ISO 4240-3
(Main)Fine bubble technology — Environmental applications — Part 3: Test method for on-site evaluation of the performance of algae bloom removal facilities
- Abstract
This document describes the test method and procedure to evaluate algae removal efficiency using microbubble in onsite algae removal facility. The evaluation is made by measuring the removal rate by comparing the amount of algae in a river or lake before and after applying microbubbles.
- Status
- Not Published
- Technical Committee
- ISO/TC 281 - Fine bubble technology
- Drafting Committee
- ISO/TC 281 - Fine bubble technology
- Current Stage
- 6000 - International Standard under publication
- Start Date
- 17-Sep-2026
- Completion Date
- 10-Oct-2026
Buy Documents
ISO/FDIS 4240-3 - Fine bubble technology — Environmental applications — Part 3: Test method for on-site evaluation of the performance of algae bloom removal facilities
REDLINE ISO/FDIS 4240-3 - Fine bubble technology — Environmental applications — Part 3: Test method for on-site evaluation of the performance of algae bloom removal facilities
ISO 4240-3, published by ISO, specifies an on-site test method for evaluating the performance of algae bloom removal facilities that use microbubbles. It tells operators and testers how to compare chlorophyll-a concentration before and after treatment in rivers and lakes to judge removal performance.
What does ISO 4240-3 specify?
ISO 4240-3 specifies a field test method for microbubble-based algae bloom removal facilities in natural water bodies. The document is written for on-site evaluation, so the test is carried out in the river or lake where the facility is used, and performance is judged from chlorophyll-a measurements taken before and after treatment.
The document is organized into the usual technical sections: scope, normative references, terms and definitions, principle, test equipment, test bench preparation, procedure, and test report. It also includes two informative annexes: one explains the flotation mechanism, and the other gives an example of facility operation.
| Annex | What it covers |
|---|---|
| Annex A | The flotation mechanism for algae bloom removal using microbubbles |
| Annex B | An example of algae bloom removal facility operation |
What are the key requirements of ISO 4240-3?
Site conditions and test setup
ISO 4240-3 requires the test to be done in a natural body of water where the facility can operate under realistic conditions. The site is a river or lake with depth of 0.5 m or more and slow or no flow, because the method is intended to evaluate floating and collecting microalgae and cyanobacteria in place, not under laboratory conditions.
Clause 6 sets the test-bench conditions, including chlorophyll-a concentration, test-bench area, average depth, water temperature at 0.5 m, and water flow rate. In practice, this means the tester must choose a water area that is suitable for measurement and that supports a meaningful on-site comparison before and after treatment.
Test equipment and sample handling
Clause 5 lists the equipment needed for the test: a water sampler, six 2 L sampling bottles, glass-fibre filters, a filter holder and vacuum pump, a cooler that blocks light and keeps samples below 4 °C, and a flow meter for the outlet of the microbubble generator. This matters because the method depends on consistent sampling and preservation of the water samples before analysis.
If filtration cannot be done on site, Clause 5 allows the samples to be kept in a cooler and filtered within 3 hours. That practical rule helps preserve the chlorophyll-a result so the before-and-after comparison remains valid.
Weather conditions for the test
Clause 7.1 requires suitable weather: cloud coverage of 3/8 or less, no precipitation, and wind speed of 5.4 m/s or less. These limits matter because wind, rain, and poor sky conditions can change microbubble behavior and affect the measured removal rate.
Sampling and treatment procedure
Clause 7.2 requires sampling from the centre of the testing place at 0.5 m ± 0.1 m below the water surface. Samples of 2 L are collected three times before treatment and again after treatment, and the same handling rule applies each time: filter immediately, or keep the sample below 4 °C away from light and filter it within 3 hours.
ISO 4240-3 also specifies the treatment period: the facility operates for 60 min ± 5 min, and the start and end of treatment are the switch-on and switch-off of the microbubble generator. After treatment, the follow-up samples are taken after 30 min ± 5 min. In practice, this gives a consistent timeline for comparing the water before treatment with the water after the scum has had time to rise and be collected.
Measurement and performance calculation
Clause 4 and Clause 7.2 require chlorophyll-a concentration to be measured in accordance with ISO 10260:1992. The performance of the algae bloom removal facility is then calculated from the chlorophyll-a concentration before and after treatment.
This is the core of the method: the standard does not rate the facility by appearance alone, but by a measurable change in chlorophyll-a. For buyers, operators, and inspectors, that makes the result suitable for comparing installations and documenting field performance.
Reporting
Clause 8 requires the test report to include the standard reference, test date, sample information, test-bench conditions, weather conditions, test results, deviations from the procedure, and unusual features observed during the test. In practice, this gives the reader enough information to understand how the result was obtained and whether the test conditions were comparable.
What terms does ISO 4240-3 define?
- chlorophyll-a - The green pigment used here as the indicator for evaluating aquatic algae and cyanobacteria biomass.
