By Rick Andrew
With the new year comes a new draft standard from NSF in the area of water treatment. As of the writing of this column in early December, NSF 419 Public Drinking Water Equipment Performance – Filtration is currently undergoing balloting to become an NSF standard and subsequently an NSF/ ANSI standard.
The scope of draft NSF 419 is to describe the performance evaluation test procedure 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. It will provide procedures to develop challenge-testing Log Removal Values (LRVC_TEST), as required in 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 was designed to protect the public from illness due to Cryptosporidium and other contaminants originating in surface water sources that can contaminate 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. The LT2 Rule also requires membrane filtration and UV products to undergo laboratory testing to verify the systems perform as specified.
These products include the following:
• Microfiltration (MF) membrane systems
• Ultrafiltration (UF) membrane systems
• Nanofiltration (NF) and RO membrane systems
• Ultraviolet (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 of the LT2 Rule
The requirements for testing are focused on Cryptosporidium reduction performance. Some highlights for membrane filtration technologies include:
• 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.
How to demonstrate conformance?
Public water supplies must be sure they are in conformance with the LT2 Rule. But how is this accomplished? A common approach has been to discuss the subject with potential equipment vendors and request test results, calculations and other documentation that their equipment will help the public water supply conform. These discussions may occur with state or other regulatory bodies involved in the project. Because these public water supplies are typically purchasing commercial products that are mass produced and not custom fabricated, the vendors often have already worked with laboratories to conduct testing to help bolster demonstration of the equipment’s performance. In some cases, when new equipment is involved, testing must be conducted and reports, calculations and other documentation generated to establish conformance.
This approach has proven to be less than ideal for several reasons:
• Piecing together test results, calculations and
documentation in various formats from different laboratories can be daunting. It can be difficult to evaluate. This can lead to lots of questions for the equipment vendors from potential customers, by the states or by other regulatory bodies, which complicates their business and ultimately may lead to marketplace confusion. This process can occur over and over again with each potential sale.
• Test results represent performance of the equipment at a single point in time. As time goes by, there is an increasing likelihood that some type of modification to the product or to the materials of construction has occurred, raising questions about whether there has been any impact on 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 the manufacturing quality-control procedures are in place and are in accordance with the test results.
Development of a standard
This scenario is a classic case describing the need for a third-party consensus standard and subsequent third-party certification. Regulations exist and it is a challenge for sellers, buyers and regulators to easily establish and confirm that there is conformance to the regulations. By developing such a standard and certifying to it, a vehicle for these stakeholders to easily accomplish this goal is created.
Certification addresses all of the shortcomings of the approach described above because:
• The testing, calculation and documentation requirements can be standardized and clarified.
• Continuity in manufacturing can be confirmed through certification facility audits.
• Facility audits can also address internal manufacturing quality-control criteria associated with the LT2 Rule.
In fact, in this case NSF actually began certifying products prior to development of the standard. The LT2 Rule provides enough clarity for certification to occur. In 2010, NSF began certifying products based on the requirements of the LT2 Rule. NSF also recognized that certification is strongest when it is conducted against a national standard developed through a consensus process. So, NSF began work on draft NSF 419 at that time, basing the standard very heavily on the LT2 Rule itself. The basic requirements of draft NSF/ANSI 419 are described in Figure 1.
NSF/ANSI 61 certification
The LT2 Rule does not address the safety of materials of construction of these products for contact with drinking water. For most non-residential products treating drinking water in most US states, however, third-party certification to NSF/ ANSI 61 is required. Therefore, NSF/ANSI 419 requires that materials in contact with drinking water must conform to NSF/ ANSI 61.
Bridging the gap
The LT2 Rule set out requirements for public water supplies. Equipment vendors are taking advantage of these requirements by developing and providing equipment to help public water supplies conform to these requirements. Demonstration of 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. This type of challenge is one that national consensus standards and third-party certification is perfectly positioned to address. By bringing stakeholders together to create common understanding and acceptance, demonstration of performance can be dramatically simplified and bolstered. Draft NSF 419 Public Drinking Water Equipment Performance–Filtration will be such a consensus standard once it is adopted early in 2015.