A look at the new EN ISO 7704:2023: Enhancing Water Testing Standards for a Safer Tomorrow

Reel Mahmoud, Global Market Development Manager – Food & Beverage 

Irene Rapti - Global Product Manager - Microbiology

Diana Pil - Global Senior Product Manager - Microbiology 

The International Organization for Standardization (ISO) has recently published the EN ISO 7704:2023 standard (ISO 7704:2023 - Water quality), a significant update that replaces the previous ISO 7704:1985 widely used in the industry and referred to in other global standards. This new standard outlines the requirements for performance testing of membrane filters used in the retention and direct enumeration of microorganisms by culture media methods.

 

These updates have created notable changes for the provision of compliant water testing solutions that should be observed by testing laboratories and manufacturers alike.

Key points of EN ISO 7704:2023

Scope: EN ISO 7704:2023 applies to all membrane filters used with culture media for tests designed to demonstrate the suitability of the entire system, including the filtration step. This comprehensive approach ensures that the membrane filter and culture medium work effectively together to provide accurate results.

 

Application: The standard is applicable to various water samples, including:

 

  • Drinking water, bottled water, and other samples with expected low numbers of microorganisms
  • Water with higher expected numbers of microorganisms, such as surface water or process water

What’s new in the standard?

Batch testing: One of the most significant updates in the updated EN ISO 7704:2023 is the requirement for batch testing of membrane filters in combination with specific selective culture media. Testing must be performed for each batch of membrane filters with each batch of different culture media, eliminating the need to evaluate membrane filters separately from the culture medium batch.

Performance criteria: The standard specifies performance testing for productivity, selectivity, and specificity, aligned with EN ISO 11133. This ensures that the membrane filters and culture media are not only effective but also meet the highest standards of reliability.

 

Procedures outlined: The steps in the procedures for batch testing of membrane filters in the new standard are:

  1. Inoculum preparation: Preparation of suspension using a working culture or certified reference material (CRM).
  2. Reference count: Conduct a reference count on a non-selective culture medium by spread plating.
  3. Testing: Assess productivity, selectivity, and specificity using membrane filters with the specific selective culture medium as given in the relevant specific standard (e.g., EN ISO 9308-1).
  4. Result determination: Determine the productivity ratio (PR) by comparing the reference count with the count from the membrane filter on the specific selective culture medium; the PR needs to reach a defined minimum limit.
  5. Batch release: Release the batch of membrane filters for use with the batch of specific culture medium.

 

Following the updated procedures outlined in EN ISO 7704:2023, requires immediate action from laboratories to ensure their membrane filtration methods are compliant but would ultimately contribute to accurate water quality testing and public health protection.

Who does it affect?

These updates are crucial for water testing microbiology laboratories to remain compliant with international standards. If laboratories are following any standard that include using membrane filtration, they will need to ensure testing and compliance with the new standard to strengthen the confidence in the overall results: 

While the impact of EN ISO 7704:2023 on these standards is more about ensuring the membrane filters are tested and used correctly within the specific testing methodologies for different microorganisms, the alignment of performance testing criteria in EN ISO 7704:2023 with those in EN ISO 11133:2014 is more significant as it highlights the importance of consistent and reliable culture media quality across different applications. This ensures that laboratories following EN ISO 11133:2014 can seamlessly integrate the new requirements of EN ISO 7704:2023.

Paving the way to compliance: A look ahead

As laboratories work to comply with the new EN ISO 7704:2023 standards and other regional and international updates, it's important to stay informed and up to date with the latest developments and best practices. In our next blog post, we will delve deeper into "How to Ensure Your Laboratory Meets ISO 7704:2023 Standards," providing practical tips and guidance on achieving compliance without compromising on efficiency or lab operations.

 

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For Research Use Only. Not for use in diagnostic procedures.