- algal bloom removal facility - A specially manufactured device for removing microalgae and cyanobacteria in natural water by using a microbubble generator and collection equipment.
- microalgae - Photosynthetic microorganisms that can form algal blooms under nutrient-rich conditions.
- cyanobacteria - Photosynthetic prokaryotes that can also form blooms and may produce toxins and irritants in freshwater.
- microalgae and cyanobacteria scum - The floating material formed when algae and microbubbles contact each other.
- coagulant - A chemical added to water to destabilize and aggregate suspended or colloidal particles, including microbubbles and algae.
Who uses ISO 4240-3?
ISO 4240-3 is used by organizations that design, install, operate, or evaluate microbubble-based algae bloom removal facilities in rivers and lakes. It is relevant to environmental engineers, water treatment specialists, field technicians, and test laboratories that need a repeatable on-site measurement method.
It also helps quality managers, buyers, and project specifiers who need to judge whether a facility performs as claimed under real water and weather conditions. The standard gives them a common test procedure and a common reporting format.
Which standards are used with ISO 4240-3?
ISO 4240-3 cites one normative reference:
- ISO 10260:1992 - Used for the spectrometric determination of chlorophyll-a concentration, which is the measurement basis for the removal performance calculation.
What does the ISO 4240-3 document contain?
ISO 4240-3 contains one principle figure, one sampling-and-filtering figure, a performance formula, and a structured test report section. These parts show how to set up the site, collect and preserve samples, run the treatment, and calculate the result.
Annex A explains the flotation process with microbubbles and includes figures on bubble rise behavior and the relationship between bubble size and treatment performance. Annex B gives an operational example of an algae bloom removal facility, including figures of a boat-type arrangement and example test results.
The annex material is informative, so it supports understanding and implementation rather than adding new requirements. For users, that means the annexes are useful for design, operation, and test planning, while the clauses contain the method to follow for evaluation.
Buy Documents
ISO/FDIS 4240-3 - Fine bubble technology — Environmental applications — Part 3: Test method for on-site evaluation of the performance of algae bloom removal facilities
REDLINE ISO/FDIS 4240-3 - Fine bubble technology — Environmental applications — Part 3: Test method for on-site evaluation of the performance of algae bloom removal facilities
Frequently Asked Questions
ISO 4240-3 is a draft published by the International Organization for Standardization (ISO). Its full title is "Fine bubble technology — Environmental applications — Part 3: Test method for on-site evaluation of the performance of algae bloom removal facilities". This standard covers: This document describes the test method and procedure to evaluate algae removal efficiency using microbubble in onsite algae removal facility. The evaluation is made by measuring the removal rate by comparing the amount of algae in a river or lake before and after applying microbubbles.
This document describes the test method and procedure to evaluate algae removal efficiency using microbubble in onsite algae removal facility. The evaluation is made by measuring the removal rate by comparing the amount of algae in a river or lake before and after applying microbubbles.
ISO 4240-3 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 4240-3 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/FDIS 4240-3
ISO/TC 281
Fine bubble technology —
Secretariat: JISC
Environmental applications —
Voting begins on:
2026-07-22
Part 3:
Test method for on-site evaluation
Voting terminates on:
2026-09-16
of the performance of algae bloom
removal facilities
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
ISO/FDIS 4240-3:2026(en) © ISO 2026
FINAL DRAFT
ISO/FDIS 4240-3:2026(en)
International
Standard
ISO/FDIS 4240-3
ISO/TC 281
Fine bubble technology —
Secretariat: JISC
Environmental applications —
Voting begins on:
Part 3:
Test method for on-site evaluation
Voting terminates on:
of the performance of algae bloom
removal facilities
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
ISO/FDIS 4240-3:2026(en) © ISO 2026
ii
ISO/FDIS 4240-3:2026(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Test equipment . 3
6 Test bench preparation . . 3
7 Procedure . 3
7.1 Weather conditions to test the algal bloom removal .3
7.2 Procedure of the test .3
8 Test report . 5
Annex A (informative) Mechanism of flotation process for algal bloom removal using
microbubbles . 6
Annex B (informative) Example of algal bloom removal facility operation .10
Bibliography . 14
iii
ISO/FDIS 4240-3:2026(en)
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 4240 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/FDIS 4240-3:2026(en)
Introduction
Algal bloom in water systems can cause a variety of damages to the ecosystem. For instance, they can lead
to a foul odour that negatively affects nearby residents. Moreover, the algal bloom reduces the amount of
usable water resources and diminishes the quality of tap water. Despite efforts to remove the algal bloom
using methods such as dredging or spraying of chemicals, they remain expensive, have limited application,
and often provide only a temporary solution.
