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3 Application of Synthetic Membranes in Water Supply Systems in Israel P. GLUECKSTERN, Y. KANTOR, and M. WILF Downloaded by UNIV OF CALIFORNIA SAN DIEGO on June 2, 2015 | http://pubs.acs.org Publication Date: May 21, 1981 | doi: 10.1021/bk-1981-0153.ch003

Mekorot Water Co. Ltd., Tel-Aviv, Israel

Israel is already exploiting a l l of its limited drinking water sources and reduction of the amount of potable water supplied to agriculture is being seriously considered. During the next decade substantial additional water quantities will come from sewage reclamation. These will release some of the potable water used in agriculture for the increasing demand of municipal water supply. The next step in water development would have to be the desalination of remaining undeveloped brackish water resources as well as seawater. Presently, desalination is used to sovle regional water supply problems, especially at remote locations which are not yet connected to the national water supply grid. The aim o f t h i s paper i s to d i s c u s s and analyze the f o l l o w i n g topics: (a) the r o l e o f d e s a l i n a t i o n i n s o l v i n g r e g i o n a l water supply problems, emphasizing the c h r o n o l o g i c a l steps of i n t r o d u c i n g reverse osmosis technology f o r t h i s purpose. (b) the comparative economics of RO b r a c k i s h water d e s a l t i n g as an a l t e r n a t i v e to the o l d e r thermal d e s a l t i n g plants. (c) d i s c u s s i o n o f the most probable d e s a l t i n g options f o r long-term a p p l i c a t i o n and p r e p a r a t i o n o f technology and operating experience f o r t h i s purpose. (d) o v e r a l l economic a n a l y s i s of d e s a l t i n g options and conc l u s i o n s regarding the most promising technology f o r near and long-term a p p l i c a t i o n . Present Status Of D e s a l t i n g In I s r a e l With one exception a l l operating p l a n t s were b u i l t at l o c a t i o n s not connected to the n a t i o n a l water g r i d . The l a r g e s t center i s i n E i l a t a small town located on the Red Sea shore. In E i l a t and at other s i t e s i n S i n a i l o c a t e d on the sea shore, seawater feed i s used. At a l l other s i t e s b r a c k i s h feed water i n the range of 2400 to 6000ppm TDS are d e s a l t e d . 0097-6156/81/0153-0063$05.00/0 © 1981 American Chemical Society

In Synthetic Membranes:; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

Downloaded by UNIV OF CALIFORNIA SAN DIEGO on June 2, 2015 | http://pubs.acs.org Publication Date: May 21, 1981 | doi: 10.1021/bk-1981-0153.ch003

64

SYNTHETIC MEMBRANES:

