Water Systems for Pharmaceutical Facilities 595 60 MULTIMEDIA FILTRATION Multimedia filtration(also called prefiltration, sand filtration or multilayered filtration)is mainly aimed at removing sediments and suspended matter. Suspended contaminants are trapped in small crevices and, as a result, water turbidity is improved. A number of media are distinctly layered with the coarsest on top so the suspended matter is collected throughout the according to siz The filter beds need to be backwashed periodically as the back pressure increases; however, backwashing removes the filter from use. To avoid downtime, often a dual filter bed system is installed During construction, the filtration unit should be installed before all the walls are erected so it can be kept upright, in which case the filters can be charged by the vendor before shipping. This would reduce chances of damage to the internals during loading. The unit, of course, should be inspe thoroughly upon receiving. Before shipping, the vendor will often disconnect controls to minimize potential damage. Sufficient time should be allowed to reconnect all of these. Finally, to avoid bacteria building up, start-up should be delayed until a constant water flow is assured
Water Systems for Pharmaceutical Facilities 595 Figure 2. Water pretreatment 6.0 MULTIMEDIA FILTRATION Multimedia filtration (also called prefiltration, sand filtration or multilayered filtration) is mainly aimed at removing sediments and suspended matter. Suspended contaminants are trapped in small crevices and, as a result, water turbidity is improved. A number of media are distinctly layered with the coarsest on top so the suspended matter is collected throughout the depth of the filter according to size. The filter beds need to be backwashed periodically as the back pressure increases; however, backwashing removes the filter from use. To avoid downtime, often a dual filter bed system is installed. During construction, the filtration unit should be installed before all the walls are erected so it can be kept upright, in which case the filters can be charged by the vendor before shipping. This would reduce chances ofdamage to the internals during loading. The unit, of course, should be inspected thoroughly upon receiving. Before shipping, the vendor will often disconnect controls to minimize potential damage. Sufficient time should be allowed to reconnect all of these. Finally, to avoid bacteria building up, start-up should be delayed until a constant water flow is assured
596 Fermentation and Biochemical Engineering Handbook 7.0 WATER SOFTENING Water is softened to remove the scale-forming hardness elements Soft water is required for boilers, water heaters, cooling towers, reverse osmosis systems, etc. Softening is an ion-exchange process which replaces almost all of the metallic or cations by sodium ions and sometimes, the anions with chlorine ions. Therefore, a constant supply of salt is required a softener may be used in conjunction with a deionizer on certain water supplies to provide softened water for use in regeneration. This will prevent the formation of insoluble precipitates within the deionizer resin bed It is important to note that softening does not remove silica, which forms a very hard scale that is not easily removed In addition, softening does not remove chloride which can cause stress corrosion cracking in stainless A freshly regenerated resin bed is in the sodium(Na)form. When in service, sodium cations are exchanged for undesirable quantities of calcium(Ca*), magnesium (Mg*), and iron(Fe)ions. Sodium ions already present in the raw water pass through the process unchanged. Upon exhaustion of the resin, as indicated by unacceptable hardness leakage, most systems are designed to go automatically into regeneration. It should be noted that although the water is softened, the total dissolved solids content remains unchanged. Further, the effluent contains the same anions as the supply water. Softeners can be a microbial concern. a dark and moist column interior can provide a growth environment. The regeneration cycle which uses concentrated brine solution and a backwash cycle aids in reducing the bioburden. Softeners should be regenerated based on a time clock set for twice weekly regenerations and on a volumetric flow of water, whichever is shorter. Since the regeneration cycle removes the softener bed from opera tion,a dual bed system is often specified 8.0 ACTIVATED CARBON Activated carbon has long been used as an effective means of removing organics, chlorine, chlorates, other chlorine compounds and objec tionable tastes and odors. The organics removed include pesticides, herbi- cides and industrial solvents for which activated carbon has diverse capacity Typically, carbon filters are operated at a flow rate of 1-2 gpm/ft'ofactivated carbon
