oSIST prEN 12255-1:2023
(Main)Wastewater treatment plants - Part 1: General construction principles
Wastewater treatment plants - Part 1: General construction principles
This European Standard specifies general requirements for structures and equipment as they relate to wastewater treatment plants for a total population of more than 50 PT.
The primary application is designed for wastewater treatment plants for the treatment of domestic and municipal wastewater.
Requirements for structures which are not specific for wastewater treatment plants are not within the scope of this European Standard. Other ENs can apply.
Equipment which is not solely used in wastewater treatment plants is subject to the applicable product standards. However, specific requirements for such equipment when used in wastewater treatment plants are included in this part.
General principles of building construction, mechanical and electrical engineering are not subject of this standard.
This European Standard does not cover the design of treatment processes.
Differences in wastewater treatment throughout Europe have led to a variety of systems being developed. This standard gives fundamental information about the systems; this standard has not attempted to specify all available systems.
Detailed information additional to that contained in this standard may be obtained by referring to the Bibliography.
Kläranlagen - Teil 1: Allgemeine Baugrundsätze
Dieses Dokument legt die grundlegenden Planungs- und Bauausführungsanforderungen an Kläranlagen für mehr als 50 EW fest.
ANMERKUNG 1 Anforderungen an Bauwerke, die nicht spezifisch für Kläranlagen sind, sind nicht Gegenstand dieses Dokuments. Andere Europäische Normen können hierfür gelten.
ANMERKUNG 2 Für technische Ausrüstung, die nicht ausschließlich auf Kläranlagen eingesetzt wird, sind die einschlägigen Produktnormen zu beachten. Besondere Anforderungen an eine solche technische Ausrüstung hinsichtlich ihres Einsatzes auf Kläranlagen sind allerdings Gegenstand dieses Teils der Normenreihe.
Stations d’épuration - Partie 1 : Principes généraux de conception et de construction
Le présent document spécifie les exigences fondamentales relatives à la conception et à la construction des stations d’épuration de plus de 50 EH.
NOTE 1 Les exigences structurelles qui ne sont pas spécifiques aux stations d’épuration ne font pas partie du domaine d’application du présent document. D’autres Normes européennes peuvent s’appliquer.
NOTE 2 Les équipements qui ne sont pas utilisés uniquement dans les stations d’épuration sont soumis à l’application des normes de produit correspondantes. Néanmoins, les exigences particulières à ces équipements, lorsqu’ils sont utilisés dans les stations d’épuration, peuvent être incluses dans la présente norme.
Čistilne naprave za odpadno vodo - 1. del: Splošna načela gradnje
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
oSIST prEN 12255-1:2023
01-september-2023
Čistilne naprave za odpadno vodo - 1. del: Splošna načela gradnje
Wastewater treatment plants - Part 1: General construction principles
Kläranlagen - Teil 1: Allgemeine Baugrundsätze
Stations d’épuration - Partie 1 : Principes généraux de conception et de construction
Ta slovenski standard je istoveten z: prEN 12255-1
ICS:
13.060.30 Odpadna voda Sewage water
oSIST prEN 12255-1:2023 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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oSIST prEN 12255-1:2023
DRAFT
EUROPEAN STANDARD
prEN 12255-1
NORME EUROPÉENNE
EUROPÄISCHE NORM
July 2023
ICS 13.060.30 Will supersede EN 12255-1:2002
English Version
Wastewater treatment plants - Part 1: General
construction principles
Stations d'épuration - Partie 1: Principes généraux de Kläranlagen - Teil 1: Allgemeine Baugrundsätze
construction
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, Türkiye 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
© 2023 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 12255-1:2023 E
worldwide for CEN national Members.