DESALINATION

The f i r s t commercial d e s a l t i n g u n i t with a c a p a c i t y o f about 4000 c u . m/day has been o p e r a t i n g i n E i l a t s i n c e 1965. By the end of 1979, 22 u n i t s with a combined c a p a c i t y of 20,000 cu. m/day were operating or used as stand-by u n i t s at 11 s i t e s . A l l commercial types of p r o c e s s e s , with the exception of f r e e z i n g , namely, d i s t i l l a t i o n , reverse osmosis and e l e c t r o d i a l y s i s , are being a p p l i e d i n the above u n i t s ; with various kinds of d i s t i l l a t i o n processes being used f o r seawater d e s a l t i n g . Two o f them, h o r i z o n t a l tube m u l t i e f f e c t d i s t i l l a t i o n and vapor compression u n i t s were developed and manufactured l o c a l l y by the I s r a e l D e s a l i n a t i o n Engineering L t d . R e c e n t l y , two small RO u n i t s with a combined c a p a c i t y o f approx. 100 c u . m/day were a l s o used to d e s a l t seawater. The main aim of these u n i t s i s to t e s t and demonstrate the f e a s i b i l i t y o f t h i s new technology. 11 out of the 12 b r a c k i s h water d e s a l t i n g u n i t s , with a combined c a p a c i t y o f 4500 c u . m/day, are u s i n g the RO p r o c e s s . Some o f the s m a l l e r RO u n i t s , which supply d r i n k i n g water to small and r e mote communities have a c a p a c i t y of about 15 c u . m/day, while each of three l a r g e r RO u n i t s has a c a p a c i t y o f 1200 c u . m/day. These three u n i t s d e s a l t i n g b r a c k i s h water o f about 6000 ppm TDS comprise the current stage o f an expanding RO d e s a l t i n g s i t e near E i l a t . At the f i n a l stage the RO systems w i l l replace a l l c u r r e n t l y operat i n g seawater d i s t i l l a t i o n p l a n t s at E i l a t . The main reason f o r r e p l a c i n g these thermal u n i t s , which are s t i l l i n good operating cond i t i o n and can be considered as r e l i a b l e water supply f a c i l i t i e s i s t h e i r p r o h i b i t i v e energy consumption. It i s g e n e r a l l y accepted that the energy r e q u i r e d f o r d e s a l t i n g b r a c k i s h feeds by the RO process i s much lower than f o r any thermal d e s a l t i n g p r o c e s s . The s p e c i f i c energy consumptions o f the four d i f f e r e n t d e s a l t i n g u n i t s c a l c u l a t e d from a c t u a l running c o n d i t i o n s and compared i n F i g . 1, i l l u s t r a t e t h i s p o i n t - T h e s p e c i f i c energy requirement o f the multistage f l a s h u n i t s , coupled to an o l d power station, expressed i n e q u i v a l e n t Kwhr/cu. m/day u n i t s , i s shown for three d i f f e r e n t operating modes: (a) without power g e n e r a t i o n , as operated p r e s e n t l y , because the I s r a e l E l e c t r i c Company came to the c o n c l u s i o n that i t i s uneconomic to operate the power s t a t i o n . (b) without power generation but a f t e r r e b u i l d i n g the two u n i t s i n t o a s i n g l e more e f f e c i e n t u n i t , more or l e s s to the l i m i t o f current technology. (c) same as ( b ) , but making use of the e x i s t i n g t u r b i n e to generate power f o r a l l pumping requirements. The l a s t two operating modes r e q u i r e s e v e r a l m o d i f i c a t i o n s which have not yet been made. By comparing the most e f f i c i e n t dual-purpose operating mode with the t o t a l s p e c i f i c energy consumption o f the RO u n i t s i t i s q u i t e c l e a r that the d i f f e r e n c e i s more than an order of magnitude. It i s t h e r e f o r e not s u r p r i s i n g that at the p r e v a i l i n g energy p r i c e s , the replacement o f thermal d e s l a t i n g i s not only a t t r a c t i v e , but an economic must.


GLUECKSTERN E T AL.

Synthetic Membranes

in Israel


44

Cu

o

?2 r

*AFTER MODIFICATION INCL. POWER RECOVERY

UJ Cu UJ O U

£

OS Su2 C H UJ

O

1.5

Cu z 2: m

Figure 1.

TWO 1 MGD MSF DUAL-

1-MGD LOW TEMP.

1-3 MGD BRACKISH

PURPOSE PLANTS

MED PLANT

RO PLANT

JZL

SMALL RO UNIT OPERATED WITH LINE PRESSURE

Energy requirements of commercial desalting plants in Israel



66

DESALINATION

The a c t u a l saving already o b t a i n e d , and those p r e d i c t e d f o r the next y e a r , due to the implementation o f RO technology i n E i l a t are shown i n Table I . Table I:

Energy saved by implementation of RO to r e p l a c e thermal d e s a l t i n g i n E i l a t


Energy Cost For Thermal D e s a l t i n g : Annual Comsumption - 2.5 x 10^ Cubic Meter Annual Energy Cost - $ 5 x 10 $ 1000 Per Family. Saving by Replacement: F i s c a l Year 1980 1981

