ISPE精品文章：制药用水系统的微生物设计与控制！
本文摘自ISPE博客，作者Tim Sandle, Dr. & PhD
MICROBIOLOGICAL CONCERNS
微生物问题
Potable water from private water companies ormunicipalities is monitored to ensure that levels of chemical pollutants remainwithin established safety criteria, and screened for microorganisms includingEscherichia coli, enterococci,Pseudomonas aeruginosa, and fecal coliforms.4In most locales the quality of the water supplied to thepharmaceutical facility is satisfactory. As a safeguard, however, manyfacilities elect to test the water for organisms like E. coli as a marker forfecal contamination. Onsite potable water is treated, softened, purified(according to the grade required), and distributed.
对私营水务公司或市政当局的饮用水进行监测，以确保化学污染物水平保持在既定的安全标准范围内，并筛查微生物，包括大肠杆菌、肠球菌、铜绿假单胞菌和粪便大肠菌群。在大多数地区，提供给制药工厂的水质都还是合格的。然而，作为一项保护措施，许多设施选择检测大肠杆菌等生物体，作为粪便污染的标志。现场饮用水经过处理、软化、纯化（根据要求等级）和分配。
While most well-designed water systems can be maintainedin a state of control, microbiological problems can develop. Microbialadherence is a consequence of the balance of attractive and repulsivephysicochemical interactions between bacteria the surface. The primary issue isbiofilm formation—slime-like microbiologicalcommunities that occur when microorganisms adhere to a surface (such aspipework with a poor flow rate).
虽然大多数设计良好的水系统可以保持在控制状态，但微生物问题可能会发生。微生物附着是细菌表面吸附性和排斥性物理化学相互作用平衡的结果。主要问题是生物膜的形成——当微生物粘附在表面时（如流速差的管道），就会发生粘液样的微生物群落。
A biofilm develops because bacterial cells, onceattached, secrete a polysaccharide known as glycocalyx (hydrated polymericslimy matrices). The glycocalyx enables each bacterium to encapsulate itself onthe surface; biofilm forms as these organisms accumulate. The steps involved inbiofilm formation are (Figure 1):
生物膜的形成是因为细菌细胞，一旦附着，会分泌一种称为糖被膜的多糖（水合聚合物粘稠基质）。糖被膜将每个细菌能够包裹；随着这些生物累计，形成生物膜。生物膜形成所涉及的步骤是（图1）：
1. Individual cells populate thesurface (initial attachment)
单个细胞在表面附着（初始附着）
2. Irreversible attachment
不可脱落的粘附
3. Extrapolymeric substances areproduced and attachment becomes
产生聚合物外物质
4. Irreversible
不可逆转
5. Biofilm architecture develops andmatures
生物膜结构形成并成熟
6. Single cells (or clumps of cells)are released from the biofilm over time
单个菌（或菌团）随着时间的推移从生物膜中释放出来
* Adenosine triphosphate (ATP) is a nucleotide found inall living organisms; ATP bioluminescence is used to monitor contamination.
·三磷酸腺苷（ATP）是所有生物体内的一种核苷酸;ATP 荧光检测可用于监测污染。
Figure 1: Generalized biofilm formation
图1：生物膜形成
Source: D. Davis (CC BY 2.5 [http://creativecommons.org/licenses/by/2.5]), via Wikimedia Commons -footer
This type of attachment occurs relatively slowly. Variousfactors affect the process, including the type of bacterium involved, the sizeof the bacterial population in the environment, and the duration of its growthphase.5 In general, Gram-negative bacteria form biofilmsmore readily,6 due in part to appendages on the bacterial cell(fimbriae) that allow such them to attach to surfaces more easily. Surfacecharge is another important phenomenon in relation to bacterial adherence.7
这种类型的附着发生得相对较慢。影响这一过程的各种因素，包括所涉及的细菌类型、环境中细菌数量及其生长阶段的持续时间。表面电荷是细菌粘附性的另一个重要现象。
Microbial growth in a biofilm is often rapid at the pointof source (Figure 2). The pattern from user outlines is often sporadic,however, because contamination is eluted from the biofilm at different ratesover time.
