The U.S. Environmental Protection Agency’s (EPA) Long Term 2 Enhanced Surface Water Treatment Rule (LT2 Rule) sets requirements for public water supplies, and vendors are developing and providing equipment to help them conform to these requirements. Demonstrating the performance capabilities of this equipment, however, has been a challenge for all stakeholders—public water supplies, state or other regulatory bodies, and equipment vendors.
To address this challenge, the new NSF/ANSI Standard 419: Public Drinking Water Equipment Performance – Filtration was developed to create a common means of validating equipment performance and compliance. It is the first consensus-based American National Standard addressing the performance of municipal water filtration technologies used to remove Cryptosporidium and other pathogens from public drinking water supplies. The standard incorporates the LT2 Rule and other state and federal regulatory requirements to streamline the testing process and assist state regulators in verifying compliance.
NSF/ANSI 419 describes the performance evaluation test procedure for the product-specific challenge testing of full-scale ultrafiltration (UF) and microfiltration (MF) membrane modules, and bag and cartridge filters for the removal of microbial contaminants. It provides procedures to develop challenge testing Log Removal Values (LRVC_TEST), as required in the LT2 Rule published in 40 CFR 141-subpart W.
Pathogen Protection
The LT2 Rule applies to all public water systems that use either surface water or groundwater that is under the direct influence of surface water. It was enacted to prevent illness due to Cryptosporidium and other pathogens originating in surface water sources that can contaminate drinking water. The rule requires community water systems to use treatment technologies to reduce exposure to these microorganisms, which are resistant to common disinfection practices. The LT2 Rule also requires membrane filtration and ultraviolet (UV) products to undergo laboratory testing to verify that the systems perform as specified. These products include:
- MF membrane systems;
- UF membrane systems;
- Nanofiltration and reverse osmosis membrane systems;
- UV reactor systems;
- Bag and cartridge filter systems; and
- Other products used in the treatment or production of drinking water that have a regulatory performance requirement.
Laboratory Testing Requirements
The test requirements focus on Cryptosporidium reduction performance. Some highlights for membrane filtration technologies include:
- Testing must be conducted on either the full-scale product or on a scaled-down version that is identical in materials and similar in construction.
- Live Cryptosporidium oocysts or a suitable surrogate that is removed no more efficiently than Cryptosporidium must be used.
- Actual counts of challenge particles in influent and effluent samples must be used to establish log reduction—no gross measurement techniques are permitted.
- The test must be conducted at the maximum flux and recovery (if applicable) as specified by the manufacturer.
Demonstrating Conformance
Public water suppliers must ensure they conform to the LT2 Rule. A common approach has been to request documentation from potential vendors that shows their equipment will help the public water supply conform to the rule. Vendors work with laboratories to conduct testing to demonstrate equipment performance and provide reports, calculations and other documentation to establish conformance. This sounds straightforward, but has proven to be less than ideal because:
- Piecing together test results, calculations and documentation in various formats from different laboratories can be daunting and difficult to evaluate, leading to lots of questions to the equipment vendors from potential customers, states and other regulatory bodies. This can occur with each potential sale, complicating business and possibly leading to marketplace confusion.
- Test results represent performance of the equipment at a single point in time. As time goes by, it is increasingly likely that the product or materials of construction will have undergone modifications that may impact performance.
- The LT2 Rule includes non-testing requirements for internal manufacturing quality control. A review of test results, calculations and documentation does not provide assurance that manufacturing quality control procedures are in place and are in accordance with the test results.
Standard Development & Requirements
Based on the requirements of the LT2 Rule, NSF developed two protocols for product-specific challenge testing: one for MF and UF membrane modules in 2011 and one for bag and cartridge filter systems in 2012. Both of these protocols were developed through NSF’s Environmental Technology Verification (ETV) Center, which was supported in part by EPA.
After EPA’s ETV program was phased out in 2013, NSF recognized the value of continuing to fill the gaps in testing as described above and decided to convert the testing protocols into an American National Standards Institute (ANSI)-accredited standard. Development of ANSI standards requires a public process that ensures balanced input from public health and regulatory officials, industry representatives and users/consumer representatives. In accordance, NSF assembled a joint committee of relevant stakeholders representing water treatment manufacturers, regulators, product specifiers and the American Water Works Assn. to create NSF/ANSI 419, following the ANSI consensus process.
In addition to meeting the testing requirements of the LT2 Rule, NSF/ANSI 419 incorporates federal and state requirements such as certification to NSF/ANSI Standard 61: Drinking Water System Components – Health Effects, which sets contaminant limits for components that come into contact with drinking water. By incorporating multiple requirements into one standard, NSF streamlines the testing process for these technologies and assists municipal water treatment facilities in sourcing compliant systems.
NSF certification addresses all of the challenges described earlier:
- The testing, calculation and documentation requirements can be standardized and clarified.
- Continuity in manufacturing can be confirmed through periodic certification facility audits.
- Facility audits also can address internal manufacturing quality control criteria associated with the LT2 Rule.
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