oSIST prEN 12255-9:2021
(Main)Wastewater treatment plants - Part 9: Odour control and ventilation
Wastewater treatment plants - Part 9: Odour control and ventilation
Part 12 will standardize the basic requirements to control odour in large waste water treatment plants.
Kläranlagen - Teil 9: Geruchsminderung und Belüftung
Dieses Dokument legt Planungsgrundsätze und Leistungsanforderungen für die Geruchsminderung und die damit verbundene Lüftungstechnik in Kläranlagen mit einem EW über 50 fest.
Stations d'épuration - Partie 9: Maîtrise des odeurs et ventilation
Le présent document spécifie les principes de conception et les exigences de performance en ce qui concerne la maîtrise des odeurs et la ventilation associée, pour les stations d’épuration d’eaux usées desservant plus de 50 équivalents-habitants (EH).
Čistilne naprave za odpadno vodo - 9. del: Kontrola vonja in prezračevanje
General Information
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Standards Content (Sample)
SLOVENSKI STANDARD
01-oktober-2021
Čistilne naprave za odpadno vodo - 9. del: Kontrola vonja in prezračevanje
Wastewater treatment plants - Part 9: Odour control and ventilation
Kläranlagen - Teil 9: Geruchsminderung und Belüftung
Stations d'épuration - Partie 9: Maîtrise des odeurs et ventilation
Ta slovenski standard je istoveten z: prEN 12255-9
ICS:
13.060.30 Odpadna voda Sewage water
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
DRAFT
EUROPEAN STANDARD
NORME EUROPÉENNE
EUROPÄISCHE NORM
August 2021
ICS 13.060.30 Will supersede EN 12255-9:2002
English Version
Wastewater treatment plants - Part 9: Odour control and
ventilation
Stations d'épuration - Partie 9: Maîtrise des odeurs et Kläranlagen - Teil 9: Geruchsminderung und Belüftung
ventilation
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee
CEN/TC 165.
If this draft becomes a European Standard, CEN members are bound to comply with the CEN/CENELEC Internal Regulations
which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.
This draft European Standard was established by CEN in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC
Management Centre has the same status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
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 supporting documentation.
Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without
notice and shall not be referred to as a European Standard.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2021 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 12255-9:2021 E
worldwide for CEN national Members.
Contents Page
European foreword . 3
Introduction . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Symbols and abbreviations . 8
5 Design principles . 8
5.1 General. 8
5.2 Sources and nature of odours . 9
5.3 Odour measurement . 10
5.4 Planning . 11
5.4.1 Preliminary considerations . 11
5.4.2 Detailed planning . 12
5.4.3 Criteria for selection . 13
5.5 Design requirements . 14
5.5.1 General. 14
5.5.2 Materials selection . 14
5.5.3 Chemical or biological addition . 14
5.5.4 Treatment of odorous air . 15
5.5.5 Design of covers . 18
5.5.6 Design of ventilation plant . 19
5.6 Process requirements . 19
5.7 Maintenance and Operation. 20
Annex A (informative) Odour potential and odour emission capacity, measurement of odour
emission rate . 21
A.1 Odour Potential and Odour Emission Capacity . 21
A.2 Measurement of Odour Emission Rate . 21
Bibliography . 23
European foreword
This document (prEN 12255-9:2021) has been prepared by Technical Committee CEN/TC 165 “Waste
water engineering”, the secretariat of which is held by DIN.
This document is currently submitted to the CEN Enquiry.
This document will supersede EN 12255-9:2002.
It is the ninth part prepared by Working Group CEN/TC 165/WG 40 relating to the general requirements
and processes for treatment plants for a total number of inhabitants and population equivalents (PT)
over 50. EN 12255 with the generic title “Wastewater treatment plants” consists of the following Parts:
• Part 1: General construction principles
• Part 3: Preliminary treatment
• Part 4: Primary settlement
• Part 5: Lagooning processes
• Part 6: Activated sludge process
• Part 7: Biological fixed-film reactors
• Part 8: Sludge treatment and storage
• Part 9: Odour control and ventilation
• Part 10: Safety principles
• Part 11: General data required
• Part 12: Control and automation
• Part 13: Chemical treatment — Treatment of wastewater by precipitation/flocculation
• Part 14: Disinfection
• Part 15: Measurement of the oxygen transfer in clean water in aeration tanks of activated sludge plants
• Part 16: Physical (mechanical) filtration
NOTE For requirements on pumping installations at wastewater treatment plants see EN 752, Drain and sewer
systems outside buildings — Sewer system management and EN 16932 (all parts), Drain and sewer systems outside
buildings — Pumping systems.
