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Desalination A part of an alternative solution to meet the water in demand? By Seong Taek Bpang Mar/07/2011.

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Presentation on theme: "Desalination A part of an alternative solution to meet the water in demand? By Seong Taek Bpang Mar/07/2011."— Presentation transcript:

1 Desalination A part of an alternative solution to meet the water in demand? By Seong Taek Bpang Mar/07/2011

2 Table of Contents Definition/Back ground Operating process Types of desalination World trend Issue of desalination

3 Current Status of water According to IDA o Fresh water is app 3% of world water deposit o Less than 30 % of the water, ground and surface water, are available for daily use within the 3 percent

4 Increasing demand and unreliable supply Increasing population and water demand o The expected population growth is about 2.6 billion in next 45 years, and it would mostly be from developing countries according to the U.S. Census Bureau. Unreliable supply o Due to the climate change and pollution, traditional method of collecting water is becoming unreliable. o Ex- Australia, a country relied on collecting rain fall water is now looking for alternatives such as desalination due to the drought and low rain fall o Ex- Southern California dependence of Colorado river.

5 Christopher Gasson of Global Water Intelligence (GWI)GWI “People do desalination when they run out of opportunities, and the problem is the world overall is running out of opportunities: groundwater is overexploited to the extent it’s becoming saline and unusable; rivers are being drained; new dams are becoming less and less viable [and] long- distance transfer is expensive and controversial.”

6 What is Desalination? Desalination is the process of removing dissolved salt and other minerals from seawater to create freshwater The fact that desalination requires sea water the construction of a plant is limited by location Majority of desalination plants are operating and being built in middle eastern country and Pacific island

7 General Process diagram of Desalination Pant Pre treatment Post treatment Desalination Unit brine Water feed Fresh water Filtering Large particles Screening Floatation Sedimentation coagulation Chlorination UV treatment pH adjustment CO2 absorption Limestone (CaCO3) pH adjustment Chlorination Re-mineralization

8 Varying post treatment according to application Drinking waterIrrigation waterProcess water Sodium chloride < 450 mg/L SAR optimization minimized Calcium, MagnesiumHardness 6-10 o Dminimized pH Boron<0.5 mg/L (WHO) <1 mg/L (EU) Crop dependent DisinfectionRequiredNot required

9 Different Types of desalination technology Thermal desalination Multi-stage flash (MSF) Multiple-effect distillation (MED) vapor-compression (VC) Membrane desalination Reverse Osmosis (RO) Electro dialysis reversal (EDR) Nano filtration Membrane distillation Others include Solar, and Geothermal desalination

10 Thermal desalination (Conventional) Usually requires large amount of energy Good combination with Power plant (Dual purpose) o Thermal Desalination plant can use thermal energy (Low grade energy) that has been exhausted from the power plant. o For MSF distillation process distillers are coupled with extraction condensing or back pressure steam turbine o Most of the desalination plant in middle eastern is dual purpose desalination plant to achieve low operating cost.

11 Multi stage flash desalination

12 Shoaiba MSF desalination plant in Saudi Arabia

13 Membrane desalination Semi permeable membrane is used for processing water Relatively lower energy consumption of Energy compared to thermal desalination Driving force is supplied by a pump (Electricity) o Typical operating pressure of sea water reverse osmosis is 600~1000 psi o Typical operating pressure of brackish water is psi

14 Reverse Osmosis Osmosis Reverse Osmosis

15 Spiral construction of membrane


17 World largest RO desalination plant in Saudi Arabia

18 Trend of desalination Plant Membrane desalination is being favored over thermal desalination o Development of membrane technology Increased durability of membrane – During 1980 and 1990 the life time of membrane was 2~3 y; life time of membrane these days are 7~7.5 y – Capacity of processing water per membrane Increased efficiency of membrane – Typical efficiency of a membrane is reported to be 48% o Reduced cost of membrane production


20 Economic side of desalinated of water Typical cost of desalinated water (1 m 3 =264 gallon) sea water desalting US $ /m 3 brackish water desalting US $ / m 3 Cost of traditional supply of water US $ /m 3 Desalinated water cost component o capital costs (%) o energy costs (%) other costs o (labor, chemicals, etc) (%) Depending on the location desalinated water can be competitive with other sources of water


22 Comparison of the two type MSF desalination Benefits: low operating cost when it is co- located with power plant Relatively low quality of feed water compared to RO. Cons: High operating cost when sources of heat is not available High rates of corrosion and scale formation RO desalination Benefits: Low energy intense (Reduced energy consumption) High quality process water Compact plant design Cons: Higher capital cost Re-mineralization is needed Comparison in terms of energy usage Average thermal desalination produce 23.41kgCO2/m 3 Average reverse osmosis would produce 1.78kgCO2/m 3

23 Issues and Misconception of Desalination Major concerns: o Effects of open water intake to marine life Fish eggs Fish larvae Plankton o Pollution due to the brine Highly concentrated brine water is denser than sea water o Increase in CO 2 emission

24 Redesigning intake pipe and discharge pipe o Offshore intake o Sub sea bed intake o Passive intakes Use of an alternative energy sources for desalination plant o Majority of the desalination plant in Australia is Wind powered o Saudi Arabia, a world’s largest producing country is investigating use of solar powered desalination plant. More energy efficient design o Combining technology's of both thermal and Membrane Efforts in conserving environment o Outfall pipe o Multi port diffusor o Blending with cooling tower water

25 Growing industry As of year 2007, approximately 7,500 desalination plants are operating world wide. 60 % of the plants are located in Middle East Desalination industry is growing 10 to 15 % on average per year

26 World wide desalination water production

27 Questions?

28 References htm htm osmosis-at-178kg-of-co2m3-clear-winner-over-thermal-distillation/ osmosis-at-178kg-of-co2m3-clear-winner-over-thermal-distillation/ water/treatment/desalination/from-seawater_to_drinking.html water/treatment/desalination/from-seawater_to_drinking.html

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