An Introduction To Membrane Techniques For Water Desalination
An Introduction to Membrane Techniques for water desalination
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Desalination & Water Purification Technologies
Introduction:
The world’s water consumption rate is doubling every 20 years, outpacing by two times the rate of population growth. The availability of good quality water is on the decline and water demand is on the rise. Worldwide availability of fresh water for industrial needs and human consumption is limited.
Various industrial and developmental activities in recent times have resulted in increasing the pollution level and deteriorating the water quality. Water shortages and unreliable water quality are considered major obstacles to achieve sustainable development and improvement in the quality of life. The water
demand in the country is increasing fast due to progressive increase in the demand of water for irrigation, rapid industrialization, and population growth and improving life standards. The existing water resources are diminishing (i) due to unequal distribution of rain water and occasional drought, (ii) excessive exploitation of ground water sources and its insufficient recharge, (iii) deterioration of water quality due to the discharge of domestic and industrial effluents without adequate treatment. This is resulting into water stress/ scarcity. Country is currently passing through social and economic transition.
The proportion of the population which is urban has doubled over the last thirty years (and is now about 30%), agriculture now accounts for about 25% of GDP and the economy has been growing at around 7-9% a year. Country has a highly seasonal pattern of rainfall, with 50% of precipitation falling
in just 15 days and over 90% of river flows in just four months
Desalination & Water Purification Technologies
Introduction:
The world’s water consumption rate is doubling every 20 years, outpacing by two times the rate of population growth. The availability of good quality water is on the decline and water demand is on the rise. Worldwide availability of fresh water for industrial needs and human consumption is limited.
Various industrial and developmental activities in recent times have resulted in increasing the pollution level and deteriorating the water quality. Water shortages and unreliable water quality are considered major obstacles to achieve sustainable development and improvement in the quality of life. The water
demand in the country is increasing fast due to progressive increase in the demand of water for irrigation, rapid industrialization, and population growth and improving life standards. The existing water resources are diminishing (i) due to unequal distribution of rain water and occasional drought, (ii) excessive exploitation of ground water sources and its insufficient recharge, (iii) deterioration of water quality due to the discharge of domestic and industrial effluents without adequate treatment. This is resulting into water stress/ scarcity. Country is currently passing through social and economic transition.
The proportion of the population which is urban has doubled over the last thirty years (and is now about 30%), agriculture now accounts for about 25% of GDP and the economy has been growing at around 7-9% a year. Country has a highly seasonal pattern of rainfall, with 50% of precipitation falling
in just 15 days and over 90% of river flows in just four months
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.
Desalination Technology Trends
Abstract:
Texas’ increased interest in desalination reflects a worldwide trend to include it as a viable alternative water supply option in any long-term water strategy. Recent technological developments and new methods of project delivery are driving this heightened level of interest to the point that desalination is now being seriously evaluated on projects where it would not have been considered ten years ago. The most significant trend in desalination is the increased growth of the reverse osmosis(RO) market. Technological improvements have both dramatically increased the performance of RO membranes. Today’s membranes are more efficient, more durable, and much less expensive. Improvements in membrane technology are complimented by improvements in pretreatment technology, which allow RO membranes to be considered on a much wider range of applications. Energy costs are directly related to the salt content of the water source, and may represent up to 50% of a system’s operational costs. There has been a growing trend to reduce energy costs through improvements in membrane performance and by employing modern, mechanical energy recovery devices that reduce energy requirements by 10-50%. The growing trend to build larger desalination plants recognizes the inherent modularity of RO systems and the fact that the development, design, and permitting costs are somewhat independent of plant size. The result is that larger plants are being constructed to take advantage of economies-of-scale, which reduce the unit cost of desalinated water. Other trends that will be reviewed in more detail include the co-siting of desalination plants with electric power generating plants and other industrial facilities, and the hybridization of distillation and membrane processes.
Desalination Technology Trends
Abstract:
Texas’ increased interest in desalination reflects a worldwide trend to include it as a viable alternative water supply option in any long-term water strategy. Recent technological developments and new methods of project delivery are driving this heightened level of interest to the point that desalination is now being seriously evaluated on projects where it would not have been considered ten years ago. The most significant trend in desalination is the increased growth of the reverse osmosis(RO) market. Technological improvements have both dramatically increased the performance of RO membranes. Today’s membranes are more efficient, more durable, and much less expensive. Improvements in membrane technology are complimented by improvements in pretreatment technology, which allow RO membranes to be considered on a much wider range of applications. Energy costs are directly related to the salt content of the water source, and may represent up to 50% of a system’s operational costs. There has been a growing trend to reduce energy costs through improvements in membrane performance and by employing modern, mechanical energy recovery devices that reduce energy requirements by 10-50%. The growing trend to build larger desalination plants recognizes the inherent modularity of RO systems and the fact that the development, design, and permitting costs are somewhat independent of plant size. The result is that larger plants are being constructed to take advantage of economies-of-scale, which reduce the unit cost of desalinated water. Other trends that will be reviewed in more detail include the co-siting of desalination plants with electric power generating plants and other industrial facilities, and the hybridization of distillation and membrane processes.
