Nonlinear Behavior of Permeate Flux in Full-Scale Reverse Osmosis Processes

Tay, Kwee Guan; Song, Lianfa; Ong, Say Leong; Ng, Wenfa

doi:10.1061/(asce)0733-9372(2005)131:11(1481)

Cited by 12 publications

(9 citation statements)

References 17 publications

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“…Figure 11 shows the permeate fluxes of the plain PA and Sil‐PA membranes at different feed pressures. As the operating pressure increases from 10.34 to 34.48 bar, the flux and rejection of plain PA membrane increase; the relationship between the flux and the operating pressure is nearly linear, which is consistent with the reported results 8, 38–40. It is noted that the flux of our PA membrane is lower than that reported in the literature 9, 41.…”

Section: Resultssupporting

confidence: 91%

Preparation of silicalite–polyamide composite membranes for desalination

Dong

et al. 2011

Asia-Pacific J Chem Eng

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Silicalite-polyamide composite membranes were synthesized via interfacial polymerization on a commercial polysulfone substrate, for the purpose of studying the effect of the addition of silicalite nanocrystals on the desalination property of polyamide membrane. The scanning electron microscopy (SEM) images showed that both plain polyamide membrane and silicalite-polyamide composite membranes exhibited rough surface morphology which is similar to the commercial polyamide membranes. The existence of silicalite nanocrystals in the silicalite-polyamide composite membrane was confirmed by energy dispersive X-ray spectroscopy (EDXS) and high-resolution transmission electron microscopy (HRTEM). The effect of loading of silicalite nanocrystals on the desalination property of membranes was examined. By increasing the loading of silicalite nanocrystals, the water flux of silicalite-polyamide composite membranes increased, whereas the salt selectivity decreased significantly. Plain polyamide membrane had salt rejection of 98.1% and a flux of 5.07 × 10 −7 m 3 /m 2 ·s, whereas the silicalite-polyamide composite membrane, prepared from trimesoyl chloride (TMC)-hexane with 0.5% (w/v) silicalite, had a water flux of 2.74 × 10 −6 m 3 /m 2 ·s and NaCl rejection of 50% at a feed pressure of 34.48 bar by using 2000 ppm salt solution as the feed. The transport mechanisms of the silicalite-polyamide composite membranes were discussed. 

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Section: Resultssupporting

confidence: 91%

Preparation of silicalite–polyamide composite membranes for desalination

Dong

et al. 2011

Asia-Pacific J Chem Eng

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“…The full-scale RO transport model of Song et al is modified in this study by integrating the Pitzer model to be able to account for the changes in ion activity and osmotic coefficient along defined segments in the membrane channel. The membrane transport and continuity equations used in this model are similar to those used by Song et al ,, to obtain the variations of concentrations along the membrane feed channel. These equations are described in Supporting Information section 1.…”

Section: Methodsmentioning

confidence: 99%

“… 9 Tay and Song reported that the thermodynamic equilibrium can be the dominant mechanism controlling the permeate flux under common run conditions. 12 When the system is operated close to the limits of the thermodynamic equilibrium, the flux becomes unaffected by the changes in membrane resistance. In the connection of fouling to the permeate flux, an experimental study for calcium carbonate fouling by Tzotzi et al found inconsistencies between observed fouling and the permeate flux decline as fouling growth continued; a delayed response was found in permeation.…”

Section: Introductionmentioning

confidence: 99%

“…Therefore, thermodynamic restriction and its impact on permeation are essential for understanding the operation of a full-scale RO . Tay and Song reported that the thermodynamic equilibrium can be the dominant mechanism controlling the permeate flux under common run conditions . When the system is operated close to the limits of the thermodynamic equilibrium, the flux becomes unaffected by the changes in membrane resistance.…”

Section: Introductionmentioning

confidence: 99%

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Robust Spatial Modeling of Thermodynamic Parameters in a Full-Scale Reverse Osmosis Membrane Channel

et al. 2021

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Full-scale reverse osmosis (RO) units usually consist of a set of pressure vessels holding up to six (1 m long) membrane modules in series. Since process parameters and water composition change substantially along the filtration channel in full-scale RO units, relevant thermodynamic parameters such as the ion activities and the osmotic coefficient change as well. Understanding these changes will lead to more accurate fouling prediction and to improvement in process and equipment designs. In this article, a rigorous thermodynamic model for RO concentrates in a full-scale module is developed and presented, which is capable of accounting for such changes. The change in concentrate composition due to permeation of water and ions is predicted locally in the membrane filtration channel. The local ionic composition is used to calculate the local activity coefficient and osmotic coefficient along the membrane channel through the Pitzer model for each modeled anion and cation. The approach developed was validated against related literature data, showing that Pitzer coefficient predictions were satisfactory. The spatial variation model was verified experimentally. It was found under the modeled conditions of high recovery that individual solute activity coefficients could be diminished up to 65%, in our case for sulfate, from their initial value from the membrane inlet to the outlet, and the water osmotic coefficient increased 3% as concentrate salinity increased from the membrane inlet to the outlet. Modeled at moderate recovery, the sulfate still achieved a statistically significant drop of 34% and an opposing trend of a decrease of 0.5% for the osmotic coefficient. These variations in internal water chemistry along the channel can significantly impact predicted recovery, fouling propensity, and permeate quality. Fouling prediction with our approach was also assessed through a theoretical fouling index to demonstrate the significance of ion activity over concentration-based calculations. Additionally, data from a pilot plant RO filtration channel was used to carry out a sensitivity analysis to show the capability of the developed model.

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“…Under normal operating conditions, the parameters -such as crossflow velocity, salt concentration, and permeate flux -change substantially along the membrane channel. Localized parameters must be considered to accurately describe the membrane system (18)(19)(20). Furthermore, the membrane resistance is a function of time because membrane fouling is a continuous process.…”

Section: Model Developmentmentioning

confidence: 99%

Advanced Membrane Fouling Characterization in Full-Scale Reverse Osmosis Processes

Song

Tay

2010

Membrane and Desalination Technologies

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Fouling alleviation and control in full-scale reverse osmosis (RO) processes can be seriously hindered by ineffective fouling characterization. Fouling characterization is currently done primarily by measuring the silt density index (SDI) of feed water and monitoring the average permeate flux of full-scale RO processes. However, the SDI or related fouling indices have been known not capable to catch all possible foulants to RO membranes, and the average permeate flux may fail to correctly reflect membrane fouling in full-scale RO processes under certain circumstances.In this chapter, an advanced characterization method is introduced for membrane fouling in full-scale RO processes. An inclusive fouling potential indicator is proposed for a better characterization of the fouling strength of feed water, which is defined in a way that it can be easily determined with a small lab-scale RO membrane device and that it is readily usable to predict fouling development in the full-scale RO processes. A model based on basic membrane filtration and mass conservation principles is presented to calculate the average permeate flux in a full-scale RO process as fouling is progressing. The main intention of the advanced characterization method is to provide a reliable assessment of membrane fouling in the full-scale RO processes, so that the need for pilot tests can be significantly reduced.

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Nonlinear Behavior of Permeate Flux in Full-Scale Reverse Osmosis Processes

Cited by 12 publications

References 17 publications

Preparation of silicalite–polyamide composite membranes for desalination

Preparation of silicalite–polyamide composite membranes for desalination

Robust Spatial Modeling of Thermodynamic Parameters in a Full-Scale Reverse Osmosis Membrane Channel

Advanced Membrane Fouling Characterization in Full-Scale Reverse Osmosis Processes

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