By Mohammed Zaki Trache

With The Middle East suffering from sever water shortages various countries in the region have resorted to relying heavily on desalination, collectively holding 33% of global planned desalination plants. The desalination process characteristically demands large quantities of energy, rendering the costs associated with desalination greater than its alternatives, which include groundwater excavation and other methods of water recycling. However, the geographic location as well as the water poor climate of the Middle East solidifies desalination as an important method to obtain consumable water.

Desalination processes traditionally are only associated with the transformation of saltwater into water fit for human consumption or irrigation purposes. However, technological advances in desalination methods is quickly allowing for a broader range of inputs into the desalination process, allowing the processing of industrial and agricultural wastewater (brackish water), all the while resulting in a more cost effective practice. 

Furthermore, while desalination methods vary depending on the application, they may be categorized into two technologies:

1. Thermal Heating Technology

Thermal technology requires energy in the form of heat to obtain pure water from the distillation process of saline water vapor. The energy requirements for thermal heating are substantial; therefore thermal desalination technology is more popular for salt-water desalination rather than brackish water. 

Thermal technology includes three different processes:

a. Multiple Stage Flash Process (MSF)

This process, which is shown here, uses evaporating chambers, called stages, at decreasing pressures to conduct the distillation process. The initial seawater is heated under high pressure and then enters the first chamber, which is at a lower pressure level. The pressure drop causes the water to boil rapidly causing it to evaporate. This process, known as flashing, is further repeated throughout the stages due to the declining pressures across each stage. 

The vapor created from each stage is then condensed through heat exchanger tubes, which are kept at low temperatures by cold seawater water, in each stage forming freshwater. A major characteristic of the heat exchanger is that only a small percentage of the feed water is converted into vapor and condensed thus producing a small amount of freshwater. 


b. Multi-Effect Distillation

Multi-effect distillation (MED), shown here, contains a series of chambers, called effects, where evaporation and condensation occurs at reduced ambient pressures. In MED, a series of evaporator effects produce water at progressively lower pressures. Due to this decrease in pressure, water is boiled at lower temperatures and subsequently the water vapor produced in the first effect serves as the heating medium for the second and so on. 

c. Vapor Compression distillation

Vapor Compression distillation (VCD) may be operated as either a stand-alone process or as an add-on to an existing process, such as MED.  As the name implies, vapor compression provides the heat required for water evaporation. The most commonly available configuration contains a mechanical compressor, compressing the vapor and providing heat. VCDs are most commonly found in small-scale applications such as desalination plants for individual neighborhoods, hotels, and hospitals. 

2. Membrane Technology

Electrodialyis/Electrodialysis Reversal (ED/EDR)

Although ED and EDR were originally conceived as a seawater desalination process, the electrical process works better for lower salinity water (brackish water). Therefore, membrane technology has been mainly used for treating of brackish wastewater.

Electrodialysis uses an electrical potential to move salts through a membrane, leaving fresh water behind as product water, where as ED relies on the fact that most salts dissolved in water are either positively charged ions called cations or negatively charged ions called anions. Therefore ions are attracted to electrodes at an opposite electric charge. This allows for the construction of selective membranes that only allow passage for either anions or cations. 

Inside the plants these membranes are placed in alternate order: Anion-permeable membrane followed by a cation-permeable membrane. As saline solution flows through the system, salt is reduced in one channel, while concentrated solutions are gathered at the electrodes in the spaces between the alternating membranes, which are called cells. One ED unit consists of several hundred cells bound together with electrodes, and is referred to as a stack. Once saline water passes through both membranes, fresh water is produced.

Reverse Osmosis (RO).

Osmosis is a naturally occurring phenomenon in which water containing a low salt concentration passes into a more concentrated solution through a semi-permeable membrane. With reverse osmosis, pressure is applied to the solution with the higher salt concentration solution allowing a reversal in the water flow through the membrane causing the salt to be blocked by the membrane, thus creating fresh water.

The RO desalination process may be subdivided into 4 different stages; the pretreatment stage, high-pressure pump stage, membrane system stage, and the post treatment stage.

