ISO/FDIS 20018-1
(Main)Fine bubble technology — Characterization of ultrafine bubbles — Part 1: Data correction to exclude particulate contaminants for evaluating size and concentration indices
- Abstract
This document specifies the evaluation method for size and concentration indices of ultrafine bubbles including the data correction to exclude particulate contaminants using the blank water.It is only applicable to ultrafine bubble dispersion (UFBD) in water.
- Status
- Not Published
- Technical Committee
- ISO/TC 281 - Fine bubble technology
- Drafting Committee
- ISO/TC 281 - Fine bubble technology
- Current Stage
- 5020 - FDIS ballot initiated: 2 months. Proof sent to secretariat
- Start Date
- 02-Sep-2026
- Completion Date
- 02-Sep-2026
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ISO/FDIS 20018-1 - Fine bubble technology — Characterization of ultrafine bubbles — Part 1: Data correction to exclude particulate contaminants for evaluating size and concentration indices
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ISO/FDIS 20018-1 is an ISO document for fine bubble technology that specifies how to evaluate size and concentration indices of ultrafine bubbles in water. It also sets out data correction using blank water to reduce the influence of particulate contaminants, so the reported results better reflect the ultrafine bubble dispersion (UFBD) being measured.
What does ISO/FDIS 20018-1 specify?
ISO/FDIS 20018-1 specifies an evaluation method for size and concentration indices of ultrafine bubbles in water, including the preparation and use of blank water for contaminant correction. It applies only to UFBD in water.
The document is organized into seven clauses and two informative annexes:
| Part of the document | What it covers |
|---|---|
| Clause 1 | Scope |
| Clause 2 | Normative references |
| Clause 3 | Terms and definitions |
| Clause 4 | Requirements for sample, measuring instruments and environment |
| Clause 5 | Data correction to exclude contaminants |
| Clause 6 | Evaluation of size and concentration indices |
| Clause 7 | Test report |
| Annex A | Example of correction on the stage of signal acquisition for ensemble methods |
| Annex B | Example of correction on the stage of calculating total concentration for counting methods |
In practice, this structure takes the reader from sample preparation through correction and evaluation, then to reporting. That makes it useful both for routine measurement and for comparing results between laboratories or products.
What are the key requirements of ISO/FDIS 20018-1?
ISO/FDIS 20018-1 focuses on controlling contamination, choosing a suitable measurement approach, and correcting the data before size and concentration indices are reported. The main point is that the measured UFBD signal is not taken at face value if particulate contaminants can distort it.
Sample, instruments and environment
Clause 4.1 requires UFBD in water to be generated with clean test systems, clean water and clean gas such as clean air, nitrogen or oxygen. If measurement accuracy is especially important, the document points to ISO Grade 1 water and ISO Class 5 air as preferred conditions. In practice, this means the generation step itself must be controlled, not only the measurement step.
Clause 4.2 says several techniques can be used, including particle tracking analysis and laser diffraction, but the sample concentration must remain within the measuring range of the chosen instrument. This matters because the sample has to fit the instrument’s operating window or the results will not be reliable.
Clause 4.3 requires air cleanliness to be considered, and ambient temperature and atmospheric pressure to be stable and recorded before evaluation. If accuracy is especially important, ISO Class 7 air is recommended for the generation and measurement environment. In practice, the lab conditions become part of the measurement record.
Blank water and contaminant correction
Clause 5.1 explains the basic correction concept: blank water is used as the baseline so particulate contaminants can be separated from the UFBD signal. The blank water should contain contaminants equivalent to those in the UFBD being evaluated, while suppressing ultrafine bubbles as much as possible. This is the core mechanism that makes the later correction meaningful.