生物膜中的微生物生长在源头处通常是很快的（图2）。然而，用户大体上的样本通常是零星的，因为随着时间的推移，生物膜的污染以不同的速率脱落。
Figure 2: Microbial numbers in a water system riseexponentially following biofilm formation
图2：水系统中的微生物数量在生物膜形成后呈指数级增长
Biofilms are of particular concern with water systems,since Gram-negative bacteria constitute the majority of the bacterialpopulations found in aquatic environments. These types of organisms, moreover,also shed endotoxins, a component of the cell wall.8
水系统特别关注生物膜，因为革兰氏阴性菌占水生环境中细菌群的大多数。此外，这些类型的生物也会释放内毒素——其细胞壁的组成部分。
Many stages of the water-purification process can createconditions which, although designed to reduce contaminants, paradoxicallypromote biofilm formation. An example is in-depth filtration through a matrix.As water percolates through the filter, microorganisms are adsorbed onto thematrix, where they form complex communities. Further on, the purificationpathway can create a series of colonizable environmental niches of varyingnutrient richness.
制水过程的许多阶段，虽然设计目的为减少污染，但矛盾地为生物膜的形成创造了条件。一个例子是，通过基质进行深过滤。当水通过过滤器渗透时，微生物被吸附在基质上，形成复杂的群落。此外，纯化路径也会创造一系列不同营养丰富的繁殖环境。
For appropriately designed and maintained systems,purified water and WFI present low risks of microbial contamination. Whenevermicroorganisms are detected (and certainly when above specification), however,this creates a significant hazard.
对于设计和维护适当的系统，纯化水和WFI具有低微生物污染风险。然而，每当检测到微生物（超过标准时），就会产生重大危害。
GOOD DESIGN PRINCIPLES
良好设计原则
While different phases of water generation can contributeto risks, there are a number of design and control steps that can reducemicrobiological proliferation:10
虽然制水的不同阶段都可以造成风险，但有许多设计和控制步骤可以减少微生物的繁殖：10
Break tanks
阻隔罐
Break tanks, which prevent water produced duringproduction from reentering the water supply, are the first areas in whichmicrobial colonization can occur. Microorganisms present in incoming potablewater attach themselves to the sides and bottom of the tank, forming a biofilm.Samples taken from the tank usually meet the specification for potable waterand give no immediate indication of the biomass that is accumulating. Regularmaintenance and tank flushing are the main preventive measures.
阻隔罐是微生物繁殖的最初可能发生的地方，它阻止生产期间产生的水重新进入供水系统。流入的饮用水中的微生物附着在水罐的侧面和底部，形成生物膜。从罐中采集的样品通常符合饮用水的标准，并且不会立即反映正在积累的生物量。主要预防措施是定期维护和冲洗。
Activated carbon beds
活性炭吸附床
The bed matrix consists of finely dividedcharcoal, which is highly efficient at removing low-molecular-weightorganic materials. It also oxidizes and removes additives such as chlorine. Thevast surface area and accumulation of nutrients on the bed, combined withchlorine removal, can lead to rapid microorganism colonization andproliferation. Most of the organisms are Gram-negative bacteria and, shouldthey undergo cell lysis, can be a source of endotoxins. An essential point ofcontrol over the entire water system is the ability to sanitize the bedsregularly with hot water or steam, coupled with frequent replacement.Sanitization should begin at a higher frequency (such as weekly) for a newwater system; this could be decreased over time (monthly) based on a microbialbioburden trend review. Six months to one year of data would be required toassess the bioburden pattern.
