ISO 20480-4:2021

INTERNATIONAL ISO
STANDARD 20480-4
First edition
2021-01
Fine bubble technology — General
principles for usage and measurement
of fine bubbles —
Part 4:
Terminology related to microbubble
beds
Reference number
©
ISO 2021
© ISO 2021
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ii © ISO 2021 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
Bibliography . 5
Foreword
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iv © ISO 2021 – All rights reserved

Introduction
The flotation process to separate the desired minerals from the gangue started over 2 000 years ago in
Ancient Greece. As the one of the flotation processes, dissolved air flotation (DAF) was used mainly in
applications in which the material to be removed, such as fat, oil, fibres and grease from water, initially.
In the late 1960s, however, the process also became acceptable for wastewater and potable water
[3]
treatment applications.
DAF has been used as an effective alternative to the more conventional separation process of sediments.
The sedimentation process removes particles by submerging them on the floor, while the DAF process
utilizes fine bubbles to float on water. Particles floating on the water surface are finally collected
through a scraper. Through DAF, low-density flocs can be removed using fine bubbles. Compared to
conventional sedimentation processes, DAF has the advantage of being an efficient process because of
[4]
high hydraulic loading rates.
There are various factors that affect the treatment efficiency of the DAF process, such as air saturation,
bubbles and particles size, coagulant, etc. Among them is the bubble bed. To increase the treatment
capacity, DAF has been developed as bubble bed become thicker by increasing in the depth of the
flotation basin.
NOTE A coagulant is a chemical that causes coagulation to increase particles size during water treatment
process.
Even though the characteristics of bubble bed influence on the removal efficiency of DAF process, it was
[6]
not possible to observe the bubble bed depth in full-scale DAF tanks until few years ago. Recently, new
theories and techniques were developed for measurement and evaluation of the bubble bed in full-scale
DAF tank. However, these technologies
...