To address this issue at its core, an algal bloom removal facility that utilizes microbubbles is a possible
solution. This technology targets the water systems where algal bloom occurs and uses microbubbles to
float the microalgae and cyanobacteria to the water surface, making them easy to collect. Compared to the
expensive and potentially harmful methods of using chemicals, this approach offers a more cost-effective
and eco-friendly way of removing microalgae and cyanobacteria from the water system.
However, the algal bloom removal facility is usually too large to be tested in a laboratory, and even if
sufficient space is available, it is often inefficient or impossible to reproduce natural water system conditions
indoors. In some cases, tests have been conducted for individual parts of the facility, but such results cannot
guarantee the overall performance once the parts are assembled. Therefore, an on-site evaluation method
is required to ensure testing precision. This document provides a method for evaluating the performance of
algal bloom removal facilities by measuring the chlorophyll-a concentration before and after treatment.
v
FINAL DRAFT International Standard ISO/FDIS 4240-3:2026(en)
Fine bubble technology — Environmental applications —
Part 3:
Test method for on-site evaluation of the performance of
algae bloom removal facilities
1 Scope
This document specifies the test method and procedure to evaluate the algal bloom removal rate using
microbubbles in on-site microbubble-based algal-bloom removal facilities.
The evaluation of the removal rate is conducted by comparing chlorophyll-a concentration before and after
treatment using microbubbles. The range of water and weather conditions are served for test because they
influence the characteristics of microbubbles and the algal bloom removal rate.
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 10260, Water quality — Measurement of biochemical parameters — Spectrometric determination of the
chlorophyll-a concentration
3 Terms and definitions
For the purposes of this document, the following terms and definitions 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
chlorophyll-a
indicator for evaluating aquatic algae and cyanobacteria (3.4) biomass as a green pigment present in all algae
and cyanobacteria
3.2
algal bloom removal facility
specially manufactured device for removing microalgae and cyanobacteria in a natural body of water using
a microbubble generator to float them on the surface of water when they occur in rivers and lakes with a
depth of 0,5 m or more with slow or no flowrate
Note 1 to entry: In cases of excessive eutrophication, the majority of microalgae and cyanobacteria tend to accumulate
within the top 0,5 m of the water column. Therefore, this depth is specified as the minimum effective treatment zone
for the microbubble-based removal facility to achieve optimal efficiency.
ISO/FDIS 4240-3:2026(en)
3.3
microalgae
eukaryotic, photosynthetic microorganisms, typically ranging in size from 1 µm to 50 µm and in density from
3 3
1,05 g/cm to 1,20 g/cm , found in aquatic and terrestrial environments, capable of forming algal blooms
under nutrient-rich conditions, with certain species, especially dinoflagellates and some haptophytes,
producing algal toxins
3.4
cyanobacteria
microscopic, photosynthetic prokaryotes typically ranging in size from 0,5 µm to 60 µm and in density from
3 3
1,05 g/cm to 1,10 g/cm , found in aquatic and terrestrial environments, capable of forming algal blooms
under nutrient-rich conditions and often producing toxins and other irritants in freshwater
3.5
microalgae and cyanobacteria scum
floating substance formed as result of contact of the algae, cyanobacteria (3.4) and microbubbles generated
by the algal bloom removal facility (3.2)
3.6
coagulant
chemical substance added to water to destabilize and aggregate suspended or colloidal particles (including
microbubble and algae)
Note 1 to entry: In algae flotation process, coagulants promote floc formation and enhance bubble attachment, thereby
increasing the efficiency of algal removal.
4 Principle
Microbubbles and microalgae or cyanobacteria combine by electrical attraction to form scum when
microbubbles are sprayed with an appropriate amount of coagulant into a river or lake where the algal
bloom have occurred. The combined scum rises to the water surface because of its lower density than water.
These floating scums are concentrated on the water surface by the continuously sprayed microbubbles.
Algae in rivers or lakes can be removed by collecting them (Figure 1).
Key
1 microbubbles and coagulant
Figure 1 — Mechanism to remove algal bloom using microbubbles
The principle is to evaluate the efficiency of the algal bloom removal facility on-site by measuring
chlorophyll-a concentration before and after treatment. Further theoretical details on the flotation
mechanism using microbubbles are described in Annex A.
ISO/FDIS 4240-3:2026(en)
5 Test equipment
The instruments listed in a) to f) below shall be used for the algal bloom removal. If filtration is impossible
to conduct on-site, the instruments listed in c) and d) shall be equipped in a laboratory. In this case, the
samples shall be kept in a cooler and the filtration shall be done within 3 h.
a) Water sampler: maximum sample depth > 0,6 m
b) Six sampling bottles, 2 l each
c) Glass-fibre filters with nominal pore sizes of 0,7 μm, 1,0 μm, or 1,2 μm, suitable for measuring
chlorophyll-a concentration
NOTE Glass-fibre filters with nominal pore sizes such as 0,7 μm, 1,0 μm, or 1,2 μm are suitable for measuring
chlorophyll-a concentration.
d) Filter holder and vacuum pump for sample filtration
e) Cooler blocking the light and keep up the temperature lower than 4 °C
f) Flow meter for measuring flowrate at outlet of the microbubble generator
6 Test bench preparation
Performance of the algal bloom removal facility shall be evaluated in the natural body of water because they
generally large in size and have a large processing capacity. The test bench for a natural water body shall
meet the following conditions:
a) chlorophyll-a concentration: 10 mg/m or higher;
2 2
b) test bench area: 100 m to10 000 m ;
c) the average depth of water: more than 0,5 m;
d) water temperature at a depth of 0,5 m: 20 °C or higher;
e) water flow rate: 0,2 m/s or less.
