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Cover story: Singapore shines at desalination conference
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Cover story
Filtration+Separation October 2005
Cover story:
Singapore shines at desalination conference R
everse Osmosis membrane technology is bringing the cost of desalinating seawater down to levels where more and more countries now view it as a viable option. But this isn’t the end of the story, as Filtration + Separation found out at the IDA’s desalination conference in Singapore...
Over 855 delegates from as far afield as the Middle East, Australia, Europe, and the USA, converged on the Raffles Convention Centre in Singapore, from 11-16 September, to find out about the latest developments in desalination and water reuse technology. The biannual conference was organised by the IDA (International Desalination Association), and Singapore turned out to be a perfect choice, being a shining example of a city that has well and truly turned round its fortunes in terms of water supply.
especially membrane technology, Singapore has been able to augment its water supply through the reclamation of NEWater and desalinated water.
Singapore – the 4 national tap strategy
With rapid advancements in desalination technology and improvements in energy efficiency, desalination has now become a viable source of water supply for Singapore. Its first seawater desalination plant, Tuas, constitutes some 10% of Singapore’s water needs.
As well as having built a new desalination plant, Tuas (officially opened by Singapore’s prime minister during the week of the conference), Singapore has developed what it calls its ‘4 national tap’ strategy, a model that other countries with water shortage problems could adopt. Singapore’s strategy is to increase its water supply by enlarging its water cachment areas and at the same time searching for alternative sources. This comes in the form of cachment water, imported water, NEWater, and desalinated water. By capitalising on and harnessing the advances in water treatment technology,
Singapore is 100% sewered and all used water is collected and treated to international standards before discharging in to the sea. With advanced dual membrane process and ultraviolet treatment, the treated water is reclaimed to produce NEWater, which is primarily supplied to non-domestic sectors (wafer fabrication plants, industrial estates etc).
Water experts hope that this model developed in Singapore can be applied to other regions with water supply problems. And this approach could be made possible with some of the latest technological developments in water treatment.
Membrane technology – an alternative to thermal desalination The impending water shortage crisis in some countries and regions (‘water stress’ zones),
together with advancements in membrane technology is now introducing a viable costeffective alternative to thermal desalination. Thermal desalination plants (that consume vast amounts of heat energy to separate water from impurities by evaporation) have been around for a long time. They first emerged in the Gulf countries, which struggle to find freshwater sources, but have at their disposal vast energy resources and wealth. This has traditionally made them much more economically viable than elsewhere in the world. But the technology that has really taken desalination forward is Reverse Osmosis (RO). Instead of using some form of distillation, semi permeable membranes form a barrier against the salts and polluting particles in the water. The feed water is pumped through the membranes at high pressure, and the tiny water molecules pass through, while the much larger mineral salts are trapped and held by the membrane. Advancements in the manufacture of membranes has had the effect of bringing down the cost of producing desalinated water, and has driven seawater desalination forward in the past decade. Not only have membranes become more efficient at rejecting salts and other ions, improvements in manufacturing
Cover story
Filtration+Separation October 2005
techniques have also reduced production costs and resulted in higher quality membranes with improved durability. In a nutshell, more water can now be produced by today’s systems for the same capital expenditure. Much of the technology that has made seawater desalination more viable, however, is already used in other aspects of water treatment, and this was a major theme that came out of the event. For example, the same Reverse Osmosis (RO) membranes found in seawater desalination are found in industrial wastewater settings, where they allow impurities to be taken out and the water to be re-used in the original (or sent to other) processes.