The pre-treatment stage includes removing any solid material that may be contained in the water, which could cause harm to the semi-permeable membranes used later in the process. It also constitutes of water pretreatment, to ensure the membranes are free from salt precipitation or microbial growth. This pre-treatment entails methods such as using chemical feed followed by coagulation/flocculation/sedimentation, and sand filtration. Different considerations may affect the type of pre-treatment chosen, which include the quality of the feed water, space considerations, and RO membrane requirements. 

The high-pressure pump stage provides the pressure needed to enable the untreated water to pass through the membrane. The pressures vary depending on the salt content of the feed water, ranging from about 150 pounds per square inch (psi) for slightly brackish water to 800 - 1,000 psi for seawater. This allows for a more effective and efficient treatment of saline water.

In the membrane system stage, RO membranes are usually either spiral wound and Hollow fiber. Spiral wound membranes, the most popular membranes, constitute of materials such as of cellulose acetate or of other composite polymers. In the spiral wound design, the membrane is wrapped around a central water collection tube. Under pressure, the feed water then flows within the spiral membrane, allowing for desalinated water to be collected within the central collecting tube (This process is shown here).


After the feed water passes through the membrane and is processed, the remaining water increases in salt content. in the post treatment stage It is necessary that a portion of the feed water is discharged without passing through the membrane, as without this, the pressurized feed water would continue to increase in salinity content, resulting in salt super saturation. The percentage of feed water which is discharged without passing through the membrane depends on the original salinity of the feed water, with an average figure ranging from 20 percent for brackish water to about 50 percent for seawater. 


Finally once these 4 processes have been completed, fresh water is produced and can be used for municipal and agricultural purposes.

Conclusion

It is evident that with a plethora of treatment processes, creating new freshwater sources should not be difficult. Furthermore, in an attempt to make these processes less energy intensive and environmentally friendly, countries across the Middle East have been attempting to incorporate renewable energy use with desalination processes to allow for a more efficient and environmentally friendly way of producing fresh water. However in order for this to be achieved heavy investment in the technology and knowledge required is key.  Only then can one look ahead for a water rich Middle East.

By Amir Dakkak

With only 1.4% of the world’s freshwater resources serving 6.3% of the global population, it is no secret that the MENA region is one of the most water scarce regions in the world. The biggest sufferer of the MENA region is most definitely the GCC region. Increasing water use efficiency, and increasing water supply (mainly through desalination, and to some extent wastewater treatment) have been used to try and solve this dilemma. Although processes such as desalination and wastewater treatment have their positive effects in terms of increasing a country’s water supply, they also have negative impacts on the environment through their intensive carbon dioxide (CO2) emissions, and aquatic habitat destruction. This has given rise to different methods aimed at reducing such detrimental effects. In fact, a very interesting article by Dr. Nasser al Saidi (founder and president of Nasser Saidi & Associates) about Solving the GCC’s water crisis (http://bit.ly/LA5q1P) has brought focus to a particular way forward: renewables-based desalination. In his article, Dr. Nasser indicates that “green desalination” along with more rational pricing of water utilization should become a clear policy priority for addressing water scarcity in the GCC region. He also states that the GCC should aim to create an ecosystem that is resource efficient, does not contribute to climate change, while addressing not only the region’s severe water scarcity but also the related complications associated with polluting energy technologies. To further expand on Dr. Saidi’s thoughts on this subject, Arab Water source conducted a more detailed interview with the man himself.

1. Amir Dakkak (AD): Since using desalination plants powered by renewable energy offers a viable solution to the GCC's water crisis, why has it taken such a long time for the GCC to construct such projects especially when all the resources seem to be available? 

Dr. Nasser Saidi (NS): Using renewable energy such as solar for desalination is still a young and evolving technology, although it is likely to spread rapidly in the GCC, which has some 40% of global desalination capacity. Although costs have substantially declined to make use financially viable, governments and public utilities are not familiar with the application of RE technologies to desalination. Two, there is a lack of established policy frameworks and tools to encourage the use of renewables. For example there are no feed-in tariff policies in place. Three, GCC governments actively promote the use of fossil fuels through large subsidies for the use of oil and gas in power production, which is directly linked to desalination. Without radical reform of strategies and policies, renewables and by extension renewables-based desalination will continue to be a sadly missed opportunity to protect our environment and gradually remove the expensive burden of subsidies, which represent some 4.5% of GDP and eat up more than 25% of government revenues in the MENA oil exporting countries. Removing subsidies will not be a trivial matter since it will be opposed by a strong lobby which has long benefited from subsidies. A good start is to move away from the existing systems of untargeted subsidies which largely benefit the rich and not the intended target of the poor.

