- Email: [email protected]
High purity water: Advances in ion exchange technology
20
Feature
Filtration+Separation July/August 2007
High purity water:
Advances in ion exchange technology T
here will always be a need for purified water in the production of pharmaceuticals. Anthony Bennett looks at the background of ion exchange technology in this field and reviews its advances and developments.
Standards and history Compared with the requirements of industries such as microelectronics manufacture and power generation the purity standards for pharmaceutical water are not very high. What makes the production and use of pharmaceutical water such a demanding application are the legislative requirements and practices that arise from cGMP and validation practices, although there are few specific references to water systems in GMP documents such as ‘Rules and Guidance for Pharmaceutical Manufacturers and Distributors’ compiled by the Medicines and Healthcare products Regulatory Agency (MHRA).
The ion exchange process was first observed in 1845 but it was not until 1905 that water was softened by replacing calcium and magnesium ions with sodium using a zeolite medium. In 1934 new materials were developed for carrying out the exchange process and the first synthetic anion resin was manufactured. In 1937 the first industrial demineralisation plant in the world was installed in Britain. In the early days of using synthetic resin it was
expensive, unstable and prone to breaking up but over the next 40 years developments made resin cheaper, more stable and smaller resin beads were developed. Since the early 1980’s development of ion exchange resins has continued but the development of applications using these resins have been of more significance.
Ion exchange resins An ion exchange resin is an insoluble matrix normally in the form of small beads, approximately 1-2 mm in diameter, fabricated from an organic polymer substrate. The ‘trapping’ of ions takes place with a simultaneous release of other ions, thus the process is called ion exchange. Most typical ion exchange resins are based on cross linked polystyrene. There are 4 general types of ion exchange resin which differ in their functional groups:
The legislative water qualities are detailed in pharmacopoeias, see Table 1. These standards have been in place now for a few years and there is currently no indication that there are going to be any changes. There have been few significant changes to water purification systems over the past 20 years, with many of the manufacturing processes and technologies used being little changed. All the major water treatment equipment suppliers have developed standard systems which produce water that meets these standards. Ion exchange technology continues to be an integral part of these treatment processes.
VNX spacer (Courtesy of Ionpure)
Strongly acidic – sulphonic acid groups; Weakly acidic – carboxylic acid groups; Strongly basic – trimethylammonium groups; Weakly basic – amino groups.
Rapide Strata (Courtesy of Veolia Water)
‘Strong’ resins have a greater affinity for all ionized constituents in water and are capable of removing even weakly ionized constituents such as acetates and silica. ‘Weak’ resins are ineffective at removing weakly ionized constituents, however, their exchange capacities are two or three times
Feature
Filtration+Separation July/August 2007
Table 1 – Purified Water Specification Parameter
Units
USP
Ph. Eur.
TOC Oxidisable substances
mg carbon per litre
0.50
< 0.5 (Optional)
n/a
Optional
Optional – faint pink colour remains
Conductivity
µS/cm @ 25 oC
< 1.3 (Stage 1 test)
< 5.1
Nitrate (NO3)
ppm
n/a
< 0.2
Heavy metals
ppm as Pb
n/a
< 0.1
Aerobic bacteria
CFU/ml
< 100 (Action level) Minimum sample – 1.0 mL for pour plate method
< 100 (Action Limit) Sample size based on expected result.
USP
Ph. Eur.
Water for Injections Specification Parameter
Units
TOC
mg carbon per litre
0.50
< 0.5
Conductivity
µS/cm @ 25 oC
< 1.3
< 1.3
Stage 1 test Nitrate (NO3)
ppm
n/a
< 0.2
Heavy metals
ppm as Pb
n/a
< 0.1
Aerobic bacteria
CFU/100 ml
< 10 (Action level)
< 10 (Action Limit) (minimum 200 ml sample, membrane filtration method)
(minimum sample – 100 mL membrane filtration method) Bacterial endotoxins
EU/ml IU/ml
that of strong resins and can be regenerated more efficiently. Ion exchange resins have a higher affinity for polyvalent ions so divalent ions are removed first as water passes through a resin bed. Monovalent ions such as sodium, can be displaced by divalent ions in the exhaustion cycle and will leak into the product stream first.
