ELSEVIER

Brackish groundwater treatment by reverse osmosis in Jordan

Maria Dina Afonsoa * , Jamal 0. Jaberb , Mousa S . Mohsenb'Chemical Engineering Department, Institute Superior Tecnico, 1049-001 Lisbon, Portugal

Tel. +351 (21) 841-7595; Fax +351 (21) 849-9242; email.: dina.afonso@ist.utl.pt'Mechanical Engineering Department, Hashemite University, POB 150459, Zarqa 13115, Jordan

Received 2 July 2003 ; accepted 1 October 2003

Abstract

Jordan is characterised by an arid to semi-arid climate and its population is increasing at an annual rate of 3 .6%.With such a high population growth rate and fast social--economical development, water demand and wastewaterproduction are steeply increasing, and the gap between water supply and demand is getting wider . Furthermore, theconstraints for water resources development are also rising due to high investment costs and water quality degradationdue to over-exploitation of aquifers . Desalination of Red Sea water by reverse osmosis (RO) and/or brackishgroundwater desalination by nanofiltration or RO might be technically and economically viable to cope with waterscarcity and overcome the water deficit in Jordan . The technical-economical feasibility of brackish groundwatertreatment by RO for potable water production was investigated in this work . Brackish groundwater samples werecollected from the Zarqa basin, Jordan, and characterised in terms of pH, conductivity, total solids, total dissolvedsolids, total suspended solids, and volatile solids . The water samples were pre-treated through a microfiltrationcartridge (5 ,am pore diameter) in order to eliminate the suspended matter . A pilot plant equipped with a FilmTec ROmembrane (SW30-2521) was operated at 20-30 bar, 40°C, natural pH and up to a water recovery ratio of 77.5%. Theresults showed that RO is actually efficient since it highly reduced the content of organic and inorganic matters presentin raw waters (rejections >98 .5%) at a relatively affordable price (0 .26 €/m 3 ) . This study contributes to thedevelopment of efficient technologies to produce affordable potable water in Mediterranean countries where the threatof water shortages is a severe problem .

Keywords : Brackish groundwater ; Desalination ; Jordan ; Potable water ; Reverse osmosis ; Water scarcity

1. Introduction

Jordan's water resources comprise surfacewater, renewable and non-renewable groundwaterand treated wastewater, which are used by

*Corresponding author .

Desalination 164 (2004) 157-171

0011-9164/04/$- See front matter © 2004 Elsevier B .V. All rights reserved

P11:SOO11-9164(04)00175-4

DESAUNATION

www.eisevteccomllocam/desal

agriculture (69%), industry (10%) and munici-palities (21%) . The estimated available water atJordan in 1995 was about 747 Mm3 surface waterand 389 Mm3 groundwater . With the exception ofsprings and the King Abdullah Canal, surfacewater resources are exclusively used for irri-gation. The municipal water supply and industry

1 58

mainly depend upon groundwater and springs,which are limited and often over-drafted . Chlori-nation is the only treatment applied to ground-water sources prior to water distribution [1] .

Jordan is characterised by an arid to semi-aridclimate: rainy seasons are short and annualrainfall ranges from 50 to 600 mm . On the otherhand, Jordan's population is increasing at anannual rate of 3 .6%, the annual consumption offresh water per capita being only 200 m 3 incomparison to the international average of7500 m3 . With such a high population growth rateand fast social-economical development, a steepincrease in water demand and wastewaterproduction is occurring, and the gap betweenwater supply and demand is getting wider .Moreover, the constraints for water resourcedevelopment are rising due to high investmentcosts and water quality degradation caused byover-exploitation of groundwater resources .

This severe problem has existed since theearly 1980s, and according to recent projections,Jordan is likely to face a potable water crisis by2010 by depleting all of its fresh water resources .Thus, it will suffer tough water rationing thisdecade if integrated measures are not immediatelytaken to ensure water availability, suitability andsustainability . The adoption of non-conventionalsources (e.g ., irrigation with saline water, desali-nation of brackish water and/or seawater, reuse oftreated municipal wastewater, rain water harvest-ing, cloud seeding and water importation) forwater supply reinforcement is inevitable in thenear future for Jordan's sustainable development .

For instance, desalination has been widely andsuccessfully used in Middle Eastern oil-produc-ing countries [2] . Although water and energyresources are scarce in Jordan, desalination ofseawater from the Red Sea/Agaba Gulf (TDS-40 g/1) and/or desalination of brackish ground-water from certain basins (TDS -1-10 g/l)emerging in the form of springs throughout thekingdom might be economically feasible byefficient use of non-conventional energy

M.D. Afonso et al. /Desalination 164 (2004) 157-171

resources [3-5] : seawater and/or brackish ground-water are the most favourable non-conventionalresources for desalination purposes ; desalinationof seawater and/or brackish groundwater byreverse osmosis (RO) appears to be a soundoption for arid lands bordering seas and saltlakes; hydropower and solar technologies are themost effective non-conventional energy resourcesfor water desalination . Hence, there is a need inJordan for capacity building of water desali-nation comprising technology transfer in mem-brane separation processes, operation andmaintenance, and skilled manpower [6] .

Membrane separation processes have exhi-bited a great potential for the treatment of watersand wastewaters by complying with the increas-ingly strict legislation concerning potable waterquality and allowable wastewater dischargesworldwide . Microfiltration (MF), ultrafiltration(UF), nanofiltration (NF) and RO have beenprogressively used for water and wastewatertreatment in order to remove suspended solidsand reduce the content of organic and inorganicmatters. Many authors have reported the appli-cation of NF and RO to highly reduce TDS,salinity, hardness, nitrates, cyanides, fluorides,arsenic, heavy metals, colour and organiccompounds, e.g., total organic carbon (TOC),biological oxygen demand (BOD), chemicaloxygen demand (COD), total organic halides(TOX), trihalomethanes (THM), THM-formingpotential (THMFP), and pesticides, besides theelimination ofbacteria, viruses, turbidity and TSSfrom surface water, groundwater, and seawater[7-411 .