When removing algal bloom by flotation using microbubbles, a minimum rise distance of 0,5 m shall be
secured. If the water depth is less than 0,5 m, alternative methods should be used.
7 Procedure
7.1 Weather conditions to test the algal bloom removal
The test of algal bloom removal shall be conducted under following weather conditions:
a) cloud coverage: 3/8 or less (sky condition: clear or mostly clear);
b) no precipitation;
c) wind speed: 5,4 m/s or less.
For practical guidance on the installation and operation of the algal bloom removal facility, see the example
provided in Annex B.
7.2 Procedure of the test
The test bench shall be prepared in accordance with Clause 6.
ISO/FDIS 4240-3:2026(en)
To test the performance of the algal bloom removal facility, the test equipment shall be prepared on-site. If
filtration is impossible to conduct on-site, samples shall be filtered within 3 h after sampling. For that, the
samples shall be kept in a cooler with low temperature, which may be carried out using an ice pack.
a) Samples shall be collected by an operator from the centre of a testing place before the treatment. The
samples of 2 l shall be collected three times at a
...
Formatted
...
Style Definition
...
Style Definition
...
Style Definition
...
Style Definition
...
ISO/DISFDIS 4240-3:2025(en)
Style Definition
...
ISO /TC 281/WG 3
Style Definition
...
Style Definition
...
Secretariat: JISC
Style Definition
...
Date: 2025-02-182026-07-07
Style Definition
...
Style Definition
...
Style Definition
...
Style Definition
...
Style Definition
...
Style Definition
...
Fine bubble technology — Environmental applications —
Style Definition
...
Style Definition
...
Style Definition
...
Style Definition
...
Style Definition
...
Part 3: Style Definition
...
Test method for on-site evaluation of the performance of algalalgae Style Definition
...
Style Definition
bloom removal facilities
...
Style Definition
...
Style Definition
...
Style Definition
...
Style Definition
...
Style Definition
...
Style Definition
...
Style Definition
...
Style Definition
...
FDIS stage
Style Definition
...
Style Definition
...
Style Definition
...
Style Definition
...
Style Definition
...
Style Definition
...
Style Definition
...
Style Definition
...
Style Definition
...
Style Definition
...
Style Definition
...
Style Definition
...
Style Definition
...
Style Definition
...
Style Definition
...
Style Definition
...
Style Definition
...
Style Definition
...
Style Definition
...
Style Definition
...
Style Definition
...
Style Definition
...
Style Definition
...
Style Definition
...
Style Definition
...
Style Definition
...
St l D fi iti
ISO/FDIS 4240-3:2026(en)
Formatted: Font: Bold
Formatted: HeaderCentered
Formatted: Default Paragraph Font
Formatted: Adjust space between Latin and Asian text,
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: Right: 1.5 cm, Bottom: 1 cm, Gutter: 0 cm,
at the address below or ISO’s member body in the country of the requester.
Header distance from edge: 1.27 cm, Footer distance
from edge: 0.5 cm
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: + 41 22 749 01 11
Formatted: English (United Kingdom)
Formatted: English (United Kingdom)
Fax: +41 22 749 09 47
EmailE-mail: copyright@iso.org
Formatted: German (Germany)
Website: www.iso.orgwww.iso.org
Formatted: zzCopyright address, Adjust space between
Latin and Asian text, Adjust space between Asian text
Published in Switzerland
and numbers
Formatted: German (Germany)
Formatted: Font: 10 pt
Formatted: Font: 10 pt
Formatted: Font: 11 pt
Formatted: FooterPageRomanNumber, Space After: 0
pt, Line spacing: single
ii © ISO #### 2026 – All rights reserved
ii
ISO/DISFDIS 4240-3:20252026(en)
Formatted: Font: Bold
Formatted: Font: Bold
Formatted: Font: Bold
Contents
Formatted: HeaderCentered, Left
Formatted: Adjust space between Latin and Asian text,
Foreword . iv
Adjust space between Asian text and numbers
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Test equipment . 3
6 Test bench preparation . 4
7 Procedure . 4
7.1 Weather conditions to test the algal bloom removal . 4
7.2 Procedure of the test . 4
8 Test report . 6
Annex A (informative) Mechanism of flotation process for algal bloom removal using
microbubbles. 8
Annex B (informative) Example of algal bloom removal facility operation . 15
Bibliography . 21
Foreword . iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Test equipment . 2
6 Test-bed preparation . 2
7 Procedure . 2
7.1 Weather conditions of algae removal test . 2
7.2 Procedure of the test method . 3
8 Test report . 3
Annex A (informative) Mechanism of flotation process for algae removal using microbubbles . 5
Annex B (informative) The example of algae removal facility operation . 8
Bibliography . 11
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
Formatted: FooterPageRomanNumber, Left, Space
After: 0 pt, Tab stops: Not at 17.2 cm
iii
ISO/FDIS 4240-3:2026(en)
Formatted: Font: Bold
Formatted: HeaderCentered
Foreword Formatted: Adjust space between Latin and Asian text,
Adjust space between Asian text and numbers
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: Font: Not Italic
A list of all parts in the ISO 4240 series can be found on the ISO website.