Developments in resins There are few published references to developments in ion exchange resins over the past 20 years. While the manufacturing processes have been developed to reduce costs, improve the consistency of the resin quality etc. the resins appear to have only subtly changed. Some collaborative developments between equipment manufacturers and resin manufacturers have taken place to develop ‘customised’ resins which may be more suitable for specific applications, for example ‘doping’ the resin. Unfortunately, the details of these are kept confidential because of commercial implications. There have also been developments in ion exchange resins used in the manufacturing of pharmaceuticals, e.g. catalyzing certain reactions, isolating and purifying pharmaceutical active ingredients. Some ion exchange resins are used as active ingredients and some are also used as excipients in pharmaceutical formulations.
Developments in Applications Pretreatment systems In pre-treatment systems ion exchange resins are used in water softeners and organic
< 0.25 < 0.25
scavengers (organic traps) and the basic design and operation of these systems remains largely unchanged. Water softening uses a cation exchange resin to exchange principally calcium and magnesium ions for sodium ions and so prevent the formation of calcium carbonate precipitates on Reverse Osmosis membranes, WFI stills and other down stream processes. Feed water is passed down through the resin bed which is in the sodium form. The polyvalent cations are absorbed onto the resin and the sodium ions are released. After a preset volume, or time, the system is taken off line and automatically regenerated with a brine solution. Usually the residual hardness after a single pass through a softener is suitable but some modern systems require a lower level of hardness so one development has been to use serial softening with the ‘lead’ softener being regenerated based on a volume throughput and the ‘polishing’ softener being regenerated after a preset number of regenerations of the lead softener. This can produced water with < 1 ppm as calcium carbonate. Organic scavengers (or organic traps) utilise a macroreticular anion exchange resin to remove a percentage of organic material from the feed water supply. As the feed water passes down through the bed of anion resin in the chloride form the negatively charged organics are preferentially absorbed onto the positively charged active sites on the resin beads to displace the chloride
ions. The large molecules also get trapped in pores in the resin beads and are removed by a size exclusion process. The resin is regenerated using a brine solution with the excess chloride ions displacing the organic acids from the active sites. The change in osmotic pressure also causes the resin beads to shrinks and so squeezes out the trapped organic material. This process works quite well but the percentage removal of organics is variable and non-predictable. No recent developments in resin technology which have improved this performance so this technology is being replaced by the use of ultrafiltration, particularly in locations which have a high organic content in the feed. The most recent development in pretreatment ion exchange systems has been the introduction of hot water sanitisation. A key objective in pharmaceutical water systems, is the control of microbiological levels in the water. Prior to the introduction of hot water sanitisable RO and CEDI systems (see below), a periodic chemical sanitisation of the whole pre-treatment system was sometimes carried out when the purification system was being sanitised. However, due to the down time and labour costs involved the frequency of chemical sanitisation varies significantly from site to site. With the development of hot water sanitisable purification equipment a demand was generated for hot water sanitisable pretreatment systems.
21
22
Feature
VNX installation (Courtesy of Ionpure)
The GRP vessels typical used for water softeners and scavengers are replaced with lined or coated metal vessels and the interconnecting ABS or PVC plastic pipework replaced with stainless steel pipework and fittings. Sanitisation temperatures up to 65 – 85 oC are possible which can achieve a good sanitisation effect. This has a substantial capital cost and operational cost impact for no improvement in the water softening or organic reduction performance of the system. This development is introduced only to provide a periodic sanitisation of the pretreatment section of the system.
