By Rick Andrew
Just as there are requirements for POU/POE treatment as defined by the NSF/ANSI DWTU Standards, there are also requirements for small potable water systems sold in the United States. In some ways, small communities are similar to homeowners when it comes to preferred drinking water treatment options—they would like to find and purchase existing products with established performance capabilities and scale them to their needs, as opposed to engineering, designing and building a unique drinking water treatment facility from the ground up. Small potable water systems are regulated under the Long Term 2 Enhanced Surface Water Treatment Rule (LT2 Rule). The rule applies to all public water systems that use surface water or groundwater that is under the direct influence of surface water. The LT2 Rule was designed to protect the public from illness due to Cryptosporidium and other contaminants in drinking water. The rule requires community water systems to use treatment technologies to reduce exposures to these microorganisms, which are resistant to common disinfection practices. LT2 regulations also require membrane filtration and UV products to undergo laboratory testing to verify the systems perform as specified.
These products include the following:
- Microfiltration membrane systems
- Ultrafiltration membrane systems
- Nanofiltration and reverse osmosis 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.
Laboratory testing requirements
The requirements for testing are focused on contaminant reduction performance, and they are specified in the LT2 Rule.
Membrane filtration technologies
• Testing must be conducted on the full-scale product, or 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 counting 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 maximum recovery (if applicable) as specified by the manufacturer.
• Testing of full scale-products is required.
• Testing uses biodosimetry in which the product is evaluated under varying conditions of flowrate, UV transmittance of the water and UV intensity of the system, using a challenge organism. Inactivation of the challenge organism is then correlated to a dose-response study conducted with a calibrated UV low-pressure mercury source.
Various organisms can be used for testing, although the most commonly used is MS2 Phage.
A common approach for communities demonstrating compliance of their water systems to these requirements has been to discuss the subject with potential vendors, and then review the documentation provided by the vendors to demonstrate compliance. Because these communities are typically purchasing standardized products that are somewhat mass-produced, the vendors often have already worked with laboratories to conduct compliance testing, so they can readily provide test results. In some cases, when new equipment is involved, testing must be conducted and a report generated to establish conformance.
This approach has proven to be less than ideal, especially because communities have had difficulty addressing the question of product consistency between the tested product and the product being selected. Over time, products can be modified for purposes of enhancement, or because of component or material vendor changes. Many of these modifications will not affect performance or will improve it, while others could possibly negatively impact product performance. The unknown potential impact of product changes increases with the age of the test data—the older the testing, the more likely the product has been modified since the time of the testing, which could impact performance and therefore, calls into question the validity of the results.
Option to certify
In order to address ongoing compliance of products tested to LT2 Rule requirements and meet the needs of both manufacturers and community water systems, a new certification option has been developed by NSF. This certification program, in addition to the testing required for LT2 Rule compliance, includes ongoing manufacturing facility inspections to verify that certified products continue to comply with LT2 Rule quality control requirements. This ongoing verification through manufacturing facility inspections helps manufacturers and communities answer questions regarding ongoing compliance of their products and drinking water systems.
Two manufacturers (The Dow Chemical Company and Hyflux Membrane Manufacturing [S] Pte. Ltd,) have become the first certified under this new program. Both have certified ultrafiltration products to the LT2 Rule requirements.
NSF/ANSI 61 certification The LT2 Rule does not address the safety of materials of construction of these products for contact with drinking water; so material safety is not addressed through the new certification program. For most non-residential products treating drinking water in most US states, however, third-party certification to NSF/ANSI 61 is required. Therefore, most manufacturers will likely pursue this certification in addition to certification to the LT2 Rule requirements Complex regulatory environment The US includes a variety of requirements for products used to treat drinking water, which vary from state to state, product technology to product technology, and also by point of application. POU/POE products have different regulations from community systems. It can be daunting indeed for manufacturers to understand and comply with the applicable regulatory requirements for their product types and markets. Third-party certifiers such as NSF work to help manufacturers understand, navigate and demonstrate compliance with these regulations in many ways. This new certification program for compliance to LT2 Rule requirements is the latest example of certifiers working to identify and serve these needs.
About the author
Rick Andrew is the Operations Manager of the NSF Drinking Water Treatment Units Program for certification of POE and POU systems and components. Prior to joining NSF, his previous experience was in the area of analytical and environmental chemistry consulting. 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: [email protected].