Evaporation, especially multi-stage flash(MSF), and membrane processes - RO andelectrodialysis (ED) - are the main separationprocesses used for potable water production dueto their remarkable efficiency. However, theenergy consumption of evaporation is too highfor brackish water desalination, besides beingunsuitable for inland installation . For desalinationof brackish waters with TDS -2 g/l, the energy

consumption of ED and RO are similar, whereasfor a TDS >5 g/l, the capital costs and the energyconsumption of RO become lower than the one ofED . Thus, ED is mainly applied for desalinationof brackish waters with a TDS <2 g/l, whereasRO is applied for desalination of brackish andseawater . RO produces water of excellent quality,e.g ., the desalinated water from most RO plantsworldwide contains a TDS <0 .3 g/l . Hollow-fiberand spiral-wound RO modules are widely usedfor sea and brackish water desalination [42] .

This study intends to assess the technical-economical feasibility of RO for the productionof potable water from brackish water in Mediter-ranean countries where the threat of watershortages is a serious problem, especially duringthe summer .

2 . Jordanian Standards 286 : 2001, Water -Drinking Water

In the Jordanian Drinking Water Standards(JDWS) [43], TDS is set at two distinct limits : thepermitted limit of 0.5 g/l and the maximumallowable limit of 1 .5 g/l, where no better sourceis available in Jordan (Table 2) . A TDS >0 .5 g/lis only recommended for areas where fresh waterresources are insufficient. Since dissolved solidscannot be removed by conventional watertreatments and a strict TDS standard may requirean expensive water treatment not essential fromthe point of view of human health requirements,the international guidelines cannot be too strictworldwide. The desalinated water in Jordanshould contain a TDS <0 .5 g/l to comply with theinternational acceptable limit and the JDWSpermitted limit .

All parameters listed in the JDWS are tested insamples from water supply stations and networks ;bacteria and residual chlorine are also checked inwater samples from pipelines for the sake ofpublic health . About 95% of the water supply inAmman and the Jordan Valley areas depends ongroundwater resources . Before distribution, the

M.D. Afonso et al. /Desalination 164 (2004) 157-171

Table 1Physical characteristics of drinking water [43]

Table 2Substances / Parameters in drinking water that may risecomplaints from consumers [43]

159

only treatment carried out is chlorination of allwater sources, except the water from the Zaiwater treatment plant where quick filtration isused for the surface water from the KingAbdullah Canal [42] . Water analysis in 2000showed that the maximum violations werereported for turbidity, colour, and total hardness

Parameter Permittedlimit, mg/l

Max. limit whereno better sourceis available, mg/t

pH 6.5-8 .5TDS 500 1500Total hardness,as CaCO 3

300 500

LAS (MBAS)(synthetic detergents)

0.2 0 .5

NH4 0.5 0 .5Al 0 .1 0.2Mn 0.1 0 .2Fe 0.3 1 .0Cu 1 .0 1 .5Zn 3 5Na 200 400Cl 200 500SO4 200 500

Parameter Permitted limit Max. limit whereno better sourceis available

Colour (TCU) 10 15Taste Acceptable to

most consumersOdour Acceptable to

most consumersTurbidity (NTU) 1 5

160

Table 3Inorganic substances in drinking water that affect publichealth [43]

[44] . Although a TDS at the maximum allowablelimit may not cause health problems, it affectswater taste and may indicate water pollution, e.g .,sewage infiltration . In fact, the quality of somegroundwaters has been enhanced with theimprovement of the sewage system. The per-mitted nitrate limit is 50 mg/1 in JDWS (Table 3) .Though the water supply in Amman complieswith JDWS, TDS and NO 3 are sometimes higherthan the permitted limits . NO 3 in a surface watersource, e.g., the Zai water treatment plant, isusually very low but some groundwaters maycontain a NO3 of 60 mg/l [42] .

3. JICA report [42]

3.1. Summary

The Japan International Cooperation Agency(JICA) presented in 1995 a strategy for the

MD. Afonso et al. /Desalination 164 (2004) 157-171

desalination of 75 Mm3/y of brackish ground-water, which would provide an essential newwater resource . They discovered a virgin brackishwater aquifer in the Jordan Valley - the Zarqaaquifer - with high potential in Deir Alla (TDS-7.5 g/1) and Kafrein/Hisban (TDS -5 g/1), whichcould ease the municipal and industrial waterdemand in northern Jordan . Hence, RO would bethe most suitable desalination process for thebrackish water from the Zarqa aquifer .

As the water quality at Kafrein/Hisban wasbetter than at Deir Alla, lower energy consump-tion was expected at the former . The target for thetreated water quality was TDS <0 .3 g/l, whichwould require a salt rejection >94-96%, commonfor RO membranes. With a water recovery ratioof 80-85%, the RO brine concentration would be5-7-fold that of raw water (TDS -25-37 .5 g/l) .This project would not cause a drastic change inthe brackish groundwater quality . The estimatedcost for water production and supply ranged from0.73 to 0.84 US$/m3 . The recommendations com-prised long-term observation of water level andquality at the Zarqa aquifer and further study onbrackish water resources .

3.2. Brackish groundwater in the Jordan Valley

Water analyses were conducted in samplescollected from wells, springs, wadis and the KingAbdullah Canal. Little difference was observed inthe water quality throughout the year . Moreover,the salinity and main ions concentrations werenearly constant throughout summer for most sites .The main cations were Na + K, Ca and Mg, whilethe main anions were Cl, HCO 3 , SO4 + NO3 .

The groundwater at the northern area of theZarqa aquifer had a relatively high salinity (TDS-7 .5 g/1) mainly with SO 4 whereas at the southernarea it had a relatively low salinity (TDS -5 g/1)with a small SO 4 content. A higher salinity (TDS>9 g/1) was found in the central area most likelybecause the water had been in contact with

Inorganic Maximum limit, mg/1

As 0.01Pb 0.01CN 0.07Cd 0.003Cr 0 .05Ba 1 .5Se 0 .05B 2Hg 0.002Ag 0.1Ni 0.07Sb 0.005F 2NO, 2NO, 50 (70 where no better

source is available)

minerals, e.g ., gypsum, for long time . NaCl in theZarqa aquifer was estimated as 3 g/l. In thesouthern area, the concentrations of scaling sub-stances (Ca, Mg, SO4 , HCO3) were lower, totalhardness was ca. 1 .5 g/1, Si02 was ca. 10 mg/l,and Fe was lower than 5 mg/l. The water qualityappeared to be stable for 10 years, most likelybecause the Zarqa aquifer is probably very oldand receives very few recharges from replenish-able water .