Purification systems The most common method of producing Purified Water were twin bed deioniser systems and these could still easily meet the required water quality. A twin bed system uses a bed of cation resin, regenerated with
Filtration+Separation July/August 2007
hydrochloric or sulphuric acid, followed by a bed of anion resin, regenerated with sodium hydroxide. After either a preset throughput, or typically when a maximum conductivity value is reached, the system is taken off line and regenerated with acid and caustic. This technology works very well and twin bed units continue to be a common technology used to produce deionised water in other industries.
(more efficient at organic removal) and strong base anion resin (more efficient removal of anions). A further development is the use of chemical ‘pulses’ rather than continuous injection when the acid and caustic regenerants are added. These changes are claimed to give better cleaning and regeneration with the typical regeneration time having been reduced to around 35 minutes.
In 1986 the Permutit company introduced a development called Scion – short cycle ion exchange – which challenged the then current design philosophy for twin bed units by introducing a short service run (typically 6 – 8 hours compared with 1 – 2 days) and a short regeneration period (typically 2 hours compared with several hours) with counter current regeneration. A further development was the use of a third, polishing, column containing cation resin. This column removes the low level of cations which ‘slip’ off the first column and results in a lower product conductivity being possible. A variety of counter current regenerated systems have since been developed.
A twin bed short cycle system can typically achieve around 5 µS/cm while with the inclusion of a second cation polishing bed qualities as good as 18 megOhm/cm can be achieved.
Recently, there have been attempts to minimise chemical consumption, reduce running costs and maximise water usage. This has been possible by incorporating the latest versions of the anion and cation resins combined with some interesting developments in the operation of the system. For example, Veolia recently launched an updated version of their short cycle system called RAPIDE Strata which incorporates the use of a stratified anion bed which incorporates both weak base anion resin
Development of these types of systems has resulted in significant reductions in the use of chemical regenerants per cubic meter of water produced, better water qualities and a system that is more tolerant of the organic content of the feed water. There are many justifications available on various web sites supporting the selection of ion exchange technology over reverse osmosis, and in many applications ion exchange is still the preferred option – but in pharmaceutical water systems this is not the case. Reverse Osmosis, combined with other technologies, is now the preferred option. This is probably due to a combination of reasons, for example the security of meeting the TOC limit, handling chemicals and effluent, and microbiological quality. Another ion exchange treatment which has also significantly decreased in use is Service Deionisation. This involves using resin in portable cylinders which are shipped off site for regeneration when these are exhausted. There have not been many technical developments in this technology but it is still commonly used, particularly in nonpharmaceutical applications. Arguably the main reason for the reduced usage of these technologies has been the development of Continuous Electrodeionisation technologies (CEDI). The first commercialized CEDI system was introduced in 1987 by Millipore and there are now many different companies manufacturing systems using a variety of system designs. All the systems are based on using cation and anion selective membranes to form ‘compartments’ in which ions are removed from the feed water (dilute or diluate) under the influence of an electric field. These ions are collected and removed from the system via waste ‘compartments’ (concentrate) which alternate with the purifying channels. Explanations of this technology are available from many sources but one useful on-line training resource can be found at www. cediuniversity.com.
Genesys Integrated System (Courtesy of PureTech)
The dilute compartments are filled with ion exchange resin and in some systems the
Feature
Filtration+Separation July/August 2007
modules which was a common feature of the systems available originally. (Spiral configured modules were originally developed in a sealed housing.) • Hot water sanitisable modules. This made it possible to hot water sanitise the entire Purified Water generation system. • Larger flow rate modules. This simplified the design of systems while also helping reduce the costs per cubic meter of water produced. (Some of modules are now 2/3rd to 9/10th cheaper.)
Osmotron Soft Select Hot Water Sanitisable system (Courtesy of Christ)
concentrate compartments are also filled with resin. Some systems use mixed bed resins while some use layers of cation and anion resin combined with different cell geometries. The majority of systems utilise ‘plate and frame’ type designs while a few systems utilise a spiral configuration. All the systems are designed to removed dissolved salts, carbon dioxide, dissolved silica, ammonia and some organic material. Different manufacturers make different claims about the effect of their system on the microbiological content of the product water, however, generally most claim that their equipment does not add particles, organics, bacteria or endotoxins to the product water.
