DESALINATION AND WATER REUSEAS AFFORDABLE SOLUTION FOR WATER SUPPLY IN WANA COUNTRIES

Dr. Noreddine Ghaffour, Principal Research Scientist, Water Desalination & Reuse Center, King Abdullah University of Science and Technology (KAUST), Saudi Arabia

1. Introduction

The WANA region except Turkey has minimal rainfall and limited aquifers.It is the driest region in the world with renewable water resources less than the critical level of 1000 m3 per inhabitant per year, as defined by the World Health Organization (WHO).

Most of the countries in the region are or, with population growth and economic development, will be dependent on desalination of sea/brackish water to cater their actual and future needs for potable water. Because of the scarcity of natural fresh water and the reduced cost of desalination, waste water processing for reuse, which uses much the same technology as desalination, is or could be another source of water for WANA region population. These, and other factors, combine to create a dire need for water with good quality as a reliable source for the future.

In many countries where desalination was unthinkable, it is now adopted as feasible and economical option for potable water supply.The measures taken to supply water to the region should not be for short term. They should utilize a technology that can be relied upon for many years and can ensure a guaranteed water supply independent of climatic conditions that prevail in the area. Desalination and water reuse fit this requirement. It has been established practice in several countries such as GCC states, Algeria and Libya that their future water demand is to be met by desalination. On the other hand, it is becoming the only viable and economic solution for countries such as Jordan, Israel, and Palestine to embark on desalination. North African countries vary in their demand for desalination from needs to supply water to sea resorts such as in Egypt and Tunisia, to provide an alternative to major water transport schemes such as Egypt in its Sinai development, and Morocco for supply to its southern region. Whereas Syria and Lebanon may not see the need for desalination, Syria with thousands of illegally drilled wells abstracting its aquifers still has to consider desalination in its interior far from rivers and sea. Yemen, on the other hand, the worst water depressed country in the world, has the additional demise of being forced to a combination of desalination and major transport schemes. Iraq is likely to undergo severe water treatment requirements equivalent to desalination, and will also need solutions involving desalination in its southern territories [1].

Desalination processes have experienced many developments in the past thirty years. These developments have led to the reduction in desalinated water cost to a level that has made desalination a viable option for potable water supply.It is now technically and economically feasible to generate large volumes of water of suitable purity through the desalination of seawater, brackish water, and water reuse.

The region has out of necessity become a world leader in water desalination. Desalination fills a significant portion of the shortfall in water supply in the region. GCC countries are among the highest producers of desalinated water in the world and produce about half the world’s desalinated water. However, some environmental impacts are associated with desalination, including entrapment of aquatic creatures in plants intakes, discharge of hot brine and the production of CO2.

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2. Desalination status and capacity

Many regions in the water stressed countries are augmenting their water supplies with desalinated water to meet the needs of the continuous growth of population and industrial, tourism and agriculture developments. Although desalination has been considered among the non-conventional water resources, it can no longer be considered as a marginal resource because some countries such as Qatar and Kuwait rely 100% on desalinated water for domestic and industrial use, whereas Saudi Arabia reliance is nearly 60% [1].

Desalination, along with water reuse, water harvesting have been classified as non-conventional water resources. This classification can easily raise controversy in countries that have been using desalination substantially for more than 50 years. Generations of water professionals in those countries have long forgotten that this resource is non-conventional.

Desalination has become the main source of potable water in all the GCC States where demand has multiplied from 1.5 bi m3/yr in 1980 to 6 bi m3/yr in 2000. It is expected that by 2015 an additional 5 bi m3/yr is to be provided through desalination. This need for desalinated water is no longer associated only with the GCC. Almost all countries of the region are now considering desalination. This growth is driven by chronic water shortages due to persisting droughts, increasing populations, increasing per capita water demand and growth of industrialization. On the other hand, this growth is also enhanced by the decrease in the costs, due mainly to technology improvements and competition, associated with the production of desalinated water where prices have fallen from around US$ 4 /m3 to less than US$ 1/m3 and even reached below US$0.5/m3 for some specific large scale projects.

Presently, the total desalination capacity is around 60 million m3/d and will reach around hundred millions m3/d by 2015 [2,3]. 64.6% of the total capacity is produced by membrane processes and 34% by thermal processes. 62.4% of the feed water is from seawater and 20% from brackish water and the remaining is from surface water and wastewater (Figure 1a) [1].Over 66% of the desalinated water is used for municipalities and 23.5% for industry (Figure 1b). These figures are susceptible for quick changes as desalination market is growing very fast with an annual growth rate of about 55%.

Figure 1: Installed capacity by feed water type and by user type [2].

In non-GCC countries, most of which are new to the desalination industry and had to consider it to augment their water supply, either nationally or at the local level in some parts of the countries. For example, Iraq has two major rivers passing through, but some of the locations in the south exhibit water shortages that have to be met by desalination.

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3. Desalination development potential and finance

Desalination has a great development potential on a global scale. This is attributed to the fact that, out of 71 large cities that do not have local access to new freshwater source, 42 are coastal [4]. Out of the entire world population, 2,400 million inhabitants representing 39% live at a distance of less than 100 km from the sea [4] including most of the large cities in WANA region.

Other than the fact that desalination may be the only option for some countries, there are driving forces behind its development potential, making it more favorable than conventional resources. Being independent of climatic conditions, rainfall and so on, a primary force is its identification as a secure source of supply.

4. Desalination technologies

Desalination is a separation process that produces two streams, fresh water and saline solution (brine). Saline water is classified as either brackish water or seawater, depending on the salinity. Two main commercial desalination technologies have gained acceptable recognition throughout the world, namely those based on thermal or on membrane processes.