Clause 5.2 gives several ways to prepare blank water. For a generating system, Method A turns off the ultrafine bubble generating function, while Method B takes the blank water just before the component that generates ultrafine bubbles. For a generating device, the device such as a nozzle or showerhead is removed, and it should be thoroughly cleaned first. If raw water cannot be obtained, blank water may be prepared by eliminating UFB from UFBD in water in line with ISO 24261-1 and ISO 24261-2, but this method cannot be used for UFBs with shell. If none of these works, raw water may be used, with the test system cleaned thoroughly.
Clause 5.3 requires a comparative measurement to confirm whether the blank water is suitable. The number concentration of particulate contaminants in the blank water should be less than 50 % of the number concentration of the UFBD including contaminants. In practice, this is a check that the blank water is clean enough to support a useful correction.
Correction methods and how to use them
Clause 5.4 covers correction on the stage of signal acquisition for ensemble methods. The blank-water signal is used as the baseline, and the signal intensities are subtracted point by point before calculating particle size distribution. The document notes that laser diffraction can use this approach. This is useful when the method produces a signal that can be corrected before the size calculation.
Clause 5.5 covers correction on the stage of calculating total concentration for counting methods. The corrected total number concentration is obtained by subtracting the blank-water total number concentration from the UFBD measurement. This is the direct route for methods that count particles or bubbles.
Evaluating the final indices
Clause 6.1 says corrected size data are used to derive a representative size index such as mean diameter, modal diameter or median diameter. If subtraction produces negative values in some size ranges, they are treated as zero. The clause also notes that modal diameter can be unstable in some distributions, so mean diameter is often more stable in practice.
Clause 6.2 says corrected concentration data are used to derive a representative concentration index. When the stage-of-signal-acquisition correction cannot be used, the particle size distribution should be corrected with blank-water data before calculating the concentration index for a specified bubble size range. This keeps the concentration result tied to the corrected distribution rather than the contaminated one.
What terms does ISO/FDIS 20018-1 define?
blank water - Water used for data correction and for collecting size and concentration indices, with contaminants equivalent to the UFBD being evaluated and with ultrafine bubble generation suppressed as much as possible.
ultrafine bubble dispersion (UFBD) in water - The water-based sample medium being evaluated, containing ultrafine bubbles and particulate contaminants.
ultrafine bubbles (UFBs) - The bubbles whose size and concentration indices are being characterized in this document.
size index - A representative size value derived from measured and corrected size data, such as mean diameter, modal diameter or median diameter.
concentration index - A representative concentration value derived from measured and corrected concentration data, including total concentration or concentration in a specified bubble size range.
ensemble methods - Measurement methods where the acquired signal is corrected against the blank-water baseline before the size distribution is calculated.
counting methods - Measurement methods that determine concentration by counting particles or bubbles and then correct the total concentration using blank-water data.
Who uses ISO/FDIS 20018-1?
ISO/FDIS 20018-1 is used by laboratories, manufacturers and technical teams that measure or compare UFBD performance. It is relevant to people working on fine bubble systems used in cleaning, water treatment, agriculture, aquaculture and biomedical fields.
In practice, this document helps:
- test and compare ultrafine bubble generating systems and devices
- prepare blank water for contamination correction
- choose between ensemble and counting methods
- document size and concentration indices for reports, audits or accreditation-related work
- support quality control where contaminants can distort the measured bubble distribution
Which standards are used with ISO/FDIS 20018-1?
ISO/FDIS 20018-1 relies on ISO 20480-1 for the shared terminology of fine bubble technology. It also cites ISO 24261-1 and ISO 24261-2 for eliminating ultrafine bubbles when blank water is prepared from UFBD in water.
The document also points to other standards for supporting tasks:
- ISO 3696 for water purity guidance in Clause 4
- ISO 14644-1 for air cleanliness guidance in Clause 4
- ISO 20298-1 for sampling and sample preparation in the test report
- ISO 13320 and ISO 19430 as examples of standards for specific measurement techniques
What does the ISO/FDIS 20018-1 document contain?
The document contains figures that explain the correction workflow, including the basic blank-water concept, blank-water preparation for systems and devices, and the two correction routes for ensemble and counting methods. It also shows how corrected size data are turned into representative size indices and how corrected concentration data are used for concentration indices.
