EN 16421 Effect of Materials on Water for Human Consumption - Enhancement of Microbial Growth (EMG)

EUROLAB laboratory provides testing and compliance services within the scope of EN 16421 standard. The EN 16421 standard specifies three methods for determining the ability of non-metallic materials to promote the growth of microorganisms. This European Standard is applicable to materials intended for use under various conditions for the transport and storage of water intended for human consumption.

The standard allows testing of a single material type or a product in which only one material is in contact with water. Not suitable for use in assembled products where more than one material is exposed to water. The results given by each method are not directly comparable.

Water intended for human consumption comes into contact with building products during storage, transport and distribution, including water systems inside buildings. The materials used in these products are selected on the basis of technical requirements and criteria regarding their impact on water quality, for example the release of substances and their effect on the odor, aroma or color of the water. However, water quality problems can also arise when such materials increase the growth of microorganisms.

A test method is required to determine the enhancement of microbial growth, as organic substances in non-metallic materials (as ingredients, contaminants or process by-products) can be used by microorganisms and cause visible degradation. in the organoleptic, physical or microbiological quality of the water they come into contact with. Microbial growth can occur in the water itself or at the material/water interface.

Materials that have the potential to support microbial growth do not in all cases cause a deterioration in water quality due to the influence of various environmental factors, such as the microbial quality of the water, temperature, presence of residual disinfectants or other growth limiting factors. The purpose of this standard is to describe three European test methods that can be applied to determine the ability of non-metallic materials to promote microbial growth in drinking water.

Method 1: Determines Biomass Production Potential (BPP) using changes in ATP concentrations as a proxy measure for active biomass. Developed by the Dutch, this method was further developed as part of the 2003 and 2006 CPDW project.
Method 2: It uses a volumetric measurement of the biofilm. This German method was first published as DVGW W 1984 in 270 and has been used for certification purposes for many years with specified limit values.
Method 3: It uses dissolved oxygen depletion in water as a proxy measure of microbial activity (Mean Dissolved Oxygen Difference – MDOD). First published in 1982 as BS DD82 and published as BS 6920 Part 2.4 (1988 and 2000), this British method is used for material approval with limit values.

Therefore, each method uses different performance characteristics that allow its use for certain materials or product types, but also have limitations. For example, multilayer pipes cannot currently be tested with the BPP (Method 1) and MDOD method (Method 3), and greases or lubricants cannot currently be tested with the BPP (Method 1) and Volumetric method (Method 2). ). Harmonized product standards will provide the specific methodology to be followed; this will take into account the building material and the type of components.

All three methods use natural mixtures of aquatic organisms to assess growth enhancement by the material sample. The native flora includes many strains adapted to live in a relatively hostile environment such as drinking water, and the results of tests using native flora have been shown to correlate well with growth on materials in practice. The numbers, types, and growth requirements of harmless microorganisms found in drinking water are highly variable, and there is no single cultural technique for counting all aquatic microorganisms that can be found in a water sample. Therefore, the number of microorganisms in general is assessed using simple indirect measures of their activity.

The technique for assessing advanced microbial growth is different in each of the test methods described in this European Standard. In the BPP method described in Method 1, surface and planktonic microbial growth are determined using adenosine triphosphate (ATP) as a surrogate method for active biomass determination. In the Volumetric method (DVGW) described in Method 2, the sum of both active and inactive biofilm on the surface of the test material (live and dead microorganisms as well as extracellular polymeric substances) is determined volumetrically.

Various factors can affect the predictably responsive capacity of living organisms, and therefore validation procedures are an essential part of any bioassay. In all three methods, validation is achieved through the use of reference materials.

It is important to note that none of the three methods allow conclusions to be drawn about the physical (including surface roughness), chemical or toxicological behavior of materials, or their resistance to detergents or disinfectants. In addition, none of the methods provide information on the pathogenicity of any microorganism that may be increased in numbers by nutrients leached from the test material.

The tests described in this document should only be performed in appropriately equipped laboratories and by suitably qualified individuals with the appropriate level of chemical and microbiological expertise. Standard microbiological procedures should be followed thoroughly.

EUROLAB, with its more than 25 years of experience, state-of-the-art accredited laboratories and expert team, helps you get precise and fast results. Do not hesitate to contact our laboratory for your testing and certification requests.