吸附床基质由细炭组成，在去除低分子量有机物方面效率很高。它还可以氧化和去除添加剂，如氯。床的大表面积和营养物质的积累，加上氯的去除，可导致微生物在此迅速繁殖。大多数生物是革兰阴性细菌，如果它们经历细胞裂解，可能是内毒素的来源。对整个水系统的一个基本控制点是能够定期用热水或蒸汽消毒活性炭床，同时经常更换。新供水系统的消毒频率应更高（如每周）;根据微生物负荷的趋势进行审查，随着时间的推移（每月）可以减少。评估生物负荷模式需要6个月至1年的数据。
Water softeners
水软化剂
In areas with hard water, softeners are required toprevent interference with the deionizers and reverse osmosis systems. As waterpasses through the resin-filled columns, divalent calcium and magnesium cationsare exchanged for sodium ions. The resin matrix provides an enormous surfacearea for potential microbial colonization, however. Sanitization and controlmeasures such as ultraviolet light and chlorine are essential in maintainingwater quality.
在有硬水的地区，需要软化剂，以防止对去离子和反渗透系统的干扰。当水通过充满树脂的柱子时，二价钙和镁阳离子被交换为钠离子。然而，树脂基质为潜在的微生物微生物提供了巨大的表面积。紫外线和氯等消毒和控制措施对于维持水质至关重要。
Deionization devices
去离子装置
Standard deionization systems consist of charged resincolumns. These may be separate for cation and anion removal, or may use amixed-bed system. The advantage of deionization is that the columns requireregeneration with 1 molarity (M) hydrochloric acid and 1M sodiumhydroxide, both of which are strongly biocidal. If the regeneration frequencyis high, the columns are maintained in a sanitized state. Unsanitized columnsor those that are not regenerated for more than a couple of days present thesame problems as activated charcoal beds, which is the risk of bacterial growthoccurring.
标准去离子系统由带电树脂柱组成。可分别用于阳离子和阴离子去除，或者使用混合床系统。去离子的优点是，这些柱可以用1摩尔（M）盐酸和1摩尔（M）氢氧化钠再生，这两者都有强杀灭性。如果再生频率较高，则该柱将保持在已消毒状态。未消毒的柱子或那些几天以上未再生的柱子与活性炭床存在同样的问题，即细菌生长的风险。
Electrodeionization systems permit continuous columnregeneration without the need to add regeneration agents. They are easy tomaintain, but they also encourage bacterial growth. A reverse osmosis membranewill filter out bacteria, but growth can occur if not properly maintained. Asfragments of the bacterial cell wall break off, endotoxins can easily pass throughthe membrane.
电去离子系统允许连续的柱再生，而无需添加再生剂。它们易于维护，但同时也促进细菌生长。反渗透膜可以过滤掉细菌，但如果维护不当，就会发生生长。当细菌细胞壁的碎片脱落时，内毒素很容易通过反渗透膜。
Storage and distribution systems
储存和分配系统
Poorly designed storage and distribution systems createopportunities for recolonization and, ultimately, product contamination.Colonization is often difficult to detect because biofilms releasecontamination slowly and randomly. (Microbial populations in water rarelyindicate normal distribution, which means levels can appear and disappear overtime before the overall trend can be discerned.)
设计不佳的储存和分配系统为二次繁殖并最终造成产品污染创造了机会。由于生物膜缓慢而随机地释放污染，因此很难检测。（水中的微生物菌落很少呈正态分布，这意味着在能够判断总体趋势之前，微生物可能会随时出现并消失。
Storage tanks
储罐
Water storage tanks are normally constructed fromstainless steel. Where they are used, it is important to determine capacity,rate of use, and frequency of flushing and sanitizing the internal surfaces.Regular water turnover helps prevent contamination; slow turnover, on the otherhand, presents a greater potential contamination risk. Storage tanks should bevented to manage water level fluctuations. To prevent microbial contaminationfrom outside air, vents should be fitted with a hydrophobic air filter. Suchfilters are also used to avoid filter occlusion, which can create vacuumconditions and lead to tank implosion. Vent filter integrity testing should beperformed regularly (e.g., once every 6 or 12 months).
