NANOFILTRATION AS A PRENANOFILTRATION AS A PRENANOFILTRATION AS A PRESCALING IN SWRO A SYSSCALING IN SWRO: A SYSSCALING IN SWRO: A SYS

Laia Llenas1, Xavier Martínez-Lladó1, Andriy YaroshchLaia Llenas , Xavier Martínez Lladó , Andriy Yaroshch

1 Environmental Technology Area CTM Centre TecnològiEnvironmental Technology Area, CTM Centre Tecnològi

2 ICREA; 3Department of Chemical Engineering Polytech2 ICREA; 3Department of Chemical Engineering, Polytech

INTRODUCTION AND OBJECTIVESINTRODUCTION AND OBJECTIVES

S t t i hi h t ti f i l l bl lt hi h liSeawater contains high concentrations of sparingly soluble salts which can cause scalinosmosis (SWRO). Nanofiltration (NF) pretreatment of seawater, prevents scaling via prefere( ) ( ) p , p g p

Several studies have shown that the rejection of scale forming ions is not the same for evSeveral studies have shown that the rejection of scale-forming ions is not the same for evavailable NF membranes with synthetic seawater in order to compare their performance andy p pcompounds susceptible to cause scaling due to salt precipitation (CaSO4 ( ) MgSO4 ( ) CaCOcompounds susceptible to cause scaling due to salt precipitation (CaSO4 (s), MgSO4 (s), CaCO

EXPERIMENTAL METHODOLOGYEXPERIMENTAL METHODOLOGYTh i l d i f SEPA CF II ll (O i )The experimental setup used consists of SEPA CF II cell (Osmonics).

The trans membrane pressure difference and cross flow velocity were monitored and conThe trans-membrane pressure difference and cross-flow velocity were monitored and cont ti ll H d d ti it l it dautomatically; pH and conductivity were also monitored.

Synthetic seawater was prepared in the laboratory following the procedure described elseSynthetic seawater was prepared in the laboratory following the procedure described else[3] During the study eleven different nanofiltration membranes supplied by s[3]. During the study, eleven different nanofiltration membranes, supplied by smanufacturers, were tested at various trans-membrane pressure differences between 2 apbar and two cross-flow velocities: 0 15 and 0 30 m/sbar, and two cross flow velocities: 0,15 and 0,30 m/s.

P t bt i d i th t t l d i th l b t b i th f ll iPermeates obtained in the tests were analyzed in the laboratory by using the following anmethods: Total Inorganic Carbon Analysis, Ionic Chromatography and ICP-MS.methods: Total Inorganic Carbon Analysis, Ionic Chromatography and ICP MS.

RESULTS AND DISCUSSIONRESULTS AND DISCUSSIONDepending on the membrane used, there were significant differences between thep g , grejections of different ions but the most important dissemblance was theirrejections of different ions, but the most important dissemblance was theirproductivities See Figure 2productivities. See Figure 2.

The rejection of scale-forming ions is represented in Figure 2. The rejection ofThe rejection of scale forming ions is represented in Figure 2. The rejection ofsulphate is very high for all membranes tested: only four out of eleven membranessulphate is very high for all membranes tested: only four out of eleven membranes

t j ti l th 90% Ab t th th th l f i i t t lpresent a rejection lower than 90%. About the three other scale-forming ions, totalinorganic carbon, calcium and magnesium, the rejection of different membranes isg , g , jmore variable and it goes from 10 to 99% depending on the membrane and themore variable, and it goes from 10 to 99%, depending on the membrane and thepressure usedpressure used.

In Figures 3 and 4 the rejections of two of the most important monovalent ions inIn Figures 3 and 4, the rejections of two of the most important monovalent ions inseawater sodium and chloride are shown In contrast to divalent ions the rejectionseawater, sodium and chloride are shown. In contrast to divalent ions, the rejection

f l t i i h l i ti j ti ld bof monovalent ions is much lower; even in some cases, negative rejections could beobserved.observed.

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Figure 3 Sodium rejection Figure 4 Chloride rejectionFigure 3. Sodium rejection Figure 4. Chloride rejection

CONCLUSIONSCONCLUSIONSCONCLUSIONS

Different nanofiltration membranes have been tested with synthetic seawater in order t Different nanofiltration membranes have been tested with synthetic seawater in order tb t f th t t t f ibest one for the pre treatment of reverse osmosis.

The rejection of monovalent ions is moderate (10-40%) for all membranes. The one thaj ( )higher rejection for these ions is NF90, a membrane with very similar properties to reveg j , y p pmembranesmembranes.

The rejection of divalent ions is so good in all membranes tested That is very impo The rejection of divalent ions is so good in all membranes tested. That is very impoprevention of scalingprevention of scaling.

The most s itable NF membranes as a pretreatment for scaling pre ention are N The most suitable NF membranes as a pretreatment for scaling prevention are: NCh i l) K SR2 (KOCH) d AL NF99HF (Alf L l)Chemical), K-SR2 (KOCH) and AL NF99HF (Alfa Laval).

C O G SACKNOWLEDGEMENTSACKNOWLEDGEMENTS

This study was financially supported by Sociedad General de Aguas de Barcelona (AGBARThis study was financially supported by Sociedad General de Aguas de Barcelona (AGBARciclo del agua urbano auto sostenible (SOSTAQUA)”ciclo del agua urbano auto-sostenible (SOSTAQUA) .

ETREATMENT FOR ETREATMENT FOR ETREATMENT FOR STEMATIC STUDYSTEMATIC STUDYSTEMATIC STUDY

huk2,3, Miquel Rovira1, Joan DePablo1,3huk , Miquel Rovira , Joan DePablo

ic Av Bases de Manresa 1 08242 Manresa Spainic, Av. Bases de Manresa 1, 08242 Manresa, Spain

hnic University of Catalonia Av Diagonal 647 08028 Barcelona Spainhnic University of Catalonia, Av. Diagonal 647, 08028 Barcelona, Spain

f b f li iti th d ti it d t f tg of membrane surface, limiting the productivity and water recovery of seawater reversential removal of scale-forming ions [1].g [ ]

very membrane [2] The main objective of this study was to test a number of commerciallyvery membrane [2]. The main objective of this study was to test a number of commerciallyd identify optimum membranes and operational conditions for shifting solubility equilibrium ofy p p g y qO3 ( ) etc )O3 (s), etc.).

ntrolledntrolled

ewhereewhereseveralseveraland 20

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Figure 1 Experimental systemFigure 1. Experimental system

NF270 NF200 NF ESNA 1‐LF2 K‐TFCS K‐SR2 K‐SR3 DL HL ALNF99 ALNF99HF

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Figure 2 Rejection of scale-forming ions for different membranesFigure 2. Rejection of scale forming ions for different membranes. a) Sulphate; b) Total Inorganic Carbon; c) Calcium; d) Magnesiuma) Sulphate; b) Total Inorganic Carbon; c) Calcium; d) Magnesium

REFERENCESREFERENCESREFERENCES

[1] N Hilal H Al Zoubi N A Darwish A W Mohammad M Abu Arabi; Ato select the [1] N. Hilal, H. Al-Zoubi, N.A. Darwish, A.W. Mohammad, M. Abu Arabi; Ah i i f filt ti b t t t

to select thecomprehensive review of nanofiltration membranes: treatment,pretreatment, modelling and atomic force microscopy; Desalination 170p , g py;(2004) 281-308at presents a (2004) 281 308p

erse osmosis

[2] A.M. Hassan, A. Farooque, A. Jamaluddin, A. A1- Amoudi, M. A1-Sofi,[ ] qA AI-Rubaian N Kither I Al-Tisan and A Rowaili A demonstration plantrtant for the A. AI Rubaian, N. Kither, I. Al Tisan and A. Rowaili, A demonstration plantbased on the new NF SWRO process Desalination 131 (2000) 157 171

rtant for thebased on the new NF-SWRO process, Desalination, 131 (2000) 157-171

NF270 (Do [3] Kester, D. R., Duedall, I. W., Connors, D. N. and Pytkowicz, R. M.NF270 (Dow [3] Kester, D. R., Duedall, I. W., Connors, D. N. and Pytkowicz, R. M.(1967) Preparation of Artificial Seawater Limnology & Oceanography 12(1967). Preparation of Artificial Seawater. Limnology & Oceanography 12,176 179176—179.

R) within the scope of CENIT project “Desarrollos tecnológicos hacia unR) within the scope of CENIT project Desarrollos tecnológicos hacia un