Water Desalination & RO
Drawing a Solution: Forward Osmosis Water Desalination
Drawing a Solution Forward Osmosis Water Desalination
Source: https://www.massacademy.org
Edited by: Stephanie Chin
Abstract
Water infiltration and tsunamis cause aquifer salinization, which threatens our main supply of freshwater. Current research suggests that forward osmosis is a novel, low-energy, and thus low cost method of desalination, and developing practical draw solutions can improve the efficiency of this process. To study this on a small scale, an osmometer was built of 1.5″ (3.81 cm) PVC piping; low pressure, flat sheet reverse osmosis membranes were used as selectively permeable membranes to separate a sodium-chloride (NaCl) feed solution from sucrose (C12H22O11) draw solutions at various concentrations. The average water flow from the feed to draw solution was calculated based on the change in the salinity of the feed solution over time. Statistical tests were performed to analyze the effect of initial concentration of the C12H22O11 solution on average water flux and to compare the performance of forward osmosis across two different membranes. Increasing membrane surface area should increase water flow. Water desalination for domestic use is important to mitigate the inconvenience of groundwater salinization and well contamination.
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Related books
California Desalination Planning Handbook
Introduction:
Desalination is receiving increased attention as a means for addressing the water supply challenges of California. Growing population, much of which is located in semi-arid regions of the state, and various other water demands pose increased pressure on existing water supplies. Much of California’s water supply depends on snow accumulation in the winter, providing spring runoff that flls reservoirs and replenishes often depleted groundwater supplies. But in periods of drought, water supply shortages can be encountered throughout the state, particularly in the central valley and southern portion of the state. All indications suggest the impacts of global warming will include a change in the timing of runoff and less snowfall. This will put more pressure on existing supplies, and exacerbate the impacts of drought. As the implications of global warming become clearer, more emphasis will likely be given to developing
new sources of water supply to meet existing and projected demand. While conservation and recycling are recommended as the frst course of action, other alternatives (such as desalination and increased surface and groundwater storage) are receiving increased attention.
California Desalination Planning Handbook
Introduction:
Desalination is receiving increased attention as a means for addressing the water supply challenges of California. Growing population, much of which is located in semi-arid regions of the state, and various other water demands pose increased pressure on existing water supplies. Much of California’s water supply depends on snow accumulation in the winter, providing spring runoff that flls reservoirs and replenishes often depleted groundwater supplies. But in periods of drought, water supply shortages can be encountered throughout the state, particularly in the central valley and southern portion of the state. All indications suggest the impacts of global warming will include a change in the timing of runoff and less snowfall. This will put more pressure on existing supplies, and exacerbate the impacts of drought. As the implications of global warming become clearer, more emphasis will likely be given to developing
new sources of water supply to meet existing and projected demand. While conservation and recycling are recommended as the frst course of action, other alternatives (such as desalination and increased surface and groundwater storage) are receiving increased attention.
Desalination Plant Basis Of Design
Overview:
The project potable water requirements will be provided using single desalination plant with the Grand Bahama Port Authority water supply serving as the backup source. The overall desalination treatment process will consist of feedwater pumping, bag filtration, optional media filtration, the addition of a scale
inhibitor, cartridge filtration, membrane separation, forced air degasification, re-pumping, and post treatment. Provisions have been included to bypass the post treatment systems for the production of irrigation water. The post aeration re-pump station will be designed to transfer either type of water to the
appropriate storage tanks located within the project. Membrane concentrate will be disposed via an injection well to be constructed as part of this project.
The desalination process will consist of a dual treatment units or “trains” each equipped with a positive displacement axial piston first pass membrane feed pump, first pass membrane array, energy recovery system, second pass membrane feed pump, second pass membrane array, high- and low-pressure
piping and instrumentation. The second pass system is designed to treat up to 60 percent of the first pass permeate. A membrane cleaning/flush system will be provided. The membrane post treatment will be designed to receive the flow from both units and consists of a forced air degasified, repumping, recarbonation, calcium carbonate up flow contactors to boost finished water hardness and alkalinity concentrations; and three chemical feed systems for the metering of a corrosion inhibitor, dilute hydrochloric acid for pH adjustment and sodium hypochlorite for residual disinfection. The final pH and chlorine residual will be controlled and recorded by a separate system. The following sections describe the various aspects of the facility in greater detail. Process flow
schematics are presented in Appendix A.
Desalination Plant Basis Of Design
Overview:
The project potable water requirements will be provided using single desalination plant with the Grand Bahama Port Authority water supply serving as the backup source. The overall desalination treatment process will consist of feedwater pumping, bag filtration, optional media filtration, the addition of a scale
inhibitor, cartridge filtration, membrane separation, forced air degasification, re-pumping, and post treatment. Provisions have been included to bypass the post treatment systems for the production of irrigation water. The post aeration re-pump station will be designed to transfer either type of water to the
appropriate storage tanks located within the project. Membrane concentrate will be disposed via an injection well to be constructed as part of this project.
