The European standard "EN 16421 Effects of materials on water intended for human consumption - Enhancement of microbial growth (EMG)" describes three methods for determining the ability of non-metallic materials to enhance the growth of microorganisms. This standard applies to materials intended for use under various conditions in the transport and storage of water intended for human consumption.
This standard allows testing of a single material type or a product where only one material is in contact with water. It is not suitable for use on assembled products where multiple materials are exposed to water. The results obtained by each method are not directly comparable.
For the purposes of this standard, the following terms and definitions apply:
This standard provides three methods for determining the ability of non-metallic materials to enhance the growth of microorganisms:
The first method describes the biomass production potential test, which determines the growth of microorganisms in the presence of a material incubated in biologically stable water for a specified period of time. Biomass production potential is a method for testing a material's ability to support microorganism growth based on the combination of two principles:
In performing the test, representative samples of the material to be tested are incubated in appropriately amended drinking water and inoculated with a mixture of naturally occurring microorganisms derived from a surface water source. The test pieces are incubated for a specified period (16 weeks) at a constant surface area-to-volume ratio of 0,16 cm-1. This ratio is maintained constant by adjusting the volume of water in the test vessels when a test piece is removed for biomass measurement. The test water is changed every 7 days. Biomass formation on the test piece and in the water is determined by measurements of adenosine triphosphate after 56, 84, and 112 days of incubation. The amount of adenosine triphosphate is used as a measure of the amount of active biomass. The biomass associated with a defined surface area of the test piece is calculated from the amounts of attached and suspended biomass. Each test is validated by the satisfactory performance of positive and negative controls under equivalent conditions.
The latter method refers to the technique of quantifying the amount of biofilm, a structured community of microorganisms attached to a surface, by measuring its physical volume. This is one of several methods used in microbiology and materials testing to assess biofilm formation, particularly on materials exposed to moist or submerged environments. This method is part of assessing material resistance to microbial growth (important for waterproofing membranes used in tunnels and underground structures where moisture and bacteria can thrive).
This method is important in the following respects:
The third method refers to microbial activity, specifically biofilm formation, which is a technique used to measure dissolved oxygen consumption over time. Dissolved oxygen is the amount of oxygen present in water. Microorganisms, including those in biofilms, consume oxygen during metabolism. Oxygen depletion indicates biological activity; the more active the biofilm, the more oxygen is used. In this method, the average decrease in dissolved oxygen over a given period (i.e., mean dissolved oxygen depletion) is used as a proxy for biofilm growth or microbial activity on a surface.
This method is non-destructive and can be used in real time or over a period of time. It provides a quantitative, indirect measure of the presence and metabolic activity of microorganisms. It is particularly useful for assessing material resistance to microbial colonization in environments where biofilms can form (e.g., tunnels, water pipelines, waterproof membranes).
This method is used in testing antimicrobial surfaces, evaluating the microbial cleanliness of construction materials, and standard test protocols.
Our organization, which has been supporting businesses across all sectors for years through a wide range of testing, measurement, analysis, and evaluation activities, has a strong team of employees who closely follow global developments in science and technology and are constantly improving themselves. In this context, we also provide testing services to businesses in accordance with the EN 16421 "Effect of materials on water intended for human consumption - Enhancement of microbial growth (EMG)" standard.
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