Analysis of the influence of module construction upon forward osmosis performance

Abstract

. (2018) 'Analysis of the in uence of module construction upon forward osmosis performance. ', Desalination., Further information on publisher's website: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. AbstractThe potential of a commercial forward osmosis (FO) module to recover water from NEWater brine, an RO retentate, was assessed by taking an innovative approach to obtaining the mass transfer coefficients. The performance comparison of the spiral wound (S-W) FO module with that of the flat sheet laboratory unit suggests that the winding involved in S-W construction can adversely affect performance; the values for the S-W mass transfer coefficients were half of those expected. This firstof-its-kind performance comparison utilised coupons of the membrane and spacers taken from the module. The module was used both in the conventional manner for FO and in the reverse manner with the active layer facing the draw solution. Estimates of membrane parameters and mass transfer coefficients experiments for the two orientations were obtained using pure water, 10mM and 25mM NaCl solution on the feed side and 1M NaCl as draw solution. The fouling potential of NEWater brine per se was found to be low. These are the first results with a S-W module that suggest potential for this niche application; nevertheless the level of the water flux through the S-W module clearly indicates that industrial applications of S-W FO will be constrained to special cases.

On boundary layers and the attenuation of driving forces in forward osmosis and other membrane processes

“…an exact parallel with Figure 2 In a recent paper Field et al [11] presented a pair of equations relating flux, 'A', 'B' and the mass transfer coefficients and where the mass transfer coefficient, designated as , is the combined mass transfer coefficient for the support layer itself and the adjacent external mass transfer layer. The mass transfer coefficient for the support layer itself can be written as ⁄ where is the diffusivity of salt in water (it has a moderate dependency upon concentration [12]) and is the structural parameter, defined as the product of the support layer thickness and tortuosity over its porosity [13]:…”

A Review of CFD Modelling and Performance Metrics for Osmotic Membrane Processes

“…The PRO process has a similar configuration to that of FO, except that the selective side of the membrane faces a higher concentration (draw) solution [ 39 , 40 , 41 ]. In PRO, the solution in the draw side is partially pressurised and kept below its osmotic pressure in order to create a net osmotic driving force for water to flow from the feed side to the draw side.…”

Extended performance study of forward osmosis during wastewater reclamation: Quantification of fouling-based concentration polarization effects on the flux decline

“…This fact is attributed to foulant-foulant-membrane interactions; accelerated flux decline (43%) was observed [51]. In contrast our results indicated that a flux of In practice, a flux determined found from a laboratory flat sheet unit should only be used as a guide because spiral wound modules themselves may well not achieve the same level of mass transfer [38] and we note that with a pilot-scale system, fouling control was achieved with a TFC spiral wound membrane as operated at a flux of 16.6 LMH [56]. Note: Flux recovery was by physical cleaning.…”

“…Based on A, B and S determined before, the methodology of obtaining the best estimates of mass transfer coefficients was to change the value of kF and kD until a sum of square error (SSerr) between measured flux and estimated flux achieve a minimum value. The method has been used previously elsewhere [38]. The outcome is summarized in Table 1.…”