of drawbacks including limited feed conversion ratio and high energy consumption. The latter issue is further aggravated by scale development and deposition on the heat exchangers. Scaling problems can be alleviated by dosing antiscalants in the feed water, though this wouldn't prevent the scaling issue over time. Furthermore, Nanofiltration (NF) filtration of seawater is sometimes carried out for the removal of scaling ions from seawater. NF coupling with thermal desalination may prevent scaling problems, but the cost of NF pretreatment was unjustifiably expensive. Alternatively, Forward Osmosis (FO) pretreatment of seawater was proposed for the removal of scaling ions from the seawater feed to the thermal desalination plants. FO operates by natural osmosis energy created across a semipermeable membrane separating two solutions having different osmotic pressure. Therefore, the cost of seawater pretreatment can be reduced significantly. FO process is relatively new technique and requires more evaluation and investigation before field application. The main challenges of FO application in seawater desalination and pretreatment, in particular, are the draw solution type and FO membrane. Important requirements the selection of the most optimal draw solution is to be inexpensive, easy to regenerate, and non-toxic material. Recent studies proposed brine reject to be the draw solution of FO process; however, brine reject osmotic pressure would induce a limited membrane flux due to its moderately low osmotic pressure. Higher membrane flux can be achieved by manipulating the operating parameters and/or using FO membrane of high water permeability. Applying positive pressure on the feed side of the FO membrane, Pressure Assisted FO (PAFO), promotes water flux across the membrane. The combination of PAFO process and high permeability membrane would enhance the performance of FO process for seawater pretreatment. Additionally, the impact of increasing the feed flow rate, Enhanced Flow FO (EFFO), on the performance of FO process should be investigated and compared with that of the PAFO process. Finally, power consumption associated with PAFO and EFFO would ultimately decide the cost-effectiveness of the pretreatment process.

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