The desalination process will consist of a dual treatment units or “trains” each equipped with a positive displacement axial piston first pass membrane feed pump, first pass membrane array, energy recovery system, second pass membrane feed pump, second pass membrane array, high- and low-pressure
piping and instrumentation. The second pass system is designed to treat up to 60 percent of the first pass permeate. A membrane cleaning/flush system will be provided. The membrane post treatment will be designed to receive the flow from both units and consists of a forced air degasified, repumping, recarbonation, calcium carbonate up flow contactors to boost finished water hardness and alkalinity concentrations; and three chemical feed systems for the metering of a corrosion inhibitor, dilute hydrochloric acid for pH adjustment and sodium hypochlorite for residual disinfection. The final pH and chlorine residual will be controlled and recorded by a separate system. The following sections describe the various aspects of the facility in greater detail. Process flow
schematics are presented in Appendix A.
Assessment Of Best Available Technologies For Desalination In Rural/Local Areas
Introduction: The Sustainable Water Integrated Management (SWIM) is a European Union(EU)-funded Regional Technical
Assistance Program [1] that “aims at supporting water governance and mainstreaming by promoting sustainable
and equitable water resources management to become a prominent feature of national development policies and
strategies (agriculture, industry, tourism, etc).” [2]
Countries in the south of the Mediterranean are facing increasing water scarcity. This scarcity is driving the need
for augmenting conventional water supply with alternative water sources. Rural and remote areas are particularly
disadvantaged because such areas are often located far away from municipal water supply systems and
conventional water sources, and are often not connected to the electric power grid. There is good potential for
addressing the water scarcity problem in rural and remote areas through sustainable saline water desalination
technologies. Seawater and brackish water desalination are well-established industries comprising a wide variety
of available technologies with decades of accumulated experience. There are many advancements and evolution in
desalination technologies. The numerous technologies and processes available have different characteristics,
advantages and disadvantages that make each suitable for particular market segments or specific niches.
Moreover, much of the cumulative technology experience is related to large urban supply plants that are either
connected to the grid, or are themselves part of large power and desalination cogeneration plants. Rural and
remote areas have special requirements that influence the appropriate selection of technologies. These include
technical requirements related to small-scale application using renewable energy sources, ease of operation and
maintenance, and simple design; requirements dictated by geographical location; as well as socio-economic and
socio-cultural requirements related to the communities that are intended to operate and benefit from the
technology. Successful implementation and long term sustainability (operational and environmental sustainability)
of desalination projects for rural and remote locations requires that all the relevant requirements be identified and
addressed from the earliest stages of the project.
Assessment Of Best Available Technologies For Desalination In Rural/Local Areas
Introduction: The Sustainable Water Integrated Management (SWIM) is a European Union(EU)-funded Regional Technical
Assistance Program [1] that “aims at supporting water governance and mainstreaming by promoting sustainable
and equitable water resources management to become a prominent feature of national development policies and
strategies (agriculture, industry, tourism, etc).” [2]
Countries in the south of the Mediterranean are facing increasing water scarcity. This scarcity is driving the need
for augmenting conventional water supply with alternative water sources. Rural and remote areas are particularly
disadvantaged because such areas are often located far away from municipal water supply systems and
conventional water sources, and are often not connected to the electric power grid. There is good potential for
addressing the water scarcity problem in rural and remote areas through sustainable saline water desalination
technologies. Seawater and brackish water desalination are well-established industries comprising a wide variety
of available technologies with decades of accumulated experience. There are many advancements and evolution in
desalination technologies. The numerous technologies and processes available have different characteristics,
advantages and disadvantages that make each suitable for particular market segments or specific niches.
Moreover, much of the cumulative technology experience is related to large urban supply plants that are either
connected to the grid, or are themselves part of large power and desalination cogeneration plants. Rural and
remote areas have special requirements that influence the appropriate selection of technologies. These include
technical requirements related to small-scale application using renewable energy sources, ease of operation and
maintenance, and simple design; requirements dictated by geographical location; as well as socio-economic and
socio-cultural requirements related to the communities that are intended to operate and benefit from the
technology. Successful implementation and long term sustainability (operational and environmental sustainability)
of desalination projects for rural and remote locations requires that all the relevant requirements be identified and
addressed from the earliest stages of the project.