3.3. RO desalination plant

Since there was a considerable amount offouling/scaling substances in the raw water (e.g .,Ca, Mg, Fe, Mn and HCO 3) before RO pro-cessing, a pre-treatment would be required toremove these substances comprising chemicalconditioning and filtering, a more severe pre-treatment than usual for brackish groundwaterdesalination . Thus, with regard to the pre-treatment required, Zarqa aquifer groundwaterseemed not to be the most ideal water resourcefor desalination .

The brackish groundwater would flow fromthe wells to the pre-treatment (degasifier, coagu-lation, dual-media filter) where turbid matter andother foulants/scalants (colloidal matter, micro-organisms, bacteria, oil and grease, ions associa-

Chemical

Raw water Dosing

H2S0

NaCIO FeCl3, NaOH

Antiacalant,NaHS03 NaOH, NaCIO

Degassng1

Coagulation

Fig . 1 . Schematic flow of RO desalination plant [42] .

M.D. Afonso et al. /Desalination 164 (2004) 157-171

161

Dual Media

Filtration

Citric Add

Chemical

Cleaning

ted to CaCO 3 precipitation, corrosive metal ionsand scaling related ions) that might damage ROmembranes would be removed . Subsequently, thewater would be fed to the RO unit where salts andsmall organic contaminants would be rejected andconcentrated in the brine, whereas fresh waterwould permeate through the membranes . Thepost-treatment (chlorination) would comprise pHadjusting and desinfection of desalted water .There would be chemical cleaning facilities formembrane cleaning and wastewater treatmentfacilities for neutralisation and biologicaltreatment of the chemical wastes which would bemixed with the brine for discharge (Fig . 1) .

The pre-treatment aimed to remove turbidity,Ca, HCO3, Fe and residual chlorine [42,45] :•

pH adjusting for HCO3 removal and reductionof water pH to 6 (0 .6 g/l H2SO4 98%)

•

degassing for the removal of dissolved CO,(blower)

•

chlorination for disinfection and oxidation ofFe, Mn and organic matter (5 mg/i NaC1O10%)

•

coagulation and dual-media filtration for tur-bidity removal (24 mg/l FeCl 3 + NaOH)

•

dechlorination for the removal of residual-freechlorine (2 mg/l NaHSO 3 )

•

Antiscalant dosing for scaling prevention(3 mg/1 SHMP or Flocon 100)

V RO unit Water Storage

& Pumping

Brine& Wastewater

Treatment

0supply

discharge

162

Spiral-wound polyamide membrane modulesof 8" diameter were selected on the grounds :•

after pre-treatment, SDI would be ca . 3-4,which is suitable for spiral-wound membranes

•

polyamide membranes provide high fluxes atlow pressures and salt rejections >95% .The RO unit would be operated at 25 bar and

a water recovery ratio of 85% . Despite the pre-treatment, membrane fouling/scaling wouldoccur, leading to the permeate flux drop . Hence,chemical cleaning would be required to recovermembrane performance. The plant maintenancewould comprise the replacement of safety filters(every 3 months), and RO modules (20%/y),membrane cleaning (every 3 months) and prepa-ration of solutions .

The post-treatment aimed to be the finalquality control of drinking water supply :•

pH adjusting, to neutralise water pH fordrinking purposes (20 mg/l NaOH)

•

disinfection, to sterilise water and achieve aresidual chlorine >0 .5 mg/l (NaC1O)The wastewater from the membrane cleaning

should be treated before mixing with the brine forsubsequent disposal, namely through :•

neutralisation by the addition of NaOH•

aeration for biological degradation of organicmatterThe Dead Sea bears an extremely high salinity

(TDS -324 g/1); thus it would be the most suit-able place for the final disposal of RO brine (TDS-25-37.5 g/1). The latter would contain highconcentrations of Ca, Mg, Na + K (main cations),and Cl, SO4, HC03 (main anions). Fe wouldrange between 10-20 mg/1 because the washingwastewater from the dual-media filter holdingferric hydroxide flocks would be mixed with RObrine. The concentration of hazardous substancessuch as heavy metals would be negligible .

3 .4. Desalination costs

The project cost included the construction ofwells, desalination plants and water transfer lines

M.D. Afonso et al. /Desalination 164 (2004) 157-171

to supply areas, besides the plant operation andmaintenance. Water supply in the Jordan Valleyis mainly served by scattered wells, thus a north-south pipeline should be built. Furthermore, adischarge line should also be built for the safedisposal at the Dead Sea of the brine from salinesprings, irrigation returns and drains, and desali-nation plants. The estimated cost for waterdesalination and distribution to the Jordan Valleywas 0 .73-0.84 US$/m3 . It clearly exceeded thecost of water production and supply in 1995, thetap water price being 0 .49 US$/m3 . The projectwould require a government subsidy to ease theburden of capital cost and reduce water pro-duction cost .

4. Experimental

4.1 . Membrane

A FilmTec spiral-wound RO element, FT30SW30-2521 (2 .4" diameter, 21" length), suitablefor saline waters with salt concentrations rangingfrom 2 to 20 g/l, was tested . The membrane activesurface area is 1 .2 m 2 . The FT30 thin-film com-posite membranes have three layers : an ultra-thinbarrier of 1,3-benzenediamine (0 .2 µm thickness),microporous polysulfone and a polyester support .FT30 elements have an outstanding performancehistory for seawater desalination due to thereduced power requirements (high productivity atreasonable cost), reduced leakage of salts, lowmolecular weight organics and silica, increasedresistance to microbiological and bacterialfouling, high tolerance to extreme pHs, long lifespan and FDA approval . The recommended flowrate per pressure vessel housing elements with adiameter of 2 .4" is 684-1140 1/h .