596 Fermentation and Biochemical Engineering Handbook 7.0 WATER SOFTENING Water is softened to remove the scale-forming hardness elements. Soft water is required for boilers, water heaters, cooling towers, reverse osmosis systems, etc. Softening is an ion-exchange process which replaces almost all ofthe metallic or cations by sodium ions and sometimes, the anions with chlorine ions. Therefore, a constant supply of salt is required. A softener may be used in conjunction with a deionizer on certain water supplies to provide softened water for use in regeneration. This will prevent the formation of insoluble precipitates within the deionizer resin bed. It is important to note that softening does not remove silica, which forms a very hard scale that is not easily removed. In addition, softening does not remove chloride which can cause stress corrosion cracking in stainless steel. A freshly regenerated resin bed is in the sodium @a+) form. When in service, sodium cations are exchanged for undesirable quantities of calcium (Ca++), magnesium (Mg++), and iron (Few) ions. Sodium ions already present in the raw water pass through the process unchanged. Upon exhaustion ofthe resin, as indicated by unacceptable hardness leakage, most systems are designed to go automatically into regeneration. It should be noted that although the water is softened, the total dissolved solids content remains unchanged. Further, the effluent contains the same anions as the supp 1 y water. Softeners can be a microbial concern. A dark and moist column interior can provide a growth environment. The regeneration cycle which uses concentrated brine solution and a backwash cycle aids in reducing the bioburden. Softeners should be regenerated based on a time clock set for twice weekly regenerations and on a volumetric flow of water, whichever is shorter. Since the regeneration cycle removes the softener bed from operation, a dual bed system is often specified. 8.0 ACTIVATED CARBON Activated carbon has long been used as an effective means of removing organics, chlorine, chlorates, other chlorine compounds and objectionable tastes and odors. The organics removed include pesticides, herbicides and industrial solvents for which activated carbon has diverse capacity. Typically, carbon filters are operated at a flow rate of 1-2 gpm/ft3 of activated carbon
Water Systems for Pharmaceutical Facilities 597 Since chlorine is removed from water by the carbon, extra care is quired from here on to protect against bioburden growth. Carbon bed themselves are good breeding grounds for bacteria. To keep the system in check, a recirculation system as depicted in Fig 3 is recommended. The constant recirculation avoids water stagnation and reduces viable bioburden Figure 3. Activated Carbon Activated carbon is manufactured by heating selected or other higher carbonaceous material in the absence of ctivation"process burns out impurities and produces a honeycomb-like structure containing millions of tiny pores. The structure provides a large total surface area that enables the carbon to adsorb(attract and hold to the surface)large quantities of contaminants. Chlorine, or its related elements are first adsorbed on the surface of the pores where they react with the carbon to liberate chloride. Because of this reaction and deterioration of chlorine the capacity of activated carbon for chlorine removal is exceedingly high. In addition to chlorine removal and adsorption oforganics, the granular carbon is an effective filter. Although removal of turbidity will shorten the carbon life by blocking pores, the carbon will function as an excellent filter. Particle removal down to 40 microns can be achieved with freshly backwashed beds
Water Systems for Pharmaceutical Facilities 59 7 Since chlorine is removed from water by the carbon, extra care is required from here on to protect against bioburden growth. Carbon beds themselves are good breeding grounds for bacteria. To keep the system in check, a recirculation system as depicted in Fig. 3 is recommended. The constant recirculation avoids water stagnation and reduces viable bioburden growth. Filtered Water 5 Mlcron Fllter 0 I Drain Figure 3. Activated Carbon. Activated carbon is manufactured by heating selected grades of coal or other higher carbonaceous material in the absence of oxygen. This “activation” process burns out impurities and produces a honeycomb-like structure containing millions of tiny pores. The structure provides a large total surface area that enables the carbon to adsorb (attract and hold to the surface) large quantities of contaminants. Chlorine, or its related elements, are first adsorbed on the surface of the pores where they react with the carbon to liberate chloride. Because ofthis reaction and deterioration of chlorine, the capacity of activated carbon for chlorine removal is exceedingly high. In addition to chlorine removal and adsorption of organics, the granular carbon is an effective filter. Although removal of turbidity will shorten the carbon life by blocking pores, the carbon will function as an excellent filter. Particle removal down to 40 microns can be achieved with freshly backwashed beds of carbon
598 Fermentation and Biochemical Engineering Handbook Carbon beds are backwashed to remove carbon fines and suspended matter which have been filtered by the bed. Backwashing does not regenerate the carbon. Sanitizing and some degree of regeneration can be effected by passing low pressure steam or hot water through the carbon bed. The degree of regeneration is limited and the carbon must be replaced periodically (once every 1-2 years). Steam is of course more effective than hot water for sanitization, but it does cause some carbon degradation 9.0 ULTRAVIOLET PURIFICATION In high purity water systems, UV light is often used in-line to control microorganism contamination. Use of uV as a disinfectant is somewhat controversial. In the authors opinion, UV as an added measure is worth- while; however, it should not be totally relied on to keep the water clear of bacterial contaminants, UV systems cannot correct for a poorly designed water system. Also, note that UV kills microorganisms and hence generates pyrogens, 2) In most cases, microorganisms can be filtered out, while pyrogens cannot be To be effective UV radiation at a wavelength of 2537 a must be applied. A minimum dosage of 16,000 microwatt-seconds per cm2 must be reached at all points throughout the water chamber. appendix ii is a summary statement by the Department of Health, Education and Welfare on the use of uv as a disinfectant During construction and installation, extra care should be taken in handling the UV unit. The UV lamp sleeves are made of quartz, since glass filters UV radiation, and are very fragile. The same is true in the start-up the lamps can break when the unit is first pressurized. It is recommended that spare lamps be kept on hand. Lamps also get broken during start-up if they are turned on when there is no flow. they get hot before the flow is established and then cold water causes them to break. Finally, avoid looking directly at the lamps while they are on. UV radiation can cause eye damage a port equipped with a thick glass cover is provided to visually check the 100 DEIONIZATION Deionization is the process of removing the dissolved ionized solids from water by ion exchange. Ion exchange can be defined as a reversible exchange of ions between a solid (resin) and a liquid (water). The major
598 Fermentation and Biochemical Engineering Handbook Carbon beds are backwashed to remove carbon fines and suspended matter which have been filtered by the bed. Backwashing does not regenerate the carbon. Sanitizing and some degree of regeneration can be effected by passing low pressure steam or hot water through the carbon bed. The degree of regeneration is limited and the carbon must be replaced periodically (once every 1-2 years). Steam is of course more effective than hot water for sanitization, but it does cause some carbon degradation. 9.0 ULTRAVIOLET PURIFICATION In high purity water systems, UV light is often used in-line to control microorganism contamination. Use of UV as a disinfectant is somewhat controversial. In the author’s opinion, UV as an added measure is worthwhile; however, it should not be totally relied on to keep the water clear of bacterial contaminants. UV systems cannot correct for a poorly designed water system. Also, note that UV kills microorganisms and hence generates pyrogens.[21 In most cases, microorganisms can be filtered out, while pyrogens cannot be. To be effective, UV radiation at a wavelength of 2537 A must be applied. A minimum dosage of 16,000 microwatt-seconds per cm2 must be reached at all points throughout the water chamber. Appendix I1 is a summary statement by the Department of Health, Education and Welfare on the use of UV as a disinfectant. During construction and installation, extra care should be taken in handling the UV unit. The UV lamp sleeves are made of quartz, since glass filters UV radiation, and are very fragile. The same is true in the start-up; the lamps can break when the unit is first pressurized. It is recommended that spare lamps be kept on hand. Lamps also get broken during start-up if they are turned on when there is no flow. They get hot before the flow is established and then cold water causes them to break. Finally, avoid looking directly at the lamps while they are on. UV radiation can cause eye damage. A port equipped with a thick glass cover is provided to visually check the lamps. 10.0 DEIONIZATION Deionization is the process of removing the dissolved ionized solids from water by ion exchange. Ion exchange can be defined as a reversible exchange of ions between a solid (resin) and a liquid (water). The major