Desalination and Water Treatment
Abstract:
This study proposes a simple design method of the Reverse osmosis (RO) system in RO brackish water desalination plants. This method is based on the application of maximum available recovery without scaling of any of the compounds present in the water as silica, calcium carbonate, calcium sulfate, barium sulfate, strontium sulfate, and calcium fluoride, and membrane manufacturer design guidelines, and the plant production. Although the method was originally
conceived for application to subterranean brackish waters in the Canary Islands, Spain (principally Gran Canaria, Fuerteventura and Tenerife), it can be extrapolated to other types of region and water treatable with RO systems. The required input data are the chemical composition of the feed water, pH, temperature, silt density index membrane manufacturer design guidelines, and the plant production. The programmed method then determines the design of the RO system. The method whose procedure is described graphically and analytically can be used as an aid in design optimization of RO brackish water desalination plants with acid-free pretreatment processes and only the use of scale inhibitor using spiral wound membranes. Practical applications are presented. The final results for different types of feed water and capacities are showed.
Desalination and Water Treatment
Abstract:
This study proposes a simple design method of the Reverse osmosis (RO) system in RO brackish water desalination plants. This method is based on the application of maximum available recovery without scaling of any of the compounds present in the water as silica, calcium carbonate, calcium sulfate, barium sulfate, strontium sulfate, and calcium fluoride, and membrane manufacturer design guidelines, and the plant production. Although the method was originally
conceived for application to subterranean brackish waters in the Canary Islands, Spain (principally Gran Canaria, Fuerteventura and Tenerife), it can be extrapolated to other types of region and water treatable with RO systems. The required input data are the chemical composition of the feed water, pH, temperature, silt density index membrane manufacturer design guidelines, and the plant production. The programmed method then determines the design of the RO system. The method whose procedure is described graphically and analytically can be used as an aid in design optimization of RO brackish water desalination plants with acid-free pretreatment processes and only the use of scale inhibitor using spiral wound membranes. Practical applications are presented. The final results for different types of feed water and capacities are showed.
An Introduction To Membrane Techniques For Water Desalination
This course is adapted from the Unified Facilities Criteria of the United States government, which is in the
public domain, is authorized for unlimited distribution, and is not copyrighted.
An Introduction To Membrane Techniques For Water Desalination
This course is adapted from the Unified Facilities Criteria of the United States government, which is in the
public domain, is authorized for unlimited distribution, and is not copyrighted.
Chemical Cleaning Effects On Properties And Separation Efciency Of An RO Membrane
Abstract: This study aims to investigate the impacts of chemical cleaning on the performance of a reverse osmosis
membrane. Chemicals used for simulating membrane cleaning include a surfactant (sodium dodecyl sulfate, SDS), a
chelating agent (ethylenediaminetetraacetic acid, EDTA), and two proprietary cleaning formulations namely MC3
and MC11. The impact of sequential exposure to multiple membrane cleaning solutions was also examined. Water
permeability and the rejection of boron and sodium were investigated under various water fluxes, temperatures and
feedwater pH. Changes in the membrane performance were systematically explained based on the changes in the
charge density, hydrophobicity and chemical structure of the membrane surface. The experimental results show that
membrane cleaning can significantly alter the hydrophobicity and water permeability of the membrane; however, its
impacts on the rejections of boron and sodium are marginal. Although the presence of surfactant or chelating agent
may cause decreases in the rejection, solution pH is the key factor responsible for the loss of membrane separation
and changes in the surface properties. The impact of solution pH on the water permeability can be reversed by
applying a subsequent cleaning with the opposite pH condition. Nevertheless, the impacts of solution pH on boron
and sodium rejections are irreversible in most cases
Chemical Cleaning Effects On Properties And Separation Efciency Of An RO Membrane
Abstract: This study aims to investigate the impacts of chemical cleaning on the performance of a reverse osmosis
membrane. Chemicals used for simulating membrane cleaning include a surfactant (sodium dodecyl sulfate, SDS), a
chelating agent (ethylenediaminetetraacetic acid, EDTA), and two proprietary cleaning formulations namely MC3
and MC11. The impact of sequential exposure to multiple membrane cleaning solutions was also examined. Water
permeability and the rejection of boron and sodium were investigated under various water fluxes, temperatures and
feedwater pH. Changes in the membrane performance were systematically explained based on the changes in the
charge density, hydrophobicity and chemical structure of the membrane surface. The experimental results show that
membrane cleaning can significantly alter the hydrophobicity and water permeability of the membrane; however, its
impacts on the rejections of boron and sodium are marginal. Although the presence of surfactant or chelating agent
may cause decreases in the rejection, solution pH is the key factor responsible for the loss of membrane separation
and changes in the surface properties. The impact of solution pH on the water permeability can be reversed by
applying a subsequent cleaning with the opposite pH condition. Nevertheless, the impacts of solution pH on boron
and sodium rejections are irreversible in most cases
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