Rheological and permeability characteristics of alginate fouling layers developing on reverse osmosis membranes during desalination

Sioutopoulos, D.C.; Goudoulas, Thomas B.; Kastrinakis, E. G.; Nychas, S. G.; Karabelas, A.J.

doi:10.1016/j.memsci.2013.01.018

Cited by 42 publications

(24 citation statements)

References 46 publications

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“…Moreover, these layers exhibit viscoelastic properties and a significant yield stress that (at least in the cases studied [32]) appears to be greater than typical mean shear stresses prevailing in the spacer-filled channels [20]; this implies that, once formed, such layers would not be detached by the flow. Measured alginate fouling-layer thickness h on a RO membrane, of magnitude order~10% of the channel gap ( [32], Table 1) was associated with a substantial trans-membrane pressure (TMP) increase (e.g., >20%), which is considered excessive in practice, requiring membrane cleaning [27]. Therefore, the range of h values selected for this work was 0-10% of filament diameter; specifically, numerical simulations were performed for four values of fouling-layer thickness (h/D = 0.025, 0.05, 0.075, 0.1) for the typical spacer geometry with characteristics: L/D = 8 and β = 90 • (Table 1, Figure 1).…”

Section: Mathematical Formulation and Numerical Simulationsmentioning

confidence: 88%

“…The assumption is made of fouling-layer uniformity at the "unit cell" spatial scale, realizing that it may be realistic only for some types of foulants but not for all of them. Indeed, as outlined in the Introduction, common foulants such as polysaccharides (including extracellular polymeric substances (EPS) in biofilms) seem to develop fairly coherent gels on membranes [8,32], impossible to detach by fluid-shear forces prevailing during desalination [32], thus prone to be fairly uniform. However, for other foulant types such as humic acids alone, the fouling-layer thickness in spacer-filled channels appears to be non-uniform [21].…”

Section: Discussionmentioning

confidence: 99%

“…In particular, the results of fouling studies with alginates [30][31][32], which are representative of a major class of common RO foulants [8,30,33], suggest that the developing fouling layers are quite coherent gels that tend to deposit fairly evenly on the RO membranes [32]. Moreover, these layers exhibit viscoelastic properties and a significant yield stress that (at least in the cases studied [32]) appears to be greater than typical mean shear stresses prevailing in the spacer-filled channels [20]; this implies that, once formed, such layers would not be detached by the flow. Measured alginate fouling-layer thickness h on a RO membrane, of magnitude order~10% of the channel gap ( [32], Table 1) was associated with a substantial trans-membrane pressure (TMP) increase (e.g., >20%), which is considered excessive in practice, requiring membrane cleaning [27].…”

Section: Mathematical Formulation and Numerical Simulationsmentioning

confidence: 99%

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Fluid Dynamics and Mass Transfer in Spacer-Filled Membrane Channels: Effect of Uniform Channel-Gap Reduction Due to Fouling

Koutsou

Karabelas

Kostoglou

2018

Fluids

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Abstract:The time-varying flow field in spacer-filled channels of spiral-wound membrane (SWM) modules is mainly due to the development of fouling layers on the membranes that modify the channel geometry. The present study is part of an approach to tackling this extremely difficult dynamic problem at a small spatial scale, by uncoupling the fluid dynamics and mass transfer from the fouling-layer growth process. Therefore, fluid dynamics and mass transfer are studied for a spacer-filled channel whose geometry is altered by a uniform deposit thickness h. For this purpose, 3D direct numerical simulations are performed employing the "unit cell" approach with periodic boundary conditions. Specific thickness values are considered in the range 2.5-10% of the spacer-filament diameter D as well as other conditions of practical significance. The qualitative characteristics of the altered flow field are found to be very similar to those of the reference geometry with no gap reduction. For a given flow rate, the pressure drop, time-average wall-shear stresses and mass-transfer coefficients significantly increase with increasing thickness h due to reduced channel-gap, as expected. Correlations are obtained, applicable at the "unit cell" scale, of the friction factor f and Sherwood number Sh, which exhibit similar functional dependence of f and Sh on the Reynolds and Schmidt numbers as in the reference no-fouling case. In these correlations the effect of channel-gap reduction is incorporated, permitting predictions in the studied range of fouling-layer thickness (h/D) = 0-0.10. The usefulness of the new results and correlations is discussed in the context of ongoing research toward improved modeling and dynamic simulation of SWM-module operation.