Although this technology has been in use for 20 years probably the most significant improvements in the technology have happened in the past 3 – 5 years. These have been: • Resin in the concentrate compartments. This improves the removal performance and can remove the requirement to add or retain electrolytes in the concentrate flow. • The selection of the ion exchange resin, the use of layers of resin rather than mixed resins and the use of resin doping. • New sealing methods for the modules has reduced or prevented leakage from the
• Integration of a membrane system with a CEDI module. Christ recently introduced the Septron Bio-Safe to assist in the production of Highly Purified Water where a typical design configuration is to use RO and CEDI followed by a second membrane stage to ensure the Endotoxin specification of Highly Purified Water is always met. With these product developments it is now possibly to continuously, reliably and without the use of regenerant chemicals, produce water which easily meets the requirements for Purified Water and with the option of automatic hot water sanitisation of the system. In fact, the water quality produced can be as good as 0.055 µS/cm conductivity, < 10 ppb TOC, < 10 cfu/100 ml and < 0.25 EU/ml. This improved water quality is arguably a less important benefit to the patient and to manufacturers than the improved consistency and reliability that the new generation of systems provides. A final ‘development’ has been a growth in the selection and sophistication of skid mounted systems which are offered by suppliers. These systems can be put through extensive FAT protocols, including IQ and OQ protocols, prior to shipping. This has not only resulted in reduced delivery times for the system but it has reduced the installation, commissioning and qualification time required on site.
•
Contact: Anthony Bennett is Technical Director at Clarity. His company provides a range of technical authoring, promotional, sales support and related services specifically for innovative companies in the environmental sector. Details on Clarity can be viewed at www.clarityauthoring.com
Orion Integrated System Hot Water Sanitisable System (Courtesy of Veolia Water)
Acknowledgements Ionpure/Siemens contact: [email protected] Veolia Water contact: [email protected] Christ Water Technologies contact: [email protected] PureTech contact: [email protected]
23
Feature
Filtration+Separation July/August 2007
High purity water:
Advances in ion exchange technology T
here will always be a need for purified water in the production of pharmaceuticals. Anthony Bennett looks at the background of ion exchange technology in this field and reviews its advances and developments.
Standards and history Compared with the requirements of industries such as microelectronics manufacture and power generation the purity standards for pharmaceutical water are not very high. What makes the production and use of pharmaceutical water such a demanding application are the legislative requirements and practices that arise from cGMP and validation practices, although there are few specific references to water systems in GMP documents such as ‘Rules and Guidance for Pharmaceutical Manufacturers and Distributors’ compiled by the Medicines and Healthcare products Regulatory Agency (MHRA).
The ion exchange process was first observed in 1845 but it was not until 1905 that water was softened by replacing calcium and magnesium ions with sodium using a zeolite medium. In 1934 new materials were developed for carrying out the exchange process and the first synthetic anion resin was manufactured. In 1937 the first industrial demineralisation plant in the world was installed in Britain. In the early days of using synthetic resin it was
expensive, unstable and prone to breaking up but over the next 40 years developments made resin cheaper, more stable and smaller resin beads were developed. Since the early 1980’s development of ion exchange resins has continued but the development of applications using these resins have been of more significance.
Ion exchange resins An ion exchange resin is an insoluble matrix normally in the form of small beads, approximately 1-2 mm in diameter, fabricated from an organic polymer substrate. The ‘trapping’ of ions takes place with a simultaneous release of other ions, thus the process is called ion exchange. Most typical ion exchange resins are based on cross linked polystyrene. There are 4 general types of ion exchange resin which differ in their functional groups:
The legislative water qualities are detailed in pharmacopoeias, see Table 1. These standards have been in place now for a few years and there is currently no indication that there are going to be any changes. There have been few significant changes to water purification systems over the past 20 years, with many of the manufacturing processes and technologies used being little changed. All the major water treatment equipment suppliers have developed standard systems which produce water that meets these standards. Ion exchange technology continues to be an integral part of these treatment processes.
