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Compendial Water Systems - Maintenance and Monitoring Considerations

Tue, 12/10/2013 - 4:21pm
William V. Collentro, Pharmaceutical Water Specialists, LLC

Inadequate maintenance and monitoring programs for compendial water systems can result in chemical and/or microbial excursions that ultimately impact “delivered” water quality at points-of-use. In general, total viable bacteria results associated with distribution loop sampling are not available for at least 3-5 days after collection. During this time period an unacceptable increase in total viable bacteria could occur as a result of an operating excursion in a water purification unit operation. The unacceptable increase in total viable bacteria levels may result in an extensive investigation with documentation of conditions producing the problem and potential loss of product manufactured during the excursion. It is suggested that a water purification equipment, storage, and distribution system proactive maintenance program supplemented with a periodic monitoring program can both avoid and/or increase the detection and potential occurrence of individual component performance issues.

Discussion
A maintenance program should be established based on specific facility policy, ranging from totally reactive to proactive. The reactive program repairs components when they are not functional and is associated with a significant risk to delivered water quality. The proactive preventative maintenance approach is conservative but virtually eliminates the risk to product water quality associated with water purification component, non personnel, related excursions. In an attempt to provide a suggested proactive preventative maintenance program for as many water purification, storage and distribution components and accessories as possible, a purified water System utilizing ozone for bacteria control in the storage and distribution system has been selected. The system will consist of a Pretreatment Section, Ion Removal and Polishing Section, and Storage/Ozonation, Distribution Section. A future article will discuss a responsive system monitoring program to detect many excursions before point-of-use water quality is affected.


Preventative Maintenance Program – Pretreatment Section
A Process Flow Diagram for a Pretreatment System is shown in Figure A. The diagram includes sample valves, discussed later in this article. Both components and arrangement of components in the Pretreatment Section may vary with application and nature of the feed water supply. As an example, the position of the activated carbon and water softening units assumes that the feed water is from a surface source and that the municipality employs monochloramine as a “secondary” disinfecting agent (1,2). The municipal feed water source must meet The United States Environmental Protection Agency’s National Primary Drinking Water Regulations (NPDWR), equivalent governmental regulating agency standard or World Health Organization (WHO) standard for Drinking Water (3,4).