T o t a l Annual $ $

2 x 10^ 4x10

Annual per Family $ 400 $ 800

Implementation Of RO Technology In I s r a e l Brackish Water D e s l a t i n g . In the e a r l y 1970 Mekorot, the n a t i o n a l water s u p p l i e r , recognized the advantages o f membrane des a l t i n g p r o c e s s e s , e s p e c i a l l y RO i n r e g i o n a l water s u p p l i e s , and s t a r t e d an a p p l i e d research and e v a l u a t i o n program p r i o r to commerc i a l a p p l i c a t i o n . A f t e r t h e o r e t i c a l economic evaluations (1), a t e s t s i t e was e s t a b l i s h e d and most commercial b r a c k i s h water technologies were f i e l d t e s t e d (2). The r e s u l t s obtained d u r i n g approximately two years of t e s t o p e r a t i o n , j u s t i f i e d the a p p l i c a t i o n of RO technology f o r a c t u a l water supply. The small u n i t s used i n the program were t r a n s f e r r e d to remote l o c a t i o n s to supply d r i n k i n g water. Larger p l a n t s were considered f o r the growing water demand o f E i l a t . Due to the r i s i n g energy p r i c e s , Mekorot q u i c k l y came to the c o n c l u s i o n that RO d e s a l t i n g o f the l o c a l b r a c k i s h water should be used a l s o to replace the d i s t i l l a t i o n u n i t s . Consequently a large RO u n i t was designed and erected at E i l a t . The f i r s t phase o f development, c o n s i s t i n g o f a 700 c u . m/day u n i t , began commercial operation i n March 1978 (3). As already mentioned, three u n i t s , with combined c a p a c i t y of 3600 c u . m/day are operating p r e s e n t l y . This c a p a c i t y i s now being expanded to 7000 c u . m/day and by the end o f the next year the t o t a l d i s t i l l a t i o n c a p a c i t y w i l l be r e p laced by an operating 10,000 c u . m/day RO p l a n t . The c h r o n o l o g i c a l steps o f the implementation of RO technology i n I s r a e l are shown i n F i g . 2.

for

Seawater D e s a l t i n g . In 1977 Mekorot a l s o s t a r t e d a program the e v a l u a t i o n o f RO f o r seawater d e s a l t i n g (4). P r e s e n t l y



1972

EVALUATION OF RO TECHNOLOGY

Figure 2.

RO

1978

3

PROCUREMENT & ERECTION

ISOm / d

COMMERCIAL MEMBRANES POWER RECOVERY

1980

1982

OF A RO SEAWATER DEMONSTRATION PLANT (RED SEA AND/OR MEDITERRANEAN S I T E )

3

80m /d

3

Research and implementation of RO technology by Mekorot Water Co. in Israel

1976

3

10m /d

SYSTEM

COMMERCIAL MEMBRANES POWER RECOVERY

3

700m /d 3,600 i» /d 10,000m /d HOLLOW FIBER $ SPIRAL WOUND TECHNOLOGY

EXPERIMENTAL RO SEAWATER

SEMICOMMERCIAL MEMBRANES

NUMEROUS SMALL PLANTS AT REMOTE LOCATIONS

OPERATION OF SABHA PLANT

TEST EQUIPMENT RELOCATED TO REMOTE SETTLEMENTS FOR WATER SUPPLY

BRACKISH WATER SYSTEM AT SABHA S I T E

DESIGN OF COMMERICAL

SABHA S I T E DU-PONT GENERAL ATOMIC DOW

EASTMAN KODAK DU PONT GENERAL ATOMIC ISRAEL DESALTING ENG.

TECHNOLOGY

EILAT SITE

FIELD TESTING OF RO BRACKISH WATER

1974

FOR DESALTING

NUMEROUS PUBLICATIONS, COST EVALUATIONS AND DESIGN OPTIMIZATIONS OF REVERSE OSOMOSIS DESALINATION PLANTS

ECONOMIC



68

DESALINATION

two small u n i t s with a combined c a p a c i t y o f about 100 cu. m/day are operated on the Red Sea shore. Along with other steps t h i s operation i s e s s e n t i a l i n order t o be ready to s e l e c t RO f o r large s c a l e seawater d e s a l t i n g i n the f u t u r e i f the water supply i n I s r a e l w i l l have t o depend p a r t i a l l y on d e s a l t i n g and RO w i l l t u r n out t o be the more competitive means f o r t h i s purpose. The object i v e s o f the e v a l u a t i o n program are shown i n Table I I :


Table I I :

O b j e c t i v e s o f RO e v a l u a t i o n program

1.

Gain Operating Experience With RO Equipment Under A c t u a l F i e l d Conditions.

2.

Confirm The Adequacy Of A l l System Components And Evaluate O v e r a l l System R e l i a b i l i t y .

3.

Compare Under P a r a l l e l Operation The Performance Of Leading RO Seawater Technologies.

4.

E s t a b l i s h Minimum Pretreatment Conditions.

5.

E s t a b l i s h Operating Experience And Demonstrate A p p l i c a b i l i t y of Power Recovery Systems.

6.

Evaluate The Economics Of Ro Seawater D e s a l t i n g Based On A c t u a l F i e l d Experience.