4.2. Set-up

A schematic diagram of the experimental set-up is shown in Fig. 2. It consists of an RO pilotunit assembled by STEM-ISI Impianti (Italy) .

Concentrate

RO module

Fig. 2 . Scheme of RO pilot plant .

4.3. Sampling and pre-treatment

Two brackish water samples (50 and 100 1)were collected from the Hussein thermal powerstation (TPS), located in the Zarqa desert, Jordan .Two other samples were collected from alaboratory tap at the Hashemite University (HU),located in the same area . The brackish waterswere filtrated through a MF cartridge with a 5 µmpore size, inserted in the RO unit, before beingfed to the RO module .

4.4. Brackish water characterisation

Samples from raw and microfiltrated brackishwaters and from the concentrate and permeate ofRO experiments were analysed with respect to pH(25°C), conductivity (25°C), total solids (TS),total dissolved solids (TDS), total suspendedsolids (TSS) and volatile solids (VS), the latterbeing a rough estimate of the organic mattercontent. The analytical equipment used was :•

pH meter (Eutech Instruments, pH 510)•

conductivity meter : Jenway 4310 (KCe1 i = 0 .98)

4.5. Membrane characterisation

Firstly, the membrane was wetted out bycirculating distilled water at 40 bar for 2 h suchthat the excess of chemicals attached to its surfacecould be released and also to prevent its com-

M. D. Afonso et al. /Desalination 164 (2004) 157-171

163

paction throughout the RO experiments. Afterthis conditioning step, distilled water permeatedat pressures ranging from 5 to 40 bar in order tomeasure the respective water permeation fluxes,J., and determine the membrane hydraulic per-meability, I, :

Jw p L1 Poper

4.6. RO permeation experiments

4.6.1 . Selection of RO optimal operatingconditions

A set of permeation runs was carried out withbrackish waters at natural pH, 40°C, and totalrecycle mode (concentrate and permeate recycleinto the feed tank), such that the feed concen-tration was kept nearly constant. The operatingpressure ranged from 15 to 30 bar, whilst the feedflow rate ranged from 200 to 600 1/h. The flowrates were lower than those recommended forelements of 2 .4" diameter (684-1140 1/h) due topump limitations. The permeate flux, J, wasmeasured after 15 min of operation at a given setof operating conditions, and samples from thefeed and permeate were collected for analysis todetermine the rejections, R, with respect to theparameters listed above :

1 Cpermeate \

Cfeed

The pressure was firstly increased, then thefeed flow rate was decreased and lastly the saltconcentration was increased to minimise cumu-lative effects of concentration polarisation and/orfouling/scaling . In between the permeation runs,the membrane was washed out with distilledwater at low pressure and a high flow rate torecover at least 90% of the initial water per-meation flux, Jw .

4.6.2. Time effect on membranefouling/scaling

Another set of permeation runs was performed

R= . 100%

164

with brackish waters at natural pH, 40°C, 20 bar,6001/h, and total recycle mode for 2 h to evaluatethe time effect on membrane fouling/scaling . Thepermeate flux was measured each 15 min ofoperation, but no samples from the feed orpermeate were collected for analysis .

4.6.3. Concentration ofbrackish waters by RORO experiments for brackish water concen-

tration were conducted at natural pH, 40°C, andthe optimal operating pressure and feed flow ratedetermined in Section 4 .6.1, i .e., 30 bar and200 1/h, respectively . The permeate flux wasmeasured for volume reduction factors (VRF) of1, 1 .5, 2, 3, 4 and 4 .4, and samples from theconcentrate and permeate were collected foranalysis .

5. Results and discussion

The hydraulic permeability of membraneSW30-2521 was 1 .6 1/(m2 .h.bar) at 40°C. Thecharacterisation of brackish water samples bothbefore and after MF pre-treatment is presented inTable 4. It may be concluded that the MFcartridge with a 5 p m pore size somewhat re-duced the suspended matter (30-50%), but a

M. D . Afonso et al. /Desalination 164 (2004) 157-171

Table 4Brackish groundwater characterisation and MF rejection (relative to TSS)

tighter MF cartridge or a physico-chemical pre-treatment is recommended to efficiently removethe suspended matter present in the brackishgroundwaters. The high pH of brackish ground-waters (7.9-8 .8) results from the contact withCaCO3 (calcite) and MgCO 3 (dolomite) for a longtime. The high conductivity of brackish waters isdue to their high salinity and hardness. A moredetailed characterisation of brackish ground-waters from the Zarqa basin is presented inTable 5 . They do not show signs of pollution(roughly measured by NO 3 ) due to human acti-vities, cesspools, irrigation return flows, over-exploitation (leading to aquifer salinisation),municipal wastewaters, solid wastes disposal orwastewater treatment plants .

The permeate flux and conductivity rejectionduring RO essays conducted with brackish watersto select the optimal feed flow rate andtransmembrane pressure are displayed in Figs . 3and 4. The time effect on the permeate flux drop(fouling/scaling) is plotted in Fig . 5. The per-meate flux and conductivity rejection duringbrackish waters concentration by RO as a func-tion of the volume reduction factor, VRF, aredepicted in Fig . 6 . Table 6 presents the rejectionswith respect to pH, conductivity, TS, TDS andVS during brackish waters treatment by RO .