The delegate and exhibitor perspective – current themes It is important to realise that the “desalting” stage of a membrane-desalination plant (SWRO – Seawater Reverse Osmosis) is not the only thing that needs to be taken into account when designing a seawater desalination process. Some other vital elements include being able to efficiently and effectively: • Pretreat the source water before it hits the RO membranes
Case study – Ashkelon and the Filmtec connection The world-renowned Ashkelon plant in Israel is an excellent example of a plant that has taken advantage of membrane technology to produce a more cost effective desalinated water supply. The world’s largest desalination plant, it now provides and sells 165 000 m3 of water per day, and uses Filmtec membrane technology from Dow for the plant’s seawater reverse osmosis (SWRO) process. Begun in April 2003, the plant is part of a Desalination Master Plan launched by Israel in 2002 to help address the country’s chronic water resource problems. The Water and Desalination Authority of Israel will use the treated water to supplement and upgrade the existing potable municipal water supply in this region, which has extremely dry conditions and limited fresh water resources. Ashkelon comprises a North and South plant, each designed to produce 165,000 m3/D making a total of 330,000 m3/D of produced water. The next phase is to begin commissioning of the South plant, which is planned later this year. “The successful operation of this plant in one of the most water-challenged areas of the world speaks to the bright future [that] seawater reverse osmosis technology has in addressing the needs of other regions, such as China, India and Africa, [regions] that are facing growing demand and limited
This is seen as a crucial issue, and is one of the most critical aspects in the success of an RO system. One of the current issues with RO membranes is that they are susceptible to fouling, especially the more polluted the source water is. This is especially apparent with high saltwater sources (seawater). Therefore, pre-treatment is used to clean water before it reaches the RO membrane – to maintain the performance as well as prevent irreversible damage of the RO membranes. Traditionally, conventional filtration methods like sand screen filtration have been used in the pre-treatment of seawater, but membranes themselves used as pre-treatment (microfiltration/ultrafiltration) is on the increase (membranes used as pretreatment is relatively common in industry already, because the source water used for industry is generally less harsh). The next step will be the more widespread take up of membrane pretreatment for seawater desalination, but this depends on the development of more advanced membranes. One expert Filtration + Separation spoke to put this at 3-5 years away in seawater desalination, though they are commonplace in industrial wastewater purification.
availability of freshwater resources,” said Ian Barbour, general manager, Dow Liquid Separations and CEO of FilmTec, a wholly owned subsidiary of The Dow Chemical Company (see interview on page 23.) The desalination facility consists of 32 Reverse Osmosis (RO) treatment trains and uses an optimised, multi-stage RO and boron removal procedure. The method selected is flexible and readily adjustable to feed water temperature fluctuations, and is capable of delivering removal efficiency greater than 92% when required. “The Ashkelon desalination facility will provide approximately 15% of the total household water consumption in Israel,” said Gustavo Kronenberg, general manager of VID Desalination Company. Jorge Redondo, Dow’s Ashkelon Project manager, commented, “These demands, coupled with a number of other key requirements, including high pH tolerance, continuous low pressure operation, low membrane fouling and cost-effective, reliable performance, led to Filmtec elements being selected for the RO operation at Ashkelon.”
• Size the plants effectively The growing trend to build larger desalination plants recognises the modularity of RO systems, and the fact that the development, design, and permitting costs are independent of plant size. But there is an issue with lead times for the supply of membranes on larger plants, especially if many membranes need to be supplied at one go from a single supplier. Currently, it is not a trend for membrane manufacturers to make membranes that would be compatible with other manufacturers’ membranes, hence making waiting time less of an issue (as a plant would have more flexibility). • Site the plants (i.e. intakes must supply a consistent supply of seawater) Electric power generating plants with oncethrough cooling systems require large volumes of cooling water to condense power-cycle steam back to high-purity water for producing new steam. Many seawater desalination plants are now co-located with a power plant with which they share a common seawater intake (see on the beach – seawater intake, pages 2427.) The avoided cost of constructing and permitting a new (continued on page 23)
The Ashkelon plant is owned and operated by VID Desalination Company, which is a consortium of IDE Technologies Ltd. (50%) equally owned by Israel Chemicals Ltd. (ICL) of the Israel Corporation Ltd. and Delek Group, as well as Veolia Water S.A. (25%).
“The Ashkelon plant contains more than 40 000 RO membrane elements, a milestone project for desalination in terms of size,” stated Lance Johnson, manager, global large projects for Dow Liquid Separations. “But even more importantly, the plant is a testament to how advances in RO membrane technology have contributed to making the production of clean drinking water from seawater more affordable and energy efficient. Over the past ten years, FilmTec Corporation has helped to decrease the cost of RO water nearly threefold, while enhancements in membrane throughput and rejection have led to significant reductions in energy consumption. Our driving vision is to help customers produce the highest quality water at the lowest possible cost, and we’re excited to see that vision achieved when put to the Ashkelon reality test.”