2. AD: Does culture play a big part in the acceptance of renewable desalination?

NS: There is no cultural issue related to accepting renewables-based desalination. There may be a lack of information and awareness of the technological possibilities. Diffusion of new technologies takes times this happens at the margin and in new investments.  If anything, there is a global lack of awareness of the benefits of adopting renewable technologies in general, and in their applicability to desalination.  But the power of supply and demand will impose itself: growing populations facing diminishing water supplies will create the economic and financial incentives to adopt renewable technologies for improved water resource management efficiency.  The problems are more of political-economy and of vested interests that actively work against the introduction of new technologies that threaten their economic interests. This is true both in developed as well as emerging economies.

3. AD: What kind of impacts would such projects have on a country's economy given their heavy financial costs?

NS: This is a false issue.  The GCC and other countries will have to invest to produce power, provide water & transport and other utilities for their young and rapidly growing populations. Such infrastructure investments can either rely on traditional, fossil fuel, high carbon generating technologies or adopt renewable technology solutions which would help decarbonise their economies. Increasingly renewable technologies are competitive. More R&D, increased diffusion and utilization of renewable technologies will lead to more innovation and discoveries that will lower cost curves of activities using renewable technologies. Eventually they will become dominant in much the same way that fossil fuel technologies drove out and replaced human and animal power based technologies. Importantly for the GCC and other countries that have the comparative advantage, given their location, to harness solar, wind and other power, the cost of adoption of renewable technologies will be lower. A household investing in solar panels or a solar power plant investment in the GCC has an absolute advantage over a household or public utility in, say, Germany that would undertake similar investments. The problem is that the incentives are highly skewed in the opposite direction in the GCC as a result of access to cheap, subsidized fossil fuel based technologies. Why would I invest in solar panels if I have access to cheap, fossil fuel based power?

4. AD: Desalination plants powered by renewable energy seem to provide a future solution to the water crisis. Is there a more immediate solution that would be as effective?

NS: The answer is yes. The most immediate solution is through infrastructure investment in “intelligent” water management and to provide incentives to encourage households, business, the public sector and the general public to use less water. The incentives should be through the efficient pricing of water resources and their utilization, as well as non-price mechanisms such as the imposition of quotas or fines. The point is that water is a scarce resource and should be priced accordingly. Many countries of the GCC and the Middle East do not even monitor or meter water usage. But the MENA region is one of the most water scarce regions of the world. Although home to 6.3% of the world’s population (and growing), the region has access to only 1.4 % of the world’s renewable fresh water (and declining). To make matters worse, the region currently exploits over 75% of its available renewable water resources due to its burgeoning population, increased urbanization, mispricing of water and rapid economic growth. Saudi Arabia in an ill-fated drive to increase food production has –over a 15 year period- largely depleted its water aquifer that had taken millions of years to accumulate! It will be forced to stop its wheat production by 2016. Yemen is already a hydrological basket case and Gaza is an ecological disaster.

Better ecosystem and water management systems, improved water use efficiency and pricing, and investment in water infrastructure are all part of the answer. Water is a shared resource and must be managed on a local, basin and national basis.

5. AD: Is it possible to use renewable energy on wastewater treatment plants in the same way as they are used in desalination plants? Would using renewable wastewater treatment provide a more sustainable option to renewable desalination?

NS: Yes, of course. Solar panels have already been installed to provide power for wastewater treatment plants in the US, Germany and China. It could easily have wide applicability in the GCC. Furthermore, energy derived from wastewater treatment can even be used as a renewable energy resource itself. Such recovery processes can produce electrical energy from the utilization of methane rich digester gas, from thermal conversion of biomass, from bio-solid products used by other entities and more. The cheap availability of fossil fuel-based energy & technologies has meant that renewable energy R&D and RE technologies and applications has been limited. This is now changing as RE is becoming cost and financially competitive and there is growing political conviction of the need to address climate change and decarbonise our economies and environment. I believe the coming decade will witness a rapid advancement in RE R&D and wide application and use.



Note: The Arab Water Source team would like to express its thanks and gratitude to Dr. Nasser Saidi for sharing his time and insights on water scarcity in the GCC with us.