Brackish water pH Conductivity, µ.S/cm TS, g/l TDS, g/l TSS, g/l VS, g/l RMF,

Hashemite 8.5 1587 1.028 1 .004 0.024University (HU) 8.4 1568 1 .012 0.948 0.064 0.224HU microfiltrated 7.9 1597 1 .136 1 .120 0.016 33 .3

8 .2 1589 0.984 0.952 0.032 50.0Thermal power station 8.3 3500 2.304 2 .196 0.108 -(TPS) 8.3 3500 2.304 2 .160 0.144 0.972

TPS microfiltrated 8.8 3225 2.364 2.288 0.076 - 29.68.7 3100 2.196 2 .124 0.072 0.476 50.0

50% HU + 50% TPSmicrofiltrated

8.7 2480 1 .620 1.524 0.096

Tabl

e 5

Wate

r qu

alit

y in

wel

ls l

ocat

ed a

t th

e in

dust

rial

are

a of

the

Zar

qa d

eser

t (p

pm)

[46]

cn

Hussein thermal

powe

r st

atio

n (2

/1/2

003)

Petroleum refi

nery

(12

/11/

2002

)ICA

Well

1199

11

23

89

1041991

34

7

1011

991

pH

7.4

7.4

7.4

7.4

7.4

7.3

6.8

6.9

7.2

7.2

EC (µS/cm)

3240

3070

3650

3250

3140

4270

4720

3970

4230 3100

TDS

2880

2074

1965

2336

2080

2010

2733

3072

1632

Si02

1818

1818

1718

25

P0

40.

020.

020.

020.

030.0

30.

02

NH,

0.1

0.1

0.1

0.1

0.1

0.1

b

Cl11

15788

746

958

710

710

987

1154

1610

1330

1260

966

593

0

TH (CaCO

3)750

730

910

720

750

940

1200

860

1050

680

0

NO

350

3838

3737

3939

4525

121

Ca

185

192

230

200

195

207

Mg

8490

102

8486

98-

b

Na

519

380

360

390

410

390

470

553

492

396

398

289

266

Fe0.

10.

10.

10.

040.

070.

10.

030.

030.0

4

0.02

SO,

144

120

135

147

184

276

500

330

530

300

ztK

99

97

77

1110

10

9a

Li0.

20.

20.

20

.20.

20.

2

Alka

lini

ty (CaCO,)

212

216

204

268

308

292

308

480

270

230

0 0

Alkalinity

(HC

O3)

259

263

249

327

376

356

Ca hardnes

s (C

aCO,

)600

460

550

380

vMg hardness (CaC03)

600

400

500 300

vCN

0.08

0.27

0.03

0.02

Zn

0.09

0.1

0.06 0.0

6

Cd

1_10-4

1.10

-42.

10-4210

-4

Pb0.

030.

010.

020.

02

Cu

0.0

050.005

0.00

6 0.0

07

Ni0.

020.

040.

020.

02

Co

0.10

30.

103

0.10

30.

103

Mn

0.2

0.4

0 .1

0.01

166

55 O HU 600/h

O HU 400/h

* HU 200th

X HU+TPS 6001/h

X HU+TPS400/h

O HU+TPS 2001/h

+ TPS 600th

-TPS400/h

IFS 2001/h

15

45-

E Nc 35-

25-

I

10

15

20

OP (bar)

Fig . 3 . Permeate flux during brackish waters treatment byRO at 40°C (HU, 1597 µS/cm ; 50% HU + 50% TPS,2480 µS/cm ; TPS, 3255 µS/cm) .

/ J w 20bar

30'=::=.

`-.~- =

=:== 8

.-: :.

U N

O HUg

0 HU+TPS-' z--_ 20 o TPS

-HUHU+TPS

10

. . ..TPS I

0

20

40

60

80

100

120t (min)

Fig . 5 . Time effect during brackish waters treatment byRO at 20 bar, 6001/h, and 40°C (HU, 1597 µS/cm ; 50%HU + 50% TPS, 2480 16/cm; TPS, 3255 µS/cm) .

The conclusions to be drawn from the datadisplayed in Table 6 and Figs . 3-6 are :

1 . Selection of RO optimal operating con-ditions : The permeate flux, J, increased linearlywith pressure, and the slight deviation between Jand JH, was attributed to the osmotic pressuredifference between the feed and permeatestreams, not to concentration polarisation and/orfouling/scaling. On the other hand, no influenceof the feed flow rate upon the permeate flux wasobserved .

The conductivity, TS and TDS rejectionsduring brackish waters desalination by RO werefairly high and nearly constant irrespective of theoperating conditions (98 .5-100%). The con-ductivity rejection increased as the feed saltconcentration (conductivity) increased, an inter-

M.D. Afonso et al. I Desalination 164 (2004) 157-171

25 30

97

100 -

99 -

98

96

95

1 .0

O HU 6001/h

O HU 4004/h *

* HU 200/h

0

O

X HU+TPS 6001/h

JK HU+TPS 400/h

O HU+TPS 2001/h

+ TPS 6004/h

-TPS 400/h

-TPS 200Uh

10

15

20

25

30AP (bar)

Fig. 4. Conductivity rejection during brackish waterstreatment by RO at 40°C (HU, 1597 K.S/cm ; 50% HU +50% TPS, 2480 AS/cm; TPS, 3255 µS/cm) .

oJHUORHUOJTPSA R TPS

o

Jw3 ,ar

1 .5 2.0 2 .5

3.0

VRF3 .5 4 .0 4 .5

Fig . 6 . Brackish waters concentration by RO at 30 bar,200 I/h, and 40°C (HU, 1589 µS/cm ; TPS, 3100µS/cm) .

esting phenomenon opposite to NF membranesbehaviour .

Since the feed flow rate did not play animportant role on the membrane performance,2001/h was chosen to carry out the concentrationruns instead of 600 1/h, for pumping energysaving. Furthermore, the pressure and tempera-ture during these runs were set at 30 bar and40°C, respectively, to take advantage of theincreased productivity at high pressures andtemperatures .

2. Time effect on membrane fouling/scaling :Once again, the permeate flux was nearly equal tothe pure water permeate flux and remainedconstant for 2 h, even for the brackish ground-water with the highest conductivity (TPS),confirming the great resistance of the FT30membrane to fouling/scaling .

Table 6Rejections during brackish groundwaters treatment byRO

3. Concentration of brackish waters by RO :The rejections with regard to conductivity, TS,TDS, and VS (related to organic matter) wereextremely high and constant (99-100%), irre-spective of the volume reduction factor, i .e .,FT30 membrane efficiently removed inorganicand organic matters from the brackish ground-waters, converting them into potable watersuitable for human consumption (after slightremineralisation, pH adjustment or blending witha small amount of raw water) .