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Cover story
The interview – Ian Barbour, general manager Dow liquid separations, and chief executive officer FilmTec Corp. In the context of this congress [2005 IDA World Congress on desalination and water reuse], what is Dow’s reason for attending as an exhibitor? “Our interest is primarily related to technologies. Dow Liquid Separations could be described as Dow’s water business. We produce ion exchange resins and reverse osmosis (RO) membranes. Both of these technologies are enabling components – supplied to OEMs, EPC (Engineer, Procure, Construct) contractors, and system integrators – meaning that the components and technology we sell pretty much determines the performance of the system that it goes into. So, for example, even though we make the membrane module and not the system that it goes into, the performance of the systems is very directly related to the technology we supply.” Many people are talking about the pretreatment issues related to SWRO… “That’s right, everyone’s talking about Ultrafiltration (UF) and Microfiltration (MF) as pre-treatment for RO. There are actually a lot of companies doing this, and there is a general sense in the marketplace that it is superior to traditional technologies. Personally, I think it is too early to say. Someone referred to typical sand filtration as ‘rocks in a box’, but it’s robust, it works, and it’s proven. And you can get very good prefiltration with a traditional system and ultrafiltration.” Would you agree that there is a good deal of optimism being directed towards SWRO as a means of providing potable water? “Yes, and I think its well founded. If you look at the macro trends of population growth, increased industrialisation, increased pollution, and less water availability, I think there are two areas where membranes can help: desalination and water reuse. With water reuse, for example, if you have an industrial process taking water and using it in a process, this water then has to be cleaned up before it is put back into a river; well, it doesn’t have to be cleaned up much more before it’s potable. And this is what the municipalities are doing – treating water and putting it back in the river. As the cost of UF and MF membranes comes down, it’s going to become more and more accepted as prefiltration technology. Is this something Dow is involved with? “Not at this point. The challenge for Dow is that we have got a component strategy, and with RO – where you pretty much specify the
Filtration+Separation October 2005
water quality expected – you can standardise very, very effectively. On the other hand, UF comes into contact with raw water, and this incoming water has different water characteristics at each installation, and it’s much more difficult to standardise a particular product or design. With RO, we specify the feed quality that has to enter the RO membranes, and we don’t really have to worry too much about pretreatment. although we are watching the developments in the industry and I think there’s definitely a lot more shake up to come.” What are the specific issues with today’s generation of membranes? “I think UF/MF development and use is going to see something similar to what we experienced in RO. Prices for RO modules have come down tremendously since 1990. An 8 inch brackish water membrane back in 1990 sold for 1200 dollars. Today that membrane sells for 500 dollars. And that 500-dollar membrane will also produce at least twice as much water as the one that cost 1200 dollars. “So, the cost of water being produced by membranes is going down. And that is what the customer cares about. Higher-quality water at lower delivery cost. “Membranes have delivered against that need effectively. That cost curve is continuing to drop, and as a result the RO market has exploded. Otherwise RO would have remained as a niche technology in high-value applications. Instead – and I think this will happen in UF/MF as well – as the costs have come down, the market for membranes has grown. A UF membrane is a barrier – that’s what fundamentally differentiates it from, say, sand filtration. So when you drive the costs down, and the membranes become even more robust, the market is going to grow.” How does Dow differentiate itself from its competitors in what is a tough field? “We have invested very heavily in our manufacturing processes. We have a very high level of automation in the way we manufacture, not only casting the sheet, but also how we fabricate the modules and roll the sheet into the modules. We have invested a huge amount in automation to improve our quality and consistency. “We have very uniform leaf spacing, and we have the ability to lay down a glue line on
