2003 Low-Pressure RO Membrane Desalination of Agricultura

8/8/2019 2003 Low-Pressure RO Membrane Desalination of Agricultura

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E L S E V I E R Desalination 155 (2003) 109-12 0D E S A L I N A T I O N

www.elsevier .conff]ocate/desal

Lo w -pressure R O m embrane desa lination o f agr iculturaldrainage waterR o n - W a i L e e " , J u l i u s G l a te r a, Y o r a m C o h e n " * , C h r i s M a r t in b , K u r t K o v a c c,

M a r ti n N . M i lo b a r d, D a n W . B a r t e l daDepartment o f Chemical Engineering, U niversity o f California, Los Ang eles, Los Angeles, CA 90095-1592, USATel. +1 (310) 825-8766; Fax +1 (310) 206-4107; em ail: yoram@ ucla.edubBoyle Engineering Corporation, 500 1 E. Com mercenter Drive, Suite 100, PO Bo x 12030, Bakersfield, CA 93309, USACDepartment o f W ater Resources, San Joaquin District, Fresno, CA 93726-6913, USAaBuena Vista Water Storage District, 525 North Main Street, Buttonwillow, CA 9320 6, USA

Received 7 O ctober 2002; accepted 18 Decem ber2002

A b s t r a c tAgricultural drainage water is a complex mixture of dissolved and suspended chem ical species and m ay contain a

wide variety of m icroorganisms. The application o f membrane systems fo r desalination o f agricultural drainage (AD)wa ter requires careful consideration of eedwater quality, suitable membrane selection and operating conditions. In o rderto evaluate the p otential applicability o f low-pressure reverse osmosis (RO ) to the treatrnent o f AD water, a diagnosticapproach to m em bran e selection and process evaluation was undertaken in support of a pilot field study in the C aliforniaSan Joaquin Valley. Five candidate membranes were evaluated in a diagnostic laboratory membrane system whichprov ided an initial selection based o n salt reject ion and product water flux performance for mo del salt solutions ofunivalent and divalent cations. Biofouling potential of he selected mem branes was also evaluated using two standardsstrains of bacteria. Preliminary pilot plant performance, based on the selected mem branes, was encouraging and hasprovided the basis for long-term pilot plant testing at higher recoveries to assess the impact of fluctuating A D w ater feedcomposition.Keywords: Agricultural drainage water; Rev erse osmosis; Mem brane diagnostics, Desalination; Biofouling

I . I n t r o d u c t i o nT i l e d r a in a g e o f i r r i g a te d l a n d s i s p r a c t i c e d in

m a n y s e m i - a r i d a g r i c u l t u r a l r e g i o n s . A d v e r s eg e o lo g i c a l c o n d i t i o n s i n s u c h a re a s o f t e n i n v o lv eim p e r v io u s l a y e r s u n d e r ly in g f er t i le l a n d [ 1 - 3 ] .*Corresponding author.

A r t i f i c i a l d r a in a g e i s p r a c t i c e d i n s u c h a r e a s i no r d e r t o p r e v e n t w a t e r - l o g g in g a n d s a l i n i t y b u i l d -u p i n t h e r o o t z o n e o f c r o ps . H y d r o l o g i c a n de n v i r o n m e n ta l im p a c t s o f a r ti f i c ia l d r a in a g e h a v eb e e n e x t e n s iv e ly r e v i e w e d b y S k a g g s e t a l . [ 4 ].

T h e f e r t i l e s e m i - a r i d Ca l i f o r n i a S a n J o a q u inV a l l e y w a s o n e o f t h e f i r s t r e g io n s t o i n s ta l l t il e

0011-9164/03/$- See front matter 2003 E lsevier Science B.V. A ll rights reservedP II : S 0 0 1 I - 9 1 6 4 ( 0 3 ) 0 0 2 8 8 - 1


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110 R . -W . L e e e t al . / D e s a l i n a t io n 1 5 5 ( 2 0 0 3 ) 1 0 9 - 1 2 0dra inage sys tem s for i r r iga tion water which hasp roved t o be t he m os t e f f ec t ive approach o f con-trol l ing root zone sal ini ty. Since the early 1970s,ser ious cons idera t ion has be en give n to sys temsfor rec lamat ion and reuse o f agr icul tura l dra inagewater . Mot ivat ion for appl ica t ion of th i s t ech-nology arose from two major issues. First , asuccessful rec lamat ion fac i l i ty would help toaugment d i mi n i sh i ng supp l i e s o f i mpor t edi r r iga t ion water . Second, volume reduct ion ofenv i ronment a l l yhazardous dra inage water couldalso be achieved. The feas ib i l ity of reverseosmosis (RO) for dra inag e water rec lamat ion wasf i rs t dem onst ra ted in 1971 a t the h i s tor ic p i lo tfaci l i ty at Firebaugh, Cal i fornia [5,6] . A largerand cons iderably more sophis t ica ted t rea tmentp l an t w as c omp l e t ed in t he nea rby t ow n o f LosBafios [7 -9] in the m id 1980s to stud y a varietyof opera t ing parameters and to assess the eco-nom ic feas ib i l ity of dra inage water rec lamat ionw i t h R O t echno l ogy a s an i mpor tan t componen t .This p lant was u nfor tunate ly shut dow n in 1987due to co ncern wi th h igh con cent ra t ions of se len-i um i n t he fo rm o f SeO 2- ion found a t Kes terson

the s i te o f a low- lying bas in for a l l ti l edra inage in tha t region. Ti le dra inage in the W estCent ra l San Joaquin val ley has s ince beenterminated , resul ting in a severe hardship for thefarming communi ty . I f not resumed, a gradualsa l in i ty bui ld-up wi l l ne cess i ta te the "re t i rement"o f large areas of fer t i le agricul tural land.

A search for solut ions to the d ra inage problemis present ly underway, and again , membranedesal ina t ion has bee n given ser ious cons idera t ionowing, in par t , to a new genera t ion of h igh-per forman ce low-pressure RO and nanof i l t ra t ion(N F) membranes deve l oped dur i ng t he l a s tdecade [10,11] . Low-pressure RO membranescan opera te a t remarkably low pressures wi thexce l lent product wa ter f lux and reasonably h ighlevels of sa l t re jec t ion . Ho wever , se lec t ion of theappropr ia te me mb rane for AD w ater desa lina t ionmu st involve careful con s idera t ion of feed w aterqual i ty.