Formatted: Font: Cambria
Any feedback or questions on this document should be directed to the user’s national standards body. A
Formatted: English (United Kingdom)
complete listing of these bodies can be found at www.iso.org/members.htmlwww.iso.org/members.html.
Formatted: English (United Kingdom)
Formatted: Adjust space between Latin and Asian text,
Adjust space between Asian text and numbers
Formatted: Font: 10 pt
Formatted: Font: 10 pt
Formatted: Font: 11 pt
Formatted: FooterPageRomanNumber, Space After: 0
pt, Line spacing: single
iv © ISO #### 2026 – All rights reserved
iv
ISO/DISFDIS 4240-3:20252026(en)
Formatted: Font: Bold
Formatted: Font: Bold
Formatted: Font: Bold
Introduction
Formatted: HeaderCentered, Left
Algal bloom in water systems can cause a variety of damages to the ecosystem. For instance, they can lead to
a foul odour that negatively affects nearby residents. Moreover, the algal bloom reduces the amount of usable
water resources and diminishdiminishes the quality of tap water. Despite efforts to remove the algal bloom
using methods such as dredging or spraying of chemicals, they remain expensive, have limited application,
and often provide only a temporary solution.
To address this issue at its core, an algal bloom removal facility that utilizes microbubbles can be theis a
possible solution. This technology targets the water systems where algal bloom occurs and uses microbubbles
to float the microalgae and cyanobacteria to the water surface, making them easy to collect. Compared to the
expensive and potentially harmful methods of using chemicals, this approach offers a more cost-effective and
eco-friendly way of removing microalgae and cyanobacteria from the water system.
However, the algal bloom removal facility is usually too large to be tested in a laboratory, and even if sufficient
space is available, it is often inefficient or impossible to reproduce natural water system conditions indoors.
In some cases, tests have been conducted for individual parts of the facility, but such results cannot guarantee
the overall performance once the parts are assembled. Therefore, an on-site evaluation method is required to
ensure testing precision. This document provides a method for evaluating the performance of algal bloom
removal facilities by measuring the chlorophyll-a concentration before and after treatment.
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
Formatted: FooterPageRomanNumber, Left, Space
After: 0 pt, Tab stops: Not at 17.2 cm
v
DRAFT International Standard ISO/DIS 4240-3:2025(en)
Formatted: Left
Fine bubble technology — Environmental application — Part 3: Test
method for on-site algal bloom removalapplications —
Formatted: Right: 1.5 cm, Bottom: 1 cm, Gutter: 0 cm,
Part 3:
Header distance from edge: 1.27 cm, Footer distance
Test method for on-site evaluation of the performance of algae bloom
from edge: 0.5 cm
removal facilities
1 Scope
Formatted: Adjust space between Latin and Asian text,
Adjust space between Asian text and numbers
This document describesspecifies the test method and procedure to evaluate the algal bloom removal rate
using with microbubble microbubbles in onsite aon-site microbubble-based algal-bloom removal facility. The
algal bloom removal facility using microbubbles is a device that removes microalgae and cyanobacteria by
floating them on the surface of water when they occur in rivers and lakes with a depth of 0,5 m or more with
slow or no flowrate.facilities.
Note 1 to entry: In cases of excessive eutrophication, the majority of microalgae and cyanobacteria tend to accumulate
within the top 0.5 m of the water column. Therefore, this depth is specified as the minimum effective treatment zone for
the microbubble-based removal facility to achieve optimal efficiency.
The evaluation of the removal rate is conducted by comparing chlorophyll-a concentration before and after
treatment using microbubbles. The range of water and weather conditions are served for test because they
influence the characteristics of microbubbles and make a difference to the algal bloom removal rate.
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,
Formatted: Default Paragraph Font
the latest edition of the referenced document (including any amendments) applies.
