the desalination plants of oman: past, present and future

ELSEVIER Desa l ina t ion 120 (1998) 5 3 - 5 9

DESALINATION

The desalination plants of Oman: past, present and future

Taher bin Mohammed Ali A1 Sajwani

Ministry of Electricity and Water, The Sultanate of Oman

Abstract

Since the Renaissance of the Sultanate of Oman in the early seventies, there has been continuous development in all fields. Oman is located in an arid region with limited ground water resources. Thus to meet the growing demand for potable water, large and small brackish and seawater desalination units have been installed in different parts of the country. This paper describes our experience in the installation, operation and maintenance of desalination plants of different types in the Sultanate of Oman and presents likely future developments to advance technology in this field. I

I. Introduction

The Sultanate of Oman in the SE of the Arabian Peninsula is an arid region with a hot dry climate. The per capita demand for fresh water is high and the water demand for various purposes - - domestic, agriculture, industry has increased dramatically along with the improvement and development of living standards. To meet this growing demand, ground water has been intensely exploited. However, replenishment of the aquifer is very low due to the shortage of rain, and some areas face increased salinity. Therefore the desalination process has to be used to reduce salinity.

The country's policy has been based on increasing the living standards in all areas to maintain regional development equilibrium and

to discourage people from immigrating to the central densely populated areas by utilizing the natural resources and increasing the variety of income sources. Adequate water resources had to be provided for all the regions in order to motivate social and economic development. This presented a great challenge because it is not that easy to provide natural water resources suitable for human use due to the increasing water demand and nonsuitability of ground water in some areas. The overall potable water production versus population by areas in 1996 is given in Table 1. As can be seen in Table 1, Muscat is the largest center in the Sultanate, its AI Ghubrah plant development history is summarized in Tables 2 A and B. A more detailed chronological development will be addressed in the following sections.

Presented at The Third Gulf Water Conference, Muscat, Sultanate of Oman, 8-13 March 1997.

0011-9164/98/$ - see front matter © 1998 Elsevier Science B.V. All fights reserved P n SOOl 1 - 9 1 6 4 ( 9 8 ) 0 0 2 0 1 - X

54 T.M.A. AI Sajwani / Desalination 120 (1998) 53-59

Table 1 Quantity of water produced in 1996 (million gal/y)

Location Population Water produced, x 1000 million gal/y

MUSCAT (A1 Ghubrah) 588 12,286

AL BATINAH 605 379 Sohar 97 NA AI Swaiq 91 37 Saham 81 19 Barka 69 13 A1 Rustaq 66 85 A1 Musannah 51 20 Shinas 48 99 A1 Khobourah 44 15 Liwa 24 28 Nakhal 15 12 Wadi AI Maawil 11 24 A1 Awabi 10 27

SHARQIAH 277 502 Sur 57 345 Mudhaibi 54 28 J.B.B. Ali 42 32 J.B.B. Hasan 24 - - Ibra 22 1 AI Kamil/AI Waft 18 6 Bidiya 17 4 Dema Wa Taeen 16 6 AI Qahil 12 8 Masirah 9 65 Wadi Bani Khalid 6 7

AL DAKHLIA 248 390 Nizwa 63 155 Bahia 50 30 Samil 41 119 Izki 32 19 Bid Bid 20 41 A1 Hamra 16 8 Adam 15 8 Manah 11 10

AL DHAHIRA 195 755 Ibri 100 66 AI Buraimi 52 525 Dhank 18 38 Yankul 16 8 Mahdha 9 118

MUSANDAM 31 574 Khasab 18 396 Diba AI-Beiah 6 81 Bukha 4 66 Madha 3 31

AL WUSTA 18 67 Mahout 8 12 AI Jazir 4 36 A1 Duqum 3 12 Haima 3 7

DHOFAR 201 NA Salalah, Taqah, Merbat, Thumrait, Shelim, A1 Halaniat, Rekhute, Dhalqut

Sadah,

2. Seventies

During this period the Government constructed several desalination plants. The first was an MSF unit commissioned in 1976 in Muscat at AI Ghubrah with a total capacity of 23,000 m3/d (5 mlgd) coupled with 3x7.5 MW steam turbines. In 1977 a lx50 MW steam turbine was added. Table 2 shows the Ghubrah plant history.