储罐通常由不锈钢制成。在使用时，确定内部表面的容量、使用率和清洗和消毒频率非常重要。保持水翻滚有助于防止污染；相反，翻滚速度慢则带来更大的潜在污染风险。储罐应通气以管理水位波动。为了防止来自外部空气的微生物污染，通气口应安装疏水空气过滤器。此类过滤器还用于避免过滤器堵塞，从而造成真空条件并导致罐体内爆。呼吸过滤器完整性测试应定期执行（例如，每 6 个月或 12 个月一次）。
Storage temperature
储存温度
It is standard practice to store WFI in a recirculatingstainless steel system, although on occasions polyvinylidene fluoride (PVDF) isused when very low mineral content water is needed. Recirculating systems thatoperate at temperatures of 65ºC to 80ºC are self-sanitizing, with the caveatthat no cold spots below 65ºC form. Purified water systems can be hot or cold.Key aspects of cold water systems are discussed in more detail below.
将 WFI 储存在循环不锈钢系统中是标准做法，尽管有时在对水要求极低矿物质含量时，会使用聚氯乙烯氟化物（PVDF）材质。在65℃至80℃温度下运行的循环系统可以自行消毒，需要注意的是，应没有低于65℃的冷点。纯化水系统可以热或冷循环。下文将更详细地讨论冷水系统的关键方面。
Pipe and tank design
管道和罐设计
If they are poorly designed or improperly maintained,pipes and tanks are more likely than any other part of the water system todevelop contamination. The general requirements for well-designed pipes are:
如果管道和罐设计不当或维护不当，则管道和罐比水系统的任何其他部分都更有可能产生污染。设计良好的管道的一般要求是：
1. Smooth internal surfaces.Microorganisms adhere less well to smooth surfaces than to rough surfaces,therefore corrosion resistance and avoiding rouging (iron oxide formation) isimportant (as can be achieved by the electropolishing of stainless steel). Pipejoints and welds can also disrupt smoothness.
内表面平滑。微生物在光滑表面的粘附性不如粗糙表面，因此耐腐蚀和避免红锈（氧化铁形成）很重要（通过不锈钢电抛光可以实现）。管道接头和焊缝也会破坏平滑度。
2. Continuous water movement in tanksand rapid flow in pipework; velocities in the range of 1–2 meters per secondhave been found to be satisfactory.11This minimizesopportunities for microorganisms to adhere to surfaces (and form biofilms).Where shear forces occur, microorganisms adhere poorly to surfaces. Where thereis no water movement, there is no shear (shear increases with the speed offlow).
罐中的水持续流动，管道中则快速流动；流速在每秒1~2米的范围内可令人满意。这将最大限度地减少了微生物粘附到表面（并形成生物膜）的机会。在剪切力下，微生物很难粘附在表面上。如水静止不动，则没有剪切力（剪切力随流速而增加）。
Avoid areas where water canremain stagnant:
3. 避免水可能保持停滞的地方：
1. If a branch pipe is too long toallow the turbulence of the flowing main to disturb itscontents, water may stagnate in “dead legs” (Figure 3). The principle is toalways minimize the length of branch pipes.
如果支管太长，主管上的湍流无法扰动支管，水可能会停滞在'死脚'中（图3）。原则尽量减少支管的长度。
2. Water can also remain stagnant invalves, particularly at user points—and especially those that not in frequentand regular use. This can be counteracted by hygienic or “zero dead leg” valveswhich, although significantly better than the alternatives (say ball valves).This should not lead to a sense of false security, however, since they canharbor endotoxin-shedding biofilms. Having the correct sloping for drainage canalso reduce contamination risk.
水也可能在阀门中保持停滞状态，尤其是在用水点，尤其是那些不频繁和不经常使用的阀门。这可以通过卫生或'零死脚'阀门来抵消，比其他阀门（如球阀）要好得多。死脚的存在将导致可以脱落内毒素的生物膜。正确倾斜排水也可以降低污染风险。
3. Ring mains should be sloped(“drop”) from point of origin to the point of return to ensure that systems arecompletely drainable.