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Section: Mathematical Formulation and Numerical Simulationsmentioning

confidence: 88%

Section: Discussionmentioning

confidence: 99%

Section: Mathematical Formulation and Numerical Simulationsmentioning

confidence: 99%

See 1 more Smart Citation

Fluid Dynamics and Mass Transfer in Spacer-Filled Membrane Channels: Effect of Uniform Channel-Gap Reduction Due to Fouling

Koutsou

Karabelas

Kostoglou

2018

Fluids

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“…Subsequent accumulation of organics on the membrane surface due to convective deposition leads to a fouling layer that makes the hydrophobicity of the membrane surface increase further [26,27]. The fouling layer on the membrane surface can also cause an increase in hydraulic resistance [27] and flow rate decline [20].…”

Section: Membrane Rejection and Flow Ratementioning

confidence: 99%

Case Study of a Small Scale Reverse Osmosis System for Treatment of Mixed Brackish Water and STP Effluent

Widiasa

Jayanti

2017

J. Eng. Technol. Sci.

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Abstract.A case study on utilizing reverse osmosis (RO) technology to fulfill fresh water needs at a mall and a hotel has been done on Bali Island, Indonesia. A mix of brackish water and sewage treatment plant (STP) effluent was used as feed water in the RO system. The system used 36 membrane elements (CSM RE 8040 BLN) arranged into two stages: 8 pressure vessels (PVs) in the first stage and 4 PVs in the second stage, each loaded with 3 membranes. The objectives of this research were to assess the cleaning effectivity in the plant, to evaluate the cleaning of 1 membrane element using a CIP system, and to assess the use of the membrane for filtration in the pre-treatment system. SEM and FTIR analysis indicated that the foulants on the membrane surface were dominated by organic foulants and inorganic deposits. To clean the discarded membrane the proposed method used NaOH solution (pH 12 and pH 13) and citric acid (pH 2 and pH 3). All membranes displayed a dramatic decline in rejection of about 80%. Based on the rejection tests of SO 4 2-, Cl -, turbidity reduction approached 100%. It can be concluded that an RO membrane that has undergone selectivity decline can be re-used as a filtration membrane in the pre-treatment system.

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“…As a result, it becomes especially important to study the rheological properties of protein-polysaccharide hybrid system. The rheological property study can provide abundant useful information, such as the interaction between food components, the selection standard of different additives, and the processing problems in many aspects such as transportation [22] . Usually, the rheological properties of protein-polysaccharide hybrid system are not simply an addition of parameters of two components.…”

Section: Introductionmentioning

confidence: 99%

Effects of xanthan gum on the rheological properties of soy protein dispersion

Bi¹,

Gao²,

Zhu³

et al. 2018

International Journal of Agricultural and Biological Engineering

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This study focused on the effects of addition of xanthan gum (XG) on the rheological properties of soy protein isolate (SPI) solution. Three types of tests (steady shear test, strain sweep test, and frequency sweep test) were performed to figure out the influences of shear rate on the viscosity of the SPI-XG hybrid system, the effects of strain variable on the storage modulus of the hybrid system, and the effects of frequency on both the storage modulus and the loss modulus of the hybrid system, respectively. SPI-XG hybrid system showed more obvious shear-thinning properties compared to pure SPI and pure XG solution. Meanwhile, it was found that the critical point of hybrid system was highly related to the XG concentration. XG can postpone the critical point strain amplitude to a higher value, and the addition of XG can enhance the strain resistance of hybrid system. The concentration of XG influenced the viscoelastic frequency dependence of the hybrid system significantly and complicatedly. After the addition of XG, the correlation between G′ and frequency changed from negative to positive.

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Rheological and permeability characteristics of alginate fouling layers developing on reverse osmosis membranes during desalination

Cited by 42 publications

References 46 publications

Fluid Dynamics and Mass Transfer in Spacer-Filled Membrane Channels: Effect of Uniform Channel-Gap Reduction Due to Fouling

Fluid Dynamics and Mass Transfer in Spacer-Filled Membrane Channels: Effect of Uniform Channel-Gap Reduction Due to Fouling

Case Study of a Small Scale Reverse Osmosis System for Treatment of Mixed Brackish Water and STP Effluent

Effects of xanthan gum on the rheological properties of soy protein dispersion

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