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
• 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
S 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: Andrew@nsf.org.