the membrane envelope very precisely, which gives us very predictable and greater active area (i.e. the area inside the glue lines). “Because of this we can be very confident in our projections and the flux our membranes are going to experience – when we say a membrane has a certain active area, we know it does because every element is made the same way without the variabilities introduced by human operators. Greater active area, of course, directly relates to throughput and operational efficiency. Many people see Boron removal as an important current theme. “Boron is a regional issue and is becoming more and more of an issue. You can use membranes or ion exchange to achieve your Boron requirements. “So, if the water is going to be used in agricultural applications for example, Boron requirements can sometimes be even tougher than the WHO (World Health Organisation) standards for Boron in drinking water. Boron is a bad player in certain crops, but you can remove it with membranes or ion exchange resins. Ashkelon for example had a fairly rigid boron specification, and they are meeting this with a membrane process. They’ve got a seawater stage, then a brackish water stage behind it, and they achieve it that way. “Or you could use a boron selective ion exchange resin.” Finally, a difficult question, but what do you feel we can look forward to in the developments of membranes for processes like SWRO? “I believe there will be a lot of technology that can bring down the cost of water for our customers. “Firstly, what can we do with the membrane itself? There are technologies we are working on that will improve flow, rejection, energy consumption, cleanability, and anti-fouling. “The second consideration is how you put the module together. For example, there is now a consortium of membrane manufacturers that has recommended a 16 inch diameter element as the optimum size to drive further cost reductions for water. So, we are working on prototypes of 16 inches. “Aside from this, there are also things going on in terms of how you stage the elements in a pressure vessel. Instead of using one type of membrane in all six positions in the pressure vessel, you use different types of membranes. For example you may have a different one at the front and at the back. What that allows you to do is to optimise that whole pressure vessel.”
Cover story
Filtration+Separation October 2005
(continued from page 21) intake may reduce the capital cost of the desalination facility by several million dollars. In addition, some countries’ (the USA is a prime example) regulatory structure and requirements makes it extremely arduos to build desalination plants. • Deliver other components such as novel energy-saving devices or high-pressure pumping systems etc. For example energy costs are directly related to the salt content of feed water, and can represent more than one third of a seawater desalination system’s operating costs. Reducing energy costs is an important goal for manufacturers of equipment used in water treatment.
Conference at a glance
• Dispose of the brine left over from the process in an environmentally acceptable manner.
In the face of increased water shortages and growing costs of ‘conventional’ treatment, this is expected to continue.
The future for desalination
The next steps for seawater desalination seem to be in optimising the process still further to reduce the cost of producing water – and therefore making it even more viable for utilities/water stakeholders.
This is an issue that has given desalination much bad press in some countries where it has been taken up. Advances in desalination membrane technologies, pretreatment technology, energy recovery, improved integration of facilities, and more environmentally conscious intake and outfall designs have resulted in better performance, lower capital and operating costs, and increased application of membranes in a variety of desalination applications. The Bahrain congress (2002) attracted 600. Amongst the high level attendees were Abdullah Al Hussayen – minister for water and electricity, Saudi Arabia.
• The last three Congresses have taken place in Singapore (2005), The Bahamas (2003), and Bahrain (2002 – rescheduled because of 9/11). It is rumoured that the next conference is scheduled to take place in the Canary Islands (though this is not official yet) in two years time.
• Singapore’s prime minister, Lee Hsien Loomg, officially turned on Singapore’s new Tuas desalination plant, during a ceremony at the conference.
• A total of 855 delegates attended this year’s event. According to the IDA, this makes it the biggest event in the association’s history, beating the Madrid show in 1997 (825 delegates.) The Bahamas congress (2003) attracted 550;
• The high-level technical conference program of over 130 papers included themes such as membrane fouling, pre and post treatment, performance advances, scaling, corrosion, wastewater reclamation, repurification and reuse, energy recovery
One of the IDA representatives summed up the desalination situation neatly in a nutshell; he said that, “even though desalination has been around for some time, making it economically viable is something of an art”. This is something that the filtration industry needs to address.
•
and automation, hybrid design, alternative desalination technology, siting and intake alternatives, as well as thermal desalination experiences. • There were approximately 35 exhibitors at the conference, including system integrators and engineering firms (of plants and systems right across the water spectrum), consultation companies that have expertise in the water sector, equipment suppliers (i.e. membranes and related equipment, pumps, chemicals etc), as well as regional water/desalination associations.