The need for desalted water was felt in other regions. Hence, an MSF desalination and power plant was constructed at Masirah Island with a capacity of 550 m3/d. Two 100 m3/d vapor compression units were constructed at Kumzar (Musandam) and 3x100 m3/d VC units were also constructed at Sheesa (Musandam).

Table 2 A1 Ghubrah power and desalination plant

A. MSF Desalination units

Unit Capacity Year Capital cost

mIgd×1000 cm/d

Distillate produced 96 mcm

1 5 22.5 1976 9.5 7.46 2 6 27.3 1982 10.0 9.20 3 6 27.3 1986 18.4 8.35 4 6 27.3 1986 18.4 9.16 5 6 27.3 1993 49.1 8.80 6 6 27.3 1997 25.0 - -

B. Power

Unit Type Design Year Remarks pacity, MW

1-3 ECST 3 ×47.5 1976 Coupled to desal, l&2

4 ECST 1 ×50 1977 Coupled to desal, l&2

5 BPST 1 ×30 1993 Coupled to desal. 1&2-5

6 BPST 1 ×30 1997 Coupled to desal. 1&2~5

1-3 FR(5) 3×17.5 1997 Single cycle

4-9 FR(5) 6×17.5 1979 Single cycle

10+11 FR(6) 2×28 1984 Single cycle

12+ ! 3 FR(9) 2×95 1996 Coupled to desal. 3&4

ECST: Extraction/Condensing Steam Turbine BPST: Back Pressure Steam Turbine FR: Frame (5) Gas Turbine

T.M.A. A l Sajwani / Desalination 120 (1998) 53-59 55

3. Eighties

During this period there was a rapid development in all fields in the country. The Government was interested in providing more services, especially primary services like water.

3.1. AI Ghubrah plant

In 1982, one MSF unit of 27,000 m3/d capacity was added to the AI Ghubrah plant utilizing the available infrastructure - - services, buildings, roads, boilers, feed water intake, concentrated brine outfall, stores, etc. (Table 2). Because of increasing consumption, another 2x27,000 m3/d units were added in 1986 so that the total production capacity was increased to 105,000 m3/d (23 mlgd).

3.2. Rural plants

Also in 1982 one unit of a once through MSF type was constructed at Film (Wilayat Mahout) which has been designed for a maximum production capacity of 100 m3/d. Three RO plants with the same capacity were constructed in the villages of Ras AI Hadd (Wilayat Sur), A1 Ruwais (Wilayat Ja'alan bani bu Ali) and Madraka (Wilayat AI Duqum) as shown in Table 3.

In 1983, one VC unit was built at Maseerah Island with a capacity of 600 m3/d (132,000 gal/d). Also one electrodialysis unit was installed at Lima (Musandam) with a design capacity of 100 m3/d. The electricity required for running this plant is supplied from the main network generated from the Khasab Power Station.

In 1985, it was decided to construct 5 more small desalination plants of capacities 50 m3/d (11,000 gal/d) in the villages of Aseelah (Wilayat Ja'alan bani bu Hasan), Abu Mudhabi (Wilayat Haima), AI Zahr and Assadanat (Wilayat AI- Duqum) and also Hitam (Wilayat A1 Jazer).

In 1988 a 60 m3/d RO desalination and power generation plant was constructed at

Halaniyat Island (previously known as Korya Moria).

4. Nineties

The fruits of rapid improvement and development are seen everywhere. There has been an increased growth in regional development. Government projects including those for water were carried out in various cities and villages.

4.1. The fourth Five Year Plan

This plan (1991-1995) included several desalination projects. At AI Ghubrah a fifth 27,000 m3/d (6 mlgd) MSF unit was added along with a 30 MW back pressure steam turbine (Table 2).

Construction of a sixth unit of the same type and capacity has begun so that the total production expected in 1997 from the AI Ghubrah plant will be about 159,000 m3/d (35 mlgd) providing potable water to Muscat from Seeb to Sidab. The distillate is post- treated in the plant, blended with well water, and fluoridized and sterilized according to Omani Standard No.8, as shown in Table 4.

The increase in water demand and rise of salinity of well water at Sur necessitated the construction of an RO desalination plant of 4545 m3/d (1 mlgd) capacity. Since 1993, this plant has been producing potable water, which is supplied to Sur town along with well water.

As development extended to every village in the Sultanate, a number of reverse osmosis desalination plants were constructed starting from 1995 to produce 100 m3/d at Haima (Wilayat Haima), Esherjah, Soqurah (AI Jazir), A1 Hej (Mahout), Lima and Kumzar (Musandam).