Introduction
Differences in wastewater treatment throughout Europe have led to a variety of systems being developed.
This document gives fundamental information about the systems; this document has not attempted to
specify all available systems. A generic arrangement of wastewater treatment plants is illustrated in
Figure 1 below:
Key
1 preliminary treatment C discharged effluent
2 primary treatment D screenings and grit
3 secondary treatment E primary sludge
4 tertiary treatment F secondary sludge
5 additional treatment (e.g. disinfection or G tertiary sludge
removal of micropollutants)
6 sludge treatment H digested sludge
7 lagoons (as an alternative) I digester gas
A raw wastewater J returned water from dewatering
B effluent for re-use (e.g. irrigation)
Figure 1 — Schematic diagram of wastewater treatment plants
Detailed information additional to that contained in this document may be obtained by referring to the
bibliography.
The primary application is for wastewater treatment plants designed for the treatment of domestic and
municipal wastewater.
1 Scope
This document specifies design principles and performance requirements for odour control and
associated ventilation for wastewater treatment plants serving more than 50PT.
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.
prEN 12255-14:2021, Wastewater treatment plants — Part 14: Disinfection
EN 16323, Glossary of wastewater engineering terms
3 Terms and definitions
For the purposes of this document, the terms and definitions given in EN 16323 and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
olfactometry
measurement of the response of assessors to olfactory stimuli
Note 1 to entry: See EN 13725 for details.
[SOURCE: EN 16323:2014-07, term 2.1.3.2]
3.2
odour concentration
number of European Odour Units in a cubic metre of gas at standard conditions
EXAMPLE If a sample has to be diluted by a factor of 300 to reach the detection threshold, the odour
concentration of the sample is cod = 300 ouE/m .
Note 1 to entry: The odour concentration has the symbol c and the unit ou /m .
od E
Note 2 to entry: The value of the odour concentration is the dilution factor that is necessary to reach the detection
threshold. At the detection threshold, the odour concentration of the mixture is 1 ouE/m by definition.
[SOURCE: EN 13725]
3.3
odorant flow rate; odour emission rate
quantity of odorous substances passing through a defined area per unit time
Note 1 to entry: The odorant flow rate has the symbol q . It is the product of the odour concentration c , the outlet
od od
velocity v and the outlet area A or the product of the odour concentration cod and the pertinent volume flow rate V .
Its unit can be expressed as ouE/h, ouE/min or ouE/s.
Note 2 to entry: Diffuse sources such as unaerated wastewater or sludge surfaces, do not have a defined waste air
flow, although they can emit odorants. In these cases, a special sampling procedure is necessary which is discussed
in EN 13725 (see Annex A). Odorant flow rates can be used in an analogous fashion to mass flow rates when
modelling the impact from a source. All odour sources will have an odorant flow rate, even where no air flow rate
is easily identifiable.
[SOURCE: EN 13725:2003-07, term 3.1.42]
3.4
volatile organic compound
VOC
organic compound with an initial boiling point less than or equal to 250 °C measured at a standard
pressure of 101,3 kPa
[SOURCE: EU Directive 2004/42/CE]
3.5
capital expenditure
CAPEX
money used to purchase and install and commission a capital asset
[SOURCE: ISO 15663-1:2000, term 2.1.6]
3.6
operational expenditure
OPEX
recurrent expenditure required to provide a service or product
[SOURCE: ISO/TS 55010:2019, term 3.9]
3.7
empty bed residence time
EBRT
total time air is retained in a considered unit in average conditions
3 3
Note 1 to entry: The EBRT is calculated as V/Q, where V (m ) is the total internal volume of the unit and Q (m /s)
is the air flow rate. The EBRT calculation assumes that the unit is empty, regardless the presence of packings or
other solid elements.