Thermal processes, except freezing, mimic the natural process of producing rain, where saline water is heated, producing water vapor that is in turn condensed to form fresh water, thus producing fresh water by distillation. These processes include Multi-Stage Flash (MSF), Multi-Effect Distillation (MED), and Vapor Compression (VC) Distillation. In all these processes, condensing steam is used to supply the latent heat needed to vaporize the water. Thermal processes, due to their high-energy requirements, are normally used for seawater desalination, and in duel power and water production plants (co-generation).

Membrane processes include Reverse Osmosis (RO) and Electrodialysis (ED). Whereas ED/EDReversal is suitable for brackish water, RO can be used for both brackish and seawater. Nanofiltration (NF), known as a softener membrane, could also be used to desalinate partly salty waters and for hazard materials removal. For example, in Senegal, groundwater supply contains high concentration of fluoride which leads to many teeth and bones diseases (Figure 2). NF was used to reduce the fluoride concentration in water to a level of acceptabledrinking water standard as recommended by WHO (< 1.5 mg/L).

Figure 2: Case study of dental (a) and bones (b) fluorosis [5]:

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(a) Dental Flurosis (F-> 2 mg/L), 10 years of exposure to 4 mg/L F-, Senegal.(b) OsseousFluorosis (F-> 4 mg/L), 15 years of exposure to 6-10mg/L F-, Senegal.

5. Water reuse

Another prominent role to the desalination industry is becoming evident. Wastewater treatment for reuse and desalination have membranes as the common denominator. Initially they were used in the pretreatment for better operations of RO plants. This has opened a wide world of opportunities. Ultrafiltration (UF) technology appears in the form of filter backwash, in the tertiary treatment after secondary treatment of wastewater and in what is known as single-stage membrane bioreactor (MBR) process. Extensive use of these technologies will be seen in the near future. MBR competes with conventional secondary wastewater treatment while UF offers cost-effective options for many tertiary treatment applications. The use of RO after the secondary and tertiary treatments offers a drinkable water quality as it is the case for New-Water in Singapore and similarly in Namibia as well as the largest wastewater treatment plant in Kuwait (Sulaibia plant). So far the product water is used for other purposes or injected into the aquifer in many countries (ASR: Aquifer Storage and Recovery) as it’s not easily accepted by humans for drinking or even for other purposes especially in Muslim countries.

6. Costs

Although desalination is not a cheap option for the provision of potable water, the cost of desalination plants, particularly RO plants, is decreasing. Membrane prices have dropped at a rate of around 10 percent yearly for the past 20 years. Prices of thermal processes are also falling due to increasing competition. Also, since technological developments affect a reduction in the cost of equipment, the overall relative plant costs are expected to decline. This trend has made desalination, once a costly alternative to the provision of potable water, a viable solution and economically competitive with other options of water supply.

Figure 3 gives the cost trends for different raw waters treated by RO. It shows that the cost of desalination and water reuse is reduced to a level to compete with traditional water supply options.

Figure 3: Water resource cost trends [4].

Table 1 gathered the main parameters related to cost as its main criterion for the selection of suitable desalination technologies though that the total water cost depends on many parameters

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0

1

2

3

4

5

6

7

1990 2000 2010 2020

Year

Co

st

$/m

3

Marginal waterwithdrawal

Freshwater treatment

Reuse

Desalination

mainly desalination process, plant size, geographical location and site specific characteristics, raw water quality, intake arrangement, requested product water quality, reject discharge type, energy, materials, chemicals and other consumablesprice, financing details and amortization period, operation and maintenance.

Table 1: energy consumption and water cost of large scale commercial desalination processes [6].

Process Thermal energykWh/m3

Electrical energykWh/m3

Total energykWh/m3

Capital costUS$/m3/day

Unit water costUS$/m3

Typical single train capacitym3/d

MSF 7.5 - 12 2.5 – 3.5 10 – 15.5 1000 – 1500 0.8 - 1 5,000-70,000

MED 4 - 7 1.5 – 2 5.5 – 9 900 – 1200 0.6–0.8 500– 12,000

SWRO - 3 – 6 3 – 6 800 – 1000 0.5-0.8 1 – 25,000BWRO - 0.5 – 2.5 0.5 – 2.5 >800 0.1–0.3 1 – 25,000

7. Conclusion

This chapter reviewed current desalinationand water reuse issues, and attempted to provide a comprehensive look at these technologies from an integrated perspective that targets decision makers to adopt these technologies to cater the actual and future water needs in the region.

Desalination is no longer a marginal water resource. It is now adopted as a reliable and economic solution for water shortage in countries where desalination was unthinkable. Water reuse also offers potable water quality and hence is part of the integrated water resource management.

8. References1. World Bank water report, 2006.2. WDR/GWI, IDA Desalination Yearbook and market profile, 2009-2010.3. T. Pankratz, MEDRC workshop on Membrane Technology Used in Desalination and

Wastewater Treatment for Reuse, Muscat, Oman, March 2008.4. K. Quteishat, Desalination and water affordability, SITeau International Conference,

Casablanca, Morocco, January 2009.5. M. Pontie, H. Dach, P. Jaouen, C. Diawara, J. Leparc, M. Hafsi, N. Ghaffour,

“Intensification of brackish water desalination using NF membranes: Case studies in Morocco and Senegal”, 3rd Oxford Water and Membranes Research Event, The University of Oxford, UK, 2010.

6. K.V. Reddy and N. Ghaffour, Overview of the cost of desalinated water and costing methodologies, Desalination 205 (2007) 340-353.

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