HWT Test Protocols: 40 Years of Testing HWT Systems Lessons Learned.

Transcription

1 HWT Test Protocols: 40 Years of Testing HWT Systems Lessons Learned. UNC Water and Health Conference 2012 Nikki Beetsch Drinking Water Treatment Units Group Lead NSF International 1

2 WHO Evaluating Household Water Treatment Options Purpose: Guiding principles for the development of new HWT testing protocols or supplementing existing protocols. Appropriate and consistent evaluation when possible, existing testing protocols should be used or adapted NSF P231, Microbiological Water Purifiers (2008) - based on the EPA Guide Standard and Protocol for Testing Microbiological Water Purifiers. Still intent of the protocol must be well understood or there will be dramatic differences in performance!! 2

3 HWT Test Protocols Lessons Learned NSF International >40 yrs of writing American National Standards for and testing of HWT products > 20 yrs testing to the NSF P213, Microbiological Water Purifiers (based on the EPA GS) > 6 yrs NSF P248, Military Operations Microbiological Water Purifiers There have been some lessons learned! 3

4 Appropriate and Consistent Evaluation Evaluation of the product relies on the a strong understanding of the technology and its limitations. Unfortunately, when this is not understood and the test does not challenge the system appropriately there is a great likelihood for a false pass (not a false fail!!) A false pass gives the user a inappropriate sense of security a dangerous situation. 4

5 KEY: Know your technology and its limitations Many elements to consider. Test operation considerations conditioning; sample collection; test water characteristics; cycling; stagnation; sampling plan, etc. Microbiological considerations seeding; organism compatibility; neutralization; surrogates; etc. too many for a 15 minute presentation 5

6 Mode of Operation Consider: How will the system operation in actual use? Gravity Flow Batch Systems consider the need to allow the system to experience the changes in flow and contact time with the media as the volume flows through the system. If a15l batch system test using 15L batch cycling Mouth Draw Filter Configuration consider maximum human draw pressure (~ -3psi) ; consider the cycling of a mouth draw batch Plumbed to Household Pressure consider the rapid changes in pressure/flow with the water hammer effect of shutting off a valve; consider how often a valve will be shut on and off 6

7 Seeding prior to Sample Collection Consider: The Void Volume of the system on test Seed with the microbiologically challenge water prior to collecting the sample to achieve influent challenge levels. If not, the system is not receiving appropriate challenge and performance will be overstated. 7

8 Organism Considerations Consider: Implications of organism selection Identified based on Some are actually pathogenic organisms Varying susceptibility to drinking water disinfectants Particle sizes that should provide useful information for mechanical size exclusion However, also need to consider Technology affects choice (method and organism) Combining compatibility considerations (organisms themselves, preservatives, test water issues, etc.) Neutralization, handling, hold times, base test water 8

9 Sample Collection Consider: The dose that may occur to the individual Infectious dose is dependent on what the person drinks, not the average that may come out of a system over time, but the dose that may occur to an individual. * Mechanical filtration water immediately ( first draw ) after flow is resumed (start, cycling, stagnation, at test water change) Disinfection first draw for systems that dose, but at the end of a cycle for leachable disinfectant (NOTE ASTERISK) 9

10 Sample Collection Consider: The dose that may occur to the individual. Infectious dose is dependent on what the person drinks, not the average that may come out of a system over time, but the dose that may occur to an individual.* *Caveat: This may not be an issue for a device that feeds into a set volume reservoir, but is extremely important for a device that delivers water directly to the user. Consider how your system delivers water! 10

11 Take home message Evaluation of the product relies on the a strong understanding of the technology and its limitations. Without this, there is tremendous risk for overstatement of performance (false pass) and a dangerous false sense of protection to the user. 11

12 Contact Nikki Beetsch ERS, DWTU Group Lead phone (734)