3.8
specific ozone demand
required ozone concentration in the odours air (g O /m or g O /l) to achieve a level of odour reduction
3 3
3.9
contact tank
tank for providing the required retention time for certain reactions to take place
[SOURCE: Modified from EN 16323:2014, term 2.3.9.4, to extend to use with gases]
3.10
advanced oxidation process
AOP
chemical process generating hydroxyl or oxygen radicals
3.11
UV efficiency (UV-C radiation conversion efficiency)
ability of a UV-C lamp to convert electrical power into UV-C radiation
Note 1 to entry: The ratio is the UV-C radiation power accounting for the electrical power of the UV-C lamp. The
UV-C conversion efficiency of a low pressure UV-C lamp at 253,7 nm is between 25 % and 45 %. The UV-C
conversion efficiency should not be less than 30 % in an air disinfection field under all circumstances due to energy
consumption of the system.
Note 2 to entry: The measurements of the output shall be performed by the manufacturer in accordance to
ISO 15727.
[SOURCE: ISO 15727:2020, term 3.6]
3.12
UV radiation demand
sum of the UV output (W) at 254 nm from all the lamps of an UV reactor, divided by the odorous air flow
rate (m /h)
required UV radiation/UV dose to achieve a level of disinfection
Note 1 to entry: Measured according to ISO 15727.
4 Symbols and abbreviations
AOX adsorbable organohalogens
AOP advanced oxidation process
CAPEX capital expenditure
COD concentration (in ppm) resulting by the sum of all the measured odorants
EBRT empty bed residence time
FFKM perfluoroelastomer, defined in ASTM D1418 (equivalent to FFPMs defined in ISO 1629)
FKM fluorocarbon, defined in ASTM D1418 (equivalent to FPM defined in ISO 1629)
FRP fibre-reinforced plastic (sometimes referred to as fiber-reinforced polymer, or fiber-
reinforced plastic)
H S hydrogen sulphide
NH ammonia
ou European odour units
E
OPEX operating expenditure
P254 the emitted UV output at 254 nm and Pin (W)
PE polyethylene
P the power input to the lamp (W)
in
PP polypropylene
PTFE polytetrafluoroethylene
UV ultraviolet, electromagnetic radiation with wavelength 100 nm to 400 nm
UV-C ultraviolet electromagnetic radiation with wavelength 100 nm to 280 nm
VOC volatile organic compounds
W Watts
5 Design principles
5.1 General
Given the nature of wastewater it is not possible to guarantee that a wastewater treatment plant will be
totally odour free. A well-designed plant minimizes the potential for odour problems.
The potential for odour generation shall be considered at the earliest stages in the design of wastewater
treatment works. The likelihood of odour emission, its impact and ease of treatment shall be considered
in all aspects of design, especially:
a) septicity of the raw wastewater – e.g. by considering the sewerage system;
b) process selection – e.g. if septic wastewater is anticipated, possibilities to minimize odour include:
• minimizing the retention time of the sludge in the primary settlement tank;
• having no primary settlement (thus avoiding a major source of odour) and applying extended
aeration;
• selecting a covered process;
c) location of the major sources of odour – e.g. wherever possible, site these away from the most
sensitive locations surrounding the plant taking into account the direction and speed of winds local
to the installation;
NOTE Situations with light wind or no wind and stable atmospheric conditions are most unfavourable for the
dispersion of odours. Thus, if these situations happen very often, then the local wind direction during these
situations is relevant instead of the generally prevailing wind direction.
d) co-location of unit processes – e.g. it may be possible to use a single abatement process to treat more
than one source of odour or to use the odorous air from one process as process or combustion air in
an adjacent process. Any decision to treat odorous air will require a process to be covered and
ventilated with the vented air ducted to treatment. Covering, venting and treatment shall be designed
as an integrated package.
Where treatment plants are not covered or housed in buildings and the effect of odour is difficult to
quantify prior to commissioning designs should allow for covering and/or ventilation at a later date.
Further general design requirements are given in EN 12255-1.
When tanks or processes are covered careful consideration is required of:
e) explosion risk;
f) corrosion prevention;
g) health and safety of operators;
h) access for maintenance.
5.2 Sources and nature of odours
Odour is generated during the conveyance and treatment of wastewater due to the degradation of organic
matter by microorganisms under anaerobic conditions. Industrial wastewater can also contain
characteristic odorous constituents. The onset of septicity can be accelerated by elevated temperatures,
high BOD concentration and presence of reducing chemicals. The range of odorous constituents is very
wide and includes:
• hydrogen sulphide;
• ammonia;
• organic sulphur compounds; thiols (e.g. mercaptans);
• organic compounds with nitrogen as amines; indole and skatole;
• volatile fatty acids;
• other Volatile Organic Compounds (VOC).