Requirements For Local

These o b j e c t i v e s are s i m i l a r to those o f the previous b r a c k i s h water RO e v a l u a t i o n program, with g r e a t e r emphasis being p l a c e d on power recovery, due t o the higher energy consumption o f seawater desalting. The r e s u l t s obtained were p a r t i a l l y r e p o r t e d elsewhere (4) and they are q u i t e s i m i l a r t o those obtained at other experimental s i t e s . Results o f long term performance, some o f them approaching 10,000 hours are shown i n F i g . 3 and F i g . 4. As can be seen i n F i g . 3 the i n i t i a l p r o d u c t i v i t y values f o r a l l membranes were b e t t e r than the s p e c i f i e d nominal values and continued to be b e t t e r than p r e d i c t e d . The r e s u l t s shown i n F i g . 4 i n d i c a t e d that the normalized r e j e c t i o n o f t h e membranes t e s t e d , except f o r one o f the hollow f i b e r membranes was b e t t e r o r w i t h i n the l i m i t s s p e c i f i e d by the membrane producers. One o f the membranes that showed an i n i t i a l l y low r e j e c t i o n was s u c c e s s f u l l y r e s t o r e d t o the nominal value a f t e r treatment as recommended by the manufacturer. The next step i n the seawater RO development program w i l l be to construct and operate a large demonstration p l a n t with a c a p a c i t y of s e v e r a l thousand cubic meters per day. This p l a n t w i l l be b u i l t at a s i t e on the Mediterranean Sea shore. T h i s sea i s much more p o l l u t e d than the Red Sea and one o f the more important o b j e c t i v e s



50

200

Figure 3.

.

1000

£i

mA •

A JT A A A

10,000

PROJECTED PRODUCTIVITY DECLINE

Productivity vs. operating time for seawater membranes tested at Eilat site

CUMULATIVE OPERATING TIME, HR.

• • • • •A • •A A A A

A

LOW FIBER • O HOL A A spi RAL WOUND


100

200

300

OS

2

w H >

50 2:

H W

a r C m o


—

—

—

~

0

.1

0

%

Figure 4.

^

•

1

o

1

—

o

o

1

o

0

1

o

A

9m9 0 #

1

#

#

*

44 44

OPERATING

1

1 TIME, HR.

6000

r -

1

GUARANTEE LIMIT

i

* *A

r

8000

GUARANTEE LIMIT

••

A A A

HOLLOW FIBER ELEMENTS

° ° ° ° o

1

SPIRAL WOUND ELEMENTS

CUMULATIVE

o

0

"

••••

*

4000

•

o

*

1

A

i

i

Normalized salt rejection vs. operating time for seawater membranes tested at Eilat site

2000

1

SPIRAL WOUND

HOLLOW FIBER

— ——

0

1


-

-


3.

GLUECKSTERN ET AL.

