DESALINATION

Desalination

• Technologies designed to produce freshwater from saline water.

• Seawater – 35000 ppm TDS• Brackish water – 2000 ppm TDS• Human Consumption – 500 ppm• Agriculture and Irrigation – less than

500 ppm• Thomas Jefferson (1791)

Desalination Processes

• Reverse osmosis• Electrodialysis• Multi Stage Flash• Multi effect

distillation• Vapor compression

distillation

Cost Considerations

• Design Parameters– Salinity– Composition– Temperature

• Equipment cost• Energy Import • O & M Costs• Service Life of Membranes

(RO)• Site-Related Costs

Problems with Instituting Desalination and Current Use

• Lack of skilled personnel• Lack of technology• Funding • Need for coordination and

planning• Currently 7500 plants.• 50% of Northern Africa

and the Middle East • Saudi Arabia –128 MGD

Arabian Gulf Countries Installed Desalination Capacity

•  

No. of units

Capacity (1,000 m³/day)

Share by process type (%)

MSF RO ED VC MED

Saudi Arabia 874 2,980 80.7 16.2 2.6 0.5

Kuwait 279 1,090 95.5 1.8 0.55 1.6 0.25

U.A.E. 99 1,020 98.3 0.9 0.5 - -

Qatar 47 310 9 7.9 - - 0.7 0.9

Bahrain 143 260 56.7 37.2 4.9 0.8 0.4

Oman 41 100 91.1 1.9 0.9 1.7

TOTAL 1,483 5,760 86.7 10.7 1.8 0.65 0.15

Source: Akkad 1990.MSF = multi-stage flash. RO = reverse osmosis. ED = electrodialysis. VC = vapour compression. MED = multi-effect distillation.

Negative Environmental Impacts

• Coastal Land Use• Aquifer Impact• Marine Environment

Impact• Noise Pollution• Intensive Energy

Requirements

Leaky Pipe

Solutions?

• Power plant/Desalination plant Combination– Dilution of Brine– Energy Source– One site

• Long Discharge Pipes• Leak Recording

Equipment• Money??????

Positive Environmental Impacts

• Improvements of Quality and Sanitation

• Softening of Water• Agriculture

– Soil– Drainage– Groundwater

• Becoming Less Expensive

Discussion• 1.      Should desalination only be considered in areas that have

water shortages? In areas with polluted waters, should clean-up be required prior to building a desalination plant? Would this be a reasonable request by a funding agency?

• 2.      Is desalination a useful technology in countries with extreme climatic changes, drought and flooding? How can the energy required to run a desalination plant be used in the wet seasons?

• 3.      Most existing desalination plants discharge brine directly back into the ocean. It has been shown that this can harm the ecosystem around the area of discharge? How should this be factored into the desalination plant design in countries that are struggling financially already? Whose responsibility should it be to ensure minimal environmental damage?

• 1.      How could desalination have an impact on land locked countries?

• 2.      Why consider desalination when there is so much water to be saved through conservation and recycling, especially in the United States?

• 3.      The operation and maintenance of a desalination plant is generally extensive. Is it a viable option for a plant to be built in an underdeveloped country and then left for that country to maintain?