Formatted: Default Paragraph Font
ISO 10260:1992, Water quality — Measurement of biochemical parameters — Spectrometric determination Formatted: Default Paragraph Font
of the chlorophyll-a concentration
Formatted: Adjust space between Latin and Asian text,
Adjust space between Asian text and numbers, Tab
3 Terms and definitions
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
For the purposes of this document, the following terms and definitions apply.
Formatted: Adjust space between Latin and Asian text,
Adjust space between Asian text and numbers
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
Formatted: English (United Kingdom)
— — ISO Online browsing platform: available at https://www.iso.org/obphttps://www.iso.org/obp
Formatted: Font: 11 pt, English (United Kingdom)
Formatted: English (United Kingdom)
— — IEC Electropedia: available at https://www.electropedia.org/https://www.electropedia.org/
Formatted: English (United Kingdom)
3.1 3.1
Formatted: TermNum2, Adjust space between Latin
chlorophyll-a
and Asian text, Adjust space between Asian text and
indicator for evaluating aquatic algae and cyanobacteria (3.4) biomass as a green pigment present in all algae
numbers
and cyanobacteria
Formatted: Font: Italic
Formatted: Footer, Left, Space After: 0 pt, Tab stops:
Not at 17.2 cm
ISO/FDIS 4240-3:2026(en)
Formatted: Font: Bold
Formatted: HeaderCentered
3.2 3.2
algal bloom removal facility
specially manufactured facilitydevice for removing algal bloommicroalgae and cyanobacteria in a natural body
of water by using a microbubble generator, collection device to float them on the surface of algae scum,
dewatering device etc.water when they occur in rivers and lakes with a depth of 0,5 m or more with slow or
no flowrate
Note 1 to entry: In cases of excessive eutrophication, the majority of microalgae and cyanobacteria tend to accumulate
within the top 0,5 m of the water column. Therefore, this depth is specified as the minimum effective treatment zone for
the microbubble-based removal facility to achieve optimal efficiency.
3.3 3.3
microalgae
eukaryotic, photosynthetic microorganisms, typically ranging in size from 1 µm to 50 µm and in density from
Formatted: Font: Not Italic
3 3
1,05 g/cm to 1,20 g/cm , found in aquatic and terrestrial environments, capable of forming algal blooms
under nutrient-rich conditions, with certain species, especially dinoflagellates and some haptophytes,
producing algal toxins
3.4 3.4
cyanobacteria
microscopic, photosynthetic prokaryotes typically ranging in size from 0,5 µm to 60 µm and in density from
Formatted: Font: Not Italic
3 3
1,05 g/cm to 1,10 g/cm , found in aquatic and terrestrial environments, capable of forming algal blooms
under nutrient-rich conditions and often producing toxins and other irritants in freshwater
3.5 3.5
microalgae and cyanobacteria scum
floating substance formed as result of contact of the algae, cyanobacteria (3.4) and microbubbles generated
Formatted: Font: Italic
by the algal bloom removal facility (3.2)
Formatted: Font: Italic
3.6 3.6
Formatted: TermNum2
coagulant
chemical substance added to water to destabilize and aggregate suspended or colloidal particles (including
microbubble and algae)
Note 2 1 to entry: In algae flotation process, coagulants promote floc formation and enhance bubble attachment, thereby
Formatted: Note, Adjust space between Latin and
increasing the efficiency of algal removal.
Asian text, Adjust space between Asian text and
4 Principle
Microbubbles and microalgae or cyanobacteria combine by electrical attraction to form scum when
microbubbles are sprayed with an appropriate amount of coagulant into a river or lake where the algal bloom
have occurred. The combined scum rises to the water surface because of its lower density than water. These
floating scums are concentrated on the water surface by the continuously sprayed microbubbles. Algae in
rivers or lakes can be removed by collecting them (Figure 1).(Figure 1).
Formatted: Font: 10 pt
Formatted: Font: 10 pt
Formatted: Font: 11 pt
Formatted: FooterPageNumber, Space After: 0 pt, Line
spacing: single
2 © ISO #### 2026 – All rights reserved
ISO/DISFDIS 4240-3:20252026(en) Formatted: Font: 11 pt, Bold
Formatted: Font: 11 pt, Bold
Formatted: Font: 11 pt, Bold
Formatted: Font: Bold
Formatted: HeaderCentered, Left
Key
Formatted: Fig Legend
1 Microbubbles microbubbles and coagulant
Formatted: None, Adjust space between Latin and
Asian text, Adjust space between Asian text and
Figure 1 — The mechanismMechanism to remove algal bloom using microbubblemicrobubbles
numbers
Formatted: Adjust space between Latin and Asian text,
The principle is to evaluate the efficiency of the algal bloom removal facility on-site by measuring chlorophyll-
Adjust space between Asian text and numbers
a concentration before and after treatment. The chlorophyll-a concentration shall be measured in accordance
Formatted: Adjust space between Latin and Asian text,
with ISO 10260:1992. Further theoretical details on the flotation mechanism using microbubbles are
Adjust space between Asian text and numbers
described in Annex A.