Annex A gives a worked example of signal-acquisition correction for laser diffraction data. Annex B gives a worked example of total-concentration correction for particle tracking analysis, and it includes a table comparing blank-water, pre-correction and post-correction results.
The test report clause lists the information to record, including the reference to the standard, the generating system or device, the water and gas used, the measuring instrument, software version, the size distribution, the derived indices, the operator and laboratory, and the date and time of the test.
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ISO/FDIS 20018-1 - Fine bubble technology — Characterization of ultrafine bubbles — Part 1: Data correction to exclude particulate contaminants for evaluating size and concentration indices
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Frequently Asked Questions
ISO/FDIS 20018-1 is a draft published by the International Organization for Standardization (ISO). Its full title is "Fine bubble technology — Characterization of ultrafine bubbles — Part 1: Data correction to exclude particulate contaminants for evaluating size and concentration indices". This standard covers: This document specifies the evaluation method for size and concentration indices of ultrafine bubbles including the data correction to exclude particulate contaminants using the blank water.It is only applicable to ultrafine bubble dispersion (UFBD) in water.
This document specifies the evaluation method for size and concentration indices of ultrafine bubbles including the data correction to exclude particulate contaminants using the blank water.It is only applicable to ultrafine bubble dispersion (UFBD) in water.
ISO/FDIS 20018-1 is classified under the following ICS (International Classification for Standards) categories: 07.030 - Physics. Chemistry. The ICS classification helps identify the subject area and facilitates finding related standards.
ISO/FDIS 20018-1 is available in PDF format for immediate download after purchase. The document can be added to your cart and obtained through the secure checkout process. Digital delivery ensures instant access to the complete standard document.
Standards Content (Sample)
FINAL DRAFT
International
Standard
ISO/TC 281
Fine bubble technology —
Secretariat: JISC
Characterization of ultrafine
Voting begins on:
bubbles —
2026-09-02
Part 1:
Voting terminates on:
2026-10-28
Data correction to exclude
particulate contaminants for
evaluating size and concentration
indices
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
Reference number
FINAL DRAFT
International
Standard
ISO/TC 281
Fine bubble technology —
Secretariat: JISC
Characterization of ultrafine
Voting begins on:
bubbles —
Part 1:
Voting terminates on:
Data correction to exclude
particulate contaminants for
evaluating size and concentration
indices
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
© ISO 2026
IN ADDITION TO THEIR EVALUATION AS
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
or ISO’s member body in the country of the requester.
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland Reference number
ii
Contents Page
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
4.3 Environment .2
5 Data correction to exclude contaminants . 3
5.1 General .3
5.2 Preparation of blank water .3
5.2.1 For the ultrafine bubble generating system .3
5.2.2 For the ultrafine bubble generating device .4
5.2.3 Elimination of ultrafine bubbles from the UFBD in water .5
5.2.4 Raw water.6
5.3 Comparative measurement confirming suitability of blank water .6
5.4 Correction on the stage of signal acquisition for ensemble methods .6
5.5 Correction on the stage of calculating total concentration for counting methods .8
6 Evaluation of size and concentration indices . 8
6.1 Analysis of measured and corrected size data to derive (representative) size index .8
6.2 Analysis of measured and corrected concentration data to derive (representative)
concentration index .10
7 Test report .10
Annex A (informative) Example of correction on the stage of signal acquisition for ensemble
methods .12
Annex B (informative) Example of correction on the stage of calculating total concentration for
counting methods .15
Bibliography . 17
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 document 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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
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.
A list of all parts in the ISO 20480 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 seen growth in its application to markets such as cleaning, water treatment,
agriculture, aquaculture and biomedical fields. Now the methods to evaluate the characteristics of fine
bubbles such as the size and concentration indices have become necessary to clarify the performances of
fine bubble generating systems used for various applications.
