Fresh water is an indispensable resource for human livelihood, agricultural irrigation and economic development (Brooks, 2007). However, due to the rapid population growth and the limited reserves, increasing regions have faced serious scarcity of fresh water (Williamson, 2010). Saudi Arabia is one of the driest countries in the world (CIA, 2011). According to World Bank (2011), the world average fresh water consumption is nearly 7000m³/year/person, while the water resource per capita in Saudi Arabia is less than 1200m³/year/person. In order to satisfy the demand for water, Saudi Arabia currently supplies fresh water via deep drilling of fossil groundwater (UNESCO, 2009).
Nevertheless, society increasingly recognises that those water resources are non-renewable and are liable to be reduced by the overexploited boreholes and wells. Thus Saudi Arabia needs to find alternative and sustainable methods to solve these issues. Since there is abundant sea water around Saudi Arabia, large-scale desalination could be the ideal solution to water scarcity. However, the expensive cost and the detrimental influence on the environment might limit the scale and sustainability of this method. Due to the cheap cost and the minor environmental damage, wastewater reuse is regarded as another potential solution. However, it seems to have a low social acceptance.
Therefore, this report will compare the feasibility of desalination and water reuse in terms of cost, social acceptance and environmental impacts, thereby exploring the most suitable method to deal with the scarcity of water in Saudi Arabia.
Saudi Arabia is located in the Middle East, bordering the Persian Gulf and the Red Sea (CIA, 2011). It is famous for the abundant reserves of oil and gas. However, the fresh water resources in Saudi Arabia are very limited. According to World Bank (2011), there is no one river and lake with perennial water throughout this country. Furthermore, due to the influence of the subtropical climate, the annual precipitation is only about 100 mm and the climate is hot and dry (ibid.). Additionally, rapid population growth has caused higher increase of demand for water (Abderrahman, 2000). Shortages of water have constrained the development of agriculture and economy (Williamson, 2010).
Since the underground water is estimated to be able to supply for 320 years, the underground water is still the principal source of water at present (UNESCO, 2009: 100). However, with the increasing awareness of defects of this method, the focus of the future development of water provision has shifted to other sustainable water technologies. In order to deal with fresh water shortages, desalination has received enormous investments. According to Abu-Arabi (2007), in 2004 the number of desalination industries reached 30 and they can supply 1.1 billion cubic metres of fresh water per year.
Wastewater reuse is regarded as another future means of water provision. According to Bashitialshaaer et al (2009), in 2009 there were 33 wastewater treatment plants with a capacity of 748 billion cubic metres per year.
Cost should be the principal consideration of water provision because an expensive cost might limit the scale of application of methods. This also includes the cost of energy consumption.
Social acceptance plays a significant role in the development of water supply technologies. If the water cannot be accepted by society, it will lead to very little consumption.
Environment has a profound influence on human beings. In order to prevent water supply technology undermining the environment, its impacts on the environment should be considered.
4. Presentation of options
Desalination is “a specific treatment process to take minerals from saline water to purify for drinking water and irrigation” (Al-Sahlawi, 1999). Sometimes this process is used to take salinity and other pollutants from wastewater. The general method of desalination is reverse osmosis or multi-stage flash distillation (Lone Star Chapter of the Sierra Club, 2008).
4.2 Water Reuse
Water reuse means treating wastewater to a specific quality, and then using treated or reclaimed water from one application for another application (McKenzie, 2005; Asano, 2006). The resources for wastewater reuse are various; according to Asano (2006), they could be domestic wastewater, industrial sewage, municipal sewage or agricultural wastewater.
5. Comparison of Options
Although the cost of desalination has decreased dramatically in the past three decades, it is still expensive to use in large scale. Alghariani (2003) points out that the expenditure of desalination consists of initial investment for equipment, running costs (including staff and maintenance), as well as chemicals or specialised parts. At present, according to the Third World Water Assessment Report (UNESCO, 2009: 155), the average cost of desalination is between $0.60/m³ and $0.80/m³. Moreover, Owens and Brunsdale (2000, cited in Alghariani, 2003: 5) claim that the cost of desalination in Florida can even be less than $0.55/m³, which is one-tenth of the cost price in 1979.
However, as Wright (2009) points out, this cost is still higher than other water supply technologies. Apart from expenditure, desalination is generally considered a high-cost process due to the enormous energy consumption (Abu-Arabi, 2007). Nevertheless, this does not seem to be a problem for Saudi Arabia. According to the CIA (2010), the proven oil and gas reserves in Saudi Arabia are respectively the first and fifth in the world. As Abu-Arabi (2007) points out, in Saudi Arabia the annual solar energy received by each square kilometre of land is equivalent to 1.5 million barrels of crude oil. Abundant energy may lead to a low price.