Formatted: Numbered + Level: 1 + Numbering Style: a,
b, c, … + Start at: 1 + Alignment: Left + Aligned at: 0
cm + Indent at: 0 cm, Adjust space between Latin and
5 Test equipment Asian text, Adjust space between Asian text and
numbers, Tab stops: Not at 0.7 cm + 1.4 cm + 2.1 cm
The list of instruments on the facility is shownlisted in a) to f) below. shall be used for the algal bloom removal. + 2.8 cm + 3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3
cm + 7 cm
If filtration is impossible to conduct on-site, the needed instruments for the pointslisted in c) and d)
shouldshall be equipped in a laboratory. In this case, the samples shall be kept in a cooler and the filtration
Formatted: Font: 10 pt
shall be done within 3 hours:h.
Formatted: Font: 10 pt
Formatted: FooterCentered, Left, Space Before: 0 pt,
a) a) waterWater sampler: maximum sample depth > > 0,6 m;
Tab stops: Not at 17.2 cm
b) b) sixSix sampling bottles, 2L2 l each;
Formatted: Font: 11 pt
Formatted: FooterPageNumber, Left, Space After: 0 pt,
Tab stops: Not at 17.2 cm
ISO/FDIS 4240-3:2026(en)
Formatted: Font: Bold
Formatted: HeaderCentered
c) c) glassGlass-fibre filters with nominal pore sizes of 0.,7 μm, 1.,0 μm, or 1.,2 μm, suitable for
Formatted: List Number 1, Numbered + Level: 1 +
measuring chlorophyll-a concentration Numbering Style: a, b, c, … + Start at: 1 + Alignment:
Left + Aligned at: 0 cm + Indent at: 0 cm
Note 3 to entry: Widely used commercial examples include GF/F (0.7 μm), GF/B (1.0 μm), GF/C (1.2 μm), and
Gelman AE (1.0 μm).
d) filterNOTE Glass-fibre filters with nominal pore sizes such as 0,7 μm, 1,0 μm, or 1,2 μm are suitable
for measuring chlorophyll-a concentration.
Formatted: Numbered + Level: 1 + Numbering Style: a,
b, c, … + Start at: 4 + Alignment: Left + Aligned at: 0
d) Filter holder and vacuum pump for sample filtration;
cm + Indent at: 0 cm, Adjust space between Latin and
Asian text, Adjust space between Asian text and
e) e) coolerCooler blocking the light and keep up the temperature lower than 4 °C;
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
f) f) flowFlow meter for measuring flowrate at outlet of the microbubble generator.
cm + 7 cm
Formatted: Adjust space between Latin and Asian text,
6 Test bench preparation
Adjust space between Asian text and numbers
Formatted: Numbered + Level: 1 + Numbering Style: a,
Performance of the algal bloom removal facility shall be evaluated in the natural body of water because they
b, c, … + Start at: 1 + Alignment: Left + Aligned at: 0
are generally having large in sizessize and have a large processing capacity. The test bench for a natural water
cm + Indent at: 0 cm, Adjust space between Latin and
body shall meet the following conditions:
Asian text, Adjust space between Asian text and
numbers, Tab stops: Not at 0.7 cm + 1.4 cm + 2.1 cm
a) a) chlorophyll-a concentration: 10 mg/m or higher;
+ 2.8 cm + 3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3
cm + 7 cm
2 2
b) b) test bench area: 100~10, m to10 000 m ;
Formatted: Numbered + Level: 1 + Numbering Style: a,
b, c, … + Start at: 1 + Alignment: Left + Aligned at: 0
c) c) the average depth of water: more than 0,5 m;
cm + Indent at: 0 cm, Adjust space between Latin and
Asian text, Adjust space between Asian text and
d) Note 4 to entry: water temperature at a depth of 0,5 m: 20 °C or higher;
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
e) water flow rate: 0,2 m/s or less.
cm + 7 cm
Formatted: Body Text
When removing algal bloom by flotation using microbubbles, a minimum rise distance of 0.,5 m shall be
secured. If the water depth is less than 0.,5 m, alternative methods should be used. Formatted: Numbered + Level: 1 + Numbering Style: a,
b, c, … + Start at: 1 + Alignment: Left + Aligned at: 0
d) water temperature at a depth of 0.5 m: 20 °C or higher; cm + Indent at: 0 cm, Adjust space between Latin and
Asian text, Adjust space between Asian text and
numbers, Tab stops: Not at 0.7 cm + 1.4 cm + 2.1 cm
a) e) water flow rate: 0,2 m/s or less.
+ 2.8 cm + 3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3
cm + 7 cm
7 Procedure
Formatted: Adjust space between Latin and Asian text,
7.1 Weather conditions to test the algal bloom removal Adjust space between Asian text and numbers
Formatted
...
The test of algal bloom removal shall be conducted under following weather conditions:
Formatted: Adjust space between Latin and Asian text,
Adjust space between Asian text and numbers
a) a) cloud coverage: 3/8 or less (sky condition: clear or mostly clear);
Formatted
...
b) b) no precipitation;
Formatted
...
Formatted: Adjust space between Latin and Asian text,
c) c) wind speed: 5,4 m/s or less.
Adjust space between Asian text and numbers
For practical guidance on the installation and operation of the algal bloom removal facility, see the example
Formatted: Font: 10 pt
provided in Annex B.
Formatted: Font: 10 pt
7.2 Procedure of the test Formatted: Font: 11 pt
Formatted: FooterPageNumber, Space After: 0 pt, Line
The test bench shall be prepared as per the conditions in clause 6.accordance with Clause 6.
spacing: single
4 © ISO #### 2026 – All rights reserved
ISO/DISFDIS 4240-3:20252026(en) Formatted: Font: 11 pt, Bold
Formatted: Font: 11 pt, Bold
Formatted: Font: 11 pt, Bold
To test the performance of the algal bloom removal facility, the test equipment shall be prepared on-site. If
Formatted: Font: Bold
filtration is impossible to conduct on-site, samples shall be filtered within 3 hoursh after sampling. For that,
the samples shall be kept in a cooler with low temperature, which may be carried out using an ice pack.
Formatted: HeaderCentered, Left
a) a) Samples shall be collected by an operator from the centercentre of a testing place before the
Formatted: Numbered + Level: 1 + Numbering Style: a,
treatment. The sample in 2Lsamples of 2 l shall be collected three times at a point of 0,5 m ± 0,1 m from
b, c, … + Start at: 1 + Alignment: Left + Aligned at: 0
water surface. Collected samples shall be filtered right away with a glass fiberfibre filter and the filter
cm + Indent at: 0 cm, Adjust space between Latin and
paper shall be kept in a frozen state within 3 hoursh (see Figure 2).Figure 2). If it is impossible to filter Asian text, Adjust space between Asian text and
numbers, Tab stops: Not at 0.7 cm + 1.4 cm + 2.1 cm
immediately, then the samples shall be put in the cooler with a temperature lower than 4 °C in a place
+ 2.8 cm + 3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3
blocked from light and shall be filtered it within 3 hoursh after sampling.
cm + 7 cm
Formatted: Adjust space between Latin and Asian text,
Adjust space between Asian text and 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
Formatted: Fig Legend, No bullets or numbering
Key
Formatted: None, Adjust space between Latin and
1 Test1 test bench
Asian text, Adjust space between Asian text and
2 Water2 water sampler
numbers
3 Depth3 depth: 0.,5± ± 0.,1 m
Formatted: Numbered + Level: 1 + Numbering Style: a,
4 Sampling4 sampling bottles, each 2L2 l
b, c, … + Start at: 2 + Alignment: Left + Aligned at: 0
5 Glass5 glass-fibre filter cm + Indent at: 0 cm, Adjust space between Latin and
Asian text, Adjust space between Asian text and
6 Filter6 filter holder
numbers, Tab stops: Not at 0.7 cm + 1.4 cm + 2.1 cm
7 Vacuum7 vacuum pump
+ 2.8 cm + 3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3
8 Cooler8 cooler: blocking the light and keep up the temperature lower than 4 ℃ °C
cm + 7 cm
Formatted: Font: 10 pt
Figure 2 — Process of sampling and filtering of samples for evaluation
Formatted: Font: 10 pt
Formatted: FooterCentered, Left, Space Before: 0 pt,
b) b) The treatment facility removes microalgae and cyanobacteria using microbubbles in the
Tab stops: Not at 17.2 cm
testing place during 60 min ± 5 min. The start and end of the process are the swichswitch on and off the
microbubbles generator.
Formatted: Font: 11 pt
Formatted: FooterPageNumber, Left, Space After: 0 pt,
Tab stops: Not at 17.2 cm
ISO/FDIS 4240-3:2026(en)
Formatted: Font: Bold
Formatted: HeaderCentered
c) c) After completing the treatment operation, the tester should move to the centre of the testing
water area for sampling. The samples for testing should be taken after 30 min ± 5 minutesmin of the
treatment. In the same way as the sampling before the treatment, the samples (2L2 l) are collected three
times at a point of 0,5 ± 0,1 m from water surface. After filtering, the filter paper should be put in the
cooler immediately and shall be kept them no more than 3 hoursh. Likewise, if filtration is impossible on-
site, the samples should be kept in the cooler with temperature lower than 4 °C in a place blocked from
light and shall be filtered it within 3 hoursh after sampling.
d) d) Using the collected samples or the filter papers, concentration of chlorophyll-a before and after
the treatment shall be measured in accordance with ISO 10260. The chlorophyll-a concen
...