The permeate flux of TPS brackish water waslower than the one of HU brackish water due toits higher salinity and obviously higher osmoticpressure difference across the membrane . Thepermeate fluxes dropped smoothly and linearlywith the increase of the volume reduction factor,e.g ., from 52 to 441/(h •m2) ( 14% drop) at VRF=4.4 (water recovery ratio = 77 .5%) in the case ofHU brackish water; and from 47 to 37 1/(h •m2 )(20% drop) at VRF = 4.0 (water recovery ratio =75%) in the case of TPS brackish water . There-fore, whereas for HU brackish water RO canoperate at water recovery ratios up to 80%, forTPS brackish water it is not reasonable to operateRO beyond 75%; otherwise the permeate fluxdecline is unbearable . The different behaviour ofthe brackish groundwaters should be due to thesettling of the suspended matter present in HUbrackish water, which occurs in a storage tankafter the extraction from the well .

M.D. Afonso et al. /Desalination 164 (2004) 157-171

167

Whenever the membrane hydraulic permea-bility reached 90% of its initial value, it wasimpossible to restore it simply by water washing,meaning that the permeate flux drop (with respectto J.) was mainly due to slight membranefouling/scaling . The membrane hydraulic permea-bility approached its initial value with an acidwashing (0 .5% H 3PO4, 40-44°C, 10 bar, 620 1/h,90 min) . To prevent biological growth during theinstallation shutdowns, the membrane was im-mersed in a protective solution containing 1 .5%sodium bisulphite .

4 . Economic evaluation [31,35,42,47-49] :The economic evaluation of brackish ground-water desalination by RO was based on thefollowing assumptions :•

RO membrane, FilmTec SW30-8040 (poly-amide; spiral-wound module; 28 m2 ; = 1000€/unit)

•

Membrane life span = 5 years (manufacturerguaranteed)

•

Permeate flux = 34 1/(h •m 2 ) ; salt rejection>98 .5%

•

Transmembrane pressure = 30 bar ; feed flowrate = 200 1/h, temperature = 35°C ; pH = 6-9

•

Water recovery ratio = 75% (equivalent toVRF = 4)

•

Flow rate of brackish water = 45 Mm'/y ; flowrate of desalinated water = 33 .75 Mm3/y

•

TDS in brackish water = 2 .3 g/l ; TDS indesalinated water <0 .035 g/l < 0 .5 g/1(JDWS)

•

Daily process duration = 24 h ; load factor =0 .9, i .e ., 330 operation d/y (35-day allowancefor shutdowns due to plant failures, routinemaintenance and membrane cleaning) .

•

Amembrane = 33 .75 . 10 9 1/(330 . 24 h) /341/(h•m )= 125,334 m 2

• Initial investment (including building con-struction, pumps, piping, energy cabling andtransformers, electronic components, auto-mation, membranes, filters, plant design andassembling) - assumed as proportional tomembrane area and depreciated linearly over20 years without considering the interest on

Parameter R (%)(total recycleruns)

R (%)(concentrationruns)

pH 22.3-35.8 19 .5-25.6

Conductivity 98.5-99 .6 99 .2-99.5

TS 98.5-100 99 .6-100

TDS 98.6-100 100

V S 99.0-100

168

M.D. Afonso et al. /Desalination 164 (2004) 157-171

Table 7Chemicals and consumables

investment : 764 €/m2

125,334 m2 =

95,755 k€ (54%)Membrane replacement - every 5 years,hence three times in 20 years: 40 €/m2125,334 m2 • 3 = 15,040 k€ (8%)

•

Maintenance - assumed as 10% of the initialinvestment: 95,755 k€ • 0.1 = 9576 k€ (5%)

•

Energy - neglecting the pumping cost tomake up for the pressure drop along themodule and manifold losses, e.g ., membranefouling :

W = J,,, - Amembrane • AP = (34 . 10-3/ 3600) m/s •125,334 m2 • 30. 105 Pa = 3551 kWElectricity cost = 3551 kW • (24 • 330 • 20 h)

•

0.046 €/(kW •h) = 25,875 k€ (14%)

•

Chemicals and consumables (see Table 7)•

Labour (plant operation and quality control),

administration and overhead - assuming ateam of 30 workers, 10 administrative, 10chemical analysts and three process engineers

and a factor of 2 to account for the overhead :[(30 + 10) • 2698 + 10 • 4796 + 3 • 5995] €/y

•

2 • 20 y = 6955 k€ (4%)

•

Total cost = capital cost + operation andmaintenance costs (per 20 y) = 178,615 k€The estimated cost of brackish groundwater

desalination by RO is 0 .26€/m3 in comparison to0 .19€/m3 , the current price of water supplied bythe Amman municipality . The cost gap is lowerthan expected, bearing in mind the cheap watertreatment practised currently (only chlorination)

and the high cost of importation to Jordan, e .g .,equipment and membranes . The costs gap wouldwiden iff the costs of land, groundwater abstrac-tion, brine disposal, water distribution, and

interests on invested capital had been taken intoaccount. The main cost parcel is the investmentdepreciation (54%), followed by chemicals andenergy (14% each), membrane replacement (8%),maintenance (5%) and labour (4%) . The imple-

mentation of RO desalination in Jordan forpotable water production will most likely requirefinancial contribution from the government tolighten the burden of capital cost and therebyreduce the water production cost to a levelaffordable by the population .

6. Conclusions

In this work, the performance of a spiral-wound RO membrane (FilmTec SW30-2521) wasinvestigated for the production of potable waterfrom brackish groundwaters collected from the

Zarqa basin, Jordan, after being pre-treated by aMF cartridge (5 am) .

Chemicals Dosage, mg/l Consumption, 10 3 ton per 20 y Price, €/kg Total, k€

H2SO4 (98%) 13 11.7 0.13 1,521NaC1O (10%) 5 4.5 0.21 945Antiscalant 3 2.7 1 .06 2,862NaHSO 3 2 1 .8 0.77 1,386FeC13 24 21 .6 0.53 11,448NaOH 20 13.5 0.35 4,725Citric acid 2790, kg/3 months 0.223 1 .17 261Safety filters 17, units/d 112,200 20.2 €/unit 2,266

25,414 (14%)

In total recycle, the permeate flux increasedlinearly with pressure, and the slight deviationbetween J and J,,, was attributed to the osmoticpressure difference across the membrane . Theconductivity, TS and TDS rejections ranged from98.5 to 100% . The membrane performance didnot depend on the feed flow rate, thus theconcentration runs were carried out at 200 1/h,whilst the pressure and temperature were set at30 bar and 40°C, respectively, to take advantageof increased productivity . During the brackishwater concentration by RO, the conductivity, TS,TDS, and VS rejections ranged from 99 to 100%,i .e ., RO is technically suited to remove inorganicand organic matters from the brackish waters andthereby produce potable water . Whether thebrackish groundwaters pre-treatment only usesMF (5 µm), it is not wise to operate RO beyonda 75% water recovery ratio ; otherwise the fluxdecline due to membrane fouling/scaling isdrastic (>20%) . The membrane hydraulic permea-bility could be restored through acid washingwhenever needed . The economic assessmentproved that RO can produce potable water at anoperating cost that is not excessively high(0 .26€/m), especially if the government subsi-dises part of the capital cost .

Further investigation should be focused onbrackish water pre-treatment, and continuousexperiments should be conducted for longerperiods to get insight into a fouling/scalingextension and thereby optimise the washing pro-cedure. It is worthy to note that currently the mostoutstanding technology for treating brackishgroundwaters is nanofiltration (e.g., FilmTecNF70), which was impossible to test in this workdue to the small size of the module assembled inthe pilot unit .

Acknowledgements

We thank the technical staff of the MechanicalEngineering and Chemistry Departments of the

M. D. Afonso et al. / Desalination 164 (2004) 157-171

1 69

Hashemite University, with a special thanks toEngs. S. Amr, 0. Alusta, T. Salameh andM. Mousa for their support throughout theexperiments and chemical analysis, as well as tothe Hussein thermal power station (Eng . M.K .Washahi) and the petroleum refinery at Zarqa,Jordan, for sample collection and providing data .

We acknowledge the Foundation for Science& Technology (FCT) for awarding a sabbaticalgrant to Dr . Dina Afonso under the scope of theCommunitarian Support Framework III, measure-ments 1 .1 and 1 .2 of the Operational Programme"Science, Technology, Innovation" and measure-ment 1 .2 of the Operational Programme "Societyof Information") .

ReferencesJordan National Agenda 21 - Pollution, Environ-mental Management & Public Health Sector - APlan ofAction, Amman, The Hashemite Kingdom ofJordan, 1999 .

[2] R.Y. Ning, Reverse osmosis process chemistryrelevant to the Gulf, Desalination, 123 (1999) 157-164 .B.A. Akash, OR. Al-Jayyousi and M .S . Mohsen,Multi-criteria analysis of non-conventional energytechnologies for water desalination in Jordan,Desalination, 114 (1997) 1-12 .

[4] J.O. Jaber and M.S. Mohsen, Evaluation of non-conventional water resources supply in Jordan,Desalination, 136 (2001) 83-92 .M.S. Mohsen and O.R. Al-Jayyousi, Brackish waterdesalination: an alternative for water supply enhance-ment in Jordan, Desalination, 124 (1999) 163-174 .

[6] O . Al-Jayyousi, Capacity building for desalination inJordan: necessary conditions for sustainable watermanagement, Desalination, 141 (2001) 169-179 .G.L. Amy, B .C. Alleman and C .B . Cluff, Removal ofdissolved organic matter by nanofiltration, J .Environ. Eng., 116 (1990) 200-205 .P. Berg, G . Hagmeyer and R . Gimbel, Removal ofpesticides and other micropollutants by nano-filtration, Desalination, 113 (1997) 205-208 .S. Bertrand, I . Lemaitre and E . Wittmann, Perfor-mance of a nanofiltration plant on hard and highly

[1]

[3]

[5]

[7]

[8]

[9]

170

sulphated water during two years of operation,Desalination, 113 (1997) 277-281 .

[10] J . Bohdziewicz, M. Bodzek and E. Wasik, Theapplication of reverse osmosis and nanofiltration tothe removal of nitrates from groundwater, Desali-nation, 121 (1999) 139-147 .

[11] R. Boussahel, S. Bouland, K.M. Moussaoui andA. Montiel, Removal of pesticide residues in waterusing the nanofiltration process, Desalination, 132(2000)205-209 .

[12] S. Choi, Z. Yun, S . Hong and K. Ahn, The effect ofco-existing ions and surface characteristics of nano-membranes on the removal of nitrate and fluoride,Desalination, 133 (2001) 53-64 .

[13] W .J . Conlon, Pilot field test data for prototype ultralow pressure reverse osmosis elements, Desalination,56(1985)203-226 .

[14] B. Ericsson and B . Hallmans, Membrane applicationsin raw water treatment with and without reverseosmosis desalination, Desalination, 98 (1994) 3-16 .

[15] B. Ericsson, M . Hallberg and J. Wachenfeldt, Nano-filtration of highly colored raw water for drinkingwater production, Desalination, 108 (1996)129-141 .

[16] I .C . Escobar, S . Hong and A.A. Randall, Removal ofassimilable organic carbon and biodegradable dis-solved organic carbon by reverse osmosis and nano-filtration membranes, J . Membr. Sci ., 175 (2000)1-17 .

[17] Y. Garba, S. Taha, N. Gondrexon, J . Cabon andG. Dorange, Mechanisms involved in cadmium saltstransport through a nanofiltration membrane : charac-terization and distribution, J . Membr. Sci., 168(2000) 135-141 .

[18] A. Hafiane, D . Lemordant and M . Dhahbi, Removalof hexavalent chromium by nanofiltration, Desali-nation, 130 (2000) 305-312 .

[19] J .A.M.H. Hofman, E.F. Beerendonk, H .C. Folmerand J.C. Kruithof, Removal of pesticides and othermicropollutants with cellulose-acetate, polyamideand ultra-low pressure reverse osmosis membranes,Desalination, 113 (1997) 209-214 .

