By Rick Andrew
Safety of materials in contact with drinking water is one of the foundational requirements of the entire family of NSF/ANSI and NSF/ANSI/CAN standards for products in contact with drinking water. The paramount importance of assuring that products in contact with drinking water will not leach contaminants into the drinking water at concentrations of toxicological significance is the reason each of these standards places great emphasis on material safety. These standards specify this requirement through extraction testing and analysis of the extraction water for potential contaminants, along with a toxicological assessment of any contaminants detected.
The NSF/ANSI Drinking Water Treatment Unit standards have specified that extraction testing for POU treatment systems that include adsorptive or absorptive media must be conducted both with and without the media. The reason for this requirement to include testing without the media is because some of these systems could be in place in the field without a replacement filter installed. In this mode, it could be possible that contaminants are leaching from the materials of the system that normally would be adsorbed or absorbed by the media, but without the media these contaminants could end up to be present in drinking water. Testing without the media provides an extra level of protection for end users who may decide to remove spent filter cartridges and just return the system to service without installing a new filter cartridge.
With this approach in mind, section 184.108.40.206 of NSF/ANSI 53 Drinking Water Treatment Units – Health Effects has read as follows: “220.127.116.11 Systems with adsorptive or absorptive media shall be tested with and without the media. Testing without media shall include removal of any granular adsorptive or absorptive media, and removal of any adsorptive or absorptive replacement elements.” This language, however, led to some questions and lack of clarity when put into practice with evaluation of certain POU treatment systems.
A need for clarification
For treatment systems with drop-in-style filter cartridges, this language is fairly straightforward to implement. The without media part of the testing involves simply removing any replacement elements that included adsorptive or absorptive media (which is typically in the form of activated carbon) and exposing the system to water. The water is then removed from the system after exposure and analyzed for contaminants, the same as is done for the testing on the system with the filter cartridges installed.
Where the situation becomes less clear is for treatment systems that involve encapsulated style filter cartridges that include adsorptive or absorptive media. Some of these systems are designed such that water will not flow through the system without the filter cartridges in place. So it is impossible to simply remove these cartridges and conduct the without media extraction test.
One approach to implement the standard for these types of products would be to modify the system such that water can flow through it without the adsorptive or absorptive media filter cartridges. Devices such as bypass plugs, or specially manufactured parts such as empty encapsulated housings with no media inside can be used to facilitate an extraction test without media. And in fact, these approaches have been put into practice, although not uniformly by all users of the standards.
While this approach can work to meet the requirement of the standard, it is important to reflect upon the reason for the requirement to test systems for extraction without absorptive or adsorptive media. This is to assure that end users who operate the system without the filters in place are protected. So the question that arises with respect to this approach is, if the system doesn’t allow water to flow without the filters in place, doesn’t that design protect users against operating the system without filters in place? The end user cannot consume any water from the system without the filters in place if no water can flow through it. And because this design does protect end users from operating the system without filters in place, then what is the reason for going to great lengths such as using modified systems to be able to conduct a without media extraction test?
Clarification from the Joint Committee
The NSF Joint Committee on Drinking Water Treatment Units recently considered this requirement and the questions posed above. The committee ultimately decided that there is not a reason to test systems that won’t flow water without the filters in place for extraction without media. The result is that NSF/ANSI 53 was updated with revised language to clarify the requirement. This updated language in the 2020 edition of NSF/ANSI 53 reads as follows: “18.104.22.168 Systems with adsorptive or absorptive media shall be tested with and without the media. Testing without media shall include removal of any granular adsorptive or absorptive media, and removal of any adsorptive or absorptive replacement elements. Systems that contain only encapsulated filter element(s) that are unable to be operated with the element removed, are exempt from without media extraction testing.” This revision does indeed make it very clear that systems that do not flow water without the filters installed are not required to be modified in some way to facilitate a without media extraction test.
The standards development process in action
One of the main functions of the Joint Committee is to engage in continuous improvement of the standards. This is an ongoing process as technology evolves, as regulations are updated and implemented, and as users of the standards bring issues such as this one forward. In some cases, revisions are made to update contaminant levels, modify testing procedures, or accomplish other goals to achieve continuous improvement. In this case, a review of the current language and how various users were interpreting it and implementing the requirement caused the committee to reflect upon the underlying reasons for the requirement and led to a clarification in the language and subsequent revision of the standard.
Through years of constant focus and continuous improvement, the Joint Committee has managed to develop some of the most robust and scientifically based standards for POU and POE products in the world. Although some may wonder why the Joint Committee continues to work on standards that were initially adopted 30 or even 40 years ago or longer, when revisions like this one are made to help clarify the standard requirements, it becomes clear why the committee continues to do this very important work.
About the author
Rick Andrew is NSF’s Director of Global Business Development – Water Systems. Previously, he served as General Manager of NSF’s Drinking Water Treatment Units (POU/POE), ERS (Protocols) and Biosafety Cabinetry Programs. Andrew has a Bachelor’s Degree in chemistry and an MBA from the University of Michigan. He can be reached at (800) NSF-MARK or email: Andrew@nsf.org