循环管路应从起点到回路倾斜（'下降'），以确保系统完全可排空。
4. Avoidance of leakage. Waterleaks can cause bridging of water to the external environment through whichbacteria may enter the system. Storage tanks should be equipped with filter ontheir air vents to prevent air-borne microbiological ingress. They may even beheld under a “blanket” of an inert gas such as nitrogen.
避免泄漏。水泄漏可能导致水与外部环境接触，细菌可通过外部环境进入系统。储罐应在其通气口上配备过滤器，以防止空气传播微生物进入。它们甚至可以用惰性气体（如氮气）'包裹'。
5 High temperature storage anddistribution. The risks of endotoxin-shedding biofilms despite the bestattempts at control above are thought to be so consequential that the mostmanufacturers require the temperature of storage and distribution to bemaintained higher than 65°C. Lower temperatures may also be acceptable,provided the manufacturer has adequate data to demonstrate that a lowertemperature works as intended.
高温储存和分配。尽管对上述控制进行最佳尝试，但内毒素脱落生物膜的风险被认为具有如此重大的影响，以至于大多数制造商要求储存和分配温度保持在65°C以上。如果制造商有足够的数据来证明较低的温度工作正常，则较低的温度也可以接受。
1. It should however be consideredthat 65°C is too high a temperature for most pharmaceutical formulationpurposes. This means that user points are generally equipped with some form ofcooling mechanism. It should be noted that heat exchangers used for thispurpose may be a source of endotoxin and bacterial contamination and may thuscancel out many of the benefits of high temperature circulation.
然而，应该认为，对于大多数药物制剂而言，65℃的温度过高。这意味着用户点通常配备某种形式的冷却机制。需要注意的是，用于此目的的热交换器可能是内毒素和细菌污染的来源，因此可能会抵消高温循环的许多好处。
6. The use of coated surfaces on pipesand in tanks, where appropriate (as not to pose a risk of leaching toxicsubstances) can help to address bio-fouling.12
在管道和储罐中使用涂层表面（如不构成释放有毒物质的风险）有助于解决生物污染问题。
Figure 3: Poorly designed water distribution pipe with a dead leg
图3：设计不良的输水管道，死脚
Cold watersystems
冷水系统
Systems forpurified water typically use ozone, ultraviolet light, and in-line filters tomaintain microbial quality instead of high temperature. Important points toconsider are:
纯化水系统通常使用臭氧、紫外灯和在线过滤器来保持微生物质量，而不是高温。需要考虑的要点包括：
Ozone is used periodically forsanitization. It attacks the outer surfaces of microorganisms and destroys cellwalls and membranes.
定期臭氧消毒。它攻击微生物的外表面，破坏细胞壁和膜。
Ultraviolet light is not asterilant, although it has some microbial reduction properties.13Efficiencydepends on path length, speed of flow, and age of the light source. The mostcommonly used wavelength for microbial reduction in pharmaceutical watertreatment systems is 254 nanometers (nm). Ultraviolet light is also very usefulfor catalyzing the breakdown of ozone or hydrogen peroxide used as sanitizingagents, although its efficacy is often diminished by poorly maintained ormalfunctioning lamps.
紫外灯虽然具有减少微生物的特性，但紫外线不是灭菌剂。制药用水处理系统中最常用的波长为 254 纳米（nm）。紫外线对于催化用作消毒剂的臭氧或过氧化氢的分解也非常有用，尽管其功效往往因为灯的维护不良或故障而降低。
Filters are ideal matrices forcolonization; they need careful monitoring of pressure differentials and frequentsanitization or changing. If a biofilm has formed on a filter, sanitizationwill kill most microorganisms within the biofilm but will probably not removethe matrix, which may be rapidly recolonized. In addition, the presence ofhighly resistant “persister cells” within the population will remain unaffectedand regrow.
