By Rick Andrew
First promulgated as a new standard in January, 2015, NSF/ANSI 419 Public Drinking Water Equipment Performance–Filtration provides a test procedure for performance evaluation for the product-specific challenge testing of full-scale UF and MF membrane modules, bag filters and cartridge filters for the removal of microbial contaminants. The standard also provides procedures to develop challenge-testing log removal values (LRVC_TEST), as required in the US EPA’s Long Term 2 Enhanced Surface Water Treatment Rule (LT2 Rule), published in 40 CFR 141-subpart W. The LT2 Rule applies to all public water systems that use surface water or groundwater that is under the direct influence of surface water. It requires these public water systems to use treatment technologies to reduce exposures to Cryptosporidium that may be entering surface waters through runoff. The LT2 Rule also requires membrane filtration and UV products used for Cryptosporidium treatment in these public water supplies to undergo testing in the laboratory to confirm the systems perform as specified.
Cryptosporidium is a tiny parasite that can affect livestock (such as cattle and chickens) and also humans. It is transmitted through the fecal-oral pathway. The reason it is of such concern in drinking water is that it exists in cyst form until it enters a mammalian host. This cyst form has a hard shell that is resistant to chlorine and other chemical disinfectants. As such, it can enter public water supplies that have a surface water source via runoff from areas with infected livestock feces and can infect people even if that public water supply is properly disinfected. This unique characteristic of Cryptosporidium (and resulting consumer infections) is why the LT2 Rule was developed. There are a number of treatment technologies that are effective in treating water that may be contaminated with Cryptosporidium. The LT2 Rule recognizes the various possibilities for treatment technologies by specifically including the following:
- Microfiltration membrane systems
- Ultrafiltration membrane systems
- Nanofiltration and RO membrane systems
- UV reactor systems
- Bag and cartridge filter systems
- Other products used in the treatment or production of drinking water for which there is a regulatory performance requirement.
The role of public water supplies
Public water supplies falling under the scope of the LT2 Rule are required to demonstrate that they are in conformance with its requirements. This demonstration requirement, however, can leave them in a challenging position. Public water supplies may be attempting to demonstrate conformance by assembling a collection of various test reports, calculations based on the data derived from the test reports and related information obtained from equipment vendors. The test reports may be issued by laboratories or engineering firms. The testing itself may be conducted under a range of conditions using a variety of procedures. If a community water system seeks to install equipment that is new to the market and has not been previously tested, this work must be completed prior to the installation occurring.
Beyond testing and calculations, the LT2 Rule includes manufacturing quality-control requirements for water treatment equipment. These requirements can be especially difficult for public water supplies to confirm because manufacturing quality control is a completely separate issue from product efficacy testing. The other consideration that public water supplies are faced with is the possibility that the manufacturer could make changes to the product or manufacturing process after the testing is completed. In these cases, even if the public water supply is aware of product modifications, it can be unclear as to the impact of the modifications on the validity of previously generated test results.
This scenario is one that is ideally addressed by the implementation of third-party certification to a standard: regulations exist, but manufacturers, buyers and regulators cannot easily establish and confirm that there is conformance to the regulations. Developing a standard and third-party certification to it creates a mechanism for all the affected stakeholders to confidently assure conformance to the requirements. With this in mind, the NSF Joint Committee on Public Drinking Water Equipment performance developed NSF/ANSI 419, allowing third-party certification. With the implementation of third-party certification, the three main challenges in assuring conformance to the regulatory requirements can much more easily be addressed:
- The testing, calculation and documentation requirements are standardized, clarified and detailed in a transparent fashion through a consensus document based on the LT2 Rule.
- Continuity in suppliers and manufacturing processes is confirmed during manufacturing facility audits.
- Adherence to manufacturing quality-control criteria required by the LT2 Rule is also confirmed during the manufacturing facility audits.
The basic content of NSF/ANSI 419 is described in Figure 1.
Safety of materials in contact with drinking water
The LT2 Rule does not address the safety of materials of construction of these products for contact with drinking water. Most US states, however, require conformance to NSF/ANSI 61 for safety for materials in contact with drinking water for non-residential water treatment equipment. As a result, NSF/ANSI 419 includes the requirement that materials in contact with drinking water must conform to NSF/ANSI 61.
Meeting the needs of stakeholders
LT2 Rule requires public water suppliers to include additional treatment for protection against contamination by Cryptosporidium. Equipment manufacturers serve this market need by developing and providing equipment to enable the public water supplies conform to the requirements of the rule. Third-party certification to NSF/ANSI 419 Public Drinking Water Equipment Performance–Filtration allows the stakeholders in this market, including manufacturers, public water suppliers and consumers, to be confident that third-party-certified equipment meets the treatment and quality assurance requirements of LT2 and that the equipment is manufactured in a consistent manner over time.
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