Evaluating the Risks and Benefits of Ambient WFI Systems

“Where there’s water, there is life” is a truism for many scientific fields – from biology and botany to NASA’s search for possible life on Mars. However, this is not a desirable aspect in the production of high-purity water for injection (WFI), which is critical for pharmaceuticals, drugs and other health care products. The US Food & Drug Administration (FDA) requires WFI to be more than merely “pure”, it specifies tight tolerances for contaminants within the water.  The allowable level of microorganisms and other organic material (bioburden) within the water is extremely low and requires the system owner to take action if the level of bacteria is at 10 CFUs/100mL or above.

Comparing Traditional Distillation with Ambient Systems

Historically, the primary method of creating WFI has been through distillation – the boiling of regular feedwater and collecting the resulting steam and allowing it to cool back to liquid form. This method had the simultaneous advantage of killing the majority of any present microorganisms with heat. In 2017, U.S., European, and Japanese regulators allowed the use of membrane filtration methods for the production of WFI.  Referred to as Ambient WFI, these systems can use reverse osmosis (RO), ultrafiltration (UF), or electrodeionization (EDI) to achieve WFI of equal – and sometimes better – quality, than the traditional method.

Advantages and Challenges of Ambient WFI Systems

Both distillation and ambient systems require some level of pre-treatment of the feed water before it enters the system, but reduced bacteria content is not the same as “no bacteria content.”

Ambient WFI production has a pair of notable advantages over the use of distillation. The first is that the facilities using the membrane treatment process can fit in less than half the space. The second, is that the distillation method requires a lot of energy to boil the water and refrigerate the distillate down to a usable temperature. The energy consumption for generating WFI via distillation can often amount to half the total energy used for a given facility.  Reducing energy costs is always a goal for those with budget oversight, and it ties closely into corporate drives for sustainability.

One of the major downsides to using ambient temperature systems is the lack of heat for sanitization purposes. As mentioned earlier, the boiling temperatures used in the distillation process kills off most of any remaining microorganisms in the water. By contrast, the ambient system relies on the membranes to prevent microorganisms from passing through, rather than boiling them to death and leaving the bioburden behind as water becomes ultra-pure steam.

Risk of Biofilm Formation in Ambient Systems

Ambient systems rely on a series of membranes to progressively filter out organisms and other impurities. As a result, there is the chance that some bacteria will make it through the first few filtration stages and deposit within the membranes or in the piping system, itself. This process can happen extremely quickly, and if left untreated, becomes increasingly more difficult to clean with time.

It’s also important to remember that there are many different varieties of bacteria found in feed water. At ambient temperatures, more than one strain can colonize the system simultaneously, complicating the biocleaning process.  Some bacteria are more resistant to hot or cold temperatures, while others flourish at lower nutrient levels that kill off competitors. This means that a process targeting one particular strain can often leave other varieties untouched. In fact, it can make things worse, as the surviving bacteria are free to rapidly colonize new territory.

Regardless of which species has established a colony within the system, the risk to the purity of the WFI is still the same. Additionally, in the case of stainless steel WFI systems, biofilms can cause microbially induced corrosion, which can degrade the protective passive film over time.

Adapting Tactics for Ambient Systems

Facilities which have changed from distillation to membrane filtration systems are finding that their tried-and-true methods of sanitization biofilm removal are no longer as effective as they had been. There has always been some level of this “arms race” dynamic as bacteria gradually evolve to resist certain combinations of chemicals and procedures, but it’s the difference in the physical operations of the two types of systems that is requiring new techniques.

Astro Pak crews are already seeing an increase in the diversity of biofilms that they are called upon to remediate in ambient systems. Some of these replacement colonies are more resistant to the temperatures used by the facility’s in-house cleaning teams’ efforts to eradicate other bioburden, requiring more powerful bioremediation techniques to fully remove.

Adding to the challenge is that biofilms are often found in places where they wouldn’t be in a distillation system. While eventually being prevented from entering the finished WFI itself, bacterial colonies have been found further into systems than would otherwise be expected. In such situations, the extent of the colonization and the thickness of the biofilm varies depending on several factors, including the location, the environmental conditions and, of course, the available food supply.

Expert Solutions for New Challenges

While the new challenges may be daunting for operators who have made the switch from distillation to membrane WFI, they are nothing new to Astro Pak’s teams and specialists. Astro Pak has been performing sanitization biofilm removal on ambient systems for several years. Our in-house experts have had many years of experience with successful remediation of biofilms. The technicians bring the same expertise to bioburden remediation of ambient systems that they deliver for distillation-based systems.

Facility operators who are contemplating an update of their WFI system to an ambient filtration system can consult with Astro Pak’s Technical Services Group (TSG) for pre-construction design to avoid pitfalls while building in features that make regular cleanings more successful.

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Chad Clements

Chad Clements works as the Chemical Engineer for Astro Pak’s Technical Services Group, providing technical guidance to field, shop, and cleanroom locations across the United States. He has a background in precision cleaning, oxygen cleaning, process engineering, chemistry, and bacterial remediation. Chad holds a bachelor’s degree in Chemical Engineering from the University of Florida. Prior to working under the Technical Services Group, he worked as a Process Engineer for Astro Pak’s Florida Cleanroom facility.

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