Since the ultrafine bubble dispersion (UFBD) usually contains contaminants, however, it is difficult to
extract the data for the size and concentration of ultrafine bubbles from the UFBD.
Therefore, on the premise that the UFBD contains contaminants, the measurement results are commonly
called size and concentration indices. To minimize the influence of contamination on the measurement
results of UFBD, the data correction using of blank water is promising.
v
FINAL DRAFT International Standard ISO/FDIS 20018-1:2026(en)
Fine bubble technology — Characterization of ultrafine
bubbles —
Part 1:
Data correction to exclude particulate contaminants for
evaluating size and concentration indices
1 Scope
This document specifies the evaluation method for size and concentration indices of ultrafine bubbles
(UFBs) in water including the data correction to exclude the influence of particulate contaminants using
blank water. Furthermore, the procedure to prepare the blank water is also described in this document.
This document is only applicable to ultrafine bubble dispersion (UFBD) in water.
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 terminological 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
blank water
water used for data collection of size and concentration indices, which contain the contaminants equivalent
to the ultrafine bubble dispersion (UFBD) in water to be evaluated, and the generation of ultrafine bubbles
is suppressed as much as possible
4 Requirements
4.1 Sample
To reduce the influence of particulate contaminants and to keep the accuracy of measurement, UFBD in
water shall be generated using clean test systems with clean water and clean gas such as clean air, nitrogen
or oxygen.
If the measurement accuracy of size and concentration indices is very important (for example, in the
case of application to the accreditation of fine bubble business), the water purity level of ISO Grade 1 (see
ISO 3696:1987) and the air cleanliness of ISO Class 5 (see ISO 14644-1:2015) should be used for the water
and the air used to generate the UFBD.
4.2 Measuring instruments
Several measurement techniques such as particle tracking analysis method, laser diffraction method and
others can be used to evaluate the size and concentration indices for ultrafine bubbles in the UFBD in water.
The measuring range of concentration is very dependent on respective measurement instruments. In order
to keep the accuracy of measurement results, the concentration of the sample including the ultrafine bubbles
and contaminants shall sufficiently be within the measuring range of concentration.
4.3 Environment
Air cleanliness should be considered for the measurement to prevent mingling of impurities. Ambient
temperature and atmospheric pressure should be stable to maintain the stability of characteristics of
ultrafine bubbles in water.
Air cleanliness, ambient temperature and atmospheric pressure depend on the local environment and can
vary. However, as they are important settings and can influence the evaluation process, they should be
recorded prior to any evaluation occurring.
If the measurement accuracy of size and concentration indices is very important, (for example, in the
case of application to the accreditation of fine bubble
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ISO /TC 281/WG2
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Secretariat: JISC
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Date: 2026-05-1808-19
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Fine bubble technology —
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Characterization of ultrafine bubbles—
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Part 1:
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Data correction to exclude particulate contaminants for evaluating
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size and concentration indices
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St l D fi iti
ISO/CDFDIS 20018-1:2026(en)
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All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication
Adjust space between Asian text and numbers
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
Formatted: Left: 1.5 cm, Right: 1.5 cm, Top: 1.4 cm,
at the address below or ISO’s member body in the country of the requester.
