Water Desalination & RO
Low Cost Nanomaterials for Water Desalination and Purification
Abstract:
While over 70 per cent of the Earth’s surface is covered by water, most of it is unusable for human consumption. Freshwater lakes, rivers and underground aquifers represent only 2.5 per cent of the world’s total freshwater supply. Unfortunately, in addition to being scarce, freshwater is also very unevenly distributed. The United Nations has compared water consumption with its availability and has predicted that by the middle of this century between 2 billion and 7 billion people will be faced with water scarcity. Increased demand for water is a global problem. In many parts of the world local demand is exceeding conventional resources. More economical use of water, reducing distribution losses and increased use of recycled water can help alleviate this problem but if there is still a shortfall then desalination of seawater or brackish water is a must. Many areas suffering from water shortages are also short of conventional energy resources and cannot afford expensive fossil fuels. More recently, there is remarkable awareness that even if fossil fuels were much cheaper, the burning of these fuels will contribute to climate change and global warming. For these reasons, the use of renewable energy for desalination has to be encouraged. Renewable energy is not a firm source of power and energy is expensive to store in large quantities. Water on the other hand is easily and cheaply stored. Thus, there is compatibility between renewable energy and desalination. This study aims to provide a review of the state of the art technologies of water desalination and discuss the benefits, disadvantage and economic impact of each. The key conclusion of this review is that desalination alone cannot deliver the promise of improved water supply unless that the desalination technology itself has evolved substantially. It has to be significantly cheaper, more reliable, less energy-intensive and more environmentally friendly. Nanotechnolgy would bring desalination technology to meet these requirements in the near future. Recently, new methodologies have been developed recently based on using nanotechnology for water desalination such as Reverse osmosis, Ultra- and Nano-filtration. Also, new technologies based on using solar concentrators for solar desalination have been developed. This report will highlight all of these new methodologies in details. New methodology which combines solar desalination and nanotechnology based on producing low cost nanocomposite to enhance the rate of solar thermal water desalination has been developed in our laboratory (patent pending). These new nanomaterials absorb light so strongly and convert it efficiently into heat energy.
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Desalination Needs and Appropriate technology
Abstract
This study investigates the desalination needs and available technologies in Sri Lanka. Lack of rainfall, pollution due to agricultural chemicals, presence of fluoride, increasing demand, exploitation of ground water and brackishness have created scarcity of fresh pure water specially in near costal and dry zones in Sri Lanka. Due to Chronic Kidney Disease (CKD) around 500 people died in dry zones annually which is suspected to cause by Arsenic and Cadmium contain
in ground water due to agriculture chemicals. The available desalination methods are Reverse Osmosis (RO), Solar distillation and conventional methods. The cost for RO is Rs.0.10 cents per liter and solar distillation Rs.2.96 per liter. Although the price shows that the RO is better but due to high initial investment as a
third world country it is very difficult to afford huge initial investment without government intervention. The experimental solar desalination units only produce nearly 5liters of potable water per day and directly impacted by availability of solar radiation.
The energy availability of Sri Lanka and future potable water demand predicted as 2188.3 Mn liters as maximum demand which will be in 2030, therefore by that time the government should have a proper plan to cater the demand and desalination plants need to be planned and built based on the demand of dry zones and specially agriculture areas. The applicability of renewable energy for desalination in local arena was also simulated taking the Delft Reverse Osmosis plant for the simulation. Results show that the optimum design is combination of Solar PV and existing 100kW Diesel generator Set with Battery bank and
converter.
Desalination Needs and Appropriate technology
Abstract
This study investigates the desalination needs and available technologies in Sri Lanka. Lack of rainfall, pollution due to agricultural chemicals, presence of fluoride, increasing demand, exploitation of ground water and brackishness have created scarcity of fresh pure water specially in near costal and dry zones in Sri Lanka. Due to Chronic Kidney Disease (CKD) around 500 people died in dry zones annually which is suspected to cause by Arsenic and Cadmium contain
in ground water due to agriculture chemicals. The available desalination methods are Reverse Osmosis (RO), Solar distillation and conventional methods. The cost for RO is Rs.0.10 cents per liter and solar distillation Rs.2.96 per liter. Although the price shows that the RO is better but due to high initial investment as a
third world country it is very difficult to afford huge initial investment without government intervention. The experimental solar desalination units only produce nearly 5liters of potable water per day and directly impacted by availability of solar radiation.
The energy availability of Sri Lanka and future potable water demand predicted as 2188.3 Mn liters as maximum demand which will be in 2030, therefore by that time the government should have a proper plan to cater the demand and desalination plants need to be planned and built based on the demand of dry zones and specially agriculture areas. The applicability of renewable energy for desalination in local arena was also simulated taking the Delft Reverse Osmosis plant for the simulation. Results show that the optimum design is combination of Solar PV and existing 100kW Diesel generator Set with Battery bank and
converter.
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.