VNX spacer (Courtesy of Ionpure)
Strongly acidic – sulphonic acid groups; Weakly acidic – carboxylic acid groups; Strongly basic – trimethylammonium groups; Weakly basic – amino groups.
Rapide Strata (Courtesy of Veolia Water)
‘Strong’ resins have a greater affinity for all ionized constituents in water and are capable of removing even weakly ionized constituents such as acetates and silica. ‘Weak’ resins are ineffective at removing weakly ionized constituents, however, their exchange capacities are two or three times
Feature
Filtration+Separation July/August 2007
Table 1 – Purified Water Specification Parameter
Units
USP
Ph. Eur.
TOC Oxidisable substances
mg carbon per litre
0.50
< 0.5 (Optional)
n/a
Optional
Optional – faint pink colour remains
Conductivity
µS/cm @ 25 oC
< 1.3 (Stage 1 test)
< 5.1
Nitrate (NO3)
ppm
n/a
< 0.2
Heavy metals
ppm as Pb
n/a
< 0.1
Aerobic bacteria
CFU/ml
< 100 (Action level) Minimum sample – 1.0 mL for pour plate method
< 100 (Action Limit) Sample size based on expected result.
USP
Ph. Eur.
Water for Injections Specification Parameter
Units
TOC
mg carbon per litre
0.50
< 0.5
Conductivity
µS/cm @ 25 oC
< 1.3
< 1.3
Stage 1 test Nitrate (NO3)
ppm
n/a
< 0.2
Heavy metals
ppm as Pb
n/a
< 0.1
Aerobic bacteria
CFU/100 ml
< 10 (Action level)
< 10 (Action Limit) (minimum 200 ml sample, membrane filtration method)
(minimum sample – 100 mL membrane filtration method) Bacterial endotoxins
EU/ml IU/ml
that of strong resins and can be regenerated more efficiently. Ion exchange resins have a higher affinity for polyvalent ions so divalent ions are removed first as water passes through a resin bed. Monovalent ions such as sodium, can be displaced by divalent ions in the exhaustion cycle and will leak into the product stream first.
Developments in resins There are few published references to developments in ion exchange resins over the past 20 years. While the manufacturing processes have been developed to reduce costs, improve the consistency of the resin quality etc. the resins appear to have only subtly changed. Some collaborative developments between equipment manufacturers and resin manufacturers have taken place to develop ‘customised’ resins which may be more suitable for specific applications, for example ‘doping’ the resin. Unfortunately, the details of these are kept confidential because of commercial implications. There have also been developments in ion exchange resins used in the manufacturing of pharmaceuticals, e.g. catalyzing certain reactions, isolating and purifying pharmaceutical active ingredients. Some ion exchange resins are used as active ingredients and some are also used as excipients in pharmaceutical formulations.
