By Rick Andrew
Much of the focus when developing test methods and requirements for point of use (POU) and point of entry (POE) products is on the product testing procedures. Typical considerations include the method of introduction of water into the product, the composition of the water, the operating conditions of the product under test, the end point of the test, sampling frequency, and pass/fail requirements. With many of these product test methods, the analytical procedures and necessary equipment required to generate water composition and contaminant concentration data are not a major consideration, although obviously there are some product tests which require specific analytical method development. But in general, accepted analytical methods to support product testing are already established, and they can be implemented with few, if any, modifications.
For this reason, it is tempting to overlook the analytical laboratory when developing test methods and requirements for point of use (POU) and point of entry (POE) products. However, when it comes to actually conducting all of the various tests in the NSF/ANSI Drinking Water Treatment Units standards, a very significant array of complex analytical instrumentation is required, and the analytical laboratory serves a critical role in the testing process.
The Long List of Equipment for a Fully Capable POU and POE Test Lab
Figure 1 outlines a list of necessary instruments required to conduct the testing under the NSF/ANSI DWTU Standards. This list is not exhaustive and may not include every piece of required analytical instrumentation to conduct all tests in these standards. It is also possible that in some cases alternate instruments and/or methods may be acceptable or even preferable. For example, colorimetric autoanalyzers can be used for a number of commonly conducted colorimetric analyses as opposed to using ion selective electrodes or other methods. The purpose of Figure 1 is to give a general appreciation for the vast array of analytical instrumentation that is necessary to run all of the many various tests included in the Standards.
An Important “Behind the Scenes” Role
Without analytical equipment, all the best and most advanced POU and POE product test stands become useless. It is impossible to know if the test water is within specifications of the Standard without analysis. Gauging the product’s performance in treating contaminants is also impossible if the contaminant concentrations in the influent and effluent water cannot be analyzed.
It is not only critical to be able to analyze the water, but in many cases, it is very important to analyze it quickly. Especially important is rapid turnaround time on analysis of the influent samples for contaminant reduction tests conducted in “batch” mode. “Batch” mode means that a volume of water, typically 2000 liters, is prepared according to the standard and will be used to challenge the product. Product testing cannot begin until the chemical composition and concentration of the test contaminant can be confirmed within the specifications of the standard. Because some batches of test water have a limited shelf life of 24 hours, this analytical confirmation must be completed within a few hours of preparing the batch of test water. In these cases, this preparation of the batch of test water and rapid analytical confirmation of composition must occur each day of testing. The importance of rapid and accurate water analysis cannot be overstated for these tests.
Although rapid turnaround of treated or effluent water samples is not as critical, this information is very helpful in assessing the product’s performance as the test proceeds. When this data is available while the test is still ongoing, it is possible to stop tests if they have failed prior to reaching the end point of the test. This can be desirable to help save costs associated with ongoing testing of a product that is not performing as well as expected.
Quality of Data is Critical
One of the realities of chemical analysis of water samples is the uncertainty of the concentrations determined. Although modern, state of the art analytical instruments, when operated by qualified chemists, are very precise and accurate, it is impossible to pinpoint exact concentrations of constituents in water. Given this inherent uncertainty, it is critical to be as precise and accurate as possible. The NSF/ANSI DWTU Standards are written with very precise acceptance and pass/fail criteria. Without very accurate and precise analytical data, there can be questions as to whether a test really passed or really failed.
For example, NSF/ANSI 53 for lead reduction requires the system to reduce an influent concentration of 150 ug/L of lead down to 10 ug/L or less in the effluents at each sample point throughout the tests. Two tests are conducted, one at pH 6.5 and the other at pH 8.5. If analysis of the effluent samples indicates a lead concentration of 10 ug/L, the system is meeting the requirements of the standard and results are acceptable. If the effluent sample concentration is 11 ug/L of lead, the test is failing. Because the analytical uncertainty surrounding this measurement is ± 1 or 2 ug/L, there is an issue to consider that some tests reported as passing may have actually failed, and vice versa. The NSF/ANSI Joint Committee on Drinking Water Treatment Units, responsible for development of the standard, understands and accepts this uncertainty because there is no better alternative way to address the issue.
However, consider the ramifications of greater uncertainty – say, if the uncertainty of the measurement was more like ± 10 or 20 ug/L with a maximum allowable effluent concentration of 10 ug/L. Would this test be meaningful? It would certainly be a greater dilemma to consider than the one faced with uncertainty of ± 1 or 2 ug/L.
Analytical Chemistry – An Important Part of POU and POE Testing
My area of concentration in undergraduate work was chemistry, and I liked analytical chemistry the best. I also worked as an analytical chemist and consultant for twelve years before making a career move to NSF nine years ago. So, I’m a little bit biased in my thoughts about the analytical lab. But all biases aside, the critical importance of rapid turnaround, precise, and accurate analytical results from a broad spectrum of highly sophisticated instruments and qualified chemists must be considered when surveying the areas and components of a full service POU and POE testing laboratory. Although analytical services are a support function to the product testing lab, the product testing laboratory cannot function without them, and cannot function well without great coordination with a high quality analytical laboratory.
About the author
Rick Andrew is the Operations Manager of the NSF Drinking Water Treatment Units Program. 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 1-800-NSF-MARK or email: [email protected] .