Synthetic

Membranes

in Israel

71

of the demonstration p l a n t i s to i n v e s t i g a t e the pretreatment problems encountered with t h i s type of feed water. At a l a t e r date the demonstration p l a n t w i l l probably be t r a n s f e r r e d to E i l a t , where the value o f d e s a l t e d water i s much h i g h e r . The a c t u a l f i e l d r e s u l t s w i l l enable to make a more r e a l i s t i c comparison between RO and other d e s a l t i n g technologies and f a c i l i t a t e the s e l e c t i o n o f the best a l t e r n a t i v e at the date when large s c a l e d e s a l t i n g can not be f u r t h e r postponed. At t h i s stage no d e f i n i t e answer can be given about the date and r e q u i r e d c a p a c i t y , but i t i s g e n e r a l l y accepted that by the end o f the c e n t u r y , I s r a e l w i l l have to develop 500 to 700 m i l l i o n cubic meters o f a d d i t i o n a l water c a p a c i t y . Of t h i s 100-200 m i l l i o n cubic meters would probably have to be s u p p l i e d by d e s a l t i n g . At l e a s t a p a r t o f the r e q u i r e d c a p a c i t y w i l l be obtained by d e s a l t i n g b r a c k i s h waters which can not be used d i r e c t l y f o r a g r i c u l t u r e . The i n v e n t o r y o f a l l b r a c k i s h water resources i s not completed as y e t , but the d e f i n i t e advantage of b r a c k i s h water d e s a l t i n g over seawater d e s a l t i n g , makes i t e s s e n t i a l to c a r r y out a comprehensive h y d r o l o g i c a l survey o f b r a c k i s h water p o t e n t i a l i n the country. A f t e r f u l l u t i l i z a t i o n o f the b r a c k i s h water feed the r e s t of the r e q u i r e d c a p a c i t y would have to be obtained by seawater d e s a l t i n g . It was common b e l i e f i n the past that the most f e a s i b l e t e c h nology f o r l a r g e s c a l e d e s a l t i n g would be seawater d i s t i l l a t i o n combined with power generation i n l a r g e dual-purpose p l a n t s . In the last few years t h i s has changed, mainly because o f the r a p i d p r o gress i n RO technology, and the g r a d u a l l y i n c r e a s i n g r e c o g n i t i o n t h a t , due to v a r i o u s reasons, large dual-purpose p l a n t s would not always be the best a p p l i c a b l e s o l u t i o n . Economic Comparison The comparison between the two major seawater d e s a l t i n g a l t e r n a t i v e s , reverse osmosis and d i s t i l l a t i o n , i s more complex then ever. The l o c a t i o n , system s i z e , time of implementation and economic parameters, e s p e c i a l l y the p r i c e o f conventional energy and a l s o the p o s s i b i l i t y o f use o f non-conventional energy i n the f u t u r e , such as s o l a r or geothermal energy s o u r c e s , may g r e a t l y a f f e c t the f i n a l d e c i s i o n . Non conventional energy options f o r d e s a l t i n g may e v e n t u a l l y be a p p l i e d by u t i l i z i n g s o l a r or geothermal heat coupled t o low temperature m u l t i e f f e c t d i s t i l l a t i o n p l a n t s and g r a v i t y pressure o f the feed water may e v e n t u a l l y be a p p l i e d as a p a r t i a l power source for RO p l a n t s l o c a t e d at the Dead Sea, i n c o n j u n c t i o n with the p r o posed Mediterranean-Dead Sea H y d r o e l e c t r i c P r o j e c t . A conceptual combination scheme o f t h i s a l t e r n a t i v e i s shown i n F i g . 5. In t h i s scheme the i n l e t o f the process pump i s connected to the r e g u l a t i n g r e s e r v o i r o f the h y d r o e l e c t r i c p l a n t through the reverse osmosis f i l t r a t i o n system. Pumping power i s r e q u i r e d only to b u i l d up the d i f f e r e n t i a l pressure between the d e f i n e d o p e r a t i n g pressure of the RO membranes and the a v a i l a b l e h y d r o s t a t i c pressure at the pump



72

SYNTHETIC MEMBRANES: DESALINATION

i n l e t . The power recovery turbine,shaft-connected d i r e c t l y to the process pump, i s designed t o use the excess head o f the r e j e c t b r i n e above that r e q u i r e d to l i f t the b r i n e back t o the r e g u l a t i n g r e s e r v o i r . The energy balance f o r the 40 MGD Plant shown on F i g . 5 i n d i c a t e s a very low energy requirement o f approx. 2 Kwhr/cu. m. This f i g u r e does not i n c l u d e however pumping power to l i f t the product water t o consumers l o c a t e d at l e v e l s higher than the Dead Sea. A summary o f a l l f e a s i b l e d e s a l t i n g options f o r I s r a e l , subd i v i d e d according t o the energy source, feed type and d e s a l t i n g technology i s given i n Table I I I : Table I I I :

Desalting alternatives f o r I s r a e l .

I

Conventional Energy: 1. RO 1.1 Brackish Water Up To 8000 ppm TDS 1.2 Reject Brine or High S a l i n e Brackish Water 1.3 Seawater 2. Low Temperature M u l t i - e f f e c t D i s t i l l a t i o n (LTMED) Combined With Power Generation (Dual-Purpose)

II

Non-Conventional Energy: 1. S o l a r LTMED 2. Geothermal LTMED 3. RO U t i l i z i n g H y d r o s t a t i c Pressure o f Feed Water 3.1 RO Seawater D e s l a t i n g In Conjunction With the Mediterrnanean - Dead Sea H y d r o e c l e c t r i c P r o j e c t . 3.2 RO Brackish (Or Reject Brine) Located At The Dead Sea

