ISO/FDIS 24261-1

Date: 2026-06-05
ISO /TC 281
Secretariat: JISC
Date: 2026-xx
Fine bubble technology — Elimination method for sample
characterization —
—
Part 1:
Evaluation procedure
Technologie des fines bulles — Méthode d'élimination pour la caractérisation de l'échantillon — —
Partie 1: Mode opératoire d'évaluation
FDIS stage
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication
may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying,
or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO
at the address below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel.Phone: + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
Contents
Foreword . iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Requirements . 1
4.1 Sample . 1
4.2 Measuring instruments . 2
5 Environment . 2
6 Evaluation of fine bubble elimination efficiency . 2
6.1 General . 2
6.2 Reduction rate . 2
6.3 Confirmation of contaminants aggregation . 3
6.4 Evaluation procedure of fine bubble elimination . 3
7 Test report . 4
7.1 Report of the testing results. 4
7.2 Report of the testing conditions . 4
Annex A (informative) Simulations of fine bubble elimination process . 6
Annex B (informative) Decrease of concentration caused by fine bubble elimination and
aggregation . 8
Bibliography . 10

iii
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types of
ISO documents should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of any patent rights
identified during the development of the document will be in the Introduction and/or on the ISO list of patent
declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 281 Fine bubble technology.
This second edition cancels and replaces the first edition (ISO 24261-1:2020), of which it constitutes a minor
revision.
The changes are as follows:
— in 7.1, the following list item was added "f)  Number of this document";
— in Figure A.1 and Figure A.2, the unit "million/ml" was revised to "×10⁶ particles/ml".
A list of all parts in the ISO 24261 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv
Introduction
Fine bubble technology has recently seen growth in its application to markets in cleaning, water treatment,
agriculture, and aquaculture as well as biomedical fields. Now, methods are required to evaluate the
generation systems. Especially characteristics like the number concentration index and the size index of fine
bubbles are indispensable for those evaluations.
Furthermore, fine bubble dispersion water may contain other solid and liquid particles. Clearly due to this is
a concern, as it may be impossible to evaluate the characteristics of fine bubbles. Therefore, it is an urgent task
to address this concern.
There are several measurement methods widely used to evaluate the number concentration index and the
size index of particles. However, there are few methods to distinguish bubbles in fine bubble dispersions from
other particles.
This issue can be resolved, using the phenomenon by which the bubbles can be eliminated without any
residues after dissolution and flotation. If a method that eliminates fine bubbles in specific size range is known,
it is possible to distinguish fine bubbles from other solid and liquid particles. The eliminated particles can be
fine bubbles. If most of fine bubbles decreased, a solution that doesn’t have them can be used as a blank
solution for measurements as background. Because it is expected that fine bubbles elimination techniques will
develop further, standardizing elimination techniques and evaluation method is required.
This document is intended to specify the evaluation method for elimination efficiency of fine bubbles from fine
bubble dispersions in water.
Standardization for evaluating elimination efficiency of fine bubbles enables easy and clear comparison among
the several elimination techniques and realizes the optimization of conditions for respective elimination
techniques.
v
Fine bubble technology — Elimination method for sample
characterization — —
Part 1:
Evaluation procedure
1 Scope
This document specifies the evaluation procedure of fine bubble elimination for fine bubble dispersion in
water. This document is applicable only to fine bubbles without shell.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 20480--1, Fine bubble technology — General principles for usage and measurement of fine bubbles — Part
1: Terminology
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 20480-1 and the following apply.
ISO and IEC maintain terminologicalterminology databases for use in standardization at the following
addresses:
— — ISO Online browsing platform: available at https://www.iso.org/obp
— — IEC Electropedia: available at https://www.electropedia.org/
3.1 3.1
elimination of fine bubbles
process for the decrease of the concentration index of fine bubbles
3.2 3.2
fine bubble dispersion
FBD
liquid which contains fine bubbles
[SOURCE: ISO 20298-1:2018, 3.1]
4 Requirements
4.1 Sample
The fine bubble dispersion to be evaluated shall be generated by cleaned fine bubble generating systems using
pure water and pure gas such as air, nitrogen and oxygen.
The purity level of water and gas depends on the sample whose size and concentration indices of fine bubbles
should be evaluated because fine bubble elimination is one of the evaluating process for specified samples. So,
the purity level cannot be generally determined as measurement condition for evaluations of the elimination
efficiency.
The fine bubble dispersion shall not contain stabilizing agents.
If the measurement accuracy of size and concentration indices is very important (e.g. for accreditation
purposes), a water purity level of Grade 1 according to ISO 3696 is recommended for the water used for
generation of FBD.
4.2 Measuring instruments
When the measuring instruments are selected for evaluating fine bubble elimination for FBD in water the
following parameters about concentration and size range shall be confirmed, which depends on the
characteristics of the sample to be evaluated.:
a) a) Total number concentration and/or total volume concentration including fine bubbles and
contaminants such as solid particles and liquid particles can be measured. Water diluent can be used for
diluting the FBD in water when the concentration is over the measuring range.
b) b) Total size range including fine bubbles, contaminants and aggregates of contaminants can be
measured. Another measuring instrument can be used to confirm the larger aggregates.
EXAMPLE Particle tracking analysis method can be used for evaluation of number concentration, and laser
diffraction method can be used for evaluation of volume concentration. ISO/TR 23015 can be referred to for details of
measurement techniques which can be used for FBD in water.
5 Environment
The classification of air cleanliness should be applied for the measurements to prevent any contamination by
impurities. Ambient temperature and atmospheric pressure should be stable to keep the stability of ultrafine
bubbles.
Air cleanliness, ambient temperature and atmospheric pressure depend on the environment to evaluating size
and concentration indices of specified samples because fine bubble elimination is one of the evaluating process
for specified samples. Therefore, the environment can
...