Advanced Reverse Osmosis System Design
Overview of Advanced RO Design
• RO system design guideline variables
• Drivers for RO system configuration selection
• Principles and benefits of RO array flux balancing
• Array selection criteria to achieve permeate quality target
• Energy recovery
Advanced Reverse Osmosis System Design
Overview of Advanced RO Design
• RO system design guideline variables
• Drivers for RO system configuration selection
• Principles and benefits of RO array flux balancing
• Array selection criteria to achieve permeate quality target
• Energy recovery
Desalination At A Glance
Introduction:
By desalination, we will be referring to the production of a useful product water from a feed
water that is too high in inorganic materials (salts) to be useful. The feed water may be
seawater, brackish water, or other “impaired” water that cannot be used directly for potable
or general industrial purposes. Notice that this definition includes the treatment of certain
wastewaters for subsequent reuse.
The principal technologies used in desalination are based on concepts that are fairly easy to
grasp by those with a modest amount of scientific training and/or technical experience. In
practice, however, choices of technology and plant design are usually determined by factors
that might appear minor to the inexperienced. Similarly, new technologies that show great
promise in the laboratory frequently fail for reasons that were earlier overlooked or dismissed
as trivial. Indeed, professional fascination with specific technical elegance has, in some
cases, led researchers to remain oblivious to inherent limitations of a process. Nonetheless,
attention to detail over the past five decades has resulted in dramatic reductions in capital
and operating costs as well as greatly increased plant reliability and performance
Desalination At A Glance
Introduction:
By desalination, we will be referring to the production of a useful product water from a feed
water that is too high in inorganic materials (salts) to be useful. The feed water may be
seawater, brackish water, or other “impaired” water that cannot be used directly for potable
or general industrial purposes. Notice that this definition includes the treatment of certain
wastewaters for subsequent reuse.
The principal technologies used in desalination are based on concepts that are fairly easy to
grasp by those with a modest amount of scientific training and/or technical experience. In
practice, however, choices of technology and plant design are usually determined by factors
that might appear minor to the inexperienced. Similarly, new technologies that show great
promise in the laboratory frequently fail for reasons that were earlier overlooked or dismissed
as trivial. Indeed, professional fascination with specific technical elegance has, in some
cases, led researchers to remain oblivious to inherent limitations of a process. Nonetheless,
attention to detail over the past five decades has resulted in dramatic reductions in capital
and operating costs as well as greatly increased plant reliability and performance
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.
Cleaning Procedures for Composite Polyamide RO Membrane Elements
Note: The Composite Polyamide type of RO membrane elements may not be
exposed to chlorinated water under any circumstances. Any such exposure may
cause irreparable damage to the membrane. Absolute care must be taken
following any disinfection of piping or equipment or the preparation of cleaning or
storage solutions to ensure that no trace of chlorine is present in the feedwater to
the RO membrane elements. If there is any doubt about the presence of chlorine,
perform chemical testing. Neutralize any chlorine residual with a sodium bisulfite
solution, and ensure adequate mixing and contact time to accomplish complete
dechlorination. Dosing rate is 1.8 to 3.0 ppm sodium bisulfite per 1.0 ppm of free
chlorine
Cleaning Procedures for Composite Polyamide RO Membrane Elements
Note: The Composite Polyamide type of RO membrane elements may not be
exposed to chlorinated water under any circumstances. Any such exposure may
cause irreparable damage to the membrane. Absolute care must be taken
following any disinfection of piping or equipment or the preparation of cleaning or
storage solutions to ensure that no trace of chlorine is present in the feedwater to
the RO membrane elements. If there is any doubt about the presence of chlorine,
perform chemical testing. Neutralize any chlorine residual with a sodium bisulfite
solution, and ensure adequate mixing and contact time to accomplish complete
dechlorination. Dosing rate is 1.8 to 3.0 ppm sodium bisulfite per 1.0 ppm of free
chlorine
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.