Bottom: 1 cm
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: + 41 22 749 01 11
Formatted: English (United Kingdom)
Fax: + 41 22 749 09 47
E-mail: copyright@iso.org
Formatted: English (United Kingdom)
Website: www.iso.org
Formatted: zzCopyright address, Adjust space between
Latin and Asian text, Adjust space between Asian text
Published in Switzerland
and numbers
Formatted: FooterCentered, Left
ii
ii
ISO/DISFDIS 20018-1:20252026(en)
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Contents
Formatted: HeaderCentered, Left, Space After: 0 pt,
Foreword . iv
Line spacing: single, Tab stops: Not at 0.71 cm
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
4.3 Environment . 2
5 Data correction to exclude contaminants . 2
5.1 General . 2
5.2 Preparation of blank water . 3
5.2.1 For the ultrafine bubble generating system . 3
5.2.2 For the ultrafine bubble generating device . 3
5.2.3 Elimination of ultrafine bubbles from the UFBD in water . 4
5.2.4 Raw water . 5
5.3 Comparative measurement confirming suitability of blank water . 5
5.4 Correction on the stage of signal acquisition for ensemble methods . 5
5.5 Correction on the stage of calculating total concentration for counting methods . 7
6 Evaluation of size and concentration indices . 7
6.1 Analysis of measured and corrected size data to derive (representative) size index . 7
6.2 Analysis of measured and corrected concentration data to derive (representative)
concentration index . 9
7 Test report . 9
Annex A (informative) Example of correction on the stage of signal acquisition for ensemble
methods . 11
Annex B (informative) Example of correction on the stage of calculating total concentration for
counting methods . 14
Bibliography . 17
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iii
ISO/CDFDIS 20018-1:2026(en)
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iv
iv
ISO/DISFDIS 20018-1:20252026(en)
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Contents
Formatted: HeaderCentered, Left, Space After: 0 pt,
Line spacing: single, Tab stops: Not at 0.71 cm
Foreword . vi
Introduction . vii
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Requirements . 2
4.1 Sample . 2
4.2 Measuring instruments . 2
4.3 Environment . 2
5 Data correction to exclude contaminants . 3
5.1 General . 3
5.2 Preparation of blank water . 4
5.3 Comparative measurement confirming suitability of blank water . 9
5.4 Correction on the stage of signal acquisition for ensemble methods . 9
5.5 Correction on the stage of calculating total concentration for counting methods . 11
6 Evaluation of size and concentration indices . 12
6.1 Analysis of measured and corrected size data to derive (representative) size index . 12
6.2 Analysis of measured and corrected concentration data to derive (representative)
concentration index . 14
7 Test report . 15
Annex A (informative) Example of correction on the stage of signal acquisition for ensemble
methods . 16
Annex B (informative) Example of correction on the stage of calculating total concentration for
counting methods . 20
Bibliography . 24
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v
ISO/CDFDIS 20018-1:2026(en)
Formatted: HeaderCentered
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 document 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).
Formatted: English (United Kingdom)
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent rights
in respect thereof. As of the date of publication of this document, ISO had not received notice of (a) patent(s)
which may be required to implement this document. However, implementers are cautioned that this may not
represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents.www.iso.org/patents. ISO shall not be held responsible for identifying any or all such
patent rights.
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.htmlwww.iso.org/iso/foreword.html.
Formatted: English (United Kingdom)
This document was prepared by Technical Committee ISO/TC 281 Fine bubble technology.
Formatted: Adjust space between Latin and Asian text,
Adjust space between Asian text and numbers
A list of all parts in the ISO 20480 series can be found on the ISO website.
Formatted: Default Paragraph Font
Formatted: Default Paragraph Font
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.
Formatted: Default Paragraph Font
Formatted: FooterCentered, Left
vi
vi
ISO/DISFDIS 20018-1:20252026(en)
Formatted: Font: 11 pt
Formatted: Font: 11 pt
Formatted: Font: 11 pt
Introduction
Formatted: HeaderCentered, Left, Space After: 0 pt,
Line spacing: single, Tab stops: Not at 0.71 cm
Fine bubble technology has seen growth in its application to markets such as cleaning, water treatment,
agriculture, aquaculture and biomedical fields. Now the methods to evaluate the characteristics of fine bubbles
such as the size and concentration indices have become necessary to clarify the performances of fine bubble
generating systems used for various applications.
Since the ultrafine bubble dispersion (UFBD) usually contains contaminants, however, it is difficult to extract
the data for the size and concentration of ultrafine bubbles from the UFBD.
Therefore, on the premise that the UFBD contains contaminants, the measurement results are commonly
called size and concentration indices. To minimize the influence of contamination on the measurement results
of UFBD, the data correction using of blank water is promising.
