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International
Standard
ISO 23138
First edition
Biological equipment for treating
2024-07
air and other gases — General
requirements
Équipements biologiques pour le traitement de l'air et autres
gaz — Exigences générales
Reference number
© ISO 2024
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Published in Switzerland
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Process principles . 4
4.1 General fundamentals .4
4.2 Steps involved in pollutant elimination .4
4.2.1 General .4
4.2.2 Mass transfer .4
4.2.3 Biochemical conversion by microorganisms (enzyme catalysed reaction) .4
4.3 Classification of techniques .7
4.4 Design parameter .8
4.5 Biofilter .8
4.5.1 General description . .8
4.5.2 General description of the procedure .9
4.5.3 Filter media .10
4.5.4 Nutrient and nutrient salt source .10
4.5.5 Moisture reservoir .11
4.5.6 Regeneration, replacement and disposal of filter media .11
4.6 Biotrickling filter .11
4.6.1 General description . .11
4.6.2 General description of the procedure . 12
4.6.3 Filter media . 13
4.6.4 Clogging in biotrickling filters for the purification of organic compounds (VOC) . 13
4.6.5 Nutrients and irrigation .14
4.6.6 Regeneration, replacement and disposal of filter media .14
4.7 Bioscrubber .14
4.7.1 General description . .14
4.7.2 General description of the procedure . 15
4.7.3 Nutrients and irrigation .16
5 Application .16
6 Measurement and testing .18
Bibliography . 19
iii
Foreword
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This document was prepared by Technical Committee ISO/TC 142, Cleaning equipment for air and other gases.
Any feedback or questions on this document should be directed to the user’s national standards body. A
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iv
Introduction
The biological exhaust air purification has experienced a very rapid spread in recent years with very positive
effects in various applications.
The most important advantage is the fact that the cleaning process is natural and carried out by
microorganisms. It is currently by far the most environmentally friendly exhaust air purification technology.
The main advantages of this technology are as follows:
— it is a natural process at ambient pressure and ambient temperature;
— the principle is comparable with the wastewater treatment technology which is also well-established
for years;
— there is no need of additional energy in the form of natural gas or oil;
— it is a nearly CO neutral air cleaning technology;
— it has low operation costs;
— it has low investment costs.
Long lasting experiences have shown that biological systems especially can be useful for the treatment of:
— odorous air from waste water treatment plants (e.g. H S, sulfides);
— odorous air from waste treatment plants as composting plants, anaerobic digestion plants (e.g. H S, NH ,
2 3
organic compounds);
— odorous air from industrial processes;
[9]
— waste air from paint houses and other industrial processes containing volatile organic compounds (VOC) .
[1]
Some parts of this document are based on the German Standards VDI 3477 (Biofilter, first published
[2] [3]
in 1984), VDI 3478-1 (Bioscrubber, first published in 1985) and VDI 3478-2 (Biotrickling filter, first
published in 1985). (With permission of the Association of German Engineers VDI).
v
International Standard ISO 23138:2024(en)
Biological equipment for treating air and other gases —
General requirements
1 Scope
This document specifies the technology of biological exhaust air purification. The relevant requirements for
a possible application are specified. The different variants of this technique are also presented.
NOTE The process principles of this method are described in Clause 4.
2 Normative references
There are no normative references in this document.
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
biofilter
bioreactor treating waste gas with the aid of biofilm attached to the packing media which moisture is
maintained by a prepositive humidifier or intermittent water feeding to the filter bed
Note 1 to entry: Organic materials are usually used as carrier materials. However, inorganic materials with a large
inner surface area and corresponding microorganism population are also used. The materials used are usually
arranged as bulk layers through which the exhaust gases flow.
[SOURCE: ISO 29464:2024, 3.5.10, modified — Note to entry has been added.]
3.2
biotrickling filter
bioreactor treating waste gas with free moving liquid layers on the surface of inert packing media to supply
nutrients, take away metabolites or control pH for the biofilm attached to the packing media
3.3
bioscrubber
absorber transferring contaminants from waste gas to liquid absorbent, and removing the dissolved
contaminants by suspended-growth microorganisms in a supplementary space
3.4
waste gas
odorant and pollutant-laden gas streams from industrial and agricultural processes and exhaust ventilation
streams from tanks and rooms unsuited for being permanently occupied by humans
3.5
acclimation
adaptation of microorganisms to the substrate volume and composition as well as other environmental factors
3.6
absorbent
liquid suitable for collecting gas components
3.7
absorber
device in which specific substances are absorbed into an absorption liquid
3.8
absorption
selective separation of one or more components from gas mixtures by scrubbing with a scrubbing medium
(typically water)
Note 1 to entry: A distinction is made between physical absorption, for the assessment of which the physical equilibrium
curve is used as a basis, and chemical or biochemical absorption, during which the absorptive and absorbent enter a
chemical reaction with each other and substances are converted.
3.9
absorptive
substance destined for abso
...