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Sustainable Desalination and Water ReuseSystem Design & Performance

Sustainable Desalination and Water Reuse: System Design & Performance CHA PT ER 4 4.1 SYSTEMDESIGN 4.1.1 SINGLESTAGEANDMULTI-STAGEARRAYS ThebasicunitofanROsystemistheSWE.AnumberofSWEs(between5and(8)arehoused inasingle“housing”or“pressurevessel.”Acollectionofpressurevesselsinparallelformsastage, and the number of stages in series forms an array. A tapered array is used when the feed flow rateisreducedsignificantlybetweenstagesduetorecoveredpermeate.Insuchacascadingarray configuration,thenumberofparallelpressurevesselsisreducedineachstage.Cascadingarrays sometimes have multiple recycle and bypass streams. In single-stage arrays, the feed is pumped into the RO module at a designated pressure, which then splits into a permeate stream and a concentrate stream. The permeate stream is the productwaterandtheconcentratestreamisconsidered“industrialwaste”[145].Inamulti-stage setup,thebrinefromonestageissentasthefeedtothenextstage,whichenableshigheroverall recovery. In some designs, an inter-stage booster pump may be required to increase hydraulic pressureabovetheosmoticpressureoftheconcentrateattheendofthefinalstage.Useofinter- stageboosterpumpscansaveenergyinexchangeforhigherCapEx.Single-stageandmulti-stage RO systems designs are depicted in Figure 4.1. The theoretic al minimum energy required for desalination is equal to the energy needed to bring the feed water to the osmotic pressure of fluid permeating across the membrane (rep- resentedbytheareaundertheosmoticpressurecurveinFigure4.1a).Inpractice,toensurethat water permeates across the membrane at all points along the membrane channel, the pressure applied to the feed volume must be at least equal to the osmotic pressure of the concentrate stream exiting the membrane channel (P D … ); the energy is represented by the area of the H c rectangleofheight P .Thedifferencebetweenthesetwoareasrepresentstheenergythatmust be used to operate with a single stage. Staged membrane operations can save RO desalination energy costs. The first http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png

Sustainable Desalination and Water ReuseSystem Design & Performance

Part of the Synthesis Lectures on Sustainable Development Book Series
Editors: Hoek, Eric M. V.; Jassby, David; Kaner, Richard B.
Wu, Jishan; Wang, Jingbo; Liu, Yiming; Rao, Unnati
Sustainable Desalination and Water Reuse — Jan 1, 2021
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Publisher
Springer International Publishing
Copyright
© Springer Nature Switzerland AG 2021
ISBN
978-3-031-79507-7
Pages
29 –47
DOI
10.1007/978-3-031-79508-4_4
Publisher site
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Abstract

CHA PT ER 4 4.1 SYSTEMDESIGN 4.1.1 SINGLESTAGEANDMULTI-STAGEARRAYS ThebasicunitofanROsystemistheSWE.AnumberofSWEs(between5and(8)arehoused inasingle“housing”or“pressurevessel.”Acollectionofpressurevesselsinparallelformsastage, and the number of stages in series forms an array. A tapered array is used when the feed flow rateisreducedsignificantlybetweenstagesduetorecoveredpermeate.Insuchacascadingarray configuration,thenumberofparallelpressurevesselsisreducedineachstage.Cascadingarrays sometimes have multiple recycle and bypass streams. In single-stage arrays, the feed is pumped into the RO module at a designated pressure, which then splits into a permeate stream and a concentrate stream. The permeate stream is the productwaterandtheconcentratestreamisconsidered“industrialwaste”[145].Inamulti-stage setup,thebrinefromonestageissentasthefeedtothenextstage,whichenableshigheroverall recovery. In some designs, an inter-stage booster pump may be required to increase hydraulic pressureabovetheosmoticpressureoftheconcentrateattheendofthefinalstage.Useofinter- stageboosterpumpscansaveenergyinexchangeforhigherCapEx.Single-stageandmulti-stage RO systems designs are depicted in Figure 4.1. The theoretic al minimum energy required for desalination is equal to the energy needed to bring the feed water to the osmotic pressure of fluid permeating across the membrane (rep- resentedbytheareaundertheosmoticpressurecurveinFigure4.1a).Inpractice,toensurethat water permeates across the membrane at all points along the membrane channel, the pressure applied to the feed volume must be at least equal to the osmotic pressure of the concentrate stream exiting the membrane channel (P D … ); the energy is represented by the area of the H c rectangleofheight P .Thedifferencebetweenthesetwoareasrepresentstheenergythatmust be used to operate with a single stage. Staged membrane operations can save RO desalination energy costs. The first

Published: Jan 1, 2021

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