ISO 20480-2:2018

INTERNATIONAL ISO
STANDARD 20480-2
First edition
2018-11
Fine bubble technology — General
principles for usage and measurement
of fine bubbles —
Part 2:
Categorization of the attributes of
fine bubbles
Technologie des fines bulles — Principes généraux pour l'utilisation et
la mesure des fines bulles —
Partie 2: Classification des attributs des fines bulles
Reference number
©
ISO 2018
© ISO 2018
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
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2018 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 General principles for usage and measurement of fine bubbles . 1
4.1 Standards system of fine bubble technology . 1
4.2 Quality of liquid medium. 2
5 Expression of attributes for fine bubbles . 2
5.1 Application of size index and number concentration index . 2
5.1.1 General. 2
5.1.2 Size index rules . 3
5.1.3 Number concentration principles . 3
5.1.4 Number concentration index rules . 3
5.2 Expression of class of fine bubbles in dimensional characteristics . 3
6 Classification of the attributes of fine bubbles by rise velocity . 4
6.1 Attributes of fine bubbles by rise velocity . 4
6.2 Classification of fine bubbles by rise velocity. 5
6.2.1 General. 5
6.2.2 Classification and definition of regions . 6
Annex A (informative) Observation examples of ultrafine bubble number stability in liquids .8
Bibliography .10
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.
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 © ISO 2018 – All rights reserved

Introduction
In recent years, readily available measurement techniques of bubbles have made it possible to
characterize microbubbles and ultrafine bubbles. Such techniques have shown that ultrafine bubbles
can almost remain as they are for a number of months.
Fine bubble technologies are very new, and their applications are useful in a number of fields today.
Developing appropriate terminology for such a diverse area of technology is therefore critical to
business trade or product acceptance, in view of the wide range of users of fine bubbles.
For better communication among the users of fine bubbles, this document introduces the quality criteria
of a medium such as water, as well as two indices, one for size and the other for number concentration.
This document also provides an explanation for classifying fine bubbles by dimensional characteristics
and by rise velocity.
It should be noted that the motion of bubbles in a medium can be determined by buoyancy forces
or randomly and thermally activated processes leading to Brownian motion. For this reason, larger
bubbles can display buoyant behaviour (rise upwards) and smaller bubbles remain in the liquid medium
displaying random motion. This document focuses on the definitions of such entities.
INTERNATIONAL STANDARD ISO 20480-2:2018(E)
Fine bubble technology — General principles for usage and
measurement of fine bubbles —
Part 2:
Categorization of the attributes of fine bubbles
1 Scope
This document establishes the general principles and descriptors to allow users to describe the quality
of the liquid media and the size and concentration of fine bubbles. It is also intended to allow users to
classify fine bubbles by rise velocity.
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 http: //www .electropedia .org/
3.1
rise velocity
velocity of a fine bubble upwards in liquid
3.2
terminal rise velocity
balancing velocity between the buoyancy of fine bubbles and the viscous drag
Note 1 to entry: It is the velocity in the opposite direction to the terminal settling velocity. If a rise velocity were
to be defined as the terminal settling velocity, the rise velocity would be negative. Therefore, in the classification
of fine bubbles, terminal rise velocity is preferred over terminal settling velocity to avoid confusion.
4 General principles for usage and measurement of fine bubbles
4.1 Standards system of fine bubble technology
The purpose of this document is to provide people who develop standards for fine bubble technology
with an overall framework and guidelines, and to facilitate communication among users of fine
bubbles. To assist in the preparation of consistent standards, a three-layered standard system has been
established.
This consists of the following.
a) The first layer (basic standards) covers common terminology, basic concepts, and principles for
measurement and usage that can be applied to fine bubble technology. This document is part of the
basic standards, and is intended to be used as a basis for the next two layers.
b) The second layer (measurement standards) covers various measurement methodologies for
characterization, such as bubble diameter and number concentration index, as well as common
methods for sampling and sample preparation.
c) The third layer (individual application standards) covers individual applications in areas
including:
1) food, plant cultivation, agriculture, drinking water, and cosmetics industries;
2) the medical and pharmaceutical fields;
3) manufacturing of new functional materials, solar cells, semiconductors, and liquid crystals;
4) processes such as cleaning, toilet flushing, soil washing, water treatment, etc.
4.2 Quality of liquid medium
The performance of the liquid medium with fine bubbles is strongly dependent on its pH value and the
inorganic and organic substances contained therein. Therefore, the important properties of the liquid
medium should be measured and clarified. This includes properties such as electrical conductivity,
total organic carbon concentration, concentration of silica, sodium, oxygen component of oxidizable
substance, evaporation residue heated at 100 °C in the case of fresh water and pH, optical absorbance
at 25 °C for wavelength 254 nm and path length 1 cm and evaporation residue after heating at 110 °C
in the case of fresh water. Typical examples of standards for the quality of fresh water are ISO 3696,
[3]
ASTM D1193 and CODEX STAN 108 .
5 Expression of attributes for fine bubbles
5.1 Application of size index and number concentration index
5.1.1 General
The terms “size index” and “number concentration index” are intended to benefit those who are
exclusively engaged in the application of fine bubble technology.
A bubble is a closed interface between gas and liquid. An ideal size measurement would distinguish a
bubble from solid particles or liquid droplets (such as oil), which may also be present in the medium.
The measurement would be able to size each material separately.
Most currently available measurement methods that use optical scattering or acoustic characteristics
cannot differentiate one type of phase from another, and will characterize them as an ensemble (even
if the particle types are different). Although the reported values for size and concentration may not
be entirely due to bubbles, in most cases they are accurate enough for users in their work. The terms
“size index” and “number concentration index” should be used in preference to size and number
concentration to better reflect the uncertainties involved.
2 © ISO 2018 – All rights reserved

5.1.2 Size index rules
The following rules apply to the use of the term “size index”.
a) The size index shall be accompanied with a description of the relevant measurement method and
applicable field for relevant fine bubbles.
1) The “measurement method” in practice includes an industrially available and agreed method.
2) The “applicable field” in practice includes a description of the application specific functional
components other than fine bubbles.
3) Example: “size index measured by the particle tracking analysis (PTA) method on untreated
raw water for aquafarming technology”.
NOTE For more information on particle tracking analysis (
...