Developments in Applications Pretreatment systems In pre-treatment systems ion exchange resins are used in water softeners and organic
< 0.25 < 0.25
scavengers (organic traps) and the basic design and operation of these systems remains largely unchanged. Water softening uses a cation exchange resin to exchange principally calcium and magnesium ions for sodium ions and so prevent the formation of calcium carbonate precipitates on Reverse Osmosis membranes, WFI stills and other down stream processes. Feed water is passed down through the resin bed which is in the sodium form. The polyvalent cations are absorbed onto the resin and the sodium ions are released. After a preset volume, or time, the system is taken off line and automatically regenerated with a brine solution. Usually the residual hardness after a single pass through a softener is suitable but some modern systems require a lower level of hardness so one development has been to use serial softening with the ‘lead’ softener being regenerated based on a volume throughput and the ‘polishing’ softener being regenerated after a preset number of regenerations of the lead softener. This can produced water with < 1 ppm as calcium carbonate. Organic scavengers (or organic traps) utilise a macroreticular anion exchange resin to remove a percentage of organic material from the feed water supply. As the feed water passes down through the bed of anion resin in the chloride form the negatively charged organics are preferentially absorbed onto the positively charged active sites on the resin beads to displace the chloride
ions. The large molecules also get trapped in pores in the resin beads and are removed by a size exclusion process. The resin is regenerated using a brine solution with the excess chloride ions displacing the organic acids from the active sites. The change in osmotic pressure also causes the resin beads to shrinks and so squeezes out the trapped organic material. This process works quite well but the percentage removal of organics is variable and non-predictable. No recent developments in resin technology which have improved this performance so this technology is being replaced by the use of ultrafiltration, particularly in locations which have a high organic content in the feed. The most recent development in pretreatment ion exchange systems has been the introduction of hot water sanitisation. A key objective in pharmaceutical water systems, is the control of microbiological levels in the water. Prior to the introduction of hot water sanitisable RO and CEDI systems (see below), a periodic chemical sanitisation of the whole pre-treatment system was sometimes carried out when the purification system was being sanitised. However, due to the down time and labour costs involved the frequency of chemical sanitisation varies significantly from site to site. With the development of hot water sanitisable purification equipment a demand was generated for hot water sanitisable pretreatment systems.
21
22
Feature
VNX installation (Courtesy of Ionpure)
The GRP vessels typical used for water softeners and scavengers are replaced with lined or coated metal vessels and the interconnecting ABS or PVC plastic pipework replaced with stainless steel pipework and fittings. Sanitisation temperatures up to 65 – 85 oC are possible which can achieve a good sanitisation effect. This has a substantial capital cost and operational cost impact for no improvement in the water softening or organic reduction performance of the system. This development is introduced only to provide a periodic sanitisation of the pretreatment section of the system.
Purification systems The most common method of producing Purified Water were twin bed deioniser systems and these could still easily meet the required water quality. A twin bed system uses a bed of cation resin, regenerated with
Filtration+Separation July/August 2007
hydrochloric or sulphuric acid, followed by a bed of anion resin, regenerated with sodium hydroxide. After either a preset throughput, or typically when a maximum conductivity value is reached, the system is taken off line and regenerated with acid and caustic. This technology works very well and twin bed units continue to be a common technology used to produce deionised water in other industries.
(more efficient at organic removal) and strong base anion resin (more efficient removal of anions). A further development is the use of chemical ‘pulses’ rather than continuous injection when the acid and caustic regenerants are added. These changes are claimed to give better cleaning and regeneration with the typical regeneration time having been reduced to around 35 minutes.
In 1986 the Permutit company introduced a development called Scion – short cycle ion exchange – which challenged the then current design philosophy for twin bed units by introducing a short service run (typically 6 – 8 hours compared with 1 – 2 days) and a short regeneration period (typically 2 hours compared with several hours) with counter current regeneration. A further development was the use of a third, polishing, column containing cation resin. This column removes the low level of cations which ‘slip’ off the first column and results in a lower product conductivity being possible. A variety of counter current regenerated systems have since been developed.
A twin bed short cycle system can typically achieve around 5 µS/cm while with the inclusion of a second cation polishing bed qualities as good as 18 megOhm/cm can be achieved.