过滤器是微生物繁殖的理想基质；需要仔细监测压差并频繁消毒或更换。如果生物膜在过滤器上形成，消毒将只能杀死生物膜内大多数微生物，但可能不会清除基质，而基质可能会迅速死灰复燃。此外，其中还存在高抗性'耐受细胞'，不会受到影响并会重新生长。
Cold water systems generallyuse thermoplastic materials because they suffer less biofouling than stainlesssteel (at low temperatures). Plastic material used to construct pipework istypically polypropylene or PVDF.
冷水系统通常使用热塑性材料，因为它们比不锈钢（低温下）遭受的生物污染更少。用于建造管道的塑料材料通常是聚丙烯或PVDF。
Bends in pipework should beas gentle and as few as possible; 2020 points should be kept to a minimum. Anydisruption to the smooth flow of water results in turbulence, which assistsbiofilm formation by creating more opportunities for circulating microorganismsto adhere to colonizable surfaces.
应尽可能减少管道中的弯曲或使其缓和；排水点应保持在最低水平。任何对水流的干扰都会导致湍流，从而为循环微生物粘附在可繁殖表面创造更多机会，从而有助于生物膜的形成。
User points
使用点
Water points inproduction areas involve the transfer of water from the circulating water loopto the point of use via transfer piping (or tubing), which should be made of asuitable nontoxic material, such as polyvinyl chloride (PVC), chlorinated PVC,polypropylene, or PVDF. The transfer piping should be drained after use andchanged regularly (such as every 24 hours); care must be taken to avoidsplash-back from sinks or recontamination from aerosols. New tubing should besanitized before fitting; it is also common for the tubing and outlet to beflushed prior to use (for a defined time or given volume of water). Thesemeasures are taken to avoid contamination of the water during the transferprocess.
生产区域的供水点涉及通过输送管道将水从循环水环路输送到使用点，该管道应采用合适的无毒材料，如聚氯乙烯（PVC）、氯化 PVC、聚丙烯或 PVDF。输送管道使用后应排空并定期更换（如每 24 小时更换一次）；必须注意避免从水槽中溅回或气溶胶再次污染。新的管道在安装前应进行消毒；在使用前之前，管道和出水口应进行冲洗（按规定的时间或水量）。采取这些措施是为了避免在输送过程中受到水的污染。
WHEN THINGS GO WRONG
当出现问题时
Loss of watersystem control and microbial contamination can have a number of causes,including aging resin, aging filters, poorly maintained ultraviolet lights,improper maintenance, failure to achieve effective heat distribution, leaks(such as heat exchangers), dead legs, and water-system modifications (e.g.,cutting through pipework).
水系统和微生物污染失控可能有多种原因，包括树脂老化，过滤器老化，紫外线灯维护不良，维护不当，未能达到有效的热分布，泄漏（如热交换器），死角和水-系统改造（例如，管道切割）。
Treating watersystems
水系统处理
Several optionsare available for treating and improving water quality. The method chosendepends on what is causing the microbial deterioration, the source of theproblem, the water quality required, the volume to be treated, and the type ofdistribution system. System design can influence the size of the microbialpopulation and the ability to remove it. Dead legs, long pipework runs to taps,undrainable pipes, and U-bends can also create microbiological problems.
有多种方案可用于处理和改善水的质量。选择的方法取决于是什么导致了微生物的恶化、问题的根源、所需的水质、需要处理的体积以及分配系统的类型。系统设计可以影响微生物种群的大小和去除微生物种群的能力。死角、出水管路过长、无法排尽的管道和 U 形弯曲也会造成微生物问题。
Four methods areroutinely used to remove microbial contamination: heat, chemicals, filtration,or ultraviolet light. Contact time is important for each one.
通常使用四种方法去除微生物污染：热力、化学、过滤或紫外线。无论选择哪一种，接触时间都很重要。
Heat, asdescribed earlier, can be used in the circulating loop of a hot-water systemmaintained at 65°C to 80°C (with ≥ 75°C being optimal). If this provesinsufficient there should be the capacity to superheat the system (taking thetemperature up to 121°C for one hour or longer).