The energy requirements and a summary o f the c o s t i n g o f the l i s t e d a l t e r n a t i v e s , based on large c a p a c i t y p l a n t s i n the range of 100,000 cu. m/day f o r seawater d e s a l t i n g and 20,000 cu. m/day or l a r g e r f o r b r a c k i s h feeds, are shown i n Table IV. The r e s u l t i n g u n i t water c o s t s , were obtained by applying a 12 percent f i x e d charge rate and a u n i t power cost o f 4.5 cents per k i l l o w a t t - h o u r which i s p r e d i c t e d to be a p p l i c a b l e i n the e a r l y n i n e t i e s . I t can be seen that f o r these economic ground r u l e s , the cost o f d e s a l t e d water from seawater, RO and dual-purpose p l a n t s are i n the same range o f 60 i to 70 i per cubic meter. The s p e c i f i c investments and energy consumption are considerable lower f o r RO but i t s higher o p e r a t i o n and maintenance cost, due mainly t o membrane replacement, counterbalance the lower c a p i t a l and energy cost of the p l a n t s u s i n g current RO technology. As f o r non-conventional energy, only u t i l i z a t i o n o f the feed g r a v i t y pressure i n RO systems seems to have an economic advantage when compared with the conventional energy o p t i o n evaluated with



Figure 5.

20,975 n i / h i PRETREATMENT

FILTRATION 33Kg/cm'

TURBINE

RECOVERY

T3.

JUL

MOTOR

ELECTRIC

I

PUMP

HIGH PRESSURI 70 Kg/cni

14,680 in /hr

1.98

12,500 * excl.motor losses

-1.91

-12,040

3.81*

SYSTEM

RO MEMBRANE

35

14,680

Power recovery turbines

KWh/m

24,040

3

SPEC.POWER

KW

POWER

REQUIREMENT

Connection diagram of a 40-mgd (151,000 cu m/d) RO plant to be operated in conjunction with the proposed Mediterranean-Dead Sea hydroelectric project

2

35 Kg/cm

LEVEL

DEAD SEA

37

20,975

High pressure pumps

E l e c t r i c motor power(@ 96% e f f i c . )

Kg/cm

2

HEAD

ENERGY

FLOW

MASS BALANCE + SPECIFIC

m Ahr

340 m



Source

25-35

Unit Water Cost,* cents/ cu. m 35-50

12-18

1.0-1.4

2.5-3.5

60-70

22-25

1.7-2.1

4.0-5.0

RO

* @ 12% f i x e d charge r a t e and 4.5 £/Kwhr power cost.

10-12

.6-1.0

1.5-2.0

RO

60-70

4-5

2.3-2.8

6.5-7.5

LTMED DualPurpose

S e a w a t e r 42,000

Conventional

B r a c k i s h 2-6,000 8-12,000

cent.cu. m

Operation § Maintenance Cost (Incl.chemicals and membrane replacement),

S p e c i f i c Investment $/cu. m - year

S p e c i f i e c Energy Req., Kwhr/cu. m

Process

Feed Source ppm TDS

Energy

65-90

4-5

1.9-2.1 excluding

-

65-100

4-5

1.9-2.1 energy

LTMED GeoSolar thermal

S e a w a t e r 42,000

50-60

22-25

1.6-2.0

2.0-2.5

25-40

12-18

.9-1.5

0.5-1.5

RO H y d r o s t a t i c Press, (Dead Sea)

B r a c k i s h 10,000

Non-Convent i ona1

Table IV: Energy requirements and c o s t i n g o f d e s a l t i n g a l t e r a n t i v e s f o r I s r a e l (current or near-term technology)



;

* @ 12% f i x e d charge r a t e

12--25 20--34

5--7

Operation § Maintenance Cost ( i n c l . c h e m i c a l s and membrane replacement), cents/cu. m

Unit Water Cost,* cents/ cu. m @ 4.5 cents/Kwhr @ 9 cents/Kwhr

.5--.8

1.0--2.0

RO

25-35 32-44

8-10

.8-1.2

1.5-2.0

B r a c k i s h 2-6 ,000 8-12,000

S p e c i f i c Investment $/cu. m - year

S p e c i f i c Energy Req., Kwhr/ cu. m

Process

Feed Source ppm TDS

40-50 54-68

12-15

1.2-1.4

3.0-4.0

RO

50-60 62-87

3-4

2.0-2.5

5.0-6.0

LTMED DualPurpose

S e a w a t e r 42,000

Conventional

Geothermal

50-80 50-80

3-4

50-80 50-80

3-4

1.8^2.0 1.8-2.0 e x c l u d i n g energy source

-

Solar

LTMED

S e a w a t e r 42,000

s h

30-40 37-49

12-15

1.0-1.3

1.5-2.0

20-30 22-37

8-10

.8-1.1

0 .5-1.5

RO H y d r o s t a t i c Press (Dead Sea)

B r a c k i 10,000

Non-Conventional

Energy requirements and c o s t i n g o f d e s a l t i n g a l t e r n a t i v e s f o r I s r a e l (advanced technology).