The features that typically cause odours to occur are:
• unfavourable conditions in the sewage systems (e.g. long retention times, poor maintenance,
industrial discharges);
• long pressure mains;
• some high rate treatment processes;
• anaerobic lagoons;
• sludge storage and treatment processes.
Odours can be present or form in the sewer system or in the treatment plant. Once formed, odours tend
to travel with the flow through the treatment process to be transferred to the atmosphere at points of
turbulence or where there is a large air-water interface. Levels of odour can be increased by the recycling
of liquors within a treatment process, particularly when recycling those produced by the thickening or
dewatering of sludge.
NOTE EN 752 and EN 16932 (all parts) give guidance on minimizing septicity in drain and sewer systems.
Particular problems can be found at:
a) inlet works: strong odours in the incoming flow lead to high levels of release at inlet works;
b) primary settlement tanks: if they receive a highly odorous flow or if excessive sludge is allowed to
accumulate in the tank, generating septicity;
c) secondary treatment: if it is highly loaded or receives a highly odorous feed;
d) sites for the transfer, storage and treatment of sludges, especially of non-stabilized sludges;
e) leaks or emissions of biogas from anaerobic digestion and the first point of discharge of digested
sludge.
5.3 Odour measurement
Quantitative measurements of odour shall be carried out when undertaking investigations into the causes
of odour, for identifying sites where odour is formed or emitted, for estimating the impact from an odour
source and for specifying the duty of odour abatement equipment.
Measurement and assessment of odorous compounds may include:
a) Measurement based on technical measurements with detection tubes or with electronic device (H S,
NH etc.). In wastewater treatment plants 4 main compounds are usually present: H S, NH ,
3 2 3
mercaptanes and amines.
b) If the wastewater results in emissions of specific odorous compounds due e.g. industrial wastewater
effluent, these compounds should be measured.
Quantitative measurements of odour include:
c) Measurement based on olfactometry:
• the odorant detection threshold concentration applicable to single compounds;
• the odour concentration applicable to air samples of unknown composition;
• the odour potential and odour emission capacity (see Annex A);
• the odorant flow rate (see Annex A).
The levels of hydrogen sulphide, ammonia, mercaptans and amines are easy to measure and provide
valuable information for odour solution.
Reliance solely on hydrogen sulfide measurements can be misleading in cases where odorants other
than hydrogen sulfide are predominant e.g. ammonia and organic sulphides. Often this can be the
case where odours:
• come predominantly from a specific industrial discharge;
• come from secondary treatment;
• come from the incineration or drying of sludge;
• follow abatement measures aimed specifically at reducing H2S.
5.4 Planning
5.4.1 Preliminary considerations
5.4.1.1 General
Discussions should be held with the appropriate authorities to ascertain what standards need to be met
by the proposed plant or proposed abatement measures at an existing plant. Most wastewater treatment
processes may require odour abatement in particularly sensitive locations.
An atmospheric dispersion model using a historical record of wind-speed and direction and atmospheric
stability class can be used to estimate the odour emission rate that will comply with such a standard. This
odour emission rate can be used as a target for design or as a specification for the performance of
abatement technology.
At existing sites with known odour emission rates, the results from a model of atmospheric dispersion
can be compared against the locations of received complaints to estimate a suitable quality standard.
New installations shall be designed where possible to minimize the problem of odour generation.
5.4.1.2 Sewer system
A sewer system designed according to the principles contained in EN 752 should minimize the
development of septicity. For more information see Bibliography [34].
