By Rick Andrew
The global landscape of POU/POE standards and requirements is highly complex and disorganized, making it difficult to track, understand and ultimately comply with applicable requirements. While this is true for all types of POU/ POE products and claims, the situation with global standards for and regulation of microbial reduction claims is especially complex and confusing. Microbial contamination is a widespread concern involving many different potential pathogenic organisms introduced into drinking water of varying quality through a variety of pathways. Because of the multiple organisms and variable water quality, many technical approaches to treating microbial contamination are utilized. Each of these approaches has strengths, weaknesses and limitations due to infrastructure or other considerations. These factors contribute to the proliferation of various global standards, protocols and guidelines for POU/ POE products making microbial reduction claims.
The Guide Standard and Protocol for Testing Microbiological Water Purifiers was first released in 1986 and revised in 1987 by a US EPA task force to be a general guide for determining the microbial removal/inactivation effectiveness of certain types of POU treatment systems on waters of unknown quality. As the first such standard, and one developed by US EPA, it has been very influential in terms of other standards, protocols and regulations issued since 1987. Table 1 provides a generalized description of the requirements included within the standard and also describes its influence globally.
Other standards, protocols and guidelines
Since 1987, a number of standards, protocols and regulations relating to POU/POE products making microbial reduction claims have been issued by a variety of organizations and in a number of countries. Table 1 summarizes many of these, although there may be some others that exist that are not included.
Four main considerations
There are four criteria that are the most significant when reviewing and comparing criteria for microbial reduction claims. These include organisms required, log reductions, test-water characteristics and technologies covered. Each of the standards, protocols or guidelines included in Table 1 is described in terms of these four criteria.
Organisms required describes the classes of organisms that must be treated in order to conform to the standard. There are three basic types of pathogenic organisms that can contaminate drinking water: bacteria, virus and protozoan cysts. Generally, there are two basic categories of criteria: those that cover bacteria only and those that cover all three types of pathogenic organisms. Obviously, re- quiring treatment of all three types of organisms is a much stricter requirement than requiring treatment of bacteria only.
Log reductions describe the level of performance that a POU or POE product must achieve to conform to the requirement. One- log reduction is equal to 90 percent, two-log reduction equals 99 percent and so forth. A requirement of six-log reduction, or 99.9999 percent, is a much more stricter than two-log reduction.
Test water characteristics describe how ‘dirty’ the water is when introducing the microorganisms into the POU or POE product. There are two basic categories of test water characteristics: clean water and water of unknown quality. Clean- water testing is usually based on tap water or deionized water that is relatively low in organic content and turbidity. Testing to cover applications of treating water of unknown quality typically includes relatively high amounts of organic content, usually in the form of tannic acid or humic acid, as well as relatively high turbidity, often resulting from the use of test dust. Testing with organic content and turbidity present is a much stricter requirement than testing with relatively clean water.
Technologies covered describes the types of POU or POE products than can be evaluated under a given standard, protocol or guideline. Because different technologies have different strengths, weaknesses and limitations, there are different considerations built into the test methods for evaluating these technologies. Some evaluation schemes address only one type of technology, whereas others are more broadly applicable.
In 2011, the World Health Organization (WHO) released Evaluating household water treatment options: Health-based targets and microbiological performance specifications (WHO HWT docu- ment). This document is significant for several reasons. First, it was released by a very influential group in terms of setting forth guidelines and criteria for developing nations. Second, it takes a unique approach to log reductions in that it has tiered levels of performance based on an assessment of improvement of quality of life associated with these varying levels of performance. This approach allows local governments to determine the value of each tier of performance for their jurisdiction, and to set rules and guidance accordingly. And third, it is not prescriptive in terms of the testing methodology, although it does provide significant guidance regarding appropriate considerations for testing.
NSF has recently developed NSF P415 Household Water Treatment Options – microbiological as a vehicle for certification to the WHO HWT document. NSF coordinated closely WHO to assure that the requirements of P415 mesh closely with their vision. As such, it is hoped that certification of products to P415 will benefit local governments and relief organizations implementing the guidance from WHO. P415 utilizes the P231/US EPA Guide Stan- dard testing methodology, specifically referenced as appropriate in the WHO HWT document. P415 is focused globally, mainly on products intended for developing nations, so it has a flexible approach to material safety evaluation. And, P415 incorporates specific statements required to convey the tiered level of perfor- mance associated with the product as certified.
Table 1 describes in general terms the global landscape of standards, protocols and requirements for POU/POE products making microbial reduction claims. Much like the challenge for
POU products of reducing six-log bacteria, four-log virus and three-log cyst in water containing significant concentrations of organic matter and turbidity as originally set forth in the US EPA Guide Standard, understanding the global regulatory landscape is also challenging. Hopefully breaking it down in terms of organisms required, log reductions, test water characteristics and technologies covered provides a useful framework to help analyze and understand it.
About the author
Rick Andrew is the General Manager of NSF’s Drinking Water Treatment Units (POU/POE), ERS (Protocols) and Biosafety Cabinetry Programs. He previously served as the Operations Manager, and prior to that, Technical Manager for the program. 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.