Nevertheless, oil is non-renewable and oil reserves are estimated to last less than one century (World Energy Council, 2010), so the consumption of energy should be taken into account as a considerable cost. Moreover, the treatment of the waste gas generated by desalination also increases the cost (Al-Sahlawi, 1999).
The cost of water reuse is influenced by various factors such as treatment level, intended reuse options, location of treatment, wastewater collection and transportation. According to Qadir et al (2009), the average cost of recycling water is approximately $1.79 per cubic metre. However, compared to desalination, wastewater reuse has the advantage of cost. Fryer (2010) demonstrates that the relative marginal cost of seawater desalination is higher than water recycling, and amounts to up to $2000 per acre-foot. The water recycling represented a general fluctuation pattern between approximately $300 and $1000 per acre-foot (Fryer, 2010). Even so, water recycling appears cheaper than desalination.
5.2 Social acceptance
While both options can generate safe water, desalination seems to have higher social acceptance. Sloane (2009) investigated the acceptance of desalination and water reuse at Nourieh Palms. As shown in Table 2, in all areas but particularly drinking water, the approval rate for desalination is higher than water reuse. This reflects that more people trust the quality of water which is generated by desalination.
Source: Sloane (2009: 128)
For most uses, reclaimed water tends to have lower social acceptance than desalination. There are various reasons why people do not trust reclaimed water. First, most people do not understand the difference between treated and untreated water (McKenzie, 2005). Secondly, they are often concerned about the type of wastewater, treatment levels and the availability of information (Qadir, 2009). There are particular concerns with the wastewater produced by the petroleum industry, brought to the surface when drilling oil.
This kind of wastewater is difficult to treat due to the high content of oil (Asatekin and Mayes, 2009). Therefore, though reclaimed water undergoes a very thorough treatment process which makes it entirely safe to drink, the public are reluctant to drink treated sewage. However, it is not impossible that people will accept drinking such treated sewage. For example, Singapore has successfully used reclaimed water, a product named NEWater, to supply drinking water (Tortajada, 2006). This reflects that treated wastewater could become widely accepted through public education.
5.3 Influence on environment
There are some environmental disadvantages of desalination. Since Saudi Arabia is rich in oil and gas, clean energy such as solar energy tends to be used less than fossil energy (Al-Sahlawi, 1999). The overuse of fossil energy may cause serious environmental pollution. For instance, oil might generate large quantities of carbon dioxide, which is the main factor leading to global warming (Al-Aza, 2005). Furthermore, the gas emissions from oil could undermine the ozone layer and cause acid rain (ibid.). In addition to environmental pollution caused by fossil energy, brine discharge is another serious problem. After desalination, the brines generally have a higher concentration of salt, nearly twice that of natural seawater (Tsiourtis, 2002). The brines are generally discharged back to the same place where the seawater comes from. This might lead to increased concentration of salt in the sea, which is a potential threat to aquatics.
In contrast with the desalination, wastewater reuse is regarded as an eco-friendly way to supply fresh water. Recycling water can maximise the use of rainfall and other current water resources so that the limited underground water resources can be conserved (Miller, 2005). In the meantime, decreased energy consumption could reduce the pollution caused by the use of fossil energy (Ghermandi et al, 2007). Therefore, recycled water is a sustainable and eco-friendly method to supply good quality fresh water.
From the information given above, the following conclusions can be drawn:
1) Both desalination and wastewater reuse are feasible water supply technologies.
2) The cost of desalination has decreased dramatically, but is still far more than water reuse. Desalination requires more capital and energy.
3) Reclaimed water has low public acceptance, especially for drinking water.
4) Desalination could undermine the environment, while water reuse is eco-friendly.
Considering the cost and the impact on the environment, wastewater reuse is recommended to be used as the main water supply technology. Although the public acceptance of recycled water is lower than desalination, the example of Singapore has proven that reclaimed water could be accepted in daily life. Desalination is a costly water supply technology. Furthermore, it needs a vast amount of energy. Even if Saudi Arabia has abundant oil and gas reserves, as these resources are non-renewable, desalination is not suitable for sustainable water supply. Additionally, it has detrimental influences upon the environment. Therefore, Saudi Arabia should improve the ratio of wastewater reuse in the whole fresh water supply system.
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