ISO 4240-2:2024
(Main)Fine bubble technology — Environmental applications — Part 2: Test method for evaluating aeration performance of fine bubble jet devices
Fine bubble technology — Environmental applications — Part 2: Test method for evaluating aeration performance of fine bubble jet devices
This document describes the test methodology to evaluate the aeration performance of fine bubble jet devices based on an evaluation of the mass transfer coefficient of oxygen from gas to water. It is applicable to evaluate the performance of fine bubble jet devices for aeration purpose.
Technologie des fines bulles — Applications environnementales — Partie 2: Méthode d'essai pour l'évaluation des performances d'aération des diffuseurs à fines bulles
General Information
Standards Content (Sample)
International
Standard
ISO 4240-2
First edition
Fine bubble technology —
2024-09
Environmental applications —
Part 2:
Test method for evaluating
aeration performance of fine
bubble jet devices
Technologie des fines bulles — Applications environnementales —
Partie 2: Méthode d'essai pour l'évaluation des performances
d'aération des diffuseurs à fines bulles
Reference number
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms, definitions, symbols and abbreviated terms . 1
4 Principle of aeration performance test . 2
5 Test system for aeration performance test . 5
5.1 Test system .5
5.2 Supplied materials for test .6
5.3 Preparation for test .6
5.4 Preliminary test for confirmation of reproducibility .6
6 Test procedures . 6
6.1 Sodium sulphite .6
6.2 Cobalt catalyst .6
6.3 Operation of fine bubble generator .7
6.4 Recording of DO concentration .7
6.5 Power input measurement .7
7 Method to explain the test results . 7
8 Test report . 8
Annex A (informative) Example of test method for evaluating pure oxygen aeration
performance of fine bubble jet devices .10
Bibliography .18
iii
Foreword
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This document was prepared by Technical Committee ISO/TC 281, Fine bubble technology.
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iv
Introduction
Recent progress in the application of fine bubble technology demonstrates success in various technical
fields. Fine bubble jet devices are generally applied in a pure oxygen aeration process to improve the
oxygen transfer from gas phase to liquid phase in the environmental engineering fields, such as wastewater
treatment and water ecological restoration. Small size jet devices (≤1 m /h) are often used for cleaning.
Medium size jet devices (1 to 10) m /h are often used in aquaculture and agricultural fields. Large size jet
devices (≥10 m /h) are often used for water treatment and water environment restoration. The fine bubble
jet devices are operated in ejector mode (self-aspiration) or injector mode (pressurized oxygen supply). The
mode of operation affects the achievable mass transfer and its energy efficiency.
To evaluate aeration device performance there is a need for a standard method for oxygen transfer
measurements which can be applied for all types of fine bubble jet devices.
This document is intended to specify the test procedure to be applied to the fine bubble jet devices for
oxygen aeration uses. Based on the performance data presented by each bubble generator manufacturer, the
engineers who designed the aeration process can calculate how many generators should be used to meet the
use requirements.
v
International Standard ISO 4240-2:2024(en)
Fine bubble technology — Environmental applications —
Part 2:
Test method for evaluating aeration performance of fine
bubble jet devices
1 Scope
This document describes the test methodology to evaluate the aeration performance of fine bubble jet
devices based on an evaluation of the mass transfer coefficient of oxygen from gas to water.
It is applicable to evaluate the performance of fine bubble jet devices for aeration purpose.
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
ISO 20480-2, Fine bubble technology — General principles for usage and measurement of fine bubbles — Part 2:
Categorization of the attributes of fine bubbles
3 Terms, definitions, symbols and abbreviated terms
For the purposes of this document, the terms and definitions given in ISO 20480-1, ISO 20480-2 and the
following 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
aeration
oxygenation
process of introducing of air/oxygen into a body of water to increase its oxygen saturation
3.2
pure oxygen
gas containing more than 90 % oxygen
3.3
fine bubble jet device
device that accelerates and releases fluid with fine bubbles, including swirling flow system, ejector system
and venture system
3.4
oxygen mass transfer coefficient
K
L,a
parameter used to assess rates of oxygen transfer from air to water
-1 -1
Note 1 to entry: Expressed in h or min .
3.5
DO
amount of dissolved oxygen in water or other liquids
Note 1 to entry: Expressed in mg/l.
3.6
standard oxygen transfer efficiency
SOTE
quantity of the introduced oxygen that dissolves in water under standard conditions
Note 1 to entry: The standard conditions are T: 293,15 K (20 °C), P: 101,325 KPa (mass %).
3.7
standard oxygen transfer rate
SOTR
oxygen mass transfer rate at standard conditions
Note 1 to entry: The standard conditions are T: 293,15 K (20 °C), P: 101,325 KPa (kg-O /h).
3.8
standard aeration efficiency
SAE
mass of oxygen transferred per unit energy at standard conditions
Note 1 to entry: The standard conditions are T: 293,15 K (20 °C), P: 101,325 KPa (kg-O /kW-h).
3.9
cycle frequency
ratio of circulating water flow rate to tank volume
-1
Note 1 to entry: Expressed in h .
4 Principle of aeration performance test
Aeration (oxygenation) is an oxygen mass transfer process. Gas liquid mass transfer is highly affected by the
generation of gas liquid interface. During the transfer of oxygen from the gas phase to the liquid phase, the
resistance mainly comes from the liquid film, the oxygen mass transfer coefficient (K ) should be given by
L,a
the following Formula (1). Integrating and sorting Formula (1) gives Formula (2).
dC
*
=−KC C (1)
()
L,a ∞
dt
**
ln CC− =−ln CC −Kt · (2)
() ()
∞∞ 0 L,a
where
C is the dissolved oxygen concentration in water corresponding to the aeration time t [mg/l];
t is the aeration time [min];
C is the dissolved oxygen concentration value at the test point at time 0 [mg/l];
*
is the dissolved oxygen concentration value when the test point reaches a steady state [mg/l].
C
∞
Therefore, K value can be obtained from an aeration experiment in clean water by taking DO
L,a
measurements over time.
According to the K value obtained in the aeration experiment, the K value at different temperatures
L,a L,as
should be calculated by Formula (3).
20−T
KK=×θ (3)
L,as L,a
where
K is the oxygen mass transfer coefficient under standard conditions (T: 293,15 K (20 °C) P: 101,325 KPa)
L,as
[1/min]:
θ is the temperature correction empirical coefficient, may take 1,024;
T is the water temperature, which is the average temperature during the test [°C].
The standard oxygen mass transfer rate (SOTR, kg/h) should be calculated according to Formulae (4)-(8).
1 n
O = O (4)
TR,S ∑ TR,S,i
i=1
n
*
OK=×00,·6 CV· (5)
TR,S,Lii,as, ∞20i
*
C
* ∞i
C = (6)
∞20i
τη⋅
*
C
st
τ = (7)
*
C
s20
P
b
η= (8)
P
b0
where
O is the standard oxygen mass transfer rate (SOTR) at the i th test or test point [kg/h];
TR,S,i
K is the standard oxygen mass transfer coefficient at the i th test or test point [1/min];
L,as,i
*
is the saturated dissolved oxygen concentration at the i th test or test point under the standard
C
∞20i
state (T: 293,15 K (20 °C) P: 101,325 KPa) [mg/l];
V is the volume o
...
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