ISO 24261-1:2020

Overview

ISO 24261-1:2020, "Fine bubble technology - Elimination method for sample characterization - Part 1: Evaluation procedure," specifies a standardized procedure to evaluate the elimination efficiency of fine bubbles in water dispersions. Applicable only to fine bubbles without shell, the standard defines how to measure changes in particle number and volume to distinguish true fine bubbles from solid or liquid contaminants and to produce blank solutions for characterization.

Key topics and requirements

• Scope and applicability: Evaluation of elimination methods for fine bubble dispersion (FBD) in water; excludes shelled bubbles.
• Sample requirements: FBD must be generated using cleaned systems with pure water and pure gases (air, N2, O2); no stabilizing agents. For high-accuracy testing, Grade 1 water (ISO 3696) is recommended.
• Measuring instruments: Instruments must cover the relevant size range and concentration range for both fine bubbles and contaminants. Examples include particle tracking for number concentration and laser diffraction for volume concentration (see ISO/TR 23015).
• Environmental controls: Maintain air cleanliness and stable temperature/pressure. For accreditation-level measurements, ISO Class 7 clean environment (ISO 14644-1) is recommended.
• Elimination techniques: Typical methods include ultrasonication, ultracentrifugal fractionation, and freezing; the standard evaluates their effectiveness but does not prescribe a single technique.
• Evaluation metrics:
  • Number reduction rate - percentage decrease in number concentration in a specified size range (pre- vs post-elimination).
  • Volume reduction rate - percentage decrease in volume concentration in a larger size range to detect aggregation.
• Aggregation confirmation: The standard emphasizes analyzing both number and volume indices because elimination processes can cause contaminants to aggregate, reducing small-particle counts while increasing larger-particle volume.
• Procedure steps: Homogenize sample, measure pre-elimination indices, apply elimination, homogenize, measure post-elimination indices, calculate reduction rates, and interpret results (steps a–k in the standard).
• Reporting: Report reduction rates, size ranges, elimination technique, testing conditions (media, environment, instruments, personnel, location), and a reliability declaration.

Applications - who uses it

• R&D and product development teams in water treatment, aquaculture, agriculture, cleaning, and biomedical fields working with fine bubble generators.
• Instrument manufacturers and calibration/test laboratories that measure bubble size and concentration.
• Certification and accreditation bodies validating measurement methods and producing blank solutions for characterization.
• Engineers optimizing fine bubble elimination methods or comparing techniques for sample preparation.

Related standards

• ISO 20480-1 (fine bubble terminology and general measurement principles)
• ISO 3696 (water purity grades)
• ISO 14644-1 (cleanroom classifications)
• ISO/TR 23015 (measurement techniques for FBD)
• ISO 20298-1 (definitions used for dispersions)

Keywords: fine bubble technology, elimination method, evaluation procedure, sample characterization, number reduction rate, volume reduction rate, fine bubble dispersion, particle aggregation, ultrasonication.