• Multimedia Filtration Unit
The initial component in the Pretreatment Section is a backwashable multimedia filtration unit. The unit consists of a vessel containing graduated levels of support and filter media to remove particles from feed water with a size of about 10 micron and larger. The unit may be equipped with multiport valve or individual valves for periodic backwash to remove entrapped particulate matter. It is suggested that filter media, generally sand and anthracite, be replaced every 5 years. Support media, generally graduated physical size gravel, should also be replaced every five years. During support and filter media replacement the internal surfaces of the vessel, and both upper and lower distribution system should be inspected and repaired/replaced if required. Valve operation should be verified annually. Valve seals, diaphragms, or entire assembly should be replaced if water leaks (to the atmosphere or by the sealing mechanism in the water flow path) are noted. Since differential pressure “across” the unit is critical to successful operation, accurate liquid filled pressure gauges are suggested with annual calibration frequency.
• Water Softening System
Generally two water softening units are provided to remove multivalent ions from feed water, replacing the ions with sodium. Multivalent cations, if not removed, will result in scaling of the downstream reverse osmosis membranes. The water softening units contain cation ion exchange resin in vessels and a brine storage tank. Suggested preventative maintenance items include the following:
    ❖ Annual inspection of valve operation
    ❖ Ongoing inspection for valve leaks to the atmosphere, with seal replacement as required
    ❖ Semiannual verification of regenerant brine introduction rate, including eductor
    ❖ Semiannual cleaning of the salt storage tank and sanitization of the tank interior with a sodium hypochlorite solution
    ❖Semiannual inspection of salt storage tank “float and make-up valve” mechanism
    ❖ Annual collection of cation resin bed “core” sample with analysis to determine physical condition, degree of “iron fouling”, and ion exchange capacity
    ❖ Replacement of cation resin every two-three years. During resin replacement inspect the interior of the column and upper and lower distributors. If gravel is used as support media, replace the gravel. Clean and sanitize the interior of the vessels with a sodium hypochlorite solution.
    ❖ Calibrate feed water and product water pressure gauges annually.
• Activated Carbon Adsorption Unit
Activated carbon adsorption units remove residual disinfecting agent from water by a chemical-adsorptive process. If not removed, disinfecting agent will gradually attack thin-film composite downstream reverse osmosis membranes in the reverse osmosis unit. Disinfecting agent will also attack ion exchange resin in the continuous electrodeionization unit downstream of the reverse osmosis unit. In fact, the rate of degradation of the ion exchange resin and ion exchange membranes in the continuous electrodeionization unit is much faster than that of reverse osmosis membranes (5,6). In addition to removing raw water disinfecting agent, activated carbon will reduce the concentration of reverse osmosis membrane fouling naturally occurring organic material (NOM). A suggested maintenance program for activated carbon adsorption units includes the following:
❖ Annual inspection of valve operation
    ❖ Ongoing inspection for valve leaks to the atmosphere, with seal replacement as required
    ❖ Periodic removal of the activated carbon media and replacement with new media. For systems with chloramines in feed water, the replacement frequency of activated carbon media should be once every six months, maximum. Replacement media should be acid washed, neutralized, and rinsed catalytic-type. For units with chlorine (hypochlorous acid/hypochlorite ion) in feed water the replacement frequency should be annually with acid washed, neutralized, and rinsed media. During media change the interior of the activated carbon vessel should be inspected and washed with a 100 ppm solution of sodium hypochlorite.
    ❖ Inlet and outlet distributors should be inspected during activated carbon media change and replaced as appropriate.
    ❖ Subsequent to activated carbon media replacement an extended backwash and rinse-to-drain should be conducted to remove any activated carbon “fines”.
    ❖ Annual calibration of feed water and product water pressure gauges shall be performed.
• Post Activated Carbon Unit Inline Ultraviolet Sanitization Unit
An inline ultraviolet sanitization unit (253.7 nanometer wave length) should be positioned downstream of the activated carbon unit to provide total viable bacteria reduction from the water purification unit operation with the highest product water bacteria level. The unit will reduce total viable bacteria by a factor of 10X to 100X if properly maintained, as follows:
    ❖ Replace ultraviolet lamps, quartz sleeves, and O-rings every six months. Physical or chemical cleaning of quartz sleeves is highly discouraged. While greater than ultraviolet unit manufacturer’s recommended replacement frequency, excellent bacteria destruction can be achieved with semiannual replacement.
    ❖ Use “certified” ultraviolet lamps. These lamps have been “preconditioned/operated” with ultraviolet radiation intensity verified using a quantitative meter. The recommended ultraviolet radiation intensity meter can be set to a value of “100%” within 24 hours of lamp replacement and verified for about one week after lamp replacement.
    ❖ Clean vent fan filters for cooling lamp ballast semiannually.
    ❖ If “plastic” compression nuts are used for quartz sleeve seals, replace every three years.
    ❖ Retain at least two spare compression nuts, O-rings, lamps, quartz.
• Final Pretreatment Section Cartridge Filtration System
Particulate filters are generally installed directly upstream of the reverse osmosis unit. Since the Ion Removal Section utilizes recirculation with continuous flow (make-up or recirculating) around a “Break Tank”, the RO prefilter is positioned as the final component in the Pretreatment Section. The following maintenance program should be considered:
    ❖Replace cartridge filter every 1-2 weeks. Filter cartridges should be selected such that a particulate removal rating (? 5 microns) with adequate particulate retention capability for this short time period is achieved. The brief replacement frequency is based on bacteria control considerations. The large surface area and partial bacteria retentive properties provide a location for accumulation and proliferation of bacteria.
    ❖ Inspect removed filters to verify the absence of ion exchange resin “fines”, activated carbon “fines”, and excessive microbial growth (slippery surface).
    ❖ Annual calibration of feed water and product water pressure gauges should be performed.
    ❖ Periodic cycling of the vent valve on the particulate removal filter housing (daily) should be performed to remove any accumulated air that will reduce the effective cartridge filtration area.
    ❖ The cartridge filtration system and all other components in the Pretreatment Section (with the exception of the activated carbon units) should be chemically sanitized with a 100-200 ppm solution of sodium hypochlorite annually. Sanitization should include a minimum “soak” period of 2 hours.
    ❖ Replace cartridge filter housing “bell-to-base” gasket annually.

Preventative Maintenance Program – Ion Removal and Polishing Section
A Process Flow Diagram for an Ion Removal and Polishing System is shown in Figure B. The diagram includes sample valves, discussed later in this article. Both components and arrangement of components in the Ion Removal and Polishing Section may vary with sanitization preference. Figure B depicts a chemically sanitized system with continuous recirculating capability.


•  Reverse Osmosis Break Tank
The RO Break Tank provides a location for feed from the upstream Pretreatment Section, with air break, a location for recirculation of Ion Removal and Polishing System recirculation flow when make-up to the Purified Water Storage System is not required, a location for recirculation of waste water from the continuous electrodeionization system, and a location for introduction of chemical sanitizing agent during periodic sanitization operations. The following maintenance program should be considered:
    ❖ Remove the cover or top access manway and chemically clean the interior of the tank every 6 months.
    ❖ Conduct chemical sanitization of the entire ion removal and polishing system every six months using a 1% Peracetic Acid-Hydrogen Peroxide solution. (Sanitization to be performed subsequent to RO membrane “rotation” discussed later in this article).
    ❖ Replace the hydrophobic vent filter semiannually.
    ❖ Replace the tank cover or manway gasket every three years.
    ❖ Calibrate the multipoint level monitoring and control system annually.
    ❖ Replace tank piping/tubing fitting gaskets every two years.
    ❖ Replace hydrophobic vent filter housing “bell-to-base” gasket every two years.
• RO Break Tank Repressurization Pump
The RO Break Tank Repressurization Pump provides pressurized feed water to the downstream RO unit and recirculation capability through the Ion Removal and Polishing Section during chemical sanitization. The following maintenance program should be considered:
    ❖Annual inspection of pump seals. Replacement of seals as required or every three years.
    ❖ Semiannual cleaning of pump motor fan intake to remove dust and dirt.
    ❖ Semiannual tightening of pump feed water and discharge connection clamps/flange nuts, bolts or clamps
    ❖ Annual calibration of pump feed water compound-type pressure gauge and pump discharge gauge.
    ❖ Annual measurement of pump motor operating temperature.
    ❖ For single stage centrifugal pumps, inspection of pump impeller and casing.
• Reverse Osmosis System
The RO System provides removal of dissolved and ions impurities bacteria, bacterial endotoxins, colloids, and organic material with a molecular weight greater than about 150 Daltons. Gases such as oxygen that will not chemically react with water and reactive gases such as carbon dioxide that will react with RO product water to produce ions are not removed. In general, the conductivity of RO product water (single pass) should be < 5 -10 µS/cm @ 25?C. The following maintenance program should be considered:
    ❖ Annual inspection of RO feed water pump seals. Replacement of seals as required or every three years.
    ❖ Semiannual cleaning of RO feed water pump motor fan intake to remove dust and dirt.
    ❖ Semiannual tightening of RO feed water pump feed water and discharge connection clamps/flange nuts, bolts or clamps
    ❖ Annual calibration of pressure, temperature, flow rate, and conductivity monitoring systems.
    ❖ Annual measurement of RO feed water pump motor operating temperature.
    ❖ Semiannual replacement of RO membranes with new or “spare” membranes that have been cleaned, off site, by a service organization. RO membrane transfer/return should be conducted using “Chain of Custody” with unique serial number on each RO membrane. Off-site cleaning shall include pre cleaning inspection and measurement with documentation of product purity/flux, visual inspection for degradation such as telescoping, three step cleaning (low pH, high pH, and sanitization), final testing for ion rejection/flux, treatment with an antimicrobial agent, placement in a sealed plastic bag, and packaged in a heavy weight cardboard box. A copy of the “Chain of Custody” with pre and post individual membrane cleaning data shall be provided with shipping documents. Individual membrane cleaning shall be conducted in “parallel configuration with other membranes used for purification of properly pretreated “Drinking Water”.
    ❖ Semiannual post RO membrane “loop” components should be performed with a 1% Peracetic Acid-Hydrogen Peroxide solution subsequent to membrane replacement and rinse of preservative.
    ❖ Annual replacement of all RO membrane interconnector O-rings and end adapter O-rings.
    ❖ Replacement of RO membrane interconnectors every two years.
    ❖ Replacement of RO System feed water, product water, and waste connections gaskets every two years.
    ❖ Replacement of RO membranes every three years.
• Continuous Electrodeionization System
The Continuous Electrodeionization System removes ions present in RO product water such that the USP/EP “Stage 1” conductivity limit for Purified Water can be achieved in the downstream Storage, Ozonation, and Distribution System. Product water from a properly designed, maintained, and operated continuous electrodeionization unit is generally < 0.1 µS/cm @ 25?C. Further, select continuous electrodeionization systems, in a recirculating or make-up mode will provide excellent total viable bacteria control with product water levels often < 1 cfu/100 ml (Membrane Filtration of a 100 ml sample through a 0.45 micron filter disc, 120 hour incubation time period, 30-35?C incubation temperature, and either R2A or PCA culture media). The following maintenance program should be considered:
    ❖ Monthly verification of ion concentrating chambers, ion depleting chambers, and waste pressure. Adjust pressure as required per manufacturer’s recommendation.
    ❖ Biannual chemical sanitization as discussed earlier in this article or consistent with continuous electrodeionization unit manufacture’s recommendation if conflicting.
    ❖ Replacement of feed water (two), product water, and waste fitting gaskets annually.
    ❖ Replacement of “plastic” feed water, product water, and waste adapters every two years.
    ❖Replacement of diaphragms in feed water and product water valves every two years.
    ❖ Calibration of pressure gauges, flow meters, and conductivity instrumentation annually.
    ❖ Replacement of continuous electrodeionization power panel cooling vent intake air filters.
    ❖ Replacement of continuous electrodeionization “stack” every 5 years.
• Post Continuous Electrodeionization System Inline Ultraviolet Sanitization Unit
An inline ultraviolet sanitization unit (253.7 nanometer wave length) should be positioned downstream of the continuous electrodeionization system and upstream of the final filtration system. Any bacteria present in product water from the continuous electrodeionization system would accumulate on the downstream final membrane filtration system and replicate. A biofilm could be established on the “dirty side of the membrane filter with potential back growth to the continuous electrodeionization. The UV unit not only provides inactivation of extremely low levels of bacteria in continuous electrodeionization product water but also serves as a “bacteria check valve” for biofilm from the downstream final membrane filtration system. The following maintenance program should be considered:
    ❖ Replace ultraviolet lamps, quartz sleeves, and O-rings every six months. Physical or chemical cleaning of quartz sleeves is highly discouraged. While greater than ultraviolet unit manufacturer’s recommended replacement frequency, excellent bacteria destruction can be achieved with semiannual replacement.
    ❖ Use “certified” ultraviolet lamps. These lamps have been “preconditioned/operated” with ultraviolet radiation intensity verified using a quantitative meter. The recommended ultraviolet radiation intensity meter can be set to a value of “100%” within 24 hours of lamp replacement and verified for about one week after lamp replacement.
    ❖ Clean vent fan filters for cooling lamp ballast semiannually.
    ❖ If “plastic” compression nuts are used for quartz sleeve seals, replace every three years.
    ❖ Retain at least two spare compression nuts, O-rings, lamps, quartz.
• Final 0.1 Micron Membrane Filtration System
The 0.1 Micron Membrane Filtration System removes any bacteria present in water, prior to the downstream Purified Water Storage, Ozonation, and Distribution System. In addition, the membrane filtration system provides a positive barrier for retention of ion exchange resin from the upstream continuous electrodeionization system should highly unlikely catastrophic failure occur releasing ion exchange resin. The following maintenance program should be considered:
    ❖Replace 0.1 micron membrane filters semiannually, prior to semiannual sanitization of the Ion Removal and Polishing Loop with 1% Peracetic Acid-Hydrogen Peroxide. Membrane material of construction shall be compatible with the chemical sanitizing agent.
    ❖ Inspect removed membrane filters to verify the absence of ion exchange resin “fines”.
    ❖ Annual calibration of feed water and product water pressure gauges should be performed.
    ❖ Periodic cycling of the vent valve on the particulate removal filter housing (daily) should be performed to remove any accumulated air that will reduce the effective membrane filtration surface area.
    ❖ Replace sanitary membrane filter housing “bell-to-base” gasket every two years.
    ❖ Replace upstream and downstream diaphragm valve diaphragms annually.

Preventative Maintenance Program – Storage, Ozonation, and Distribution Section
A Process Flow Diagram for the Purified Water Storage, Ozonation, and Distribution System is shown in Figure C. The diagram includes sample valves, discussed later in this article. The Storage, Ozonation, and Distribution System provides a method for storing make-up water from the Ion Removal and Polishing Section, a very effective method for obtaining total viable bacteria control, and a method of delivering Purified Water to individual points-of-use.


* Purified Water Storage Tank and Accessories
The Purified Water Storage Tank provides a location for multiple functions in the system. The tank provides a reservoir of water to allow recirculation through the distribution loop back to the tank. The tank also provides storage of water to meet point-of-use draw-off requirements that exceed the make-up capability of the water purification system. Finally, for Purified Water Systems utilizing ozone for control of bacteria, the tank provides a location for injection of ozone and adequate contact time to allow inactivation of bacteria prior to distribution of water with removal by a dissolved ozone destruct inline ultraviolet system. The following maintenance program should be considered:
    ❖ Annual calibration of the tank level monitoring and control system.
     ❖ Semiannual replacement of the hydrophobic vent filtration system membrane cartridges. Inspection of removed hydrophobic vent filter element(s) for thermal degradation from housing heating blanket (electrical) and presence of water vapor. Adjustment of housing heating blanket temperature set point if water or thermal degradation is noted.
    ❖ Annual replacement of the compound-type rupture disc.
    ❖ Annual inspection of the interior of the tank for rouging. Replacement of tank manway gasket subsequent to inspection.
    ❖ Derouging and repassivation of the storage tank and distribution system every two years or annually if unacceptable levels of rouge are noted in the tank.
    ❖ Annual inspection of any internal tank accessories to enhance/retain ozone in a dissolved state not gaseous state. This would include “spargers” and “dip tubes”.
    ❖ Annual measurement of gaseous ozone concentration at the discharge point to the atmosphere from the vapor space above the water in the tank to verify compliance with OSHA guidelines. Inspection and repair of the vent system gaseous ozone thermal destruct system as required if unacceptable gaseous ozone exhaust levels are detected.
    ❖Annual calibration and alarm verification of ambient gaseous ozone monitoring system (s).
    ❖ Replacement of all sanitary ferrule gaskets in fittings on the tank every two years.
•  Purified Water Distribution Pump
The Purified Water Distribution Pump feeds the distribution loop with return water flowing through a pressure sensing and control system and modulating-type back pressure regulating system. The pump is generally sanitary type of 316L Stainless Steel construction. The following maintenance program should be considered:
    ❖ Annual replacement of pump seals and gaskets with inspection of casing and impeller.
    ❖ Semiannual cleaning of pump motor fan intake to remove dust and dirt.
    ❖ Semiannual tightening of sanitary ferule clamps at pump inlet and discharge.
    ❖ Annual calibration of pump feed water compound-type pressure gauge and pump discharge gauge.
    ❖ Annual measurement of pump motor operating temperature.
    ❖ Annual replacement of feed water and discharge valve diaphragms.
    * Dissolved Ozone Destruct Inline Ultraviolet System
A Dissolve Ozone Destruct Inline Ultraviolet System (253.7 nanometer wave length) is positioned downstream of the Distribution Pump. The system removes dissolved ozone from Purified Water prior to distribution. Electrical power to the ultraviolet system is periodically inhibited to provide dissolved ozone sanitization of the Purified Water Distribution Loop. Point-of-use Purified Water draw-off is inhibited during dissolved ozone distribution loop sanitization. The following maintenance program should be considered:
    ❖ Replace ultraviolet lamps, quartz sleeves, and Viton O-rings every six months. Physical or chemical cleaning of quartz sleeves is highly discouraged. While greater than ultraviolet unit manufacturer’s recommended replacement frequency, complete removal of ozone, an antimicrobial agent, is critical.
    ❖ Use “certified” ultraviolet lamps. These lamps have been “preconditioned/operated” with ultraviolet radiation intensity verified using a quantitative meter. The recommended ultraviolet radiation intensity meter can be set to a value of “100%” within 24 hours of lamp replacement and verified for about one week after lamp replacement.
    ❖ Clean vent fan filters for cooling lamp ballast semiannually.
    ❖ Semiannual inspection of the stainless steel compression nuts for “galling of threads”. Replace compression nuts if noted.
    ❖ Retain at least two spare stainless steel compression nuts, Viton O-rings, lamps, quartz sleeves and ballast.
    ❖ If online dissolved ozone analyzers are used, verify the absence of dissolved ozone in product water at least once a week using chemical analysis.
•  Purified Water Distribution System and Accessories
The Purified Water Distribution Loop delivers Purified Water to individual points-of-use with return to the ozonated Purified Water Storage Tank. Suggested loop construction is orbitally welded 316L Stainless Steel (7,8). Point-of-use valves should be zero dead leg type. Accessories such as pressure gauges should be mounted on short outlet tubing tees. The following maintenance program should be considered:
    ❖ Annually perform calibration of instrumentation including pressure gauges, sensing elements/transmitters/controllers, and online analyzers (conductivity and TOC).
    ❖ Conduct “System Suitability” testing for the TOC analyzer monthly and calibrate if criteria set forth in USP Physical Tests Section <643> are not met.
    ❖ Calibration of conductivity cells, performed annually, may be easier to execute by the cell manufacturer at their facility. The use of two conductivity cells for each monitored point (loop supply and return) may be considered. A calibrated cell should be available for installation prior to a scheduled annual shutdown.
    ❖ Distribution loop rouging should be performed annually or by on ongoing “side stream” monitoring program. A typical location for determining the degree of rouging is the first elbow/tee downstream of the Purified Water Distribution Pump. As a minimum, derouging and repassivation should be considered every two years.
    ❖ All diaphragms in distribution loop valves should be replaced annually.
    ❖ Distribution loop sanitary ferrule gaskets should be replaced once every three years or more frequently if gasket leaks are noted.
    ❖ Monthly inspection of sanitary ferrule clamps should be performed. Clamps should be tightened securely.
    ❖ Operation of the modulating-type back pressure regulating valve should be verified every six months.
•  Dissolved (Electrolytic) Ozone Generator
The system depicted in Figure C uses electrolytic ozone generation. Gaseous ozone generation may also be used particularly for high capacity (tank volume and flow rate) systems. Electrolytic ozone generation periodic maintenance is critical. The following maintenance program should be considered:
    ❖ If the electrolytic ozone generator is equipped with “short duration” battery back-up for cells, replace the batteries annually.
    ❖ Replace the anode, cathode, and semipermeable membrane in each electrolytic cell annually.
    ❖ Verify operation and accuracy of temperature monitoring systems, including thermal “cut-off” provisions for each cell semiannually.
    ❖ Verify the operation of each electrolytic cell by placing any parallel cells in “standby”, setting the cell amperage/voltage at a predetermined value, and measuring the dissolved ozone product water concentration by sample collection and analysis every six months.
    ❖ Verify the flow of wastewater and hydrogen gas from the system monthly.
 Conclusion
A proactive maintenance program minimizes potential system excursions that may result in significant manufacturing issues. While seemingly extensive, the suggested maintenance items can be executed during scheduled facility shutdown periods. The program provides a truly “controlled” state for a validated system.

References
(1) Collentro, W.V., “Monochloramine Removal by Activated Carbon – Design, Operating, and Maintenance Considerations”, presented at the International Water Conference, The Engineer’s Society of Western Pennsylvania, presentation IWC 11-14, November 13-17, 2011, Orlando, Florida
(2) Collentro, W.V., “The Effect of Municipal Water Treatment Techniques on Compendial Water System Design, Operation, and Maintenance – Case Histories”, Pharmaceutical Processing, Volume 28, No. 9, Reed Business Information, Highlands Ranch, Colorado, November, 2011
(3) United States Pharmacopeia 36, National Formulary 31 with First Supplement, “Purified Water Monograph”, The United States Pharmacopeial Convention, Rockville Maryland, August 1, 2013, pg 5591
(4) World Health Organization, “Guidelines for Drinking-Water Quality”, Fourth Edition, ISBN: 978 92 4 154815 1, 2011
(5) Wu, L., and Krpan, N., “Chlorine Species Passage through Polyamide Reverse Osmosis Membranes, presented at the UltraPure Water Executive Forum, May 20-21, 2010, East Brunswick, New Jersey
(6)Collentro, W.V., “A Novel Approach to Control Microbial Fouling of Reverse Osmosis Membranes”, presented at the International Water Conference, The Engineer’s Society of Western Pennsylvania, presentation IWC 12-46, November 4-8, 2012, San Antonio Texas
(7) ASME BPE, Bioprocessing Equipment 2012, Part MJ, “Material Joining”, New York, NY, The American Society of Mechanical Engineers, pp 110-122
(8) Collentro, W.V., “Pharmaceutical Water - System Design, Operation, and Validation”, Second Edition Informa Healthcare, ISBN 9781420077827, New York, New York, January 2011n

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