Con s idera t ion of water qual i ty in re la t ion toopt imizat ion of the desa l ina t ion process i sespecia l ly cr i t i ca l wi th AD water , which i s acompl ex mi x t u r e o f d i s so l ved and suspendedorganic and inorganic components as wel l as aw i de va r ie t y o f m i c roorgan i sms . The accep tab l eTDS for i r r iga t ion water i s about 750 mg/L.H ow ever , TD S o f A D w a t e r f r om t he SanJoaqu i n V a l l ey va r i e s be t w een 3 , 000 and15,000 mg/Lm and most samples are c lose tosa tura t ion w i th respect to gypsu m (CaSO a2H20) .Water reuse necess i ta tes desa l ina t ion of th i sw a t e r t o ach i eve the des i r ed TD S l eve l . More -over , the cont rol of gypsum scale format ion i scr i t ical to establ ish ing pract ical f ield instal lat ionso f membrane desa l i na t i on o f A D w a t e r . A n t i -sea lants , cons i s t ing pr imar i ly ofpoly elec t ro ly tes ,have met wi th some success in inhibi t ingmembrane su r f ace s ca l i ng by gypsum. O t he rimpor tant aspects af fec t ing membrane per for -mance are col lo idal par t i c les and potent ia lmicrobiologica l growth.

O pt i mi za t i on o f membrane desa l i na t i onsys tems for AD water presents a chal lenge forsys tem des igners and plant opera tors . O f pr imaryconcern i s mem brane se lec t ion for th is spec i f ictask . An assessment may, in par t , be based oncont rol led labora tory exper iments , but overa l lsu i tabi li ty can be determ ined only by lon g- termopera t ion in the f ie ld . In addi t ion to m em bran eselec tion , the d es igner must be conc erned wi thopera t ing parameters and appropr ia te fee d waterpre t rea tmen t sys tems. Pref il t ra t ion can be ef fec-t ive in reducing the problem of col lo idal andbiofoul ing. Des ign o f such pre t rea tmen t sys temsis as impor tant as proper choice of the mem braneitself.In the present wo rk we present l abora tory andpilot plant invest igat ions to evaluate the feasi-b i l ity of me mb rane desa l ina t ion o f agr icul tura ldra inage water in the Cal i fornia San JoaquinVal ley . The f i rs t objec t ive was conc erned wi thse lec t ion of sui table low pressure RO mem branesbased on tes t ing under careful ly cont rol led


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R.-W. Lee et al. / Desalination 155 (2003) 109-120 111l abora tory condi t ions wi th d iagnos t ic modelso l u t i ons o f t he ma j o r un i va l en t and d i va l en tca t ions found in f ie ld dra inage water . Theses t ud i e s w ere fo l l ow ed by eva l ua t i on o f t heb i o fou l i ng po t en t ia l o f t he cand i da te m embranes .The second ob j ec t i ve w as conce rned w i t h acr i t ica l a ssessm ent of m emb rane sui tabil ity andopera t ing con di t ions , in prepara t ion for a long-term pi lo t p lant opera t ion , based o n shor t - te rmproces s da t a g ene ra t ed from a m embrane p i lo tp lant a t the Bu ena V is ta W ater Storage d i st r ic t inBut ton wi l low, Cal i fornia .

2 . L a b o r a t o r y s t u d i e s2 .1 . M e m b r a n e s a n d m a t e r i a l sFi ve commerc i a l a romat i c po l yami de com-

pos i te low-pressure RO mem branes were se lec tedf rom three major manufacturers based onrepor ted ion re jec t ions and f lux a t a speci f ic ap-pl ied pressure . The se mem branes , Hydranaut icsLFC-1 an d ESPA-1 (Oceans ide , CA) , Dow-Fi l mTec N F-90 (Mi nneapo l is , MN ) , and K ochMembrane Sys t ems TFC -U LP and TFC -H R ,were s tored in accordance wi th manufacturerspeci f ica t ions . Diagnos t ic solut ions were a l lprepared us ing ul tra-pure de- ionized waterobta ined by f i l t e r ing di s t i l l ed water through aMiUi-Q Water Sys tem (Mi l l ipore Corp. , SanJose , CA ) . C alc ium c hlor ide d ihydra te (cer t if i edACS) , magnes ium sul fa te (cer t i f i ed ACS) ,sodium chlor ide (USP/FCC granular ) , andsodium meta-bi sul f i t e (cer t i f i ed ACS) wereob taine d from F isher Scien t i f ic (Pit tsburgh, PA).

2 . 2 . M e m b r a n e t e s t u n i tA smal l l abora tory p la te-and- frame rec ircu-

lat ion uni t (Fig. 1) was used as a diagnost icmem brane p e r fo rmance eva l ua ti on sys tem. Th i suni t cons i s t s o f two tes t ce l l s ( Indust r ia l ResearchMachine Products , El Cajon, CA) ar ranged inpara l le l wi th each ce l l having a f low area of

2 .6 cm x 7 .6 cm (mem brane area of 19 .76 c m 2 )and channe l he i gh t o f 0 . 266 cm. ) . The mag-net ica l ly s t i r red polyethylene reservoi r accom-mo dates up to 18 L o f feed water . A ref r igera tedrec i rcula tor (model 625, Fi sher Scient i f i c ,Pi t t sburgh, PA) mainta ined cons tant reservoi rtempera ture . A pos i t ive d i splac em ent pum p(Hydra-Cel l, Wan ner Engineer ing, M inneapo l i s ,M N) del ivers up to 1 .1 gp m o f feed solut ion. Al lmem brane pe r fo rmance expe r i men t s w ere con-ducted a t a c ross f low veloci ty of 40 cm/s( co r r e spond i ng t o a R eyno l ds numb er o f 1 ,336,based on the channel he ight ) . A back-pressureregula tor (US Parapla te , Auburn, CA ) served toadjus t the appl ied t ransmembrane pressure . Adigi ta l f low m eter (model 1000, Fi sher Scient i fi c ,Pi t tsburgh, PA), interfaced with a PC, providedfo r con t inuous m oni t o ri ng o f pe rmea t e f l ux andaccum ula ted volume. Permeate condu ct iv i ty , a td i f ferent t imes dur ing opera t ion o f the uni t , w asmeasured us i ng a conduc t i v it y me t e r (m ode l W D -35607-30, Oak ton Research, Vern on Hil ls , IL) .