5.4.1.3 Wastewater treatment plants
The following points shall be considered during the design:
a) control of the discharge of particularly odorous industrial wastewater;
b) location of the plant;
c) minimizing of the exposure of non-stabilized or pseudo-stabilized sludges during storage and
treatment;
d) avoiding the development of septicity in settlement tanks by minimizing the retention time of the
accumulating sludge layer;
e) choosing processes which minimize emissions where a highly odorous feed-stream is unavoidable
(see 5.1);
f) minimizing turbulence e.g. by minimizing the drop over weirs (unless used for stripping);
g) the addition of odorous return flows as close to aerobic secondary treatment processes as possible;
h) choosing compact designs where process covering is unavoidable;
i) locating the major sources of odour as far as possible from the most sensitive receptors in the
vicinity;
j) grouping the main odour sources to allow the use of common abatement measures;
k) use of odorous air from one process as the process or combustion air for another process. In this case
air quality shall be considered;
l) prevention of increased evaporation of odour compounds;
m) when waste air is removed from a closed vessel or other closed part of wastewater treatment plant,
only minimum under pressure should be introduced to prevent larger evaporation. Some fresh air
could be introduced to the system to reduce the under pressure.
5.4.1.4 Remedial measures
When designing remedial measures to overcome an unacceptable odour impact in the vicinity, thorough
investigations should be undertaken to identify how odour is generated, where it is emitted and, if
possible, to estimate the odour emission rates of the major sources. Specific compound analysis and the
measurement of odour potentials in the liquid streams will show where odours are being formed.
Analysis for specific compounds in air samples can help to locate the significant points of odour emission.
Preparation of a map of hydrogen sulphide concentrations within and around a treatment works can be
very valuable. For techniques for measuring odour emission rates see Annex A.
5.4.2 Detailed planning
5.4.2.1 Odour abatement
Methods for odour abatement from a number of basic categories include:
a) process design and layout;
b) process operation;
c) industrial wastewater limits and controls;
d) chemical addition to prevent septicity, to ameliorate its effects or otherwise reduce odour;
e) cover odour sources, provide ventilation and treat the collected air.
Methods a), b) and c) are described in 5.4.1.1 and 5.4.1.2. When using chemicals, great care shall be taken
to ensure that no detrimental by-product is produced as a consequence.
5.4.2.2 Chemical additives
Chemical additives can be divided into:
a) strong oxidising agents (e.g. ozone, hydrogen peroxide and sodium hypochlorite) which will oxidize
many odorous compounds after they have been formed;
b) sources of oxygen (e.g. air, oxygen concentrators, liquid oxygen and nitrate salts) which act primarily
as sources of oxygen to prevent the development of septicity. In a secondary range some treatment
of pre-formed odours can occur;
c) metal salts, (typically of iron) which are used to fix sulphide as insoluble metal sulphides, preventing
any transfer to the atmosphere.
When using sodium hypochlorite the formation of adsorbable organohalogens (AOX) compounds shall
be investigated and minimized.
5.4.2.3 Treating odorous air
Methods of treating odorous air that may be considered include:
a) biofiltration;
b) ozonation;
c) advanced oxidation based on UV radiation combined with ozonation;
d) wet chemical, biological or ozone scrubbing;
e) regular bed adsorption e.g. active carbon adsorption;
f) enhanced bed adsorption e.g. impregnated activated carbons adsorption;
g) selective bed adsorption e.g. metal oxides;
h) thermal oxidation.
Odorous air can be used as the process air in most secondary wastewater treatment processes of a
suitable configuration, such as the diffused air in the activated sludge process [3]. Secondary treatment
processes used in this way should be lightly loaded and not themselves generators of significant odour.
5.4.3 Criteria for selection
The main criteria for selection of methods of treating odorous air are performance and cost. Performance
should be evaluated from pilot tests, field tests or by comparison with similar plant operating under
similar conditions.
The cost of the system shall consider both CAPEX and OPEX. Considering the estimated operation time of
the odour control system, the selected treatment method shall minimize the sum of CAPEX and OPEX
over a minimum timeframe of five years, without compromising the performance of the system during
that time.
The CAPEX shall also include indirect costs such as upgrading ancillary equipment, for example fans to
cope with increased pressure drop over a system. The OPEX shall also include indirect increase in
operation costs such as higher required fan power consumption due to increased pressure drop or
destruction/post-treatment of chemical scrubber effluent. The following restrictions should also be
considered. Space limitations can restrict the use particularly of odour biofilters, while height limitations
can restrict the use of counter-current scrubbers, both chemical, biological and ozone. The implications
of handling hazardous chemicals for chemical scrubbers shall be considered. Access difficulties can limit
the use of solid adsorbers and odour biofilters that require regular replacement. Other considerations
include the availability of electricity, water or fi
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