Recently, there have been attempts to minimise chemical consumption, reduce running costs and maximise water usage. This has been possible by incorporating the latest versions of the anion and cation resins combined with some interesting developments in the operation of the system. For example, Veolia recently launched an updated version of their short cycle system called RAPIDE Strata which incorporates the use of a stratified anion bed which incorporates both weak base anion resin
Development of these types of systems has resulted in significant reductions in the use of chemical regenerants per cubic meter of water produced, better water qualities and a system that is more tolerant of the organic content of the feed water. There are many justifications available on various web sites supporting the selection of ion exchange technology over reverse osmosis, and in many applications ion exchange is still the preferred option – but in pharmaceutical water systems this is not the case. Reverse Osmosis, combined with other technologies, is now the preferred option. This is probably due to a combination of reasons, for example the security of meeting the TOC limit, handling chemicals and effluent, and microbiological quality. Another ion exchange treatment which has also significantly decreased in use is Service Deionisation. This involves using resin in portable cylinders which are shipped off site for regeneration when these are exhausted. There have not been many technical developments in this technology but it is still commonly used, particularly in nonpharmaceutical applications. Arguably the main reason for the reduced usage of these technologies has been the development of Continuous Electrodeionisation technologies (CEDI). The first commercialized CEDI system was introduced in 1987 by Millipore and there are now many different companies manufacturing systems using a variety of system designs. All the systems are based on using cation and anion selective membranes to form ‘compartments’ in which ions are removed from the feed water (dilute or diluate) under the influence of an electric field. These ions are collected and removed from the system via waste ‘compartments’ (concentrate) which alternate with the purifying channels. Explanations of this technology are available from many sources but one useful on-line training resource can be found at www. cediuniversity.com.
Genesys Integrated System (Courtesy of PureTech)
The dilute compartments are filled with ion exchange resin and in some systems the
Feature
Filtration+Separation July/August 2007
modules which was a common feature of the systems available originally. (Spiral configured modules were originally developed in a sealed housing.) • Hot water sanitisable modules. This made it possible to hot water sanitise the entire Purified Water generation system. • Larger flow rate modules. This simplified the design of systems while also helping reduce the costs per cubic meter of water produced. (Some of modules are now 2/3rd to 9/10th cheaper.)
Osmotron Soft Select Hot Water Sanitisable system (Courtesy of Christ)
concentrate compartments are also filled with resin. Some systems use mixed bed resins while some use layers of cation and anion resin combined with different cell geometries. The majority of systems utilise ‘plate and frame’ type designs while a few systems utilise a spiral configuration. All the systems are designed to removed dissolved salts, carbon dioxide, dissolved silica, ammonia and some organic material. Different manufacturers make different claims about the effect of their system on the microbiological content of the product water, however, generally most claim that their equipment does not add particles, organics, bacteria or endotoxins to the product water.
Although this technology has been in use for 20 years probably the most significant improvements in the technology have happened in the past 3 – 5 years. These have been: • Resin in the concentrate compartments. This improves the removal performance and can remove the requirement to add or retain electrolytes in the concentrate flow. • The selection of the ion exchange resin, the use of layers of resin rather than mixed resins and the use of resin doping. • New sealing methods for the modules has reduced or prevented leakage from the
• Integration of a membrane system with a CEDI module. Christ recently introduced the Septron Bio-Safe to assist in the production of Highly Purified Water where a typical design configuration is to use RO and CEDI followed by a second membrane stage to ensure the Endotoxin specification of Highly Purified Water is always met. With these product developments it is now possibly to continuously, reliably and without the use of regenerant chemicals, produce water which easily meets the requirements for Purified Water and with the option of automatic hot water sanitisation of the system. In fact, the water quality produced can be as good as 0.055 µS/cm conductivity, < 10 ppb TOC, < 10 cfu/100 ml and < 0.25 EU/ml. This improved water quality is arguably a less important benefit to the patient and to manufacturers than the improved consistency and reliability that the new generation of systems provides. A final ‘development’ has been a growth in the selection and sophistication of skid mounted systems which are offered by suppliers. These systems can be put through extensive FAT protocols, including IQ and OQ protocols, prior to shipping. This has not only resulted in reduced delivery times for the system but it has reduced the installation, commissioning and qualification time required on site.
•
Contact: Anthony Bennett is Technical Director at Clarity. His company provides a range of technical authoring, promotional, sales support and related services specifically for innovative companies in the environmental sector. Details on Clarity can be viewed at www.clarityauthoring.com
Orion Integrated System Hot Water Sanitisable System (Courtesy of Veolia Water)
Acknowledgements Ionpure/Siemens contact: [email protected] Veolia Water contact: [email protected] Christ Water Technologies contact: [email protected] PureTech contact: [email protected]
23