2 .3 . M e m b r a n e r e je c t io n , f l u x , a n d b i o f o u l i n gp o t e n t i a l

A per formance tes t ing protocol for each o f thepre-se lec ted membranes was car r ied out a t af ixed tempera ture of 20C and appl ied t rans-mem brane pressure of I00 and 200 ps i. Fee dsolut ions cons i s ted of aq ueous solut ions of 0 .05,0 .10, and 0 .15 M sodium chlor ide (NaCI) and0.01, 0.02, and 0.05 M calcium ch lorid e (CaCI~),respect ive ly . Concen t ra tions of sodium and ca l -c ium chlor ide were chosen based on se lec tedanalyt ica l va lues of dra inage water samples(Tables 1 and 2) a t the Bue na Vis ta Si te in theSan Joaquin V al ley .

Steady-s ta te condi t ions for both membranecomp act ions and the d iagnos t ic exper imentsw e r etypica l ly achieved wi th in a per iod o f 2--6 h . T hesys tem was opera ted in a to ta l recycle modew hereby t he pe rmea t e and concen t r a t e w erere turned to the feed reservoi r. In addi t ion to on-


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112 R.-W. Lee et al. / Desalination 155 (2003) 109-120

III[ ~ D i g i t a lf l o w me t e r

i -I. . . . [II~ w

~ a c kp r e s s u r er e g u l a t o rt ' - - . . I -

I ~ I i R e f r i g e r a t e dI i i I ~ B y p a s sI : , . ' I ~ va lve

S t i rr e d r e s e r v o i r ~ g a u g eI P u m p

R O / N F m e m b r a n e c e llR e t e n t a t e f l o w

L _ _ _ P e r m e a t e f lo wR O / N F m e m b r a n e c e ll

Fig. 1. Laboratory-scaleRO/NFmembrane system

Table 1Basic properties of typical Buena V ista drainage waterTotal dissolved solids (TDS ), mg /L 5250Total organic carbon (TOC), mg/L 2.77Hardn ess, mg /L 1630Turbidity, NT U 0.8Table 2Concentrations of m ajor ions in Buena V ista drainagewaterS u b s t a n c e C o n c e n t r a t i o n

mg/L mol/LCat i ons :N a 1150 0.0500Ca+ 555 0.0139M g+ 60.7 0.0025Anions :CI- 2010 0.0567SO~2 1020 0.0106HCO~ 291 0.0048

l in e c o n d u c t i v i t y a n d f l u x m e a s u r e m e n t s , p er -m e a t e s a m p l e s w e r e c o l l e c t e d a t v a ri o u s i n te r v al sa n d r e t u r n e d t o t h e r e s e r v o i r f o l l o w i n g t h ec o m p l e t i o n o f c o n d u c t i v i t y o r i o n - s p e c i f i cm e a s u r e m e n t s .

M e m b r a n e b i o f o u l i n g p o te n t i a l w a s e v a l u a t e du s i n g t h e b i o f o u l i n g p o t e n ti a l a s s a y d e v e l o p e d b yR i d g w a y a n d c o - w o r k e r s [ 1 2 ,1 3 ] a t t h e O r a n g eC o u n t y W a t e r D i s t r ic t B i o t e c h n o l o g y L a b o r a t o r y .T h e a s s a y s w e r e p e r f o r m e d f o r e a c h m e m b r a n ew i t h t h r e e r e f e r e n c e m e m b r a n e s i n c l u d e d t oa c c o u n t f o r p o t e n t i a l e x p e r i m e n t a l v a r i a t i o n s .T h e t h r e e r e f e re n c e m e m b r a n e s w e r e t h e n e w a n do l d v e r s i o n s o f a f u l l y a r o m a t i c c r o s s - l i n k e dp o l y a m i d e F T - 3 0 R O m e m b r a n e f r o m th e D o wC h e m i c a l C o m p a n y ( M i d l a n d , M I ) , a n d a lo w -p r e s s u r e c e l l u l o s e a c e t a t e m e m b r a n e d e v o i d o fa n y p o s t - s y n t h e s i s s u r f a c e t r e a t m e n t f r o mA p p l i e d M e m b r a n e s ( S a n M a r c o s , C A ) . T h e t e stb a c t e r i a w e r e a h y d r o p h o b i c s t r a i n o f Myco-bacterium ( B T 1 2 - 1 0 0 ) a n d a h y d r o p h i l i c s tr a in o fFlavobacterium ( P A - 6 ) , b o t h r a d i o - l a b e le d w i t hN a~ 35SO 4 T w o s e t s o f b i o f ou l i ng a s s a ys w e r ep e r f o r m e d . I n t h e f i r s t s et , t h e m e m b r a n e s w e r ec on t a c t e d i n a g l a s s f l a s k ( i n a s ha ke ba t h ) c on -t a in i n g N P M ( s o d i u m p h o s p h a t e + m a g n e s i u mc h l o r i de ) b u f f e r a nd t he t e s t ba c t e r i a f o r 5 h a t2 8 C . I n t h e se c o n d s e t , t h e N P M b u f f e r w a sr e p l a c e d b y a c t u a l A D w a t e r . T h e b a c t e r i a la t t a c h m e n t c o u n t ( i .e ., n u m b e r o f b a c t e r i a /c m 2)w a s d e t e r m i n e d b y a L K B R a c k b e t a 1 2 1 9 li q u ids c i n t il l a ti on c oun t e r ( L S C ; W a l l a c , G a i t he r be r g ,M D ) .


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R.-W. Lee et al. / Desalination 155 (2003) 10 9-1 20 1133 . M e m b r a n e s e le c t i o n

M e m b r a n e s e l e c t i o n f o r A D w a t e r d e s a l i -na t ion was based on in it ia l pe r fo rmance eva lua -t ion (sa l t re jec t ion and p erme ate f lux) a t 100 ps it r ansme mb rane p re s su re and subsequen t sc r een -ing ana lys i s o f b io fou l ing po ten t i a l . F ina lse l ec t ion was based on pe r fo rmance t e s t i ng a t200 ps i t r ansme mb rane p re s su re .