At Adam and A1-Khum-Kham plants constructed were of 1000 m3/d and 50 m3/d, re- spectively.

The capital cost of these ten plants comes to 4 million Omani Rials (10 MUS$).


Table 3 Water desalination plants in Wilayats outside Muscat area

S1. Name Type Capacity Year of Capital cost Water prod. Energy No. of plant starting (1000 Omani in 1996, m 3 used

m3/d 1000 gal/d Rials)

Average cost

Bz/gal US$/m 3

1. Masirah Island

2. Sur

3. Ras AI-Hadd (Sur)

4. Ruwais (B.B.Ali)

5. Aseelah (B.B. Ali)

6. Abu-Mudhaibi (Haima)

7. Saadanat (Duqum)

8. Zahar (Duqum)

9. Hiram (Gazir)

10. Madrakah (Duqum)

11. Film (Mahout)

12. Kumzar (Musandam)

13. Shisah (Musandam)

14. Limah (Musandam)

15. AI-Hallanyat (Dhofar)

16. Haima (Wusta)

17. Khum-Kham (Wusta)

18. Esheirja (Wusta)

19. Soqara (Wusta)

20. Adam (Dakhliya)

MSF 550 120 1976 312 296,436 Diesel/ 18.7 10.66 VC 600 130 1984 1047 elect.

RO 4545 1000 1993 4621 1,603,000 do 2.6 1.49

RO 100 22 1982 319 30,773 do 14.3 8.17

RO 172+100 37+22 1982 308+214 32,749 do 14.5 8.29

RO 95+100 21+22 1985 249+214 24,307 do 16.2 9.26

RO 50 11 1985 175 16,256 do 13.2 9.26

RO 50 11 1985 222 15,723 do 14.3 8.18

RO 50 11 1985 166 12,928 do 18.2 10.47

RO 50 11 1985 174 14,514 do 14.4 8.28

RO 100 22 1982 234 22,843 do 13.0 7.43

MSF 100 22 1981 271 15,217 do 32.2 18.42

VC 200 44 1976 Unknown 27,749 do 11.5 6.58

- - 300 66 1976 do

ED 100 22 1983 do RO

RO 60 13 1988 220

RO 100 22 1996 381

RO 50 11 1996 357

RO 100 22 1996 494

RO 100 22 1997 501

RO 1000 220 1997 1,068

21,409

33,609

14,863

m

m

m

Direct power supply

Diesel/ elect.

do

do

d o

do

Diesel power supply

14.6 8.33

6.4 3.66

10 5.70

m

m

m

m

m

m

T.M.A. Al Sajwani / Desalination 120 (1998) 53-59 57

5. Omani standard No. 8 for drinking water specifications

Physical properties • The water shall in general be colorless,

tasteless, odorless and free from turbidity.

Chemical properties

• Toxic chemicals: the maximum permissible levels are (mg/l): lead, 0.10; selenium, 0.01; arsenic, 0.05; cadmium, 0.01; cyanide, 0.05; mercury, 0.001.

• Chemicals that affect the suitability of water for domestic and drinking purposes (the percentage of the contents mentioned below should not exceed the following levels in Table 4):

Table 4 Allowable limits of chemicals

Substance Highest desirable Maximum permissible level, mg/1

Total dissolved solids Copper Iron Magnesium

Manganese Zinc Calcium Chloride Sulphate Fluoride Nitrate Phenolic compounds (as phenols) Total hardness pH range

500 1500 0.05 1.50 0.10 1.0 Not more than 30 mg/l 150 if there are 250 mg/l of sulphate; if there is less sulphate, magnesium up to 150 mg/l may be allowed 0.05 0.50 5.0 15 75 200 200 600 200 400 0.80 45 0.001 0.02

100 500 7.0-8.5 6.5-9.2

Minimum residual chlorine concentrations required for effective disinfection of drinking water. Treated water should contain a minimum residual chlorine of 0.2 to 0.5 mg/l.

Bacteriological properties

• Treated water: a. No sample should contain E. coli in 100 ml; b. No sample should contain more than 10 coliform organisms in 100 ml; c. Throughout any year, 95% of the samples examined should not contain any coliform organisms in 100 ml.

• Untreated water: a. No sample should contain E. coli in 100 ml; b. No sample should contain more than 10 coliform organisms in 100 ml.

6. Water desalination

In producing potable water from desalination the first thing that comes to mind is the high cost compared with ground or sur- face water. The issue is more complex so, therefore, the following factors should be taken into account:

a. Capital cost and expenses for operation and maintenance of new plants.

b. Choice of a suitable site of the plants so as to ensure a constant source of feed water for at least 20 years, and easy supply of the water to consumers without harming the environment.

c. Ease of operation and maintenance, safety, security and social factors.

d. Choice of the most suitable energy source to run the plants (gas, Diesel, electricity, renewable energy, etc.).

e. Determine suitable capacity and materials to be used with proper commercial accounting methods.

f. Studies for construction of plant auxiliaries and infrastructures like buildings, reservoirs, services, etc.


7. Other desalination plants

There are several other organizations in the Government of the Sultanate of Oman that own desalination plants. Some of these are: the Ministry of Defense, Royal Omani Police, Ministry of Water Resources (pilot plant), Dhofar region, oil companies and private sector units.

8. The future

To ensure the future needs of the country it has become vital to explore new ways to establish a safe, continuous and economical source of water supplies. The Government has, therefore, initiated work, which is summarized in the following subsections.

salination field in coordination with other research centers worldwide, mainly those from the Middle East region.

8.3. Coordination with the university and other organizations

To improve the performance, it is necessary to gain from organizations which have knowledge and experience. Hence, it is very important to maintain constant contact and coordination with all ministries and organizations involved in this subject such as Sultan Qaboos University, Ministry of Water Resources, Ministry of Regional Municipalities and Environment in the Sultanate, and also with GCC countries in addition to other scientific and technical organizations.

8.1. Preliminary studies

The future planning and pre-feasibility studies have been prepared to construct desalination plants in some of the areas of the Sultanate taking into account the requirement of potable water and water resources available for future total development.

8. 2. Middle East Desalination Research Center

Considerable research work has been done in the field of desalination since the middle of this century. Methods and systems of desalination have been significantly improved.

Methods, systems, materials, equipment and instrumentation of desalination plants have been significantly improved in this period, and still there are many topics, which need more research and development.

It has been decided to construct the Middle East Desalination Research Center in Muscat with the cooperation of participating countries in the peace process in the Middle East.

The main objective of this center is to sup- port theoretical and applied research in the de-

8. 4. Environmental consideration

The effect on the environment has to be considered especially regarding construction of feed intake, waste brine outfall, disposal of toxic chemicals, air and noise pollution.

8.5. Water conservation

The production of water from the desalination plants is totally dependent on mechanical and electrical equipment. This equipment is costly, has a limited life span and is subject to constant wear and tear. So it is necessary to decrease dependence on them by means of conservation and good management of the water supply systems.

8. 6. Human resources

The proper use of equipment depends on expertise. Experience and knowledge leads to better utilization of these equipment. This can be achieved by developing human resources through training, participation in seminars and conferences, and research and development in the field of desalination.

T.M.A. AI Sajwani / Desalination 120 (1998) 53-59 59

8. 7. Development in the desalination f ie ld

Continuous efforts should be made for development in the desalination field. The improvement of technical standard specifications, encouragement for local manufacturing units, improving ways of using chemicals and spare parts and search for alternative power sources are areas where improvement is possible.

8.8. Privatization

The Government is presently studying ways to privatize the drinking water sector including desalination plants. The study includes considering the advantages and disadvantages, alternative methods to meet the future product water demand, financing of water projects and future strategies for ensuring continuous water supply.

9. Conclusion and recommendations

In the framework of total development, to which the Sultanate is committed, it has become necessary to provide sufficient supply of drinking water for domestic, commercial and industrial use. Due to non availability of natural water in some areas, the Sultanate is concentrating on construction of desalination

plants and also extension of existing plants. In order to regulate the process for construction of desalination plants, it is recommended to con- sider the following:

1. Choose a long term strategy when con- structing desalination plants and maximize its utility, taking into account medium and short term planning to match the other economical developments.

2. Use suitable environment friendly technology.

3. Strictly follow the rules and regulations and specifications in production of water either from wells or desalination plants.

4. Encourage scientific research on science and technology related to water by universities, institutes, research centers and other organizations.

5. Work out the capital and O&M costs for desalination plants based on internationally recognized commercial accounting.

6. Properly develop an appropriate work force for this industrial field.

7. Encourage the local private sector to par- ticipate in this field by consultancy, manufacturing, building, O&M, and management.

the desalination plants of oman: past, present and future

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