Desalination is a water treatment process that separates salts from saline water to produce potable water. The desalination process uses large amount of energy to produce pure water from salt water source. Salt water is fed into the process, and the result is an output stream of pure water and another stream of waster with high salt concentration. Desalination techniques are mainly classified into two types:
- Processes based on physical change in the state of the water, and
- Processes using a membrane that employ the concept of filtration.
There are more than 15,000 industrial-scale desalination units worldwide, with combined capacity exceeding 8.5 billion gallons per day. The market leader is the membrane desalination process with around 44 percent of total capacity, followed closely by the thermal process of multi-stage flash (MSF) with about 40 percent market share. The main sources of feed water for desalination are seawater (58 percent), brackish ground water (23 percent), and other sources such as rivers and small salt lakes.
Water Problems in MENA and Desalination
Access to clean drinking water is one of the major health issues today. The Middle East and North Africa (MENA) region is the most water scarce region of the world. High population growth rate, urbanization and industrialization, coupled with limited availability of natural potable water resources are leading to serious deficits of freshwater in many parts of MENA. Freshwater sources in the MENA region are being continuously over-exploited and increased use of desalted seawater is unavoidable in order to maintain a reasonable level of water supply.
Conventional large-scale desalination is cost-prohibitive and energy-intensive, and not viable for poor countries in the MENA region due to increasing costs of fossil fuels. In addition, the environmental impacts of desalination are considered critical on account of emissions from energy consumption and discharge of brine into the sea. Brine has extremely high salt concentration and also contains leftover chemicals and metals from the treatment process which poses danger to marine life.
The negative effects of desalination can be minimized, to some extent, by using renewable energy to power the plants. Renewable energy-powered desalination offers a sustainable method to increase supply of potable water in MENA countries. The region has tremendous wind and solar energy potential which can be effectively utilized in desalination processes like reverse osmosis, electrodialysis, and ultrafiltration and nanofiltration. The cost of renewable energy desalination is expected to become more attractive with technological advancements and coupled with rising costs of freshwater and fossil fuels.
Solar-Powered Desalination for MENA
Solar energy can be directly or indirectly used in the desalination process. Collection systems that use solar energy to produce distillate directly in the solar collector are called direct collection systems while systems that combine solar energy collection systems with conventional desalination systems are called indirect systems. The major drawbacks with the use of solar thermal energy in large-scale desalination plants are low productivity rate, low thermal efficiency and large area requirement. Solar thermal-based desalination plants are more suitable for small-scale production especially in remote arid areas and islands having scarce conventional energy resources.
Concentrating solar power (CSP) offers an attractive option to power industrial-scale desalination plants that require both high temperature fluids and electricity. CSP can provide stable energy supply for continuous operation of desalination plants based on thermal or membrane processes. Infact, several countries in the region, such as Jordan, Egypt, Saudi Arabia are already developing large CSP-based solar power projects that promises to usher in a new era in the Middle East.
The MENA region has tremendous solar energy potential that can facilitate the generation of energy required to offset the alarming freshwater deficit. The region would be facing a grave water crisis with the population expected to be double by 2050. Solar-powered desalination combined with efficient use of water reserves and re-use of wastewater can help in easing the water crisis in the region. It will also help in reducing the financial load on MENA governments from power and water sectors, and thus diverting funds to much-needed educational, health and industrial sectors.