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Cover story
Filtration+Separation October 2005
Cover story:
Singapore shines at desalination conference R
everse Osmosis membrane technology is bringing the cost of desalinating seawater down to levels where more and more countries now view it as a viable option. But this isn’t the end of the story, as Filtration + Separation found out at the IDA’s desalination conference in Singapore...
Over 855 delegates from as far afield as the Middle East, Australia, Europe, and the USA, converged on the Raffles Convention Centre in Singapore, from 11-16 September, to find out about the latest developments in desalination and water reuse technology. The biannual conference was organised by the IDA (International Desalination Association), and Singapore turned out to be a perfect choice, being a shining example of a city that has well and truly turned round its fortunes in terms of water supply.
especially membrane technology, Singapore has been able to augment its water supply through the reclamation of NEWater and desalinated water.
Singapore – the 4 national tap strategy
With rapid advancements in desalination technology and improvements in energy efficiency, desalination has now become a viable source of water supply for Singapore. Its first seawater desalination plant, Tuas, constitutes some 10% of Singapore’s water needs.
As well as having built a new desalination plant, Tuas (officially opened by Singapore’s prime minister during the week of the conference), Singapore has developed what it calls its ‘4 national tap’ strategy, a model that other countries with water shortage problems could adopt. Singapore’s strategy is to increase its water supply by enlarging its water cachment areas and at the same time searching for alternative sources. This comes in the form of cachment water, imported water, NEWater, and desalinated water. By capitalising on and harnessing the advances in water treatment technology,
Singapore is 100% sewered and all used water is collected and treated to international standards before discharging in to the sea. With advanced dual membrane process and ultraviolet treatment, the treated water is reclaimed to produce NEWater, which is primarily supplied to non-domestic sectors (wafer fabrication plants, industrial estates etc).
Water experts hope that this model developed in Singapore can be applied to other regions with water supply problems. And this approach could be made possible with some of the latest technological developments in water treatment.
Membrane technology – an alternative to thermal desalination The impending water shortage crisis in some countries and regions (‘water stress’ zones),
together with advancements in membrane technology is now introducing a viable costeffective alternative to thermal desalination. Thermal desalination plants (that consume vast amounts of heat energy to separate water from impurities by evaporation) have been around for a long time. They first emerged in the Gulf countries, which struggle to find freshwater sources, but have at their disposal vast energy resources and wealth. This has traditionally made them much more economically viable than elsewhere in the world. But the technology that has really taken desalination forward is Reverse Osmosis (RO). Instead of using some form of distillation, semi permeable membranes form a barrier against the salts and polluting particles in the water. The feed water is pumped through the membranes at high pressure, and the tiny water molecules pass through, while the much larger mineral salts are trapped and held by the membrane. Advancements in the manufacture of membranes has had the effect of bringing down the cost of producing desalinated water, and has driven seawater desalination forward in the past decade. Not only have membranes become more efficient at rejecting salts and other ions, improvements in manufacturing
Cover story
Filtration+Separation October 2005
techniques have also reduced production costs and resulted in higher quality membranes with improved durability. In a nutshell, more water can now be produced by today’s systems for the same capital expenditure. Much of the technology that has made seawater desalination more viable, however, is already used in other aspects of water treatment, and this was a major theme that came out of the event. For example, the same Reverse Osmosis (RO) membranes found in seawater desalination are found in industrial wastewater settings, where they allow impurities to be taken out and the water to be re-used in the original (or sent to other) processes.
