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Standards for portable microfilters and purifiers

Standards for portable microfilters and purifiers

The greatest challenge in selecting a treatment device is evaluating the varied and sometimes outrageous claims made by manufacturers about the effectiveness of their products.

In Canada and Europe there are currently no guidelines or regulations by which to evaluate the effectiveness of water treatment devices. In the US, the EPA creates the regulations. In order to receive an EPA registration number, manufactures must meet or exceed the standards set out in the 1986 (revised 1987) EPA publication ‘Guide Standard and Protocol for Testing Microbiological Water Purifiers.’ While this manual is currently the only regulation that protects consumers, it has come under heavy criticism.

The ‘Guide Standard and Protocol’

The purpose of the ‘Guide Standard and Protocol’ is to establish microbiological challenges and testing procedures that devices must pass in order to be certified as ‘microbiological water purifiers.’ Microbiological water purifiers are devices that make water safe to drink by removing, killing or inactivating all microorganisms that cause disease.

The ‘Guide Standard and Protocol’ requires that devices be tested under specific laboratory conditions with microbiologically contaminated ‘worst case water.’ This test water is made in the lab by adding ‘challenge organisms,’ which are actual pathogens or bacteria, viruses and protozoa with the same size, toughness and general characteristics of disease causing organisms.


To receive certification, three identical units must pass specific tests over a predetermined time period. During the tests, water laced with specific challenge organisms is run through the devices. Currently the challenge organism for bacteria is the usually non-pathogenic Klebsiella terrigena. For viruses the challenge organisms are poliovirus and rotavirus. For protozoa the challenge organism is Giardia lamblia.

The quantity of each challenge organism in test water is based upon so called ‘worst-case’ water out in the environment. In order to pass, no more than ten percent of the two water samples from the three test units can fall below the removal tolerances. These tolerances are expressed as log reductions or percentages. For example, the minimum required reduction for bacteria is six logs or 99.9999% removal. This means that in one litre of water laced with 108 bacteria, only 100 living organisms are allowed to make it through the treatment device. The following chart outlines the EPA microbiological challenge for certifying microfilters and purifiers.

US EPA ‘Guide Standard and Protocol’ Microorganism Challenge
Organism Test Water Minimum reduction
to pass
Log reduction Percentage
Klebsiella terrigena 108 / litre 6 99.9999
Poliovirus type 1 107 / litre 4 99.99
Rotavirus 107 / litre 4 99.99
Giardia lamblia 106 / litre 3 99.9

Note that devices that are designed to strain out bacteria or protozoa, such as ceramic microfilters, can receive credit for passing the bacteria and protozoa challenges for which they were designed, but they are not certified as ‘purifiers’ because they do not inactivate viruses.

Non-Microbiological Parameters

The ‘Guide Standard and Protocol’ also includes ‘worst case’ parameters for non-microbiological factors including water pH, total organic carbon (TOC) such as decaying vegetation, turbidity (suspended particles), total dissolved solids (TDS) such as calcium and other naturally occurring minerals and elements and temperature.

Standards for these parameters are included because they can greatly affect how well devices work. For example, total organic carbon reduces the effectiveness of chemical treatments such as iodine which some purifiers rely on to deactivate viruses and bacteria.

Weaknesses of the ‘Guide Standard and Protocol’

While the “Guide Standard and Protocol” was designed to protect consumers and establish basic benchmarks for manufacturers, in the last decade the criteria have come under heavy criticism by some manufacturers and independent testers.

  • The ‘Guide Standard and Protocol’ does not establish standards or testing requirements for the removal of dissolved inorganic compounds and elements such as heavy metals and other potentially harmful substances. Nor does it require the removal of dissolved organics such as pesticides, herbicides, fertilizer and bacterial toxins. Currently no device that the EPA certifies as a ‘water purifier’ is required to protect the user from non-microbiological contaminants such as elements, chemicals, and heavy metals.
  • Some critics suggest that the ‘Guide Standard and Protocol’ allows devices to pass in a dubious manner. For example, ‘worst case water’ can be passed through a device several times, water is allowed to sit for 20 minutes or longer so that chemical additives from iodine cartridges can inactivate viruses and bacteria and the device can be intentionally pumped at slower than maximum rate. The danger is that a device can be certified even though it relies on the user to assess the level of microbiological contamination in the water they are treating, which is impossible. The user then has to take special measures such as passing water through the device several times, allowing sit time between pass-throughs, or slow pumping. The major problem is that devices that require special measures to pass the tests, can be certified as ‘purifiers’ along with superior devices that pass the tests without any extraordinary measures.
  • Some devices may be certified as ‘purifiers’ without having been tested because the ‘Guide Standard and Protocol’ allows for products with the same basic technology, construction, and operation as a tested unit to be passed and certified without testing.
  • Critics have suggested that non-microbiological parameters, in particular turbidity and total organic carbon, are too low and are not typical of conditions in mountain streams or low-lying bogs and fields. This is important because high turbidity and total organic carbon concentrations can significantly reduce the effectiveness of iodine, which is often used in devices certified as ‘purifiers.’ The danger is that devices may pass the EPA lab tests but then fail in field conditions where the turbidity or total organic carbon is much higher than the test parameters.
  • There is no testing requirement for halogen treatment products such as water purification tablets. Currently manufacturers are free to say anything they want about the effectiveness of their products, especially against resilient organisms such as Giardia and Cryptosporidium, without providing a shred of laboratory evidence to support their claims

Improving the ‘Guide Standard and Protocol’

Some critics of the ‘Guide Standard and Protocol’ have suggested changes that will raise the bar for manufacturers. These changes will better protect thirsty hikers standing on the edge of a stagnant pond wondering if their treatment devices are adequate.

  • Devices must pass the microbiological tests after passing water through only once, at maximum possible flow and pressure rates, and without a waiting period. These changes will ensure that users do not have the impossible task of assessing the level of microbiological contamination in the water.
  • Non-microbiological parameters, particularly turbidity and total organic carbon, should be adjusted to reflect more arduous “worst case” scenarios.
  • Devices should be tested with the exact accessories that consumers get when they buy the devices.
  • Devices that have a filter element that is worn down during cleaning, such as in ceramic filters, should be tested at the minimum filter thickness to simulate ‘worst case’ conditions.
  • Guidelines and testing criteria should be established for inorganic and organic chemicals and other non-microbiological contaminants, including heavy metals. A separate label, distinct from “microbiological water purifier,” should be created for devices that pass these tests.
  • Testing criteria should be created to test the effectiveness of stand-alone halogen treatment products. Manufacturers of these products should have to substantiate claims with lab results from standardized tests.
  • Only specific independent laboratories should be permitted to do testing, rather than labs chosen by manufacturers, and lab test results should be made public.

What this Means for You

The world of device manufacturing and testing is a maze of government regulation or non-regulation, manufacturer claims, marketing and scientific debate. In recent years, some manufactures have even threatened multi-million dollar lawsuits against other manufacturers and independent testers who have threatened to release private lab reports that show competitors’ devices failing to meet EPA standards after being certified by the EPA.

For the average traveller or trekker who just wants to purchase a reliable treatment device the situation is a unclear at best and potentially dangerous at worst. Each manufacturer markets its product as the best available with all of the expected hyperbole. Yet the problems with the ‘Guide Standard and Protocol’ indicate that manufacturer claims must be viewed with great skepticism and should not be accepted as definitive proof that a product works properly.