Sod ium and ca l c ium re j ec t ion , R , de f ined asR = 100 (1 -Cp/Cr), w he re Cp and Clare the so lu teconcen t r a t i ons i n the pe rmea te and f eed s tr eams ,r e spec t ive ly , by the f i ve s e l ec t ed memb ranes , a t100 ps i t r ansme mb rane p re s su re and 0 .1 N NaCIand CaCl2 solu t ions , i s shown in Fig . 2a . Asexpec t ed , t hese mem branes cons i s t en t ly demon-s t ra te a h igher sa l t re jec t ion and permeate f luxfo r t he so lu t ions o f t he d iva l en t ca l c ium ion thanfo r t he un iva l en t sod ium ion . Th i s behav io r i scons i s t en t w i th pu b l i shed s tud i e s fo r mu l t i va len te lec t ro ly tes [14 ,15] . Permeate f lux , shown inFig . 2b , ranged f rom 2 to 9 .5 gfd for the NaC1feed so lu t ion and 4 .8 t o 13 .6 g fd fo r t he CaCI :f eed so lu tion , w i th t he f l ux gene ra l ly dec reas ingwi th i nc reased r e j ec t i on . M embrane NF-90 ,

wh ich exh ib i t ed t he l owes t r e j ec t i on ou t o f t hesef ive membranes , was e l imina t ed f rom fu r the rt e s t i ng because i t s pe r fo rmance was be low them i n i m u m d e s i r e d f o r t h e e x p e c t e d f e e dconcen t r a t i ons i n t he f i e ld .R e j e c t i o n o f c a l c i u m a n d s o d i u m o v e r t h erange o f concen t r a t i ons expec t ed in t he f i e ld(ove r t he cour se o f the d ra inage season) r evea l edtha t h ighe r f eed concen t r a t i ons caused a dec reasein sod ium re j ec t ion bu t had a l e s s p ronouncedeffec t on ca lc ium re jec t ion (Fig . 3) . I t i s a l soappa ren t f rom F ig . 3 t ha t , ove r t he r ange o fconcen t r a t i ons o f i n t e re s t and fo r t he i nd iv idua lsa lt so lu t ions , t hese l ow-pres su re RO me mb ranesp rov ided a h ighe r r e j ec ti on o f ca l c ium comp aredwi th sod ium. For bo th NaCI and CaCI2 f eedso lu t ions , t he pe rmea te f l ux dec reased wi thinc reasing f eed concen t r a t i on fo r t he r e spec t ivesa lt so lu tions (F ig . 4 ). The TFC -ULP mem brane ,wh ich show ed the l owes t s a lt r e j ec ti on , exh ib i tedthe h ighes t pe rmea te f l ux fo r a l l f eed compo-s i t ions tes ted . In genera l , exper imenta l resul t sconf i rmed the f ac t t ha t membrane se l ec t ioninvo lves a t r ade -o f f be tween so lu t e r e j ec t i on and

( a ) ( b )

1 0 01 0.1 N CaCI2 ~ 0.1 NNaC1

15

o

L

9 59 0

8 58075

L F C

1 29

630

E S P A T F C - T F C - N F - 9 0 L F C E S P A T F C - T F C - N F - 9 0U L P H R U L P H RFig. 2. Com parison of rejection (a) and permeate flux (b) for fiv e comm ercial low-pressure RO mem branes(transmembrane pressure = 100 psi, T = 20C).


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114 R - W . L e e e t a l. / D e s a l i n a t i o n 1 5 5 ( 2 0 0 3 ) 1 0 9 - 1 2 0

0

100

908070

60

(a) ~- --] L FC ESPA l TFC-ULP I TFC-HR (b)10090

7060

0.05 0.1 0.15 0.02 0.04 0.1F ee d concentration ofNaC l (N) Feed ~tmeenlralionofChC l2 (N)

Fig. 3. C omp arison of percent rejection for fou r candidate mem branes, using (a) different Na CI feed con centrations and(b) different CaCI2 feed con centrations. (Transm embran e pressure = 100 Psi, T = 20 C).

2 52 01 5

~ 1 0

0

(a) ~ L F C I~'~ ESPA 1 TFC-ULP 1 TFC-HR ~ )

0 . 0 5 0 . 1 0 . 1 5F e e d c o n c e n t r a t io n o f N aC I ( N )

2 52 01 51 0

~" 50 . 0 2 0 . 0 4 0 . 1

F e e d c o n c e n t r a t io n o f C a C I ~ ( N )Fig. 4. Permeate flux comp arison for four candidate membranes using (a) different NaC I feed concentrations and(b) different CaC i2 feed concentrations. (Transmembranepressure = 100 ps i, T = 20C).p e r m e a t e f l u x . W e a l so n o t e t h a t i n t h e p r e se n td i a g n o s t i c e v a l u a t i o n , th e " t r u e " r e c o v e r y w a sn o t d i r e c t l y e v a l u a t e d d u e t o t h e s m a l l m e m b r a n es u r f a c e a r e a s i n th e l a b o r a t o r y R O s y s t e m .H o w e v e r , t h e m e a s u r e d p e r m e a t e f l u x a n d a nove r a l l s a l t r e j e c t i on c a n be u s e d t o e s t i m a t er e c o v e r y f o r f u l l -s c a l e o p e r a t io n .

W h i l e t h e f i r s t s et o f e x p e r i m e n t s a t 1O0 ps it r a n s m e m b r a n e p r e s s u r e p r o v i d e d a n i n it ia l b a se -l i n e f o r m e m b r a n e p e r f o r m a n c e e v a l u a t i o n , t h e

n e x t s t e p i n s c r e e n i n g t h e r e m a i n i n g c a n d i d a t em e m b r a n e s w a s a c c o m p l i s h e d b y m e m b r a n eb i o f ou l i ng po t e n t i a l a na l y s is . A n a l y s i s o f f i l t e r e dA D w a t e r s a m p l e s r e v e a l e d a b a c t e ri a l c o u n t o f1 . 36 106 ba c t e r i a pe r m L . T h i s m e a s u r e dba c t e r i a l c oun t i s a t a l e ve l o f c onc e r n ove r a l ongp e r i o d o f o p e r a t io n a n d t h u s s u g g e s t e d t h ee v a l u a t io n o f m e m b r a n e b i o f o u l i n g p o t e n ti a l.T h i s a na l y s i s , c a r r i e d ou t i n bu f f e r s o l u t i ons( F ig . 5 ) , re v e a l e d t h a t t h e L F C - 1 , T F C - U L P a n d