[20] S. Kimura, Analysis of reverse osmosis membranebehaviors in a long-term verification test, Desali-nation, 100 (1995) 77-84 .

[21] Y. Kiso, Y . Nishimura, T . Kitao and K . Nishimura,Rejection properties of non-phenylic pesticides withnanofiltration membranes, J . Membr. Sci., 171

M.D. Afonso et al. /Desalination 164 (2004) 157-171

(2000) 229-237 .[22] Y. Kiso, Y. Sugiura, T . Kitao and K . Nishimura,

Effects of hydrophobicity and molecular size onrejection of aromatic pesticides with nanofiltrationmembranes, J . Membr. Sci ., 192 (2001) 1-10 .

[23] Z.V.P. Murthy and S .K. Gupta, Sodium cyanideseparation and parameter estimation for reverseosmosis thin film composite polyamide membrane,J. Membr. Sci ., 154 (1999) 89-103 .

[24] A.G. Pervov, Y.V. Reztsov, S .B. Milovanov, V .S .Koptev and A.G. Melnikov, Production of qualitydrinking water with membranes, Desalination, 108(1996) 167-170.

[25] R. Rautenbach and A. Groschl, Separation potentialof nanofiltration membranes, Desalination, 77 (1990)73-84 .

[26] R. Rautenbach, T . Linn and D .M.K. Al-Gobaisi,Present and future pretreatment concepts - strate-gies for reliable and low-maintenance reverse osmo-sis seawater desalination, Desalination, 110 (1997)97-106 .

[27] J.A. Redondo, Brackish-, sea- and wastewaterdesalination, Desalination, 138 (2001) 29-40 .

[28] J .A. Redondo, Development and experience withnew FILMTEC reverse osmosis membrane elementsfor water treatment, Desalination, 108 (1996) 59-66 .

[29] G.T. Szabo, G. More and Y. Ramadan, Filtration oforganic solutes on reverse osmosis membrane . Effectof counter-ions, J . Membr. Sci ., 118 (1996) 295-302 .

[30] J .S. Taylor, D .M. Thompson and J .K. Carswell,Applying membrane processes to groundwatersources for trihalomethane precursor control, J .AWWA, 79(8) (1987) 72-82 .

[31] B . Van der Bruggen, K . Everaert, D. Wilms andC. Vandecasteele, Application of nanofiltration forremoval of pesticides, nitrate and hardness fromground water: rejection properties and economicevaluation, J . Membr. Sci., 193 (2001) 239-248 .

[32] B . Van der Bruggen, J . Schaep, W. Maes, D. Wilmsand C . Vandecasteele, Nanofiltration as a treatmentmethod for the removal of pesticides from groundwaters, Desalination, 117 (1998) 139-147 .

[33] B. Van der Bruggen, J . Schaep, D . Wilms andC. Vandecasteele, Influence of molecular size,polarity and charge on the retention of organic mole-cules by nanofiltration, J . Membr. Sci ., 156 (1999)29-41 .

[34] C. Ventresque and G. Bablon, The integrated nano-filtration system of the Mery-sur-Oise surface watertreatment plant (37 mgd), Desalination, 113 (1997)263-266 .

[35] C. Ventresque, V . Gisclon, G . Bablon and G. Chag-neau, An outstanding feat of modem technology : theMery-sur-Oise nanofiltration treatment plant(340,000 m'/d), Desalination, 131 (2000) 1-16 .

[36] N.G. Voros, Z .B. Maroulisand and D . Marinos-Kouris, Salt and water permeability in reverseosmosis membranes, Desalination, 104 (1996) 141-154 .

[37] B.M. Watson and C .D. Homburg, Low-energymembrane nanofiltration for removal of color, or-ganics and hardness from drinking water supplies,Desalination, 72 (1989) 11-22 .

[38] H. Winters, Twenty years experience in seawaterreverse osmosis and how chemicals in pretreatmentaffect fouling of membranes, Desalination, 110(1997)93-96 .

[39] E. Wittmann, P . Cote, C . Medici, J. Leech and A.G.Turner, Treatment of a hard borehole water contain-ing low levels of pesticide by nanofiltration,Desalination, 119 (1998) 347-352 .

[40] A. Yaroshchuk and E. Staude, Charged membranesfor low pressure reverse osmosis properties andapplications, Desalination, 86 (1992) 115-134 .

[41] C.K. Yeom, S.H. Lee and J.M. Lee, Effect of theionic characteristics of charged membranes on thepermeation of anionic solutes in reverse osmosis,J. Membr. Sci., 169 (2000) 237-247 .

M.D. Afonso et al. /Desalination 164 (2004) 157-1 71 171

[42] Japan International Cooperation Agency (JICA), Thestudy on brackish groundwater desalination in Jordan- Final Report (Summary and Main Reports),Ministry of Water and Irrigation, Amman, TheHashemite Kingdom of Jordan, 1995 .

[43] Jordanian Standards JS 286 : 2001, Water -Drinking Water, 4th ed., Department of Standardsand Specifications, Amman, The Hashemite King-dom of Jordan, 2001 .

[44] Annual Environmental Statistic 2000, Department ofStatistics, Amman, The Hashemite Kingdom ofJordan, 2000 .

[45] J. Kucera, Properly apply reverse osmosis, Chem .Eng. Progress, 93(2) (1997) 54-6 1 .

[46] E. Salameh and H. Bannayan, Water resources ofJordan - present status and future potentials, RoyalSociety for the Conservation of Nature, FriedrichEbert Stiftung, Amman, Jordan, 1993 .

[47] G. Filteau and P. Moss, Ultra-low pressure ROmembranes: an analysis of performance and cost,Desalination, 113 (1997) 147-152 .

[48] A. Poullikkas, Optimization algorithm for reverseosmosis desalination economics, Desalination, 133(2001) 75-81 .

[49] Y. Al-Wazzan, M. Safar, S . Ebrahim, N. Burneyand A. Mesri, Desalting of subsurface water usingspiral-wound reverse osmosis (RO) system : technicaland economic assessment, Desalination, 143 (2002)21-28 .