苏丹新供水技术可行性研究

发布时间：2016-04-28 09:34

1.0 INTRODUCTION介绍

获得干净的水是人类的基本权利，在许多国家，在可持续发展的考虑，水是在优先级列表的顶部（Omer，2008）。水的价值是在诸如苏丹越来越感到，，在降水不足而温度高导致干燥或干旱条件（粮食和农业组织（FAO），引用了美国国际开发署，2010）。三分之二的土地是干旱和降雨量小于400mm每年。尽管大约60%苏丹位于尼罗河流域内，它不仅吸引18.5x109 M3从每年尼罗河的流量84x109m3和添加到它的内部供应12x109m3，水的可用性大幅下降低于人均1000m3的水应力极限（同上）。
根据联合国粮农组织（在美国国际开发署，2010引），苏丹可再生水资源人均在2008站在726m3 /人/年，预计将在2015 617m3 /人/年。它是低和迅速下降，每年（同上），除非采取措施，许多市民将生活没有基本人权。由于苏丹不能依靠降雨是零星的，集中在4个月的大部分地区（俄梅珥，2008），水管理技术才能保证饮用水的供应。
Access to clean water is considered a basic human right and in many countries when sustainable development is considered, water is at the top of the list of priorities (Omer, 2008). The value of water is increasingly felt in areas such as Sudan, where precipitation is inadequate while temperatures are high resulting in dry or arid conditions (Food and Agriculture Organisation (FAO), cited in USAID, 2010). Two-thirds of the country is arid and rainfall is less than 400mm annually. Regardless of the fact that about 60% of Sudan lies within the Nile basin, it only draws 18.5x109 m3 from the Nile’s annual flow of 84x109m3 and added to its internal supply of 12x109m3, the water availability falls considerably below the water stress limit of 1000m3 per head (ibid).
According to FAO, (cited in USAID, 2010), in Sudan the renewable water resource per capita at 2008 stood at 726m3/person/year and is projected to be 617m3/person/year in 2015. It is low and rapidly dropping every year (ibid) and unless measures are taken, many citizens will be living without a basic human right. Since Sudan cannot rely on rainfall which is sporadic and concentrated in 4 months for most areas (Omer, 2008), water management techniques need to be implemented to ensure availability of potable water.
Sudan is bordered by the Red Sea to the east which makes desalination a viable option but the cost implications and negative effects on the environment make it unattractive. Another option worth considering is water recycling which seems to be lower in cost while having fewer negative effects on the environment. This report will compare the feasibility of both desalination and water recycling techniques, in terms of cost implications, social acceptance and environmental effects, and will recommend water recycling as the more viable option for Sudan. 

2.0 BACKGROUND背景

Sudan is in North-Eastern Africa and it borders the Red Sea, between Egypt and Eritrea and occupies 1,861,484 km2 (CIA, 2011). With a population of 25,946,220, the majority of whom are centred around the Nile (Omer, 2008), and a Gross Domestic Product (GDP) per capita of USD 2,800, (CIA, 2011) it is an extremely poor country that has faced years of social conflict and civil war and only in the past year, been separated from South Sudan through a referendum that passed in favour of secession of South Sudan (ibid). 
In addition to its earnings from oil resources, agriculture forms a large part of Sudan’s economy and accounts for about 80% of the workforce, contributing to a third of the GDP (CIA, 2011). As such, water is of the essence in Sudan because in addition to being used for human and animal consumption, it drives an important economic activity. According to FAO (2005,cited in Omer, 2008), projections to the year 2020 show that agriculture in Sudan will require 69% of the country’s water supply while industrial and hydropower activities together with potable needs will require 18% and 13% respectively. 
Under the 1959 Nile Waters Agreement, Sudan shares the Nile’s resources with nine other countries; Burundi, Congo, Egypt, Eritrea, Ethiopia, Kenya, Rwanda, Tanzania and Uganda (Omer, 2008). This means that though it has a large resource at its disposal, it cannot exploit it beyond what is dictated in the agreement and needs to supplement its fresh water supply. 

3.0 PRESENTATION OF OPTIONS.展示方式

3.1 Desalination

Desalination is a process of purifying saline water that involves using energy to separate the saline seawater into two streams; a fresh water stream that has dissolved salts in low concentration and a stream with concentrated salt levels or brine (Khawaji et al, 2008). The three most commonly used methods of desalination are; multieffect distillation (MED), multi-stage flash (MSF) and reverse osmosis (RO). These modern processes can trace their history to the traditional method of removing salt from salty water by evaporation (Lattemann et al, 2010). 
3.2 Water recycling
Water recycling refers to treating of waste or used water to make it potable and also fit for irrigation and other domestic uses. The two principal methods used to recycle water are the microfiltration (MF) and reverse osmosis (RO) (Drewes et al, 2003). 

4.0 REQUIREMENTS要求

The two options mentioned above will be analyzed against a backdrop of the following requirements:
4.1 Cost
For Sudan, which is a poor developing country with a GDP of USD 2,800 per capita (CIA, 2011), cost is a major consideration when looking for a water management technique and an expensive option would not be viable. 
4.2 Social Acceptance 
Islam, the predominant religion in Sudan (CIA, 2011), has beliefs that emphasise the importance of water as an agent for purification and though recycling of water is acceptable (Farooq et al, 1981), lack of knowledge may hinder successful implementation. 
4.3 Effects on Environment
Lastly, the environment is another key factor to consider. Sudan’s environment has suffered from overgrazing and degradation (Sulieman et al, 2012:133), and a water supply method that is not environmentally friendly would only cause more damage.  

5.0 COMPARISON OF OPTIONS比较选项

5.1 Cost
5.1.1 Water Desalination
Though technological advances have allowed for a reduction in the total cost of water desalination by improving energy efficiency, the cost in environmental pollution is high (Karagiannis et al, 2008). It is important to note that desalination cost is dependent on the method chosen, the salinity level, the energy source being used and the desalinating plant’s capacity (ibid). The primary feed water would come from the Red Sea which when compared to other sea water bodies has atypical chemical compositions making it more saline due to the high amounts of hot brine and salt deposits in the middle bottom of the sea (Hafez et al, 2002). The cost of desalination would therefore be higher and would rise further depending on the size of the plant. As Karagiannis et al (2008) note, the difference in cost between a plant producing over 60,000m3/day and one producing below 1,000m3/day is quite significant as is seen in the table below. The larger plant is more economical in terms of production costs but more expensive in terms of capital and maintenance. It is also important to bear in mind that over 30% of the unit production cost in desalination is attributed to energy costs (Hafez et al, 2002).
Cost in relation to production capacity:
Plant output (m3/day) Cost (per m3)
<1000 1.78

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