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R.-W. Lee et al . / Desalination 155 (2003) 1 09 -12 0 11 5- 0.0 6 ~ ~ ....................... ........................... ........................... .......................i o o., _ . . .o . . t o . , . m0 . 0 4 . . _ i o ., ! Io.o ! I 1 "~ -~ 0.06 l I I

0.05 ] 0. 04 1 m 0 CA FT.30~W-30 LFC ESP ATFC- ~'C - NF- CA FT..30 FT-30 LFC ESP A TF C- N F-~(std) (o) (n) ULP HR 90 (std) (o) (n) ULPFig. 5. Com parison o f biofouling potential for selectedmem branes. CA , FT-30 (n), and F T-30 (o) are mem-branes used as controls. NP M solution (10 mM sodiumphosphate 4- 1 mM MgCI2, pH 7.0) was used as buffer. Ahydrophobic strain of M ycobac ter ium and a hy drophilicstrain of Flavobac ter ium were used as the test bacteria.Bacterial attachment (B/F) is the ratio of bacterial counton the mem brane to the number of free bacteria insolution.

Fig. 6. Comparison o f biofouling potential for candidatemem branes. CA, F T-30 (n ), and FT-30 (o) are mem-branes used as controls. Note: Buena Vista water wasused without buffer. A hydrophobic strain of M y c obac -terium and a hy drophilic strain of F lavobac ter ium wereused as the test bacteria.

1 00= 9 0@o 8 0.~ ,! -~ 7o

6 0

(11) ["--'-7 LFC I TFC-UL P 1 TFC-HR1 0 0

9 5= 9 0 8 5e~

8 0' - 757 0

6 56O

( b )

0 . 0 5 0.1 0.15 0 . 0 2 0 . 0 4 0 .1F e e d c o n c e n tr a t io n o f N a C I ( N ) F e e d c o n c e n t ra t i o n o f C a C I 2 ON )

Fig. 7. Comparison o f percent rejection for four candidate mem branes, using (a) different Na CI feed concentrations and(b) different CaC I2 feed concentrations. (Transmem brane pressure = 200 ps i, T = 20C).

T F C - H R m e m b r a n e s d i s p l ay e d t he lo w e s tb i o f o u l i n g p o t e n t ia l , w h i l e th e E S P A - 1 a n d N F -9 0 m e m b r a n e s h a d t h e h i g h e s t b i o f o u l i n gp o t e n t i a l . I n o r d e r t o c o n f i r m t h e s e r e s u l t s , t h es a m e b i o f o u l i n g a s s a y w a s r e p e a t e d w i t h s e le c t e dm e m b r a n e s u s i n g t h e f i l t e r e d A D w a t e r . T h er e s u l t s , a s s h o w n i n F i g . 6 , c l e a r l y i n d i c a t e t h et r e n d o b s e r v e d w i t h b u f f e r s o l u t io n s c o n t a in i n gt h e t e s t b a c t e r i a .

I n t h e s u b s e q u e n t m e m b r a n e s e l e c t io n s t e p ,p e r f or m a n c e o f t h e l o w e s t b i o f o u l in g m e m b r a n e s( L F C - 1 , T F C - U L P a n d T F C - H R ) w a s e v a l u a t e da t a h i g h e r t r a n s m e m b r a n e p r e s s u r e o f 2 0 0 p s i ino r d e r t o a p p r o x im a t e t h e h i g h e r r a n g e o f o p e r a t -i n g p r e s s u r e i n t h e p i l o t p l a n t s t u d y . A s e x p e c t e d ,a h ig h e r r e j e c t i o n ( F i g . 7 ) a n d f l u x ( F i g . 8 ) w e r eo b t a i n e d r e l a t i v e t o t h e d a t a c o l l e c t e d a t 1 0 0 p si .D i v a l e n t c a l c i u m i o n s w e r e r e j e c t e d t o a g r e a t e r


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116 R . - W . L e e e t a l. / D e s a l i n a t i o n 1 5 5 ( 2 0 0 3 ) 1 0 9 - 1 2 0( a ) I I L FC T F C - U L P 1 T F C-H R (b )

5 04 030

= 2 010

0 .0 5 0 .1 0 .1 5F e e d c o n c e n t ra t io n o f N a C i (N )

5 04 030201 0

00 .02 0 .04 0 .1

F e e d c o n c e n t r a t i o n o f C a C l 2 (N )Fig. 8. Perm eate flux com parison for four candidate mem branes using (a) different N aC I feed c oncen trations and(b) different CaC12 feed con centrations. Transm emb ranepressure = 200 p si , T = 20C).

e x t e n t t h a n s o d i u m i o n s i n b o t h p r e s s u r e r a n g e s.A l l t h r e e m e m b r a n e s e x h i b i t e d r e je c t io n s a b o v e90% f o r a ll th r ee f eed con cen t r a t i ons o f ca l c i uma n d s o d i u m c h l o r id e e x c e p t f o r 8 9 % s o d i u mr e j e c t i o n f o r t h e T F C - U L P m e m b r a n e u s i n g0 . 15 N N aCI f eed . I t s hou l d a ls o be n o t ed t ha t theL F C -1 a n d T F C - H R m e m b r a n e s d e m o n s tr a te dg r ea t e r t han 99% r e j ec t i on f o r a l l f eed concen -t r a t i o n s o f c a l c i u m c h l o r i d e . T h e a b o v e t h r e em em br anes w er e a l l s u i t ab l e cand i da t e s f o r t hep i l o t p l an t f i e l d s t udy .