Formatted: Font: 10 pt
Formatted: Font: 10 pt
Formatted: FooterCentered, Left, Space Before: 0 pt,
Tab stops: Not at 17.2 cm
Formatted: Font: 11 pt
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After: 0 pt, Tab stops: Not at 17.2 cm
vii
DRAFT International Standard ISO/DIS 20018-1:2025(en)
Fine bubble technology —
Characterization of ultrafine bubbles—
—
Formatted: Main Title 2, None, Adjust space between
Part 1:
Latin and Asian text, Adjust space between Asian text
Data correction to exclude particulate contaminants for evaluating
and numbers
size and concentration indices Formatted: Left: 1.5 cm, Right: 1.5 cm, Top: 1.4 cm,
Bottom: 1 cm
1 Scope
Formatted: Adjust space between Latin and Asian text,
Adjust space between Asian text and numbers
This document specifies the evaluation method for size and concentration indices of ultrafine bubbles (UFBs)
in water including the data correction to exclude the influence of particulate contaminants using blank water.
Furthermore, the procedure to prepare the blank water is also described in this document.
This document is only applicable to ultrafine bubble dispersion (UFBD) in water.
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.
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ISO 20480--1, Fine bubble technology — General principles for usage and measurement of fine bubbles —
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Part 1: Terminology
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ISO 24261-1:2020, Fine bubble technology — Elimination method for sample characterization — Part 1:
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Evaluation procedure
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ISO 24261-2:2021, Fine bubble technology — Elimination method for sample characterization — Part 2: Fine
stops: Not at 0.7 cm + 1.4 cm + 2.1 cm + 2.8 cm +
bubble elimination techniques
3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
3 Terms and definitions Formatted: Adjust space between Latin and Asian text,
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For the purposes of this document, the terms and definitions given in ISO 20480-1 and the following apply.
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ISO and IEC maintain terminological databases for use in standardization at the following addresses:
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— — ISO Online browsing platform: available at https://www.iso.org/obphttps://www.iso.org/obp
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— — IEC Electropedia: available at https://www.electropedia.org/https://www.electropedia.org/
stops: Not at 0.7 cm + 1.4 cm + 2.1 cm + 2.8 cm +
3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
3.1 3.1
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blank water
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water used for data correctioncollection of size and concentration indices, which contain the contaminants
numbers
equivalent to the ultrafine bubble dispersion (UFBD) in water to be evaluated, and the generation of ultrafine
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bubbles is suppressed as much as possible
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spacing: single, Tab stops: Not at 17.2 cm
ISO/CDFDIS 20018-1:2026(en)
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4 Requirements
4.1 Sample
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To reduce the influence of particulate contaminants and to keep the accuracy of measurement, UFBD in water
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shall be generated using clean test systems with clean water and clean gas such as clean air, nitrogen or
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oxygen.
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If the measurement accuracy of size and concentration indices is very important (for example, in the case of
application to the accreditation of fine bubble business), the water purity level of ISO Grade 1 (see ISO
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3696:1987) and the air cleanliness of ISO Class 5 (see ISO 14644-1:2015) are recommendedshould be used
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for the water and the air used to generate the UFBD.
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4.2 Measuring instruments
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Several measurement techniques such as particle tracking analysis method, laser diffraction method and
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others can be used to evaluate the size and concentration indices for ultrafine bubbles in the UFBD in water.
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The measuring range of concentration is very dependent on respective measurement instruments. In order to Formatted: Adjust space between Latin and Asian text,
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keep the accuracy of measurement results, the concentration of the sample including the ultrafine bubbles
and contaminants shall sufficiently be within the measuring range of concentration.
4.3 Environment
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Air cleanliness should be considered for the measurement to prevent mingling of impurities. Ambient
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temperature and atmospheric pressure should be stable to maintain the stability of characteristics of ultrafine
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bubbles in water.