Tailoring Advanced Desalination Technologies for 21st Century Agriculture
Abstract: Substantial parts of the U.S., particularly drier landlocked regions, are facing acute water shortages and water quality issues that decrease agricultural productivity. Reduced crop yields cause billions of dollars in losses annually, affecting the livelihoods of thousands. A combination of population growth, inefficient agricultural practices, and resource demanding consumption trends is only expected to increase pressure on our water supplies. This research proposal seeks to address water and food security issues by cost-effectively and energy-efficiently enhancing water quality and water supply in greenhouses; a $22.93 billion dollar industry in 2017 that is rapidly growing at an annual rate of 8.92%. Greenhouses widely practice desalination of salty irrigation water to improve their operations. However, currently used desalination methods do not tailor greenhouse waters based on crop requirements. This work investigates a fully integrated desalination solution that treats and tailors brackish source waters ingreenhouses to save fertilizer and water. Specifically, this project experimentally studies multi-ion transport in and assesses the economic viable of monovalent selective electrodialysis (MSED). MSED allows for the selective removal of monovalent ions damaging to crops and the retention of divalent ions beneficial for crops, unlike the widely used reverse osmosis (RO), which removes all ions from greenhouse source water. First, we evaluate the techno-economic feasibility of MSED compared to other brackish desalination technologies for agricultural applications, based on primary market research we conduct with over 70 greenhouses.
These include conventional technologies, such as reverse osmosis (RO) and electrodialysis (ED), and advanced technologies, such as closed circuit reverse osmosis (CCRO). The analysis determines the levelized costs of water, the capital costs and energy requirements of these technologies, and how these vary with feed salinity, system capacity and recovery ratio. Then, we build a bench-scale setup to experientially characterize MSED membrane properties, including monovalent selectivity, ion transport, limiting current and resistance, for multiple brackish feedwaters and for two sets of MSED membranes: the widely used Neosepta ACS/CMS membranes and the new Fujifilm Type 16 membranes. Both MSED membranes show notable monovalent selectivity for all tested compositions, reflecting the potential of the technology for selective desalination in greenhouses. The measurements are compared to a model for MSED in multi-ion solutions. The model predicts multi-ion transport for the Neosepta and Fujifilm MSED systems within 6% and 8%, respectively.
Tailoring Advanced Desalination Technologies for 21st Century Agriculture
Abstract: Substantial parts of the U.S., particularly drier landlocked regions, are facing acute water shortages and water quality issues that decrease agricultural productivity. Reduced crop yields cause billions of dollars in losses annually, affecting the livelihoods of thousands. A combination of population growth, inefficient agricultural practices, and resource demanding consumption trends is only expected to increase pressure on our water supplies. This research proposal seeks to address water and food security issues by cost-effectively and energy-efficiently enhancing water quality and water supply in greenhouses; a $22.93 billion dollar industry in 2017 that is rapidly growing at an annual rate of 8.92%. Greenhouses widely practice desalination of salty irrigation water to improve their operations. However, currently used desalination methods do not tailor greenhouse waters based on crop requirements. This work investigates a fully integrated desalination solution that treats and tailors brackish source waters ingreenhouses to save fertilizer and water. Specifically, this project experimentally studies multi-ion transport in and assesses the economic viable of monovalent selective electrodialysis (MSED). MSED allows for the selective removal of monovalent ions damaging to crops and the retention of divalent ions beneficial for crops, unlike the widely used reverse osmosis (RO), which removes all ions from greenhouse source water. First, we evaluate the techno-economic feasibility of MSED compared to other brackish desalination technologies for agricultural applications, based on primary market research we conduct with over 70 greenhouses.
These include conventional technologies, such as reverse osmosis (RO) and electrodialysis (ED), and advanced technologies, such as closed circuit reverse osmosis (CCRO). The analysis determines the levelized costs of water, the capital costs and energy requirements of these technologies, and how these vary with feed salinity, system capacity and recovery ratio. Then, we build a bench-scale setup to experientially characterize MSED membrane properties, including monovalent selectivity, ion transport, limiting current and resistance, for multiple brackish feedwaters and for two sets of MSED membranes: the widely used Neosepta ACS/CMS membranes and the new Fujifilm Type 16 membranes. Both MSED membranes show notable monovalent selectivity for all tested compositions, reflecting the potential of the technology for selective desalination in greenhouses. The measurements are compared to a model for MSED in multi-ion solutions. The model predicts multi-ion transport for the Neosepta and Fujifilm MSED systems within 6% and 8%, respectively.
Cleaning Your RO
Eventually the day comes when your RO system will require cleaning. Cleaning is recommended when your RO shows evidence of fouling, just prior to a long term shutdown, or as a matter of scheduled routine maintenance. Fouling characteristics that signal you need to clean are a 10-15% decrease in normalized permeate flow, a 10-15% decrease in normalized permeate quality, or a 10-15% increase in normalized pressure drop as measured between the feed and concentrate headers
Cleaning Your RO
Eventually the day comes when your RO system will require cleaning. Cleaning is recommended when your RO shows evidence of fouling, just prior to a long term shutdown, or as a matter of scheduled routine maintenance. Fouling characteristics that signal you need to clean are a 10-15% decrease in normalized permeate flow, a 10-15% decrease in normalized permeate quality, or a 10-15% increase in normalized pressure drop as measured between the feed and concentrate headers
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