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Contents Page
European foreword . 3
Introduction . 5
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 7
4 Symbols and abbreviations . 10
5 Requirements . 11
5.1 General requirements . 11
5.2 Design requirements . 12
5.3 Modularity . 14
5.4 Structural requirements . 15
5.5 Requirements for equipment . 17
6 Test methods . 23
6.1 Function and performance . 23
6.2 Tightness testing of concrete structures . 23
6.3 Tightness testing of other structures and equipment . 23
7 Cost Comparison Analysis . 24
Annex A (informative) Design Service Life . 25
Annex B (normative) Structural tolerances . 27
B.1 Circular tank . 27
Annex C (normative) Wall tracks . 28
C.1 Tracks . 28
C.2 Walls . 28
C.3 Wheels . 28
C.4 Freezing conditions . 28
Annex D (normative) Scraper Design . 29
D.1 Physical loads . 29
D.2 Driver control . 29
D.3 Bar and chain scrapers . 29
D.4 Monitoring . 29
D.5 Maintainability . 30
D.6 Design life . 30
Bibliography . 31
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European foreword
This document (prEN 12255-1:2023) 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 12255-1:2002.
The main changes compared to the previous edition are listed below:
a) update of title and scope to incorporate design;
b) comprehensive revision and additions in all sections;
c) adaptation to the current state of the art;
d) updating of the Normative references;
e) editorial revision.
This is the first 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.
The EN 12255 series with the generic title “Wastewater treatment plants” consists of the following
parts:
— Part 1: General design and construction principles
1
— Part 2 : Storm management systems
— Part 3: Preliminary treatment
— Part 4: Primary treatment
— 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
1
Part 2 is under preparation.
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— 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
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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.
Key
1 preliminary treatment
2 primary treatment
3 secondary treatment
4 tertiary treatment
5 additional treatment (e.g. disinfection or removal of micropollutants)
6 sludge treatment
7 lagoons (as an alternative)
A raw wastewater
B effluent for re-use (e.g. irrigation)
C discharged effluent
D screenings and grit
E primary sludge
F secondary sludge
G tertiary sludge
H digested sludge
I digester gas
J returned water from dewatering
Figure 1 — Schematic diagram of wastewater treatment plants
The primary application is for wastewater treatment plants designed for the treatment of domestic and
municipal wastewater.
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NOTE For requirements on pumping installations at wastewater treatment plants see EN 752, Drain and
sewer systems outside buildings and the EN 16932 series, Drain and sewer systems outside buildings — Pumping
systems:
— Part 1: General requirements;
— Part 2: Positive pressure systems;
— Part 3: Vacuum systems.
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1 Scope
This document specifies the basic design and construction requirements for wastewater treatment
plants for over 50 PT.
NOTE 1 Requirements for structures which are not specific for wastewater treatment plants are not within the
scope of this document. Other ENs can apply.
NOTE 2 Equipment which is not solely used in wastewater treatment plants is subject to the applicable product
standards. However, specific requirements for such equipment when used in wastewater treatment plants are
included in this part.
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.
EN ISO 9001:2015, Quality management systems - Requirements (ISO 9001:2015)
EN 809, Pumps and pump units for liquids - Common safety requirements
EN 10088-2, Stainless steels - Part 2: Technical delivery conditions for sheet/plate and strip of corrosion
resisting steels for general purposes
EN 12255-9, Wastewater treatment plants - Part 9: Odour control and ventilation
EN 12255-10, Wastewater treatment plants - Part 10: Safety principles
EN 12255-13, Wastewater treatment plants - Part 13: Chemical treatment - Treatment of wastewater by
precipitation/flocculation
EN 16323, Glossary of wastewater engineering terms
EN 60529, Degrees of protection provided by enclosures (IP Code)
EN 60034-1, Rotating electrical machines - Part 1: Rating and performance
EN 16932 (all parts), Drain and sewer systems outside buildings - Pumping systems
EN ISO 14122-2:2016, Safety of machinery - Permanent means of access to machinery - Part 2: Working
platforms and walkways (ISO 14122-2:2016)
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 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/
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3.1
structure
construction intended to fulfil a function
[SOURCE: EN 16323:2014, definition 2.1.6.11]
3.2
equipment
any component which is installed in, mounted on, attached to, or operated on structures, in the
performance of their intended function
3.3
unit
any structure including any related equipment which is used as a process stage and which can be
isolated from other parallel, upstream or downstream structures
Note 1 to entry: Examples for a unit are: a grit chamber, a clarifier, an aeration tank, a thickener, a digester.