如前所述，热力消毒可用于保持温度65°C 至 80°C（75°C 为最佳温度）的热水系统循环回路。如经证明不够，应具有对系统过热（温度升至 121°C 维持一小时或更长时间）的能力。
Chemicaltreatment (e.g., ozone, chlorine, chlorine dioxide, hydrogen peroxide,peracetic acid, and sodium hydroxide) is applicable to raw mains water, but canalso be used to treat distribution systems of water produced by distillation,deionization, and reverse osmosis. Concentration of the chemical used dependson the location of the water in the distribution system. Chlorination, forexample, is generally effective if minimum levels of 0.2milligrams (mg) perliter (L) of free chlorine are attained. The contact time will vary with watertemperature and pH; typical times for 0.2mg/L of free chlorine are between 30and 60 minutes. Importantly, any chemical added must, at some point, beremoved.
化学处理（如臭氧、氯、二氧化氯、过氧化氢、过氧乙酸和氢氧化钠）适用于原自来水，但也可用于蒸馏、去离子和反渗透产生的水的分配系统。所用化学品的浓度取决于水在分配系统中的位置。例如，达到每升0.2毫克自由氯的最低水平，通常是有效的。接触时间会随水温和pH值而变化；0.2mg/L自由氯的典型时间在30至60分钟之间。重要的是，任何添加的化学物质必须在某个阶段被清除。
Membranefiltration using a 0.22 micrometer (μm) porosity filter is applicable whereusage is moderate and continuous water circulation can be maintained (i.e.,water is continually returned to the storage tank and refiltered, except whatis drawn off for use). While filtration works well in principle, it isrelatively expensive for high throughputs because they need regular changing toprevent blockage and “grow-through.” For this reason, using 0.22 μm filters tocontrol contamination in water used for product manufacture is frowned upon.Filters should be used only prior to the distribution process.
使用 0.22 微米（μm）过滤器进行膜过滤，适用于使用适中且可保持连续水循环的情况（即，除了放出来使用的外，水不断返回储罐并重新过滤）。虽然过滤原则上效果良好，但对于高吞吐量的系统来说，成本相对较高，因为它们需要定期更换，以防止堵塞和'增长'。因此，使用0.22 μm过滤器来控制产品制造用水中的污染是令人不快的。过滤器应仅在分配过程之前使用。
Figure 4:Membrane filtration test
膜过滤检测
“Most of theorganisms are gram-negative bacteria, and should they undergo cell lysis, canbe a source of endotoxins”
'大多数生物体都是革兰氏阴性细菌，如果它们细胞裂解，可能是内毒素的来源'
Ultravioletradiation (254 nm) is used to disinfect water of good optical clarity; it worksparticularly well in a recirculating system where water flows over a multiplelamp system. While contact times vary according to dose and flow rate, they arenormally in the region of 1 to 10 seconds. This time is required to allow UVlight to penetrate through the water and make contact with any bacteriapresent.
紫外线辐射（254纳米）用于消毒具有良好光学清晰度的水；它在循环系统中特别有效，水流通过多灯系统。虽然接触时间因剂量和流速而异，但它们通常在 1 到 10 秒之间。这一时间需要让紫外线穿透水中，并接触任何细菌存在。
MICROBIOLOGICAL MONITORING
微生物监测
Frequentmonitoring is important to verify microbiological control. This involves abioburden assessment, typically using microbial count methods with membranefiltration, and a low-nutrient agar such as R2A as the method of choice (Figure4). Where applicable, a Limulus amebocyte lysate test for bacterial endotoxinis also recommended. In both cases, action or alert limits must be based onvalidation data and must be set low enough to signal significant changes fromnormal operating conditions.
频繁监测对于确认微生物控制非常重要。这涉及到生物负荷评估，通常使用带膜过滤的微生物计数方法，以及低营养琼脂（如R2A）作为选择方法（图4）。适当时，建议对细菌内毒素进行鲎试剂裂解测试。在这两种情况下，行动限或警戒限制必须基于验证数据，并且必须设置得足够低，以表示正常运行条件下的重大变化。
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