4 . P i lo t p lant studyT h e p i l o t p l a n t , d e s i g n e d a n d o p e r a t e d b y

B o y l e E n g i n e e r i n g , w a s l o c a t e d a t t h e B u e n aV i s t a W at e r S t o r age D i s t r i c t i n Bu t t onw i l l ow ,Ca l i f o r n i a . The p l an t , s how n s chem at i ca l l y i nF i g . 9 , cons i s t ed o f a p r e t r ea t m en t m u l t i -m e d i af i l t r a t i on s ys t em and a t w o- s t age po r t ab l e ROuni t . Pre- f i l t r a t ion co ns i s t e d of three ga rnet f il t e r sand a s and f i l t e r . D ur i ng ope r a t i on , a l um ands ca l e i nh i b i to r H yp er s pe r s e A S 20 ob t a i ned f r omG E B e t z ( T r e v o s e , P A ) w e r e b o t h i n je c t e d in t ot he f eed w a t e r a t a r a te o f 5 m g / L . A c i d w as a l s oi n j ec t ed t o ad j us t t he f eed w a t e r pH t o 6 . 8 i no r de r t o f u r t he r r educe po t en t i a l ca l c i um

car bona t e s ca l i ng . Th e p l an t w as des i g ned toh a n d l e a w a t e r f e e d f l o w r a te o f u p to 2 7 g p m .T h e s y s t e m w a s c o n f i g u r e d w i th s i x p r e s s u r eves s e l s each con t a i n i ng th r ee s p i r a l - w ou ndm e m b r ane e l em en t s , a r ranged i n a 2 :2 : 1 :1 a r r ayw i t h a t o t a l m em br ane s u r f ace a r ea o f 133 .2 m 2( 1 4 4 0 f t2 ) .

M e m b r a n e s c o n s i d e r e d f o r t h e p i l o t s t u d yi n c lu d e d t h e T F C - U L P a n d T F C - H R . T h e T F C -U L P m e m b r a n e d i s p l a y e d h i g h e r f lu x r e l a ti v e tot h e o t h e r l o w - f o u l in g c a n d id a t e m e m b r a n e s( F igs . 4 and 8 ). Th i s m em br an e had an accep t ab l er e j ec t i on f o r ca l c i um ove r t he concen t r a t i onr a n ge s o f i n te r e st a n d p e r f o r m e d r e a s o n a b l y w e l lf o r s od i um a t the m i d - t o l ow con cen t r a t i on r ange( F ig . 3 ). The o ve r a l l r e j ec t i on pe r f o r m a nce o f h i sm e m b r a n e w a s l o w e r t h a n t h a t m e a s u r e d f o r th eo t he r c a n di d at e m e m b r a n e s . T h e T F C - H R m e m -b r a n e h a d t h e b e s t r e je c t io n p e r f o r m a n c e ( > 9 3 % )f o r a l l cond i t ions t e s t ed bu t ha d a s i gn i f i can t lyl o w e r f lu x c o m p a r e d to t h e T F C - U L P m e m b r a n e .S i n c e c a lc i u m r e m o v a l i s o f p a r a m o u n t i m p o r -t a n c e f o r A D w a t e r, th e L F C m e m b r a n e w a s n o ts e l ec t ed s i nce m eas u r ed f l ux f o r t he ca l c i ums o l u t i ons (F i gs . 4h and 8b ) w as l ow er r e l a t ive t ot h e T F C - H R a n d T F C - U L P m e m b r a n e s .

I n o r de r t o eva l ua te an t i c i pa t ed pe r f o r m ancei n t he p i l o t p l an t f ac i l i t y a p r oces s s c r een i ng


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R.-W. Lee et aL / Desalination 155 (2003) 109-120 117Well #2Wel l #1 (Sou th)

( N ~ ) ~ L F i lt e r T r ai n # 1~ - ~ ~ ~ " ~ ~ ' ~ l A R T e F EE DW I ~ I I I I I I1 1 I I I | B O O S T C R I D G P U M P

T i le Dra in T i le Dra in F i lte r T ~ n #2Sump Pump

I CONCENIRATE CONCENTRATE

LEGEND-~ PRESSUREGAI~ E

O FLOWMETER) ~3HDIJCTIVITYMETER~p H METER

CONCENTRATE v

BackpressureNeedle Valve

CONCB~TRATE

RO PRESSURE I . ~ 1 4 2 I ~ 3 , 4VE SSE L (TYP.) T T . . . .

q 1s t STAGE ; I ~ 2nd STAGE p#1, #2, #3, and #4 are perm eate sample points .

Fig. 9. Pro cess flow diagram of p ilot plant.

PERMEATE

ana lys i s was ca r r i ed ou t , u s ing the POPRO6sof tware (Koch M embrane Sys t ems) , f o r d i f -f e r en t con f igu ra t ions i nvo lv ing TFC-HR andT F C - U L P m e m b r a n e m o d u l e s (8 0 f t~ permod u le ) . The ana lyzed conf igu ra t ions i nc luded :(a) s tage 1 : TFC-ULP, s tage 2 : TFC-ULP;(b) s tage 1 : TFC-ULP, s tage 2 : TFC-HR;(c) s tage 1 : TFC-HR, s tage 2 : TFC-ULP; and(d) s tage 1 : TFC-HR, s tage 2 : TFC-HR. Inputva r i ab le s i nc luded t empera tu re , pH, f eed w a te rcompos i t i on , f eed f l ow ra t e , pe rcen t r ecove ry ,n u m b e r o f p r e s s u re v e s se l s, n u m b e r o f m e m b r a n ee l emen t s pe r p re s su re ves se l , t ype o f mem brane ,and fou l ing a l l owance fo r t he membranes .Assuming p reven t ive measu res a r e t aken toreduce fo u l ing and sca l ing , t he fou l ing a l l owance(expres sed a s p e rcen t l o s s o f ne t tr ansmembranepressure) w as se t a t 15% for th is analys is . Feedwa te r com pos i t i on was se t as i n Tab le s 1 and 2 ,

r e spec tive ly , and f eed wa te r pH and t emp era tu rewere se t to 6 .8 and 22C, respect ive ly . Thedes i r ed ope ra tion was se t a t a f eed f l ow ra t e o f20 gpm wi th a t a rge t p roduc t r ecove ry o f 50%,wi th an ove ra l l pe rmea te f l ow r a t e o f 10 gpm[16] . Severa l assumpt ions were made in thesescreening s imu la t ions : the perm eate backpressureand in t erbank p ressu re l o s s were neg lec t ed andthe impac t o f an t is ca l an t s and ac id ( t o m in imizeca l c ium ca rbona te s ca l ing ) were no t d i r ec t l ycons ide red .The s imula t ion resul t s revealed tha t for thespec if i ed r ecove ry and pe rmea te f l ow, t he pe rcen tTDS re j ec t ion fo r t he fou r con f igu ra t ions a -dw ere 96 .3 , 96 .8 , 97 .3 and 97.8 , respect ive ly , wi ththe corresp ond ing in le t pressures o f 127.2 , 131.1 ,151.4 and 165.4 psi . The rat io o f stage 1 to stage2 permeate f lux was approximate ly 1 .1 forconf igura t ion c wh i le it ranged f rom 1 .8-5 .75 for