The delegate and exhibitor perspective – current themes It is important to realise that the “desalting” stage of a membrane-desalination plant (SWRO – Seawater Reverse Osmosis) is not the only thing that needs to be taken into account when designing a seawater desalination process. Some other vital elements include being able to efficiently and effectively: • Pretreat the source water before it hits the RO membranes
Case study – Ashkelon and the Filmtec connection The world-renowned Ashkelon plant in Israel is an excellent example of a plant that has taken advantage of membrane technology to produce a more cost effective desalinated water supply. The world’s largest desalination plant, it now provides and sells 165 000 m3 of water per day, and uses Filmtec membrane technology from Dow for the plant’s seawater reverse osmosis (SWRO) process. Begun in April 2003, the plant is part of a Desalination Master Plan launched by Israel in 2002 to help address the country’s chronic water resource problems. The Water and Desalination Authority of Israel will use the treated water to supplement and upgrade the existing potable municipal water supply in this region, which has extremely dry conditions and limited fresh water resources. Ashkelon comprises a North and South plant, each designed to produce 165,000 m3/D making a total of 330,000 m3/D of produced water. The next phase is to begin commissioning of the South plant, which is planned later this year. “The successful operation of this plant in one of the most water-challenged areas of the world speaks to the bright future [that] seawater reverse osmosis technology has in addressing the needs of other regions, such as China, India and Africa, [regions] that are facing growing demand and limited
This is seen as a crucial issue, and is one of the most critical aspects in the success of an RO system. One of the current issues with RO membranes is that they are susceptible to fouling, especially the more polluted the source water is. This is especially apparent with high saltwater sources (seawater). Therefore, pre-treatment is used to clean water before it reaches the RO membrane – to maintain the performance as well as prevent irreversible damage of the RO membranes. Traditionally, conventional filtration methods like sand screen filtration have been used in the pre-treatment of seawater, but membranes themselves used as pre-treatment (microfiltration/ultrafiltration) is on the increase (membranes used as pretreatment is relatively common in industry already, because the source water used for industry is generally less harsh). The next step will be the more widespread take up of membrane pretreatment for seawater desalination, but this depends on the development of more advanced membranes. One expert Filtration + Separation spoke to put this at 3-5 years away in seawater desalination, though they are commonplace in industrial wastewater purification.
availability of freshwater resources,” said Ian Barbour, general manager, Dow Liquid Separations and CEO of FilmTec, a wholly owned subsidiary of The Dow Chemical Company (see interview on page 23.) The desalination facility consists of 32 Reverse Osmosis (RO) treatment trains and uses an optimised, multi-stage RO and boron removal procedure. The method selected is flexible and readily adjustable to feed water temperature fluctuations, and is capable of delivering removal efficiency greater than 92% when required. “The Ashkelon desalination facility will provide approximately 15% of the total household water consumption in Israel,” said Gustavo Kronenberg, general manager of VID Desalination Company. Jorge Redondo, Dow’s Ashkelon Project manager, commented, “These demands, coupled with a number of other key requirements, including high pH tolerance, continuous low pressure operation, low membrane fouling and cost-effective, reliable performance, led to Filmtec elements being selected for the RO operation at Ashkelon.”
• Size the plants effectively The growing trend to build larger desalination plants recognises the modularity of RO systems, and the fact that the development, design, and permitting costs are independent of plant size. But there is an issue with lead times for the supply of membranes on larger plants, especially if many membranes need to be supplied at one go from a single supplier. Currently, it is not a trend for membrane manufacturers to make membranes that would be compatible with other manufacturers’ membranes, hence making waiting time less of an issue (as a plant would have more flexibility). • Site the plants (i.e. intakes must supply a consistent supply of seawater) Electric power generating plants with oncethrough cooling systems require large volumes of cooling water to condense power-cycle steam back to high-purity water for producing new steam. Many seawater desalination plants are now co-located with a power plant with which they share a common seawater intake (see on the beach – seawater intake, pages 2427.) The avoided cost of constructing and permitting a new (continued on page 23)
The Ashkelon plant is owned and operated by VID Desalination Company, which is a consortium of IDE Technologies Ltd. (50%) equally owned by Israel Chemicals Ltd. (ICL) of the Israel Corporation Ltd. and Delek Group, as well as Veolia Water S.A. (25%).
“The Ashkelon plant contains more than 40 000 RO membrane elements, a milestone project for desalination in terms of size,” stated Lance Johnson, manager, global large projects for Dow Liquid Separations. “But even more importantly, the plant is a testament to how advances in RO membrane technology have contributed to making the production of clean drinking water from seawater more affordable and energy efficient. Over the past ten years, FilmTec Corporation has helped to decrease the cost of RO water nearly threefold, while enhancements in membrane throughput and rejection have led to significant reductions in energy consumption. Our driving vision is to help customers produce the highest quality water at the lowest possible cost, and we’re excited to see that vision achieved when put to the Ashkelon reality test.”
