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3 Hydro-powered reverse-osmosis desalination in water-resources development in Kuwait

3.1 Background and objectives
3.2 Potential water resources
3.3 Water-resources development projects
3.4 Experimental seawater reverse-osmosis desalination
3.5 Experimental brackish -ground water reverse -osmosis desalination
3.6 Hydro-powered brackish-groundwater reverse-osmosis desalination: A new proposal
3.7 Development alternatives and a conjunctive-use plan

3.1 Background and objectives

3.1.1 Background

Kuwait is located at the north-western corner of the Arabian Gulf, between latitudes 28°30' and 30°05' north and longitudes 46°30' and 48°30' east. The country is bounded to the north and north-west by Iraq and to the south-west and south by Saudi Arabia, and has a land area of 17,818 km² and a coastline of 195 km (fig. 3.1).

The population was estimated at 1.79 million in 1987. Crude-oil production and petroleum-related investments provide the main governmental revenue. The gross national product (GNP) per capita was estimated to be US$19,610 in 1987. The occupation of Kuwait by Iraq in August 1990 and its subsequent liberation in March 1991 are too recent for further comment except that water development is the key to the future habitability of Kuwait as it was before.

During the period 1925-1950, Kuwait imported fresh water by chow from the Shatt al-Arab in Iraq, some 100 km north-west from Kuwait, to supplement water obtained from wells. Further exploitation of water resources was initiated by the rapid development of the oil industry and commerce in the 1950s, when shortage problems became a constraint to economic development.

Fig. 3.1 Kuwait and water resources

Limitations of water are likely to impact increasingly on the economic development of other states in the Middle East and North Africa to the extent that "by the year 2000, water-not oil-will be the dominant resources issue of the Middle East" (Starr and Stoll 1987). The situation is particularly acute in Arabian Gulf states such as Kuwait, Bahrain, Qatar, and Saudi Arabia. Of these, Kuwait has been the pioneer state in developing desalination to supply fresh water for domestic use since the 1950s.

Kuwait had no alternative but to develop non-conventional options such as (1) importing water from Iraq or Turkey from the Euphrates River, (2) exploiting brackish groundwater, or (3) desalting seawater. The first option may not be realistic in political terms. Thus desalination became the key issue, with cost then becoming the major constraint.

Two experimental desalination trials were carried out in the 1980s-seawater reverse-osmosis (RO) desalination at the Doha co-generation station, and brackish-groundwater RO desalination with skid-mounted units-which give an opportunity to compare the unit cost of water produced by these different approaches.

3.1.2 Objectives

The main purpose of studying the application of hydro-powered RO desalination is to examine its technical feasibility and cost effectiveness.

3.2 Potential water resources

The climate of Kuwait is characterized by an extremely hot summer, from June to September, with occasional periods of extreme humidity and an average maximum daily temperature of 45°C. The winter season is mild to cool, with a minimum temperature of-1°C.

The average annual rainfall is about 115 mm, with a minimum of 30 mm in 1960 and a maximum of 360 mm in 1954. The rainfall records at four gauging stations-the International Airport, Ahmadi, Umm al-Aish, and Showaikh-since 1952 are shown in fig. 3.2. Histograms of monthly rainfall at the International Airport and Shuwaikh are shown in fig. 3.3, which indicate that 75% of the rainfall occurs in the four months from November to February. There is also spatial variation of rainfall, such as 136.2 mm at Ahmadi station in 1972 while it was only 18.1 mm at Alomaria.

The mean annual potential evaporation values as measured by class A-pan and Piche evaporimeters were 3,460 mm (1962-1977) and 5,460 mm (19571977) respectively. The theoretical annual average potential evaporation as estimated by the Penman method was approximately 2,630 mm (1957-1977). The monthly average potential evaporation and rainfall at Kuwait International Airport is shown in fig. 3.4.

Fig. 3.2 Rainfall variation, 1953-1986: Kuwait International Airport, Ahmadi, Umn al-Aish, Shuwaikh (Source: Abusada 1988)

Fig. 3.3 Monthly rainfall, Kuwait International Air. port and Shuwaikh (Source: Abusada 1988)

Kuwait is a hyper-arid state without rivers or fresh-water aquifers. Nonconventional water resources, including brackish groundwater, seawater desalination, and reclamation of treated waste water are the main current sources of water supply, of which the quality is as saline as 1,000-45,000 mg of total dissolved solids (TDS) per litre:

• groundwater (shallow), 1,000-2,000 mg/l,
• brackish groundwater, 2,000-8,000 mg/l,
• seawater, 45,000 mall,
• product water from MSF desalination, 25-50 mg/l,
• reclaimed treated waste water, 2,500 mg/l.

