ISO 4240-3:2026

International
Standard
ISO 4240-3
First edition
Fine bubble technology —
2026-10
Environmental applications —
Part 3:
Test method for on-site evaluation
of the performance of algae bloom
removal facilities
Technologie des fines bulles — Applications environnementales —
Partie 3: Méthode d'essai pour l'évaluation in-situ des
performances des installations d'élimination des proliférations
d'algues
Reference number
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ii
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 site 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
Foreword
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iv
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 across 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
International Standard ISO 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.

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.

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
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 site 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 site for a natural water body shall meet
the following conditions:
a) chlorophyll-a concentration: 10 mg/m or higher;
2 2
b) test site 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 site shall be prepared in accordance with Clause 6.

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 depth of 0,5 m ± 0,1 m from water surface. Collected samples
shall be filtered right away with a glass fibre filter and the filter paper shall be kept in a frozen state within
3 h (see Figure 2). If it is impossible to filter immediately, then the samples shall be put in the cooler with a
temperature lower than 4 °C in a place blocked from light and shall be filtered it within 3 h after sampling.
Key
1 test site
2 water sampler
3 depth: 0,5 ± 0,1 m
4 sampling bottles, each 2 l
5 gla
...