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Cover story
The interview – Ian Barbour, general manager Dow liquid separations, and chief executive officer FilmTec Corp. In the context of this congress [2005 IDA World Congress on desalination and water reuse], what is Dow’s reason for attending as an exhibitor? “Our interest is primarily related to technologies. Dow Liquid Separations could be described as Dow’s water business. We produce ion exchange resins and reverse osmosis (RO) membranes. Both of these technologies are enabling components – supplied to OEMs, EPC (Engineer, Procure, Construct) contractors, and system integrators – meaning that the components and technology we sell pretty much determines the performance of the system that it goes into. So, for example, even though we make the membrane module and not the system that it goes into, the performance of the systems is very directly related to the technology we supply.” Many people are talking about the pretreatment issues related to SWRO… “That’s right, everyone’s talking about Ultrafiltration (UF) and Microfiltration (MF) as pre-treatment for RO. There are actually a lot of companies doing this, and there is a general sense in the marketplace that it is superior to traditional technologies. Personally, I think it is too early to say. Someone referred to typical sand filtration as ‘rocks in a box’, but it’s robust, it works, and it’s proven. And you can get very good prefiltration with a traditional system and ultrafiltration.” Would you agree that there is a good deal of optimism being directed towards SWRO as a means of providing potable water? “Yes, and I think its well founded. If you look at the macro trends of population growth, increased industrialisation, increased pollution, and less water availability, I think there are two areas where membranes can help: desalination and water reuse. With water reuse, for example, if you have an industrial process taking water and using it in a process, this water then has to be cleaned up before it is put back into a river; well, it doesn’t have to be cleaned up much more before it’s potable. And this is what the municipalities are doing – treating water and putting it back in the river. As the cost of UF and MF membranes comes down, it’s going to become more and more accepted as prefiltration technology. Is this something Dow is involved with? “Not at this point. The challenge for Dow is that we have got a component strategy, and with RO – where you pretty much specify the
Filtration+Separation October 2005
water quality expected – you can standardise very, very effectively. On the other hand, UF comes into contact with raw water, and this incoming water has different water characteristics at each installation, and it’s much more difficult to standardise a particular product or design. With RO, we specify the feed quality that has to enter the RO membranes, and we don’t really have to worry too much about pretreatment. although we are watching the developments in the industry and I think there’s definitely a lot more shake up to come.” What are the specific issues with today’s generation of membranes? “I think UF/MF development and use is going to see something similar to what we experienced in RO. Prices for RO modules have come down tremendously since 1990. An 8 inch brackish water membrane back in 1990 sold for 1200 dollars. Today that membrane sells for 500 dollars. And that 500-dollar membrane will also produce at least twice as much water as the one that cost 1200 dollars. “So, the cost of water being produced by membranes is going down. And that is what the customer cares about. Higher-quality water at lower delivery cost. “Membranes have delivered against that need effectively. That cost curve is continuing to drop, and as a result the RO market has exploded. Otherwise RO would have remained as a niche technology in high-value applications. Instead – and I think this will happen in UF/MF as well – as the costs have come down, the market for membranes has grown. A UF membrane is a barrier – that’s what fundamentally differentiates it from, say, sand filtration. So when you drive the costs down, and the membranes become even more robust, the market is going to grow.” How does Dow differentiate itself from its competitors in what is a tough field? “We have invested very heavily in our manufacturing processes. We have a very high level of automation in the way we manufacture, not only casting the sheet, but also how we fabricate the modules and roll the sheet into the modules. We have invested a huge amount in automation to improve our quality and consistency. “We have very uniform leaf spacing, and we have the ability to lay down a glue line on