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118 R . - ~ L e e e t a l. / D e s a l i n a t i o n 1 5 5 ( 2 0 0 3 ) 1 0 9 - 1 2 0t he o the r t h r ee conf igu ra tions t e st ed . A l thoughal l conf igura t ions y ie lded a h igh re jec t ion level ,having both s tages opera te a t a s imi lar level ofpermeate f lux , as obta ined in conf igura t ion c ,was sough t a s t he p re fe r r ed ope ra t ing cond i t i onwhi l e ma in t a in ing a r easonab ly l ow t r ans -me mb rane p re s su re. F o r a l l con f igu ra t ions , t heprocess analys is resul t s revealed tha t the con-cent ra te was a t the sa tura t ion level wi th respectto ca lc ium sul fa te and about 24 t imes thesa tura t ion level for bar ium sul fa te . These over-sa tu ra t ion l eve l s ar e i ndeed o f conce rn and thussugges t a poss ib l e need fo r add i t i ona lp re t r ea tmen t cons ide ra ti ons .

The p i lo t p l an t was ope ra t ed f rom pe r iod o fAugust 1 , 2000 to September 13 , 2000. Dur ingp lan t ope ra t i on , f eed TDS va r i ed f rom 3 ,500-8 ,800 mg/L, s imi lar to the concent ra t ion rangecovered in the d iagnos t ic labora tory-sca lemembrane sc reen ing s tudy . The p l an t wasopera ted a t a feed pressure of 145-235 ps i. In thein i ti a l ope ra ti on o f t he f ac i l i t y ESPA-1 mem -brane was used fo r bo th s t ages s ince i t wasava i l ab le and a l r eady in s ta l led f rom a p rev iouspi lo t p lant s tudy. How ever , a f ter the f i r s t 530 h ofope ra t ion , t he TFC-H R m emb rane was i n s t a ll edin the f i r s t s tage and af ter opera t ing for 720 h the

T F C - U L P m e m b r a n e w a s i n st a ll e d i n t h e s e c o n dstage.

Du r ing the f ir s t 530 h , f eed co nduc t iv i t yva r i ed f rom 5080 to 8770 mS/cm and pe rcen tr e j ec t i on r ema ined in t he r ange o f abou t 84 -91 %(Fig . 10 ). The pe rcen t r eco ve ry and no rm a l i zedf lux fl uc tua t ed by up to 78% fo r pe rcen t r ecove ryand 220% fo r no rma l i zed f l ux (F ig . 11 ). It shou ldbe no ted tha t a r e j ec t ion l eve l o f 91% wo u ld be a tt he l imi t o f t rea t i ng a f eed TD S o f 8333 mg /Lw h i l e m e e t i n g t h e r e q u i r e m e n t o f a 7 5 0 m g / m LTDS p roduc t fo r ag r i cu l tu ra l wa te r app l i ca t i on .Clea r ly , h ighe r TDS l eve l s o f t en encou n te red inAD wa te r wo u ld r equ i r e a h ighe r r e j ec t ion . Af t e rin s ta l la t ion o f t he TF C-H R me mb rane in t he f ir s ts t age (new 1s t s t age membrane on F ig . 11 ) ,r e j ec ti on inc reased and was sus t a ined a t a l eve labove 90%. Al though some dec l ine i n r ecove ryand no rma l i zed f lux was obse rved , t hese were r e -e s t ab l i shed once the ESPA-1 membrane in t hesecond s t age was r ep l aced (new 2nd s t agemem brane on F ig . 11 ) by the h ighe r f l ux lowerb i o f o u l i n g T F C - U L P m e m b r a n e . D u r i n g t h epe r iod fo l lowing the r ep l acem en t o f s t age 2 , f eedconduc t iv it i es de c reased s ign i f ican t ly (down to~4300 m s /cm) , wh ich a long wi th t he pe r fo rmancecha rac te r i s ti c s o f TFC -HR, a l l owed sa lt r e j ec t i on

20 .0 (X) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18 , (X)0 - - ~ I - ' c~~ ~ Couceat~ale16,00~ ~ ' ' - ~ p~mcate

~ , o , o o o

'~ 8 , 0 0 o{ {8 6 . o o o

4 , ( X X I . ~ " ~ "Ne~2 , ~ t i ng e2,ooo ~ : / .~b,o ~,

.......................................................................................................................................................................0 240 480 720 960 12O0

Elapsed operating hoursFig. 10. Measu red fe ed , concen trate, and p ermeateconductivities of the RO system during operation of thepilot plant.

I ~ 0.3~90

I L808

~,.70

i "~ 50w

% R e j e c t i O n-O- % Recove~

Nom~at izcd F'}Uw.

0.250

0.2(N) ~

0.151)

0 . 1 0 0

0.050/ / tr~mbrm~,,30 ................... ...................... ...................... ..................... ............. OOOO

0 120 240 360 4g0 600 720 840 9bO 1080 1200E l a p s e d o p e r a t in g h o u r s

Fig. 11. Percent rejection based on measured con-ductivites, p ercent recov ery,and normalized flux of theRO system during he o peration of the pilot plant.


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R . - W . L e e e t a l. / D e s a l i n a t i o n 1 5 5 ( 2 0 0 3 ) 1 0 9 - 1 2 0 119to r each 95%. Fo l lowing the r ep lacemen t o fs t age 2 m emb ranes , the RO sys t em was a l so ab leto ach ieve r e l a t i ve ly s t abl e no rma l i zed f l ux ( anave rage o f 0 .09 GF D/ps i ) and r ecov e ry o f abou t5 0 % .Whi le the above f ie ld s tudy resul t s a rep re l imina ry and con duc ted ove r a pe r iod tha t wasl imi t ed by the unusu a l ly sho r t d r a inage season ,the ove ra l l pe r fo rmance i s encourag ing andsugges ts fu r the r eva lua t ion o f m emb rane desa l i-na t ion for agr icul tura l dra inage water . Currentef for t s a re focused on a longer f ie ld s tudydes igned to eva lua t e l onge r - te rm pe r fo rmance a th ighe r p roduc t wa te r r ecove ry .

