Q&A: Residential Drinking Water Treatment Protocols

  • Open How do I choose between certification to NSF P231: Microbiological Water Purifiers and NSF P248: Military Operations Microbiological Water Purifiers?

    A discussion about your market would help with this decision. More importantly, P248 was based on the EPA Guide Standard, while P231 uses it in its entirety, unaltered. As such, the protocols have much testing similarity and the government reviewing agency (the U.S. Army Public Health Command) has agreed that for those manufacturers with both a commercial and military market, where it is possible to write a hybrid protocol without compromising the intent of P248, it will allow and will review the PSTPs.

  • Open Should I seek full NSF certification or NSF P248, Appendix B?

    The answer lies with your market. If you are solely targeting the military, NSF P248, Appendix B is the data that the government reviewing agency (GRA) requires for receiving its Government Reviewing Agency Letter of Compliance. The GRA will do a separate review of the wetted materials in the product, but it does not require full NSF certification. If your market is commercial or a mix of commercial and military, NSF certification may be needed. Full certification includes the steps necessary to receive the GRA P248 Letter of Compliance as the military reviews all purifier specific test plans (PSTPs) as well as material safety, structural integrity, auditing, literature and labeling under NSF’s certification program. If a product is NSF certified, the GRA will not have to perform an additional materials review as the NSF evaluation is recognized as at least as protective.

  • Open Why does the NSF P248 protocol require two sequential challenges for microbiological challenging?

    Some test-required organisms are not compatible for combining due to method issues or organism competition. Examples found in NSF P248 are MS2 and fr, which should not be combined. It is important to consider not only if one organism will outcompete the other, but also if the stock of an organism contains a preservative, etc. that may inhibit the growth of a mixed organism. Sequentially challenging allows for the same unit to see all organisms, but eliminates the concerns associated with organisms that cannot be combined. An important test consideration with sequential challenging is to be certain to undergo the 10 void volume ‘seeding’ of each organism or organism pairing prior to challenging for sample collection. Seeding was included in the EPA Guide Standard and included in NSF P248 to ensure that there is no dilution of challenge water with the un-microbiologically challenged water that was left in the system. Seeding during serially challenging also ensures that the previous organism(s) was/were completely displaced prior to the actual sample collection for the next organism(s) sample collection.

  • Open Under NSF Protocol P248, why are elevated total organic carbon (TOC) and turbidity required throughout the full challenge test-water phase when testing individual water purifiers (IWPs), but only during seeding and sampling points in the challenge test-water phase when testing small unit water purifiers (SUWPs)?

    During military operations, IWPs are used for emergency or short-term missions where water selection may be limited. The design of many IWPs allows, and intends, for very shallow surface water sources, such as a puddle, to be accessed as drinking water. If an IWP is used with a larger body of water, the typical design allows filling the bladder or an on-demand filter (such as a straw) with water that is most likely near the more shallow areas and, thus, likely to be more turbid and contain more TOC than water on the surface of the deeper parts of the body of water. Therefore, requiring the full challenge test-water throughout provides a realistic worst case test. SUWPs, with the higher draw and flow, are designed to make use of larger bodies of available surface water, such as ponds or lakes. Typically the intake hose will allow for use of water that is deeper than the immediate shallow shoreline. Additionally, missions requiring SUWPs are expected to have more latitude in source water selection, including seeking out the cleanest source available. For these reasons, it was decided that requiring elevated TOC and turbidity only at the seeding and sampling points, but also including a ‘clogging’ point, will sufficiently challenge the systems to document capabilities under realistic conditions.

  • Open Why does an individual water purifier (IWP) have a set test capacity (135 L) while the small unit water purifier (SUWP) has a daily operation period (four hours)?

    By definition, IWPs supply needed water to a single individual. It has been identified that the volume needed for an individual is 15 L/day. Although the actual capacity of most systems varies with the quality of the source water, IWPs must meet the rigorous waters and test capacity of 135 L for NSF Protocol P248 so that the soldiers can be sufficiently equipped with IWPs to complete a mission. SUWPs have varying production rates and can service varying numbers of soldiers, with system selection based on mission needs. It was not practical to create test plans for an SUWP to serve a specific number of soldiers. Depending on the mission, all may have a place in the field. Defining a test capacity for an SUWP would result in excluding systems that may be valuable but not at the scale of production to meet the test or in greatly understating or not sufficiently challenging the capacity of a larger flowing/capacity system. The solution was to have an expectation on the daily production as flowing time. This would provide valuable information about the capacity and performance at that capacity for equipping decisions when choosing a system. The test capacity for an SUWP is the product water volume accumulated when flowing for four hours per day for ten flowing days. Due to varying system sizes and flow rates, four hours provides a test volume sufficient to evaluate system capabilities without benefitting any single-size system.

  • Open Why is seeding necessary for testing against NSF Protocol P248?

    A system holds water after flow has stopped, which the protocol refers to as void volume. When microbiologically spiked water is introduced into the system, this void volume, which does not have any microbiological addition, causes a dilution of the microbiologically challenged water being introduced. This void volume, therefore, must be displaced before it can be assured that the microbiological challenge exposed to the system equals that of the targeted influent concentration. If this is not done, the performance may be overstated. The EPA Guide Standard identifies 10 void volumes (vv) as appropriate for seeding. For batch systems, a full batch (as long as 10 vv is achieved) is used for ease of testing.

  • Open What is radioactive iodine?

    Radioactive iodine (I-131) is produced by the fission of uranium atoms during the operation of nuclear reactors. Iodine is a solid substance that can go directly from a solid to a gas, without first becoming liquid. This vapor is irritating to the eyes, nose and throat. Radioactive iodine products form within fuel rods. Reactor chemistry must be carefully controlled, to avoid rapid build-up and increased pressure that may cause corrosion, cracks or other breaches in the rods.

  • Open Why was NSF/JWPA Protocol P72 developed?

    NSF International and the Japan Water Purification Agency (JWPA) began developing P72: DTWU - Iodine Radioisotope Reduction at the request of water treatment systems manufacturers following the tragic earthquake in Japan in March 2011, to help solve consumer confusion and provide a means to evaluate drinking water systems that reduce radioactive iodine. Manufacturers felt water systems certified to the protocol would provide consumers additional reassurance. The protocol was developed by a team of industry experts, including representatives from JWPA and the U.S. Army, as well as scientists at NSF International, to validate the performance claims of point of use (POU) drinking water treatment units (DWTU) to effectively remove all common forms of iodine from drinking water.

  • Open What types of products are tested by NSF/JWPA Protocol P72?

    The scope of this protocol covers point of use applications of drinking water treatment units.

  • Open Does NSF/JWPA Protocol P72 incorporate additional regulatory standards?

    No, this protocol only addresses the reduction performance of iodine. Other criteria, including material safety, structural integrity and general product marking, are not addressed. This protocol assumes that the system being evaluated has met appropriate standards for the intended market, e.g. in the United States of America, the requirements of NSF/ANSI Standard 42 or 53 for adsorptive or absorptive media and NSF/ANSI Standard 58 for reverse osmosis (current editions), Sections 4, 5, 6 and 8.

  • Open Who benefits from NSF/JWPA Protocol P72?

    Both consumers and manufacturers can benefit from this protocol:

    • Consumers can be assured that by using products certified to NSF/JWPA Protocol P72, their drinking water has all common forms of iodine reduced by at least 50 percent and up to 99 percent.
    • Through claims validation, manufacturers can be confident that their product performs effectively and that the needs of the consumer have been met by providing a product that ensures the reduction of iodine contaminants from drinking water.