ISO 7383-1:2024

International
Standard
ISO 7383-1
First edition
Fine bubble technology —
2024-03
Evaluation method for determining
gas content in fine bubble
dispersions in water —
Part 1:
Oxygen content
Technologie des fines bulles — Méthode d'évaluation pour
déterminer la teneur en gaz dans les dispersions de fines bulles
dans l'eau —
Partie 1: Teneur en oxygène
Reference number
© ISO 2024
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Interferences . 2
4.1 Iodometric method .2
4.2 Electrochemical probe method .2
5 Implication of measurement result . 2
6 Requirement . 2
6.1 General .2
6.2 Correction for the salinity of sample water .3
7 Apparatus . 3
7.1 Optical sensor method .3
7.2 Electrochemical probe method .3
7.3 Iodometric method .3
8 Procedure . 3
8.1 General .3
8.2 Optical sensor method .3
8.2.1 General .3
8.2.2 Sampling, measuring technique and precautions to be taken .4
8.2.3 Calibration . . .4
8.2.4 Determination .4
8.3 Electrochemical probe method .4
8.3.1 General .4
8.3.2 Sampling, measuring technique and precautions to be taken .4
8.3.3 Calibration . . .4
8.3.4 Determination .4
8.4 Iodometric method .4
9 Calculation and expression of results . 5
9.1 Optical sensor and electrochemical probe methods .5
9.2 Iodometric method .5
10 Test report . 5
Annex A (informative) Influence of UFB on the measurement of the oxygen content . 6
Annex B (informative) Influence of bubble attachment to sensor surface . 9
Bibliography .12

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
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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
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This document was prepared by Technical Committee ISO/TC 281, Fine bubble technology.
A list of all parts in the ISO 7383 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 dispersion in water has been used in various industries in recent years. Particularly in the
fishery and food-processing industries, fine bubble technology is widely accepted as means for controlling
dissolved oxygen level. For example, air fine bubbles are used to prevent oxygen depletion in the water of
aquafarm and nitrogen fine bubbles are applied to reduce oxidization of fresh fish fillet.
The determination of the oxygen content in water is necessary to monitor the quality of object to be
controlled by fine bubble dispersion in water. In the measurement of the oxygen content in fine bubble
dispersion in water, however, attention should be paid to the possibility that the presence of fine bubbles
themselves influences the measurement results.
In the case of air microbubble, air inside the bubbles is being dissolved during their slow floatation resulting
in the increase in the oxygen content when oxygen is not oversaturated. In contrast, ultrafine bubbles (UFBs)
have little influence on the oxygen content because the total amount of oxygen in UFBs is negligibly small
compared to the intrinsic dissolved oxygen content in raw water. Furthermore, there is a possibility that
the precipitation of visible bubbles on the surface of oxygen sensor, which is originated from dissolved gas,
influences its measurement result.
Therefore, to evaluate the oxygen content of fine bubble dispersion in water, the state of bubbles in a sample
water during the measurement is figured out.
This document is intended to specify the evaluation method of the oxygen content in fine bubble dispersion
in water by three measurement methods: optical sensor, electrochemical probe and iodometric methods,
which are widely accepted in industries. The standardized evaluation method for the oxygen content enables
easy and solid comparison among fine bubble dispersion in various states.

v
International Standard ISO 7383-1:2024(en)
Fine bubble technology — Evaluation method for determining
gas content in fine bubble dispersions in water —
Part 1:
Oxygen content
WARNING — Persons using this document should be familiar with normal laboratory practice. This
document does not purport to address all of the safety problems, if any, associated with its use. It
is the responsibility of the user to establish appropriate safety and health practices and to ensure
compliance with any national regulatory conditions.
IMPORTANT — It is essential that tests conducted in accordance with this document be carried out
by suitably trained staff.
1 Scope
This document specifies evaluation methods for the oxygen content in fine bubble dispersion in water.
Three test methods which are adopted include the optical sensor, the electrochemical probe and the
iodometric method. The first two methods have an advantage in availability of in situ and real-time
measurement, and high accessibility to commercially available instruments. The last one, composed of a
well-established chemical analysis procedure, is advantageous in the situation where the instruments to be
used in the first two methods are unavailable.
The detection limits of the electrochemical and optical sensor methods are stated in the instruction manuals
of the instruments, in most cases 0,1 mg/l or 0,2 mg/l. The upper limit depends on the specification of the
instrument used. Most instruments allow measurement of a supersaturated sample.
Measurement range of the iodometric method is between 0,2 mg/l and 20 mg/l.
[1]
NOTE Chemical analysis methods other than the iodometric method can be applied as an alternative.
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 5813:1983, Water quality — Determination of dissolved oxygen — Iodometric method
ISO 5814:2012, Water quality — Determination of dissolved oxygen — Electrochemical probe method
ISO 17289:2014, Water quality — Determination of dissolved oxygen — Optical sensor method
ISO 20480-1, Fine bubble technology — General principles for usage and measurement of fine bubbles — Part 1:
Terminology
ISO/TR 23015, Fine bubble technology — Measurement technique matrix for the characterization of fine bubbles
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 20480-1 apply.

ISO and IEC maintain terminology 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
UFB dispersion
UFBD
liquid which contains ultrafine bubbles
[2]
[SOURCE: ISO 21255:2018, 3.2 ]
4 Interferences
4.1 Iodometric method
Readily oxidizable organic substances such as tannins, humic acid and lignins, interfere. Oxidizable sulfur
compounds such as sulfides and thiourea also interfere.
To avoid such interferences, it is preferable to use the electrochemical probe, or the optical sensor method
described in ISO 5714 or ISO 17289 respectively.
In the presence of suspended matter capable of fixing or consuming iodine, or if in doubt about the presence
of such matter, the modified procedure described in ISO 5813:1983, Annex, shall be used.
Preferably, however, determine the oxygen content with the electrochemical probe or the optical s
...