On the potential of forward osmosis to energetically outperform reverse osmosis desalination

McGovern, Ronan Killian; Lienhard, John H.

doi:10.1016/j.memsci.2014.05.061

Cited by 209 publications

(107 citation statements)

References 48 publications

Supporting

Mentioning

107

Contrasting

Order By: Relevance

“…The type of FO modelled in this study transports water from a feed solution into a more concentrated draw solution, which would then typically be regenerated by another separation process [3]. The distance coordinate x is defined as zero at the feed-facing edge of the membrane active layer and positive in the direction of water flow in typical FO and RO operation, i.e., from feed to draw or feed to permeate (direction shown in Fig.…”

Section: Fo Modelmentioning

confidence: 99%

Quantifying osmotic membrane fouling to enable comparisons across diverse processes

Tow

Lienhard

2016

Journal of Membrane Science

Self Cite

View full text Add to dashboard Cite

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.

show abstract

Section: Fo Modelmentioning

confidence: 99%

Quantifying osmotic membrane fouling to enable comparisons across diverse processes

Tow

Lienhard

2016

Journal of Membrane Science

Self Cite

View full text Add to dashboard Cite

show abstract

“…An FO pilot system with RO regeneration (FO-RO) was used to concentrate low-salinity O&G wastewater [2,18]. FO-RO has also been suggested to be more efficient than RO for seawater desalination [19,20], but other studies have shown that this is unlikely [21,22]. Another FO pilot plant forgoes draw regeneration in favor of "osmotic dilution" [2,18]: the dilution of a pure sodium chloride solution powers the concentration of O&G wastewater.…”

Section: Assessment Of Technologiesmentioning

confidence: 99%

“…At brackish and seawater salinities, RO is more efficient than FO. Due to irreversible water transport in the FO exchanger, this will probably always be the case [21]. At high salinities, the efficiency of FO with thermal draw regeneration is currently lower that of MVC [11] because of that pilot plant's use of simple distillation for draw regeneration.…”

Section: Assessment Of Technologiesmentioning

confidence: 99%

Raising forward osmosis brine concentration efficiency through flow rate optimization

2015

Self Cite

View full text Add to dashboard Cite

An exergetic efficiency is defined in order to compare brine concentration processes including forward osmosis (FO) across a wide range of salinities. We find that existing FO pilot plants have lower efficiency than reverse osmosis plants in the brackish and seawater salinity ranges. High salinity FO, in its current form, is still less efficient than mechanical vapor compression. We show that efficiency is the product of FO exchanger and draw regenerator efficiencies, and therefore FO system energy efficiency benefits from improvements to both. The mass flow rate ratio (between draw and feed flow rates) is identified as a crucial parameter in the design of efficient FO systems because of its effect on exchanger efficiency. We demonstrate a method of thermodynamically balancing an FO system by choosing flow rates that lead to equal osmotic pressure differences at both ends of the exchanger, and show the method's potential to increase efficiency by 3-21% based on current system designs.

show abstract

“…Table 1. Specific energy consumption, as reported in literature [9,16,17,[19][20][21][22][23][24][25][26][27][28], varies for different desalination technologies. Total equivalent specific energy consumption is equal to the sum of kilowatt-hours (electric) and kilowatt-hours (thermal), converted based on an assumed 45% efficiency of a modern power station [16]: equivalent electric kWh/m 3 = kWh e /m 3 + 0.45 kWh th /m 3 .…”

Section: Introductionmentioning

confidence: 99%

Predicting the Specific Energy Consumption of Reverse Osmosis Desalination

Stillwell

Webber

2016

Water

View full text Add to dashboard Cite

Desalination is often considered an approach for mitigating water stress. Despite the abundance of saline water worldwide, additional energy consumption and increased costs present barriers to widespread deployment of desalination as a municipal water supply. Specific energy consumption (SEC) is a common measure of the energy use in desalination processes, and depends on many operational and water quality factors. We completed multiple linear regression and relative importance statistical analyses of factors affecting SEC using both small-scale meta-data and municipal-scale empirical data to predict the energy consumption of desalination. Statistically significant results show water quality and initial year of operations to be significant and important factors in estimating SEC, explaining over 80% of the variation in SEC. More recent initial year of operations, lower salinity raw water, and higher salinity product water accurately predict lower values of SEC. Economic analysis revealed a weak statistical relationship between SEC and cost of water production. Analysis of associated greenhouse gas (GHG) emissions revealed important considerations of both electricity source and SEC in estimating the GHG-related sustainability of desalination. Results of our statistical analyses can aid decision-makers by predicting the SEC of desalination to a reasonable degree of accuracy with limited data.

show abstract

On the potential of forward osmosis to energetically outperform reverse osmosis desalination

Cited by 209 publications

References 48 publications

Quantifying osmotic membrane fouling to enable comparisons across diverse processes

Quantifying osmotic membrane fouling to enable comparisons across diverse processes

Raising forward osmosis brine concentration efficiency through flow rate optimization

Predicting the Specific Energy Consumption of Reverse Osmosis Desalination

Contact Info

Product

Resources

About