Combined organic and colloidal fouling in forward osmosis: Fouling reversibility and the role of applied pressure

Kim, Yeowon; Elimelech, Menachem; Shon, Ho Kyong; Hong, Seungkwan

doi:10.1016/j.memsci.2014.02.038

Cited by 157 publications

(112 citation statements)

References 33 publications

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“…Draw hydraulic pressure Figure 1: Methods of isolating the effect of pressure on osmotic membrane fouling taken by past studies (Refs. [7], [8], [14], and [15]) and the present study. All studies varied feed hydraulic pressure, but other variables that could potentially affect fouling were changed as well to avoid altering flux.…”

Section: Introductionsupporting

confidence: 70%

“…Apparent effects of (a) feed pressure (equal to TMP in these studies) and (b) draw/permeate concentration on alginate fouling reversibility revealed by studies by Mi and Elimelech [8], Lee at al. [7], Xie et al [15], and Kim et al [14], in which feed pressure and draw solution concentration were varied together to maintain a particular initial flux. Points represent experimental data; dashed lines are only a guide for the eye.…”

Section: Literature Review: Role Of Pressure In Osmotic Membrane Foulingmentioning

confidence: 99%

“…[7,8,10,11,12,13,14,15], attribute differences between RO and FO membrane fouling to foulant compaction by high hydraulic pressure. The most compelling evidence comes from studies that show a marked difference in the effectiveness of physical cleaning between identical membranes fouled under identical hydrodynamic conditions at the same initial flux in RO and FO [7,8,14,15,16]. According to the theory that foulant cake density increases with feed hydraulic pressure, the less-compact cake layer formed near atmospheric pressure in FO should be easier to remove.…”

Section: Introductionmentioning

confidence: 99%

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Unpacking compaction: Effect of hydraulic pressure on alginate fouling

Tow

Lienhard

2017

Journal of Membrane Science

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High hydraulic pressure is often considered to be the cause of the high fouling propensity of reverse osmosis (RO) relative to forward osmosis (FO). Several experimental studies have shown that alginate fouling is more susceptible to cleaning in FO than in RO, but the proposal that foulant compaction causes this disparity seems to be contradicted by the incompressibility of alginate hydrogels. In addition, the effect of hydraulic pressure on fouling in osmotic membrane desalination has never been experimentally isolated, because fixedflux comparisons at different hydraulic pressures require different draw solution osmotic pressures. In this study, a new approach to isolating the effect of hydraulic pressure on alginate fouling and cleaning is introduced: operating FO with elevated but equal feed and draw hydraulic pressures of up to 40 bar. The same concentration of sodium chloride is used as the draw solution in all trials to eliminate possible effects of draw solution composition or osmotic pressure on membrane fouling or cleaning. Theoretical modeling of the effect of alginate foulant compaction on flux reveals that foulant compaction should accelerate flux decline with low salinity feeds but retard flux decline at high salinity. However, in lowsalinity alginate fouling trials, for which foulant compaction should accelerate flux decline, the measured flux decline rate was not affected by hydraulic pressure. Furthermore, when fouled membranes were cleaned by increasing the feed velocity and reducing the draw osmotic pressure, there was no apparent relationship between hydraulic pressure and cleaning effectiveness. Finally, in situ visualization of foulant removal during the cleaning process revealed no difference in foulant removal mechanisms between different hydraulic pressures. These findings demonstrate that alginate gel compaction by high feed hydraulic pressure does not occur and suggest that other explanations should be sought for FO's fouling resistance relative to RO.

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Section: Introductionsupporting

confidence: 70%

Section: Literature Review: Role Of Pressure In Osmotic Membrane Foulingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Unpacking compaction: Effect of hydraulic pressure on alginate fouling

Tow

Lienhard

2017

Journal of Membrane Science

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“…Many fouling studies are concerned with comparisons, such as the relative fouling propensity of FO vs. RO [5], pressurized vs. unpressurized FO [6,7], or new membrane coatings vs. commercial membranes [8]. Although flux decline comparisons often keep initial flux constant because of the dependence of fouling rate on flux [9], differences in membrane properties and solution composition can lead to differences in flux decline between experiments even if the foulant layers are identical in size and structure.…”

Section: Limitations Of Flux Declinementioning

confidence: 99%

Quantifying osmotic membrane fouling to enable comparisons across diverse processes

Tow

Lienhard

2016

Journal of Membrane Science

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In this study, a method of in situ membrane fouling quantification is developed that enables comparisons of foulant accumulation between desalination processes with different membranes, driving forces, and feed solutions. Unlike the conventional metric of flux decline, which measures the response of a process to fouling, the proposed method quantifies the foulant accumulation. Foulant accumulation is parameterized by two variables, cake structural parameter and hydraulic diameter, that are calculated from flux measurements using a model for salt and water transport through fouled reverse osmosis (RO) and forward osmosis (FO) membranes, including dispersive mass transfer in the FO membrane support layer. Model results show that pressure declines through the foulant layer and can, in FO, reach negative absolute values at the membrane. Experimental alginate gel fouling rates are measured within a range of feed ionic compositions where cake hydraulic resistance is negligible. Using both flux decline and cake structural parameter as metrics, the effect of feed salinity on RO fouling is tested and RO is compared to FO. When RO is fouled with alginate, feed salinity and membrane permeability affect flux decline but not foulant accumulation rate. Between FO and RO, the initial rates of foulant accumulation are similar; however, FO exhibits slower flux decline, which causes greater foulant accumulation over time. The new methodology enables meaningful quantification and comparison of fouling rates with the aim of improving fundamental understanding of fouling processes.

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“…The absence of applied hydraulic pressure in the FO process has not only the potential to lower both capital and operating cost but can also be useful for fouling control compared to pressure driven membrane processes. Where, fouling in the FO process was found to be physically reversible which reduces the use of chemical cleaning [5], [6]. FO technology is faced by several challenges that limit its application in large scale processes.…”

Section: Introductionmentioning

confidence: 99%

Enhancement of nonwoven cellulose triacetate forward-osmosis membranes by surface coating modification

Aly¹,

Gadallah²,

Ali³

et al. 2017

IJET

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Forward osmosis (FO) is considered as one of the emerging techniques in membrane technology. The enhancement of FO performance is governed by two major factors: the first one is development of high-performance draw solutions and the second is utilizing of high efficient FO membranes. The aim of this work is to investigate chemical surface coating modification of commercial nonwoven forward osmosis membrane with new hydrophilic coating materials namely, o-phenylene di-amine and benzoyl chloride. The effect of coating addition at different concentrations was studied. The membrane morphology and chemical structure characterization of modified membranes proved the formation of dense layer and higher membrane porosity. Finally, it was demonstrated that increasing of coating material concentration gradually increases porosity and membrane performance till 0.75 g/l. By further increasing of coating materials, the porosity and membrane performance tend to decrease.

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Combined organic and colloidal fouling in forward osmosis: Fouling reversibility and the role of applied pressure

Cited by 157 publications

References 33 publications

Unpacking compaction: Effect of hydraulic pressure on alginate fouling

Unpacking compaction: Effect of hydraulic pressure on alginate fouling

Quantifying osmotic membrane fouling to enable comparisons across diverse processes

Enhancement of nonwoven cellulose triacetate forward-osmosis membranes by surface coating modification

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