By Robert Herman
The protection of public water supplies from contamination by microbiological contaminants is a continuing concern by public health officials. The greatest leap forward in this area began in Jersey City, NJ in 1908, when chlorination of the water supply began. Chlorination was adopted in almost every community and resulted in the virtual elimination of cholera, typhoid, dysentery and hepatitis A The number of lives saved by the use of chlorine in our water supplies over the last 100 years is immeasurable. The advent of chlorination was one of the most significant public health advances in the 20th century.
Chlorination, however, doesn’t do the entire job and has some negative effects that have brought its use into question. Public water supplies are not perfect and treatment failures, as well as distribution system contamination, can occur and result in illness. The most famous of these treatment failures is the 1993 Cryptosporidium outbreak in Milwaukee, Wisc. The treatment system was operating properly at the time (using chlorination), but the oocyst, Cryptosporidium parvum, was able to escape treatment barriers and infect hundreds of thousands. In response to this outbreak the NSF Drinking Water Treatment Unit (DWTU) Joint Committee of users, manufacturers and public health regulators developed a drinking water treatment unit test for the reduction of Cryptosporidium (as well as other cysts) from drinking water supplies that are otherwise considered safe. NSF/ANSI Standard 53 was the first standard that specifically evaluated a consumer point of use microbial water treatment device to supplement the water treatment provided by a municipality . These devices were required to have a statement that “Systems certified for cyst reduction may be used on disinfected waters that may contain filterable cysts”. This is in contrast to the U.S. EPA Guide Standard for Microbiological Purifiers which evaluates devices for the reduction of viruses, bacteria, and cysts from water of unknown quality. It is interesting to note that the U.S. EPA Guide Standard references NSF/ANSI 53 cyst reduction protocol as an acceptable method of evaluating the performance of a purifier for cyst claims.
In 2000 the DWTU Joint Committee launched the development of a full standard devoted to evaluating drinking water treatment products for supplemental treatment of not only cysts, but also bacteria and viruses. The Standard was divided into several parts based on the treatment technology used to achieve the supplemental treatment. The mechanical filtration standard is currently being reviewed by the Council of Public Health Consultants (which is responsible for public health overview of the Joint Committee). If the review is successful, NSF/ANSI Standard 244, Supplemental Microbiological Water Treatment Systems – Filtration will be validated by several testing laboratories and be adopted as an NSF/ANSI standard. It is expected that the validation will take approximately one year so the standard would not be available until mid 2006. The halogen-based technology standard is also nearing completion and may be adopted in the same time frame as the mechanical filtration technology. The development of these supplemental microbiological treatment standards has been controversial due to concerns about miss-application and types of claims the devices may make so the CPHC may return these to the Joint Committee for further refinement.
Since 9/11 there has been concern by public health officials that intentional contamination of our country’s water supplies is possible. The U.S. EPA has developed with NSF International and others an evaluation protocol for Homeland Security that looks at point of use drinking water treatment systems’ ability to protect individuals from intentional microbiological or chemical contamination of public water supplies (see sidebar). The supplemental microbiological treatment standard would enhance these efforts by allowing products to be tested and certified to provide additional protection from intentional microbiological contamination.
The supplemental microbiological treatment standard is focused on the “supplemental treatment of microbiologically safe drinking water … for protection against intermittent accidental or intentional microbiological contamination of otherwise safe drinking water”. The products would not, however, provide long term protection from continuous contamination and once an alert is provided by the authorities, the use of the product must be terminated. The products that provide full protection from continuous or known microbiological contamination are called microbiological purifiers and are designed specifically for this purpose. Microbiological purifiers are currently evaluated under a U.S. EPA guide standard that was developed in 1987. The DWTU Joint Committee is beginning the task of updating these test methods and developing a new microbiological purifier standard.
The development of the supplemental microbiological treatment standards has taken several years and a lot of negotiation and study. The mechanical filter standard has been designed to look at the weaknesses of mechanical filtration technology and select test organisms that will exploit these weaknesses. The four-week test includes testing under multiple use conditions (stagnation, clogging, and hydraulic stress) and several water types. The protocol also simulates a water main break that results in high levels of contamination and very poor water quality.
The claims the products can make and how they are made are strictly limited. Only two claims are permitted under the standard, supplemental cyst reduction only or supplemental reduction of bacteria, virus and cysts. To prevent the misrepresentation of these products as purifiers, the Standard requires not only statements regarding what the product has been tested for, but also what is has not been tested for and even how the information is presented. For example, the instructions must have a clear statement that these products can only be used on water that has been determined to be microbiologically safe by routine testing (either by municipality or by well owner). This statement must be made in the same font and size as the microbiological claim and both the claim and the statement must be simultaneously visible to the reader. This prevents over emphasizing the claim while minimizing the clarifying statements.
If the product is only making a claim for cyst reduction the product will have to carry a disclaimer that it has not been evaluated for the reduction of bacteria or viruses. Other literature requirements are to clarify that the product is not for use during a boil water advisory (in lieu of boiling the water) and what service must be performed before returning the product to use.
As with any product, it is always possible that someone will misrepresent the product and/or mis-apply it. These literature requirements, however, make it much clearer to a consumer what the product will and won’t do. This is important since the entire concept behind the standards and the tested products are to protect and improve public health.
About the author
Robert Herman is the assistant director of the NSF International Drinking Water Treatment Systems Laboratory. A 20-year veteran of NSF, Herman has an M.S. in Environmental Health Science from the School of Public Health, University of Michigan. He can be reached at 1-800-NSF-MARK or email: [email protected].
EPA ETV Homeland Security Verifications of POU Treatment Systems
U. S. Environmental Protection Agency’s (EPA) National Homeland Security Research Center and Environmental Technology Verification Program (ETV) have recently completed the first phase of verification tests to evaluate point-of-use (POU) drinking water treatment units (DWTU) using reverse osmosis (RO) and carbon filtration for their ability to remove microbial and/or chemical contamination agents intentionally introduced into drinking water. NSF International (NSF), which administers the ETV Drinking Water Systems (DWS) Center, has tested three devices using the bacteria Brevundimonas diminuta and Hydrogenophaga psuedoflava, and the coliphage viruses fr, MS2, and Phi X 174. The ETV reports for the microbial agents tests have been published. Three devices have also been tested using chloroform, benzene, cadmium, cesium, mercury, strontium, and eight pesticides. The data for these chemical agents tests is currently under review. The ETV reports will be available in early 2006.
The test results show that the use of a verified system could significantly reduce the risk of exposure to harmful levels of a contaminant in the event of intentional contamination of a municipal or private water supply. The systems tested for bacteria and virus removal all reduced the number of bacteria in the challenge water by an average of more than six logs, and the number of viruses by an average of more than four logs. The systems tested for removal of chemical agents reduced most of the substances by 99% or more.