In traditional seawater reverse osmosis (SWRO) desalination plants there is the need to overcome existing limitations by increasing water quality, enhancing the overall recovery factor, reducing the environmental impact of brine and its management costs, and extending membrane lifetime, thus making seawater (SW) desalination more affordable economically. Integrated membrane systems have been receiving recently increasing consideration as efficient means for the implementation of process intensification strategy and the optimization of productive cycles [1]. A possible application of such strategy in SWRO desalination has been put in practice by integrating advanced pre- and post-treatment membrane operations with reverse osmosis (RO), thus realizing systems working on the concepts of (quasi)zero-liquid discharge and total recovery of raw materials [2]. According to this scenario, conventional pressure-driven membrane operations are used as pretreatment to RO, while Membrane Contactors, in the form of Membrane Crystallization, operate on the brines of NF and RO [3]. In order to achieve these results, advanced water pre-treatment operations are necessary to reduce/remove natural organic substances existing in seawater with the aim: (1) to reduce the amount of those species which might act directly as foulant for the RO membranes or would be nutrients for microorganisms which generate bio-fouling, and (2) to avoid their hindrance/influence with the crystallization mechanism, by adsorption over the crystal embryos or by incorporation into the crystal lattice, thus leading to the cessation of growth or to the production of crystals with undesired or uncontrolled properties. This paper focuses on the study of submerged hollow fibers UF as pre-treatment to control natural organic matter content in the seawater to be fed to RO units, in the logic of an integrated membrane desalination system, and on the investigation of the influence of a set of operating conditions on process performance and fouling dynamics when working under subcritical flux conditions for relative long operation time. Experimental results demonstrated that submerged UF hollow fiber is effective as pretreatment to seawater in reducing natural organic matter, thus supporting its utilization as seawater pretreatment in the logic of integrated membrane desalination systems, provided the identification of the operating conditions and their opportune optimization, including transmembrane flux, periodical aeration/filtration frequency, operation time and back-flushing strategy. [1] J.-C. Charpentier, Modern Chemical Engineering in the Framework of Globalization, Sustainability, and Technical Innovation, Industrial & Engineering Chemistry Research 46 (2007) 3465-3485. [2] E. Drioli, A. Criscuoli, E. Curcio, Integrated membrane operations for seawater desalination, Desalination 147 (1-3) (2002) 77-81. [3] E. Drioli, E. Curcio, A. Criscuoli, G. Di Profio, Integrated system for recovery of CaCO3, NaCl and MgSO4·7H2O from nanofiltration retentate, Journal of Membrane Science 239 (1) (2004) 27-38.
Submerged hollow fiber ultrafiltration as pre-treatment in seawater reverse osmosis desalination
Di Profio G;
2011
Abstract
In traditional seawater reverse osmosis (SWRO) desalination plants there is the need to overcome existing limitations by increasing water quality, enhancing the overall recovery factor, reducing the environmental impact of brine and its management costs, and extending membrane lifetime, thus making seawater (SW) desalination more affordable economically. Integrated membrane systems have been receiving recently increasing consideration as efficient means for the implementation of process intensification strategy and the optimization of productive cycles [1]. A possible application of such strategy in SWRO desalination has been put in practice by integrating advanced pre- and post-treatment membrane operations with reverse osmosis (RO), thus realizing systems working on the concepts of (quasi)zero-liquid discharge and total recovery of raw materials [2]. According to this scenario, conventional pressure-driven membrane operations are used as pretreatment to RO, while Membrane Contactors, in the form of Membrane Crystallization, operate on the brines of NF and RO [3]. In order to achieve these results, advanced water pre-treatment operations are necessary to reduce/remove natural organic substances existing in seawater with the aim: (1) to reduce the amount of those species which might act directly as foulant for the RO membranes or would be nutrients for microorganisms which generate bio-fouling, and (2) to avoid their hindrance/influence with the crystallization mechanism, by adsorption over the crystal embryos or by incorporation into the crystal lattice, thus leading to the cessation of growth or to the production of crystals with undesired or uncontrolled properties. This paper focuses on the study of submerged hollow fibers UF as pre-treatment to control natural organic matter content in the seawater to be fed to RO units, in the logic of an integrated membrane desalination system, and on the investigation of the influence of a set of operating conditions on process performance and fouling dynamics when working under subcritical flux conditions for relative long operation time. Experimental results demonstrated that submerged UF hollow fiber is effective as pretreatment to seawater in reducing natural organic matter, thus supporting its utilization as seawater pretreatment in the logic of integrated membrane desalination systems, provided the identification of the operating conditions and their opportune optimization, including transmembrane flux, periodical aeration/filtration frequency, operation time and back-flushing strategy. [1] J.-C. Charpentier, Modern Chemical Engineering in the Framework of Globalization, Sustainability, and Technical Innovation, Industrial & Engineering Chemistry Research 46 (2007) 3465-3485. [2] E. Drioli, A. Criscuoli, E. Curcio, Integrated membrane operations for seawater desalination, Desalination 147 (1-3) (2002) 77-81. [3] E. Drioli, E. Curcio, A. Criscuoli, G. Di Profio, Integrated system for recovery of CaCO3, NaCl and MgSO4·7H2O from nanofiltration retentate, Journal of Membrane Science 239 (1) (2004) 27-38.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