the membrane envelope very precisely, which gives us very predictable and greater active area (i.e. the area inside the glue lines). “Because of this we can be very confident in our projections and the flux our membranes are going to experience – when we say a membrane has a certain active area, we know it does because every element is made the same way without the variabilities introduced by human operators. Greater active area, of course, directly relates to throughput and operational efficiency. Many people see Boron removal as an important current theme. “Boron is a regional issue and is becoming more and more of an issue. You can use membranes or ion exchange to achieve your Boron requirements. “So, if the water is going to be used in agricultural applications for example, Boron requirements can sometimes be even tougher than the WHO (World Health Organisation) standards for Boron in drinking water. Boron is a bad player in certain crops, but you can remove it with membranes or ion exchange resins. Ashkelon for example had a fairly rigid boron specification, and they are meeting this with a membrane process. They’ve got a seawater stage, then a brackish water stage behind it, and they achieve it that way. “Or you could use a boron selective ion exchange resin.” Finally, a difficult question, but what do you feel we can look forward to in the developments of membranes for processes like SWRO? “I believe there will be a lot of technology that can bring down the cost of water for our customers. “Firstly, what can we do with the membrane itself? There are technologies we are working on that will improve flow, rejection, energy consumption, cleanability, and anti-fouling. “The second consideration is how you put the module together. For example, there is now a consortium of membrane manufacturers that has recommended a 16 inch diameter element as the optimum size to drive further cost reductions for water. So, we are working on prototypes of 16 inches. “Aside from this, there are also things going on in terms of how you stage the elements in a pressure vessel. Instead of using one type of membrane in all six positions in the pressure vessel, you use different types of membranes. For example you may have a different one at the front and at the back. What that allows you to do is to optimise that whole pressure vessel.”
Cover story
Filtration+Separation October 2005
(continued from page 21) intake may reduce the capital cost of the desalination facility by several million dollars. In addition, some countries’ (the USA is a prime example) regulatory structure and requirements makes it extremely arduos to build desalination plants. • Deliver other components such as novel energy-saving devices or high-pressure pumping systems etc. For example energy costs are directly related to the salt content of feed water, and can represent more than one third of a seawater desalination system’s operating costs. Reducing energy costs is an important goal for manufacturers of equipment used in water treatment.
Conference at a glance
• Dispose of the brine left over from the process in an environmentally acceptable manner.
In the face of increased water shortages and growing costs of ‘conventional’ treatment, this is expected to continue.
The future for desalination
The next steps for seawater desalination seem to be in optimising the process still further to reduce the cost of producing water – and therefore making it even more viable for utilities/water stakeholders.
This is an issue that has given desalination much bad press in some countries where it has been taken up. Advances in desalination membrane technologies, pretreatment technology, energy recovery, improved integration of facilities, and more environmentally conscious intake and outfall designs have resulted in better performance, lower capital and operating costs, and increased application of membranes in a variety of desalination applications. The Bahrain congress (2002) attracted 600. Amongst the high level attendees were Abdullah Al Hussayen – minister for water and electricity, Saudi Arabia.
• The last three Congresses have taken place in Singapore (2005), The Bahamas (2003), and Bahrain (2002 – rescheduled because of 9/11). It is rumoured that the next conference is scheduled to take place in the Canary Islands (though this is not official yet) in two years time.
• Singapore’s prime minister, Lee Hsien Loomg, officially turned on Singapore’s new Tuas desalination plant, during a ceremony at the conference.
• A total of 855 delegates attended this year’s event. According to the IDA, this makes it the biggest event in the association’s history, beating the Madrid show in 1997 (825 delegates.) The Bahamas congress (2003) attracted 550;
• The high-level technical conference program of over 130 papers included themes such as membrane fouling, pre and post treatment, performance advances, scaling, corrosion, wastewater reclamation, repurification and reuse, energy recovery
One of the IDA representatives summed up the desalination situation neatly in a nutshell; he said that, “even though desalination has been around for some time, making it economically viable is something of an art”. This is something that the filtration industry needs to address.
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and automation, hybrid design, alternative desalination technology, siting and intake alternatives, as well as thermal desalination experiences. • There were approximately 35 exhibitors at the conference, including system integrators and engineering firms (of plants and systems right across the water spectrum), consultation companies that have expertise in the water sector, equipment suppliers (i.e. membranes and related equipment, pumps, chemicals etc), as well as regional water/desalination associations.
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