3.4
assembly
mechanical equipment that can be removed and replaced as a whole
Note 1 to entry: Examples for an assembly are a pump, a compressor, a gas engine, an aerator.
3.5
wastewater treatment plant
facility for the physical, biological and/or chemical treatment of wastewater
[SOURCE: EN 16323:2014, definition 2.3.9.18]
3.6
tracks
those parts of a structure on which wheels run
3.7
design mechanical load
Y
N
effective average load in continuous operation under full loading
Note 1 to entry: It is greater than or equal to the value of the operating loading which, for example, fluctuates as a
function of the given load.
[SOURCE: EN 16323:2014, definition 2.3.10.8]
3.8
continuous load bearing capacity
Y
C
load bearing capacity in continuous operation under full load
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3.9
maximum loading
Y
max
peak loading which is taken as the switch-off value
Note 1 to entry: E.g. value to which overload circuit breakers are adjusted.
3.10
maximum load bearing capacity
YB
highest possible load bearing capacity limited to short-term load peaks, such as occur on switching on
and off
Note 1 to entry: In addition, alarm loadings Y , lying between the design loading Y and the switch-off loading
S N
Ymax, can be agreed as required, YN and Ymax being stated by the equipment supplier.
3.11
utilisation factor
K
A
parameter for the effects on drive units etc., intrinsic to their operation
Note 1 to entry: Usually K includes, either directly or indirectly, information on the loading, running time and
A
temperature and is an overall value of the relationship between load bearing capacity and loading.
3.12
design service life
operating time until break-down of a machinery element stressed due to wear under design mechanical
load which is reached by a certain percentage of the elements tested
Note 1 to entry: As an example, the percentage for rolling bearings is 90 %.
Note 2 to entry: The design service life is different from both the warranty time and an average service life of use,
as used for cost efficiency calculations.
Note 3 to entry: The design service life is different from the cyclic design life (see 3.19).
Note 4 to entry: The design service life is often expressed as the mean time between failures.
3.13
design working life
assumed period for which a structure or part of it is to be used for its intended purpose with anticipated
repair and maintenance but without renovation or replacement being necessary
Note 1 to entry: Design working life can often be significantly longer than “design life” and is of critical
importance when calculating the longer-term resilience of drainage infrastructure, to, for example, climate change
impacts.
[SOURCE: EN 1990:2023, modified to provide consistency with the terminology in EN 16323:2014]
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3.14
expected service life
anticipated usage time of the plant, unit or equipment
Note 1 to entry: The horizon of cost calculations shall be based on the expected design service life. It shall include
investment and repeated investment and operational costs during the design service life. Such calculations shall
include expected price increases as well as expected interest rates. Such cost calculations can be compared as
current worth values or annuities.
3.15
design horizon
length of time (or a date) in the future for which the use of the facility can be reasonably anticipated to
be required
Note 1 to entry: The design Horizon is usually equal to (or a multiple of) the Design Working Life. E.g. a design
Horizon of 60 years may be chosen for assets made up of predominantly civil structures.
3.16
mode of operation
condition or manner in which a unit can operate or function
Note 1 to entry: Examples of condition include. frequency of starts, temperatures, etc.
3.17
degree of protection
condition related to the effects on motors and other electrical equipment intrinsic to their operating
environment
Note 1 to entry: E.g. environmental conditions can include effects of water or dust.
3.18
relevant authority
organization with appropriate statutory powers of control
[SOURCE: EN 16323:2014, definition 2.1.3.10]
3.19
cyclic design life
period of time to be applied in computational verifications for alternating or threshold loads (e.g. in
fatique verifications)
Note 1 to entry: The cyclic design life is different from the warranty time, the design service life (see 3.12) and an
expected service life (see 3.15).
4 Symbols and abbreviations
MCC Motor Control Centre
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5 Requirements
5.1 General requirements
Design and construction of wastewater treatment plants shall meet the following requirements:
a) compliance with discharge limits;
b) capability to satisfactorily treat the full range of flows and loads;
c) minimizing the Health Safety and Wellbeing risks to all personnel
d) elimination or management of nuisance, odour, noise, toxicity, aerosols and foam. Each shall meