Euromembrane 09 seawater


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Euromembrane 09 seawater

  1. 1. NANOFILTRATION AS A PREETREATMENT FOR SCALING IN SWRO: A SYS SWRO STEMATIC STUDY Laia Llenas1, Xavier Martínez Lladó1, Andriy Yaroshch 2,3, Miquel Rovira1, Joan DePablo1,3 Martínez-Lladó huk 1 Environmental Technology Area, CTM Centre Tecnològi Av Bases de Manresa 1 08242 Manresa Spain Area ic, ic Av. 1, Manresa, 2 ICREA; 3Department of Chemical Engineering, Polytech Engineering hnic University of Catalonia Av Diagonal 647 08028 Barcelona, Spain Catalonia, Av. 647, BarcelonaINTRODUCTION AND OBJECTIVESSeawater contains hi h concentrations of sparingly soluble salts which can cause scaling of membrane surface, li itiS t t i high t ti f i l l bl lt hi h li f b f limiting th productivity and water recovery of seawater reverse the d ti it d t f tosmosis (SWRO). Nanofiltration (NF) pretreatment of seawater, prevents scaling via preferential removal of scale-forming ions [1]. ( ) ( )p ,p g p g [ ]Several studies have shown that the rejection of scale forming ions is not the same for ev scale-forming very membrane [2] The main objective of this study was to test a number of commercially [2].available NF membranes with synthetic seawater in order to compare their performance and identify optimum membranes and operational conditions for shifting solubility equilibrium of y p p d y p p g y qcompounds susceptible to cause scaling due to salt precipitation (CaSO4 ( ), MgSO4 ( ), CaCO3 ( ), etc ) (s) (s) O (s) etc.).EXPERIMENTAL METHODOLOGYTheTh experimental setup used consists of SEPA CF II cell (O i l d i f ll (Osmonics). i )The trans membrane pressure difference and cross flow velocity were monitored and con trans-membrane cross-flow ntrolledautomatically; pH and conductivity were also monitored. t ti ll H d d ti it l it dSynthetic seawater was prepared in the laboratory following the procedure described else ewhere[3].[3] During the study eleven different nanofiltration membranes supplied by s study, membranes, severalmanufacturers, were tested at various trans-membrane pressure differences between 2 a p and 20bar,bar and two cross-flow velocities: 0 15 and 0 30 m/s cross flow 0,15 0,30 m/s.Permeates obtained i th t t were analyzed i th l b tP t bt i d in the tests l d in the laboratory b using th f ll i analytical by i the following l ti lmethods: Total Inorganic Carbon Analysis, Ionic Chromatography and ICP-MS. ICP MS. Figure 1. Experimental system 1RESULTS AND DISCUSSIONDepending on the membrane used, there were significant differences between the p g , g NF270 NF200 NF ESNA 1‐LF2 K‐TFCS K‐SR2 K‐SR3 DL HL ALNF99 ALNF99HFrejections of different ions but the most important dissemblance was their ions,productivities.productivities See Figure 22. a) b) 100The rejection of scale-forming ions is represented in Figure 2. The rejection of scale forming 100 90sulphate is very high for all membranes tested: only four out of eleven membranes 80 80present a rejection l t j ti lower th than 90% Ab t th th 90%. About the three other scale-forming i th l f i ions, t t l total 70inorganic carbon, calcium and magnesium, the rejection of different membranes is g , g , j % R ection ejec on 60 % Re ctio 60more variable and it goes from 10 to 99% depending on the membrane and the variable, 99%, Reje 50pressure used used. 40 40 30In Figures 3 and 4 the rejections of two of the most important monovalent ions in 4, 20 20seawater,seawater sodium and chloride are shown In contrast to divalent ions the rejection shown. ions, 10 0 0of monovalent i f l t ions i much l is h lower; even i some cases, negative rejections could b in ti j ti ld be 0 20 40 60 80 100 120 140 160 0 20 40 60 80 100 120 140 160observed. Permeate flow (L/h·m2) (L/h m Permeate flow (L/h·m2) (L/h m c) d) 100 100 100 90 100 90 80 90 80 80 70 80 70 % Rej tion ject n tion 60 60 70 % Reject % Reje on 60 50 50 R ectio 60 % Rej tion ject n 40 40 50 40 30 30 40 20 20 30 20 10 10 20 0 10 0 0 0 20 40 60 80 100 120 140 160 0 20 40 60 80 100 120 140 160 0 0 20 40 60 80 100 120 140 160 Permeate flow (L/h·m2) Permeate flow (L/h·m2) 0 20 40 60 80 100 120 140 160 ‐20 2 Permeate flow (L/h·m ) (L/h m Permeate flow (L/h·m2) (L/h m Figure 2. Rejection of scale forming ions for different membranes. 2 scale-forming membranes Figure 3 Sodium rejection 3. Figure 4 Chloride rejection 4. a) Sulphate; b) Total Inorganic Carbon; c) Calcium; d) MagnesiumCONCLUSIONS REFERENCES Different nanofiltration membranes have been tested with synthetic seawater in order t select the to [1] N Hilal H Al Zoubi N A Darwish A W Mohammad M Abu Arabi; A N. Hilal, H. Al-Zoubi, N.A. Darwish, A.W. Mohammad, M. best b t one f th pre t t for the treatment of reverse osmosis. t f i comprehensive review of nanofiltration membranes: t t h i i f filt ti b treatment, t p pretreatment, modelling and atomic force microscopy; Desalination 170 , g py; The rejection of monovalent ions is moderate (10-40%) for all membranes. The one tha presents a j ( ) at p (2004) 281-308 281 308 higher rejection for these ions is NF90, a membrane with very similar properties to reve g j , y p p erse osmosis membranes. membranes [ ] [2] A.M. Hassan, A. Farooque, A. Jamaluddin, A. A1- Amoudi, M. A1-Sofi, q The rejection of divalent ions is so good in all membranes tested That is very important for the tested. A. AI Rubaian, N. Kither, I. Al Tisan A AI-Rubaian N Kither I Al-Tisan and A Rowaili A demonstration plant A. Rowaili, prevention of scaling scaling. based on the new NF SWRO process Desalination 131 (2000) 157 171 NF-SWRO process, Desalination, 157-171 The most s itable NF membranes as a pretreatment for scaling pre ention are N suitable prevention are: NF270 (Do (Dow [3] Kester, D. R., Duedall, I. W., Connors, D. N. and Pytkowicz, R. M. Chemical), K-SR2 Ch i l) K SR2 (KOCH) and AL NF99HF (Alf L d (Alfa Laval). l) (1967). (1967) Preparation of Artificial Seawater Limnology & Oceanography 12 Seawater. 12, 176—179. 176 179ACKNOWLEDGEMENTS C O G SThis study was financially supported by Sociedad General de Aguas de Barcelona (AGBAR within the scope of CENIT project “Desarrollos tecnológicos hacia un R) Desarrollosciclo del agua urbano auto sostenible (SOSTAQUA)”. auto-sostenible (SOSTAQUA)