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Air cleanliness, ambient temperature and atmospheric pressure depend on the local environment and can
vary. However, as they are important settings and can influence the evaluation process, they should be
recorded prior to any evaluation occurring.
If the measurement accuracy of size and concentration indices is very important, (for example, in the case of
application to the accreditation of fine bubble business), the air cleanliness of ISO Class 7 (see ISO 14644-
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1:2015) is recommendedshould be used as the environment for generation and measurement of the UFBD in
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water.
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ISO/DISFDIS 20018-1:20252026(en)
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5 Data correction to exclude contaminants
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5.1 General
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Key
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1 raw water
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2 UFBD in water stops: Not at 0.7 cm + 1.4 cm + 2.1 cm + 2.8 cm +
3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
3 blank water
4 corrected data of the UFBD in water
5 generation of UFB
6 taking the blabk water
7 data correction
8 UFB (ultrafine bubble)
9 contaminant (solid/liquid particle)
1 raw water
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2 UFBD in water
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3 blank water
4 corrected data of the UFBD in water Formatted: FooterCentered, Left, Space Before: 0 pt,
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5 generation of UFB
6 taking the blabk water
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ISO/CDFDIS 20018-1:2026(en)
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7 data correction
UFB (ultrafine bubble)
contaminant (solid/liquid particle)
Figure 1 — Data correction to exclude contaminants
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Asian text, Adjust space between Asian text and
numbers
Figure 1Figure 1 shows the basic concept of the data correction to exclude the influence of particulate
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contaminants using blank water.
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Appropriate blank water shall be prepared to perform size and concentration correction for UFBD using blank
water. The contaminants contained in blank water should be equivalent to the contaminants contained in
UFBD in water, and it is necessary toshall suppress the existence of ultrafine bubbles as much as
possible.Clause 5.2 Clause 5.2 describes how to prepare the blank water.
5.2 Preparation of blank water
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5.2.1 For the ultrafine bubble generating system
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For the general ultrafine bubble generating systems, there are two possible methods, method A and method
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B, to prepare the blank water as shown in Figure 2.Figure 2. Method A is the best way but its possibility
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strongly depends on the specification of each ultrafine bubble generating system.
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— — Method A: Turn off the ultrafine bubble generating function and take the blank water.
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— — Method B: Take the blank water just before the component which generates ultrafine bubbles.
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numbers, Tab stops: Not at 0.7 cm + 1.4 cm + 2.1 cm
+ 2.8 cm + 3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3
cm + 7 cm
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Key
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1 raw water stops: Not at 0.7 cm + 1.4 cm + 2.1 cm + 2.8 cm +
3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
2 UFB generating system
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ISO/DISFDIS 20018-1:20252026(en)
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3 UFB generating function
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a
Turn off the UFB generating function and take the blank water.
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b
Take the blank water just before the component which generate UFBs.
1 raw water
2 UFB generating system
3 UFB generating function
a
Turn off the UFB generating function and take the blank water.
b
Take the blank water just before the component which generate UFBs.
Figure 2 — Preparation of blank water for the ultrafine bubble generating system
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Asian text, Adjust space between Asian text and
numbers
5.2.2 For the ultrafine bubble generating device
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The preparation of blank water for the ultrafine bubble generating device is very simple. It involves only the
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removal of the ultrafine bubble generating device such as the nozzle and the showerhead device from the test stops: Not at 0.71 cm + 0.99 cm + 1.27 cm
system to evaluate the size and concentration indices of UFBD as shown in Figure 3.Figure 3.
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It is very important that the device should be thoroughly cleaned before the test to prevent the generation of
contaminants from the inside of ultrafine bubble generating device.
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ISO/CDFDIS 20018-1:2026(en)
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ISO/DISFDIS 20018-1:20252026(en)
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Key
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1 raw water storage tank
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2 pump stops: Not at 0.7 cm + 1.4 cm + 2.1 cm + 2.8 cm +
3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3 c
...