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
A Primer On Brackish And Seawater Desalination
Abstract: This publication was produced as an activity of the Texas Living Waters Project. This project
is a collaborative effort of the National Wildlife Federation, Environmental Defense, and the Lone
Star Chapter of the Sierra Club. The goals of the project are to 1) ensure adequate water for people
and environmental needs, 2) reduce future demand for water and foster efficient and sustainable use
of current water supplies, 3) educate the public and decision makers about the impact of wasteful
water use and the opportunities for water conservation, and 4) involve citizens in the decision
making process for water management.
A Primer On Brackish And Seawater Desalination
Abstract: This publication was produced as an activity of the Texas Living Waters Project. This project
is a collaborative effort of the National Wildlife Federation, Environmental Defense, and the Lone
Star Chapter of the Sierra Club. The goals of the project are to 1) ensure adequate water for people
and environmental needs, 2) reduce future demand for water and foster efficient and sustainable use
of current water supplies, 3) educate the public and decision makers about the impact of wasteful
water use and the opportunities for water conservation, and 4) involve citizens in the decision
making process for water management.
Concentrating Solar Power For Seawater Desalination
Introduction:
The general perception of “solar desalination” today comprises only small scale technologies for decentralized water supply in remote places, which may be quite important for the development of rural areas, but do not address the increasing water deficits of the quickly growing urban centers of demand. Conventional large scale desalination is perceived as expensive, energy consuming and limited to rich countries like those of the Arabian Gulf, especially in view of the quickly escalating cost of fossil fuels like oil, natural gas and coal. The environmental impacts of large scale desalination due to airborne emissions of pollutants from energy consumption and to the discharge of brine and chemical additives to the sea are increasingly considered as critical. For those reasons, most contemporary strategies against a “Global Water Crisis” consider seawater desalination only as a marginal element of supply. The focus of most recommendations lies on more efficient use of water, better accountability, re-use of waste water, enhanced distribution and advanced irrigation systems. To this adds the recommendation to reduce agriculture and rather import food from other places. On the other hand, most sources that do recommend seawater desalination as part of a solution to the water crisis usually propose nuclear fission and fusion as indispensable option.
Concentrating Solar Power For Seawater Desalination
Introduction:
The general perception of “solar desalination” today comprises only small scale technologies for decentralized water supply in remote places, which may be quite important for the development of rural areas, but do not address the increasing water deficits of the quickly growing urban centers of demand. Conventional large scale desalination is perceived as expensive, energy consuming and limited to rich countries like those of the Arabian Gulf, especially in view of the quickly escalating cost of fossil fuels like oil, natural gas and coal. The environmental impacts of large scale desalination due to airborne emissions of pollutants from energy consumption and to the discharge of brine and chemical additives to the sea are increasingly considered as critical. For those reasons, most contemporary strategies against a “Global Water Crisis” consider seawater desalination only as a marginal element of supply. The focus of most recommendations lies on more efficient use of water, better accountability, re-use of waste water, enhanced distribution and advanced irrigation systems. To this adds the recommendation to reduce agriculture and rather import food from other places. On the other hand, most sources that do recommend seawater desalination as part of a solution to the water crisis usually propose nuclear fission and fusion as indispensable option.
Desalination For Safe Water Supply
Preface:
Access to sufficient quantities of safe water for drinking and domestic uses and also for commercial and industrial applications is critical to health and well being, and the opportunity to achieve human and economic development. People in many areas of the world have historically suffered from inadequate access to safe water. Some must walk long distances just to obtain sufficient water to sustain life. As a result they have had to endure health consequences and have not had the opportunity to develop their resources and capabilities to achieve major improvements in their well being. With growth of world population the availability of the limited quantities of fresh water decreases. Desalination technologies were introduced about 50 years ago at and were able to expand access to water, but at high cost. Developments of new and improved technologies have now significantly broadened the opportunities to access major quantities of safe water in many parts of the world. Costs are still significant but there has been a reducing cost trend, and the option is much more widely available. When the alternative is no water or inadequate water greater cost may be endurable in many circumstances.
Desalination For Safe Water Supply
Preface:
Access to sufficient quantities of safe water for drinking and domestic uses and also for commercial and industrial applications is critical to health and well being, and the opportunity to achieve human and economic development. People in many areas of the world have historically suffered from inadequate access to safe water. Some must walk long distances just to obtain sufficient water to sustain life. As a result they have had to endure health consequences and have not had the opportunity to develop their resources and capabilities to achieve major improvements in their well being. With growth of world population the availability of the limited quantities of fresh water decreases. Desalination technologies were introduced about 50 years ago at and were able to expand access to water, but at high cost. Developments of new and improved technologies have now significantly broadened the opportunities to access major quantities of safe water in many parts of the world. Costs are still significant but there has been a reducing cost trend, and the option is much more widely available. When the alternative is no water or inadequate water greater cost may be endurable in many circumstances.
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.
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