Analysis, made by Abengoa, about the the current challenges of desalination and water reuse technologies.

1. Innovative Technology Solutions
for Sustainability
June, 2014
Desalination and water reuse technologies
Singapore International Water Week – 2014

2. Current water challenges
Increasing water scarcity problems
•Increasing water demand
•Uneven population distribution
•Climate change
•Rapidly growing cities
Increasing water quality problems
•The use of pesticides, fertilizers and chemicals in agriculture
•Over exploitation of underground water
•Emerging pollutants
Water sustainability for industries
•Water – energy nexus
•Water and energy demand due industry development
•Managing the effluents from the industries
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3. 3
Desalination and Water Reuse Technologies
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4. 4
Desalination and Water Reuse Technologies
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5. 5
Selected Pretreatment Technologies
MF/UF
MF and UF membranes are used to remove particles that are suspended in a solution
Used in:
-Treatment of drinking water
-Pretreatment process for RO
-For producing a concentrated waste stream
UF water increases the life span of RO membranes
Under study for preventing harmful algal bloom effects
Cross-flow filtering does not need to be cleaned as frequently as dead-end systems
Pore size range of various membranes*
*Source: Advanced membrane technology and applications (Li et al.)
UF racks in Qingdao desalination plant
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6. 6
Selected Desalination Technologies
Multi-Effect Distillation
Reverse Osmosis
Produces water with a low concentration of dissolved salts
In each distillation chamber, saltwater is sprayed and vaporized on contact with a steam-filled heat exchanger
Cost effective when there is a cheap source of steam, and contaminants cannot be removed by any other method
Producing freshwater from seawater by reverse osmosis requires the feedwater to be under a high pressure
It is necessary to reach a balance between the required levels of water recovery and salt rejection
Energy consumption has decreased significantly as with the use of energy recovery devices (ERDs)
Image of Qingdao RO racks
Scheme of MED process with three distillation chambers*
*Source: Industrial desalination and water reuse repor – GWI
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7. 7
High Recovery Technologies
Brine Concentrators
Cristallizers
Are used to purify industrial wastewater. Wastewater that is introduced to the concentrator is separated into distilled water and concentrated brine.
Distilled water can be reused in an industrial plant.
The rest of the water in the concentrated brine can be recovered in a crystallizer.
Crystallization is the final step in many water reuse processes
Can recover most of the water from the concentrated brine solution that is produced by RO and thermal processes and brine concentrators
If ZLD is desired, the crystallization step is always necessary (i.e. Evaporation pond or cristallizer unit)
Scheme of falling film brine concentrator with vapour compression*
Scheme of concentrate crystallizer**
*Source: Industrial desalination and water reuse report – GWI **Source: Desalination engineering planning and design, Voutchkov
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8. 8
Water reuse
Membrane bioreactors
Is a modification of the activated sludge process. An MF/UF membrane is added to the bioreactor to increase the removal of organic matter and suspended solids
The treated wastewater is drawn from the permeate stream of the membrane
Existing membrane configurations are flatsheet and hollow fibers
3D schemes of MBR project
a) view from above, b) lateral section view
a)
b)
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9. 9
Summary
Pretreatment technologies selection is relevant for process optimization, MF/UF membranes can increase the life span of RO membranes, thermal desalination technologies require lime softening.
Most relevant desalination technologies are MED and RO, energy consumption for RO desalination has decreased thanks to the use of ERDs.
High recovery technologies are necessary for industrial reuse of effluents, brine concentrators and crystalization are necessary for ZLD or near ZLD.
MBR stands out as one of the main technologies to be used in reuse applications, since the use of porous membranes enhaces the quality of regenerated water over activated sludge treatment.
Technology development will be fundamental for solving satisfactorily unmet water challenges, such as emerging pollutants.
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10. Thanks!
Innovative Technology Solutions
for Sustainability