6 . C o n c l u s i o n s

of fou l ing due to bo th m ine ra l s ca le and m ic ro -organisms can, in pr inc ip le , involve su i tablef i lt r a ti on p re t r ea tmen t , u se o f che mica l add i t ivesand appropr i a t e membrane se l ec t ion . In t hep resen t s tudy , i t was shown tha t w hen se l ec t inga mem brane , one may hav e to con s ide r t he t r ade -o f f s be tween r educ t ion in b io fou l ing po ten t i a la n d m e m b r a n e p e r fo r m a n c e a s w e l l a s b e t w e e nmem brane sa l t r e j ec t i on and pe rmea te f l ux . W o rkpresen t ly unde rway invo lves expanded f i e ldtes t ing and the evaluat ion of s t ra tegies forr e d u c in g m e m b r a n e f o u l in g v i a t h e c o m b i n a t i o nof p re t r ea tmen t s t r a t eg i e s and op t imiza t ion o fmem brane sys t em co nf igu ra tion , a ll spec i f i ca l l yt a rge ted fo r desa l ina t ion o f ag r i cu ltu ra l d r a inagewa te r i n t he Ca l i fo rn i a San Joaqu in Va l l ey .

The p re sen t s tudy p re sen t s an approach toeva lua t ing me mb rane d esa l ina t ion o f ag r i cu ltu rald ra inage wa te r based on the combina t ion o f alabora tory d iagnos t ic s tudy wi th a p i lo t f ie ldeva lua t ion . T wo d i f f e r en t h igh -pe r fo rmance ROme mb ranes w ere i n s ta l led i n t he two- s tage p l an twi th a de s igned f eed w a te r capac i ty o f app rox i -ma te ly 39 ,000 gpd . T he p l an t p rov ided p roduc twa te r r ecove ry on the o rde r o f 50% f rom a f eedw a t e r sa l in i ty ra n g e o f - 3 5 0 0 - 8 8 0 0 m g / L T D S .Th e f i r s t- s tage p i lo t p lant per form ance evaluat ionwas r e l a t ive ly sho r t due to a d imin i shed f low o fdra inage water dur ing the 2000 year i r r iga t ionseason. D espi te the shor t dura t ion of th ispre l iminary f ie ld s tudy, the feas ib i l i ty of e f fec-t ive agr icul tura l dra inag e water desa l ina t ion wi thh igh -pe r fo rmance low-pres su re RO membraneswas c l ea r ly demons t r a t ed i n t h i s coope ra t ivee f fo r t be tween gove rnmen t , i ndus t ry andacademia .

The s tudy points out tha t the se lec t ion ofsu i t ab l e membranes fo r desa l ina t ion o f ag r i -cu l tu ra l d r a inage wa te r r equ i r e s membranecharac ter iza t ion wi th regard to f lux , ion re jec t ion ,b iofoul ing potent ia l and propens i ty for sca leformat ion . T he ch oice o f s t ra tegies for reduct ion

A c k n o w l e d g e m e n t sThe p resen t s tudy was suppor t ed by the

Ca l i fo rn i a Depa r tmen t o f W ate r Resources andb y a N o r t h A m e r i c a n M e m b r a n e S o c i e t yResea rch Fe l lowsh ip to M r . Ron-W ai Lee .

R e f e r e n c e s[1] E. Raveend ranand I.M. M adany, Characteristics ofagricultural drainage water in Bahrain, Sc i. TotalEnv iron., 104 (1991 ) 239--247.[2] M.H.Sorour,A.G. Abulnourand H.A.Talaat,Desali-nation of ag riculturaldrainagewater,Desalination,86(1992) 63-75 .[3] B.E.Smith,Proc.InternationalDesalinationAssocia-tion MeetingNew port Beach, CA, 1992.[4] R.W.Skaggs, M.A . Breve and J.W. G illiarn, Hydro-logic and water quality impacts of agriculturaldrainage, Crit. R ev. E nviron. Sci. Tec hnol., 24(1)(1994) 1-32.[5] W .J. McC utchan, University of Califom ia SalineWater Progress Repo rt, 62 (1974-1975) 2 5-34.[6] W .J. McC utchan, Saline W ater Research, UCLA -ENG-7201, W ater Resources Desalination ReportNo. 47, 1972.[7] B.E.Smith,D.B.Price,D.R. KasperandW.R.Everst,


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120 R..W. Lee et al. / Desaffnation 155 (2003) 109-120Agricultural wastewater desalting in California:DW Rtest facility description, Department of Water Re-sources, Sacramento, CA, 1981.

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[9] B.J. Marinas and R.E. Selleck, Desalination ofagricultural drainage return water. Part II: Analysis o fthe performance of a 13,000 GDP RO unit, Desali-nation, 61 (1987) 263-274.

[10] R. Rautenbach an d A. Gm schl, Separation potentialofnanofiltration mem branes, Desalination, 77 (1990)73 .

[11] R. Petersen, Composite reverse osmosis and nano-filtration membranes, J. Membr. Sc i., 83 (1993) 8 1-150.

[12] T. Kno ell, J. Safarik, T. Cormack, R. Riley, S.W. Linand H. Ridgway, Biofouling potentials of micro-

porous polysulfone membranes containing a sulfo-nated polyether-ethersulfone/polyethersulfone bloc kcopolymer: correlation o f mem brane surface proper-ties with bacterial attachment, J. Membr. Sci., 157(1999) 117.

[13] H. Ridgway, K. Ishida, G. Rodriguez, J. Safarik,T. Knoell and R. Bold, B iofouling of membranes:mem brane preparation, characterization, and analysiso f bacterial adhesion, Methods E nzymo l., 310 (I 999)463.

[143 N.C . V oros, Z.B. M aroulis and D. Marinos-Kouris,Salt and permeability in reverse osmosis m embranes,Desalination, 104 (1996) 141.

[15] A.M. Hanra and V. Ranmchandhran, RO perfor-mance analysis of cellulose acetate an d T FC poly-amide membrane systems for separation of tracecontaminants, Desalination, 104 (1996) 175 .

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2003 Low-Pressure RO Membrane Desalination of Agricultura