The WHO standard for the maximum permissible level for drinking water is 1,000 mg of TDS per litre.

Fig. 3.4 Monthly avenge potential evaporation and rainfall at Kuwait International Airport (Source: busada 1988)

3.2.1 Surface water

The prevailing hyper-arid climate of Kuwait is not favourable to the existence of any river systems in the country. There are no rivers or lakes, but small-scale wadis are developed in the shallow depressions in the desert terrain. Surface run-off sometimes occurs in the large wadi depressions during the rainy season from November to April. There is no permanent stream-gauging station, but flash floods are reported to last for only a few hours to several days. Due to the extremely high evaporation losses and the high deficit in soil moisture, only a small percentage of the precipitation infiltrates into the groundwater. The run-off ratio must be extremely small.

The average annual rainfall within Kuwait is estimated to be 1,780 million m³, assuming a mean annual rainfall of 100 mm. However, with such high evaporation losses, the net annual run-off is estimated to be merely 17.8 million m³, assuming a run-off ratio of 1%.

3.2.2 Groundwater

Thick geological sequences are of sedimentary origin from Palaeocene to Recent, in two groups, known as Hasa and Kuwait. The Hasa group, which consists of limestone, dolomite, anhydrite, and clays, comprises three formation units, known as Umm el-Radhuma in the Palaeocene to Middle Eocene, Rus in the Lower Eocene, and Damman in the Middle Eocene. The Kuwait group, which consists of fluviatile sediments of sand and gravel, calcareous sand and sandstone with some clays, gypsums, limestones, and marls, comprises three formation units, known as Ghar in the Miocene, Fars in the Pliocene, and Dibdibba in the Pleistocene (fig. 3.5).

Two economic aquifers are found in the Damman formation in the Hasa group and the Dibdibba formation in the Kuwait group.

Fig. 3.5 Schematic geological profile of Kuwait

Fig. 3.6 Salinity (TDS) contour map of the Darnman aquifer in Kuwait (Source: Abusada 1988)

DAMMAN LIMESTONE AQUIFER. The Damman aquifer of the Middle Eocene, which consists of carbonate rocks and extends all over the country, has a thickness varying from about 150 m in the south-west to about 275 m in the north.

The dissolution of gypsum and anhydrite in the Kuwait group, Damman formation, and Rus anhydrite formation is an important factor conditioning the chemical quality of groundwater in Kuwait. The total dissolved solids of groundwater in the Damman limestone aquifer vary from 2,500 mg/l, in the extreme south-west to about 200,000 mg/l in the north-east (fig. 3.6).

Groundwater isotope analysis of 14C in the Damman aquifer has been performed by taking water samples from 13 wells in southwestern Kuwait. From the absence or zero concentration of 14C the age of the groundwater in the Damman aquifer is estimated to be more than 400,000 years, while the 14C concentration in the Kuwait group groundwater indicates an age of 14,000-22,000 years (Abusada 1988).

Owing to the nature of limestone geology, the permeability of the Damman limestone aquifer varies considerably. The aquifer parameters vary from 27 to 7,100 m²/day transmissivity and 3.4-8.9 x 10 -4 storage coefficient, based on results obtained from 38 testing sites in south-western and southern Kuwait (Abusada 1988).

No natural groundwater recharge from rainwater is likely in the confined Damman limestone aquifer, although there is some lateral inflow or recharge through the Saudi border, which is preliminarily estimated to be 8.3-24.9 million m³ per year (Abusada 1988).

DIBDIBBA AQUIFER. The Dibdibba aquifer, which is composed of unconsolidated sands and gravels, is generally a water-table aquifer with fresh to brackish groundwater.

Most of the groundwater recharge of the Kuwait group is dependent on upward leakage from the underlying confined Damman limestone aquifer. The quality of the groundwater is generally similar to that of the Damman aquifer. The total dissolved solids of the groundwater in the Kuwait group increase generally from about 3,000 mg/l in the south-west to about 130,000 mall in the north-east over a distance of about 150 km. Some lenses of fresh water with TDS ranging between 800 and 1,200 mg/l, are perched on the brackishgroundwater body in the Rawdatain and Um al-Aish wellfields in northern Kuwait, which are recharged by infiltration through the wadi beds during occasional flash floods in the wadi depressions (fig. 3.1).