Energy Source

Table V:



76

SYNTHETIC MEMBRANES: DESALINATION

the r a t h e r o p t i m i s t i c energy p r i c e s . The e f f e c t of d i f f e r e n t energy p r i c e s : low (4.5 £/Kwhr)and high (9£/Kwhr), on product water cost obtained by p r o j e c t e d technologies i s shown i n Table V. This comp a r i s o n i s based on more advanced t e c h n o l o g i e s , such as less expens i v e and more e f f i c i e n t membranes, and p a r a l l e l improvements i n the d i s t i l l a t i o n technology. It i s b e l i e v e d that RO has more p o t e n t i a l f o r f u r t h e r improvments. This i s r e f l e c t e d by the comparative f i g u r e s shown. Due to i t s lower energy requirement RO i s l e s s a f f e c t e d by i n c r e a s i n g energy p r i c e s and i s s i g n i f i c a n t l y more competitive i n t h i s undes i r a b l e s i t u a t i o n . RO has i n a d d i t i o n s e v e r a l more advantages which are o u t l i n e d i n Table VI. Table VI:

Main advantages o f RO technology i n comparison to other a l t e r n a t i v e s

1.

Lower Energy Requirement Than Any Dual-Purpose P l a n t s .

Other Process,

Including

2.

S i z i n g , Timing and Location Of D e s a l t i n g Plants Are Not Dependent On The Development Of the N a t i o n a l Power G r i d .

3.

Capacity Can Be Staged According Time A f t e r D e c i s i o n .

4.

Large P o t e n t i a l For

5.

Large P o t e n t i a l For Improvement.

6.

Technological Plants.

To Demand Within a Short

Flexibility.

Improvement Can A l s o Be A p p l i e d In

Operating

Some o f the l i s t e d f a c t o r s are very important f o r I s r a e l ' s c o n d i t i o n s and t h e r e f o r e the RO technology w i l l probably be the most s u i t a b l e f o r near term and long term needs. Summary D e s a l t i n g i n I s r a e l , i n i t i a t e d i n the m i d - s i x t i e s to s o l v e the r e g i o n a l potable water shortage, would have to be enhanced i n the future to supply an a d d i t i o n a l amout of 100-200 m i l l i o n cubic meters per year o f desalted water r e q u i r e d f o r the country's development. According to the present status o f d e s l a t i n g technologies and forseen developments, the p r o s p e c t i v e o p t i o n a l methods can be c l a s s i f i e d i n the f o l l o w i n g f e a s i b i l i t y order. 1. Reverse osomosis d e s a l t i n g o f a l l a v a i l a b l e b r a c k i s h water feeds.


3.

GLUECKSTERN ET AL.

in Israel

77

2.

Seawater reverse osmosis, e s p e c i a l l y when feed pressure can be u t i l i z e d .

3.

Low temperature m u l t i e f f e c t d i s t i l l a t i o n , e s p e c i a l l y i f s o l a r o r geothermal energy can be a p p l i e d economically.

Literature


Synthetic Membranes

gravity

Cited:

1.

Glueckstern, P., Arad, N., Kantor, Y., Greenberger, M., "Proceedings of the 4th International Symposium on Fresh Water from the Sea", Athens, 1973, 2, 335.

2.

Glueckstern,P., Greenberger, M., "Proceedings of the 5th International Symposium on Fresh Water from the Sea", Athens, 1976, 4, 301.

3.

Glueckstern,P., Kantor, Y., Mansdorf, Y., "Proceedings of the 6th International Symposium on Fresh Water from the Sea", Athens, 1978, 3, 278.

4.

Glueckstern, P., Wilf, M., Kantor, Y., "Desalination",1979, 30, 235.

RECEIVED December 4, 1980.


Synthetic Membranes - ACS Publications - American Chemical Society

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