The piezometric level in the Kuwait group varies from about 90 m in the south-west to zero along the coast. The groundwater flows generally northeastwards.

3.2.3 Seawater

Seawater is an unlimited water source for Kuwait, which has a long coastline along the Arabian Gulf, which covers an area of 3,683 million km² and holds 10.07 x 10 12 m³ of water (Korzun et al. 1976)

The high mineral content of water from the Arabian Gulf requires special attention for the control of salt deposition in plants located there. The total dissolved solids of the feed water from Kuwait bay at Doha average 44,885 mg/l, (Al-Zubaidj 1989), which is as much as 1.3 times that of other standard seawaters, such as 33,600 mall in the Pacific Ocean and 36,000 mg/l, in the Atlantic (Howe 1962). Seawater has been the major source of the fresh-water supply in Kuwait since the 1960s and is likely to continue to be the key source for developing water resources in Kuwait in the twenty-first century.

3.2.4 Treated sewage effluents

Marginal waters in the artificial category are composed primarily of municipal waste water and urban storm drainage water. The potential reclaimed sewage effluents in Kuwait city were estimated to be 190 million m³ per year in 1988, assuming a water supply of 293 million m³ per year with a 65% rate of return flow. The actual amount of reuse of sewage effluents in 1988 was 97 million m³ per year, which was one third of the volume of water supplied. The potential for water reuse will increase, corresponding to the increasing water use in the future.

3.3 Water-resources development projects

The water needs of Kuwait expanded after crude-oil marketing was initiated in 1946, requiring the import of water by lighter and barge from the Shatt alArab in Iraq, some 100 km to the north-west. Intensive test well drillings in 1945 discovered an extensive brackish-water aquifer in the Abduliya area. The first desalination plant was commissioned in 1950 at Fahahil in Kuwait city. A parallel development followed to meet the growth of the city, including the Sulaibiya brackish-water wellfield. The combined development of cogeneration and this brackish-water wellfield was commissioned in 1953. Kuwait is now dependent on distilled water to blend with brackish groundwater as the main source of its water supply. Another source of water is treated sewage effluents, which are being used for landscape irrigation and agriculture.

The present sources of water supply for municipal and industrial use in Kuwait, with their salinity (milligrams of TDS per litre) and annual volumes, are as follows:

• groundwater, shallow (1,000-2,000 mg/l 2.5 million m³,
• brackish groundwater (2,000-8,000 mg/l), 10⁹ million m³,
• seawater desalination by MSF (25-50 mg/l), 184 million m³,
• reclaimed waste water (2,500 mall), 97 million m³.

Small-scale crop irrigation is exploiting 57-67 million m³ of brackish groundwater per year. Water-resources development projects undertaken in Kuwait since the 1950s are described as below.

3.3.1 Surface water and artificial recharge

Kuwait's hydrology, topography, geology, and surface water resources do not favour the country, and no promising storage-dam scheme may be possible. The possibility of effective use of temporary surface runoff in the wadis was examined in a research project on groundwater recharge at Rawdatain in 1962, in which recharge pits with a total volume of 25,000 m³ were dug in the wadi depression to evaluate the infiltration potential of the run-off into the upper Kuwait group aquifer where the water table is shallow. The prospects of increasing the potential of fresh groundwater in the shallow Kuwait group are good, but artificial recharge will not be a key application, owing to the limited amount of surface run-off.

3.3.2 Groundwater exploitation

Groundwater has been exploited in two major aquifers, in the Kuwait group of the Neogene-Quaternary and in the Hasa group of the Eocene.

The selection of wellfields in Kuwait has been governed by many factors. In areas such as the Jahara, Abdali, and Wafra farms, groundwater exploitation has been concentrated on the shallow-water-table aquifer with a salinity of 2,000-8,000 mg of TDS per litre for local irrigation. At the initial stage of development, large-diameter handdug wells were constructed in the shallow aquifer at a depth of between 10 and 15 m. Later, tube wells 50-60 m deep were drilled in the saturated section of the Kuwait group at the end of 1960s. Relatively deep groundwater wells penetrating into the upper part of the confined Damman aquifer were drilled by the Kuwait Oil Company in the early 1940s to provide brackish water for the oil industry and gardening at Abdali and other areas. The Sulaibiya wellfield was developed in the early 1950s to supply water for gardening and mixing with distilled water. The exploitation of fresh groundwater resources in Rawdatain and Umm el-Aish was later initiated for Kuwait city. In view of the limited sustainable yield of the aquifer system and possible leakage contamination from the underlying saline water body, the abstraction has been controlled since the mid-1970s. The Damman aquifers in remote areas were also explored by steps in the mid1960s to coordinate with the substantial increase in water demand in Kuwait city. The Shigaya wellfield south-west of Kuwait city was commissioned for use in the early 1970s.

Fig. 3.7 Production of brackish groundwater and distilled water in Kuwait

Annual abstraction of groundwater for water supply is estimated at 10⁹ million m³ of brackish water and 2.5 million m³ of rather fresh water (fig. 3.7). Crop irrigation is being carried out by pumping 53-67 million m³ of brackish groundwater per year from the wellfields in Wafra and Abdali-Um Nigga. The existing yield, estimated potential yield, and water salinity of each wellfield are shown in table 3.1.

3.3.3 Seawater desalination

Kuwait is one of the world's leaders in the production of fresh water from the sea. Co-generation stations, using the multi-stage flash process to distil seawater, were developed in the early 1950s and have been in use since then (table 3.2). The annual production of fresh (distilled) water is estimated to be now 184 million m³, as shown in fig. 3.7.

SHUWAIKH CO-GENERATION STATION Shuwaikh was the first cogeneration station in Kuwait to be built since 1953. Between 1965 and 1982 distillation units were installed in response to a rapid increase in the demand for fresh water. In 1987 the installed capacities of the power generation units and distillation plants were 324 MW and 32 mig (145,500 m³) per day respectively. Distillation plants were installed as a part of the following co-generation stations (Al-Farhoud 1988).

Table 3.1 Wellfields in Kuwait, 1985

Source: Kuwait Institute for Scientific Research, in 1990.

Table 3.2 Installed capacity of co-generation stations in Kuwait

Source: Kuwait Institute for Scientific Research, in 1990.

SHUAIBA CO-GENERATION STATION. The Shuaiba station is composed of two stations, Shuaiba North and Shuaiba South. The installed capacity of the power generation units is 1,204 MW in total, being 400 MW at Shuaiba North and 804 MW at Shuaiba South. Distillation plants with a total installed capacity of 44 mig per day were installed between 1965 and 1975, including 14 mig (63,650 m³) at Shuaiba North (1965-1971) and 30 mig (136,400 m³) at Shuaiba South (1971-1975).

DOHA CO-GENERATION STATION. The Doha station is also composed of two stations, Doha West and Doha East. The installed capacity of the power generation units is 3,558 MW in total, 1,158 MW at Doha East and 2,400 MW at Doha West. Distillation plants with a total installed capacity of 139 mig per day were installed between 1978 and 1985, including 43 mig (195,500 m³) at Doha East (1978-1979) and 96 mig (436,500 m³) at Doha West (1983-1985).

AL-ZOUR CO-GENERATION UNIT. The Al-Zour station, scheduled to be completed by 1991, was designed to have an installed capacity of 2,511 MW of power generation and 72 mig (327,300 m³) of distillation per day.

The problem with seawater distillation is the high cost of the MSF evaporation process. The cost of the thermal process is largely dependent on the rate of energy (fuel) consumption for operating the system, which can account for as much as about 50% of the unit water cost and is sensitive to the unstable world market price of crude oil.

3.3.4 Reuse of treated sewage effluents

The amount of reuse of the sewage effluents in Kuwait in 1988 was 97 million m³, which was one third of the volume of water supply.

Three municipal waste-water treatment plants, at Ardiya, Rekka, and Jahara, were designed to treat municipal waste-water through tertiary treatment for reuse in landscape irrigation. The installed capacity of these plants is 290,000 m³ per day in total, comprising 150,000 m³ at Ardiya, 65,000 m³ at Rekka, and 80,000 m³ at Jahara. The output is 265,000 m³ per day, including 175,000 m³ at Ardiya, 30,000 m³ at Rekka, and 60,000 m³ at Jahara. After tertiary treatment by sand filtration, the quality of the treated water is controlled to be 10-20 mg of BOD, 3-40 mg of NH3-N, and 2,500 mg of TDS per litre (table 3.3). Some of the reclaimed sewage water is being used for landscape irrigation and some for agriculture.

Table 3.3 Sewage treatment plants for reuse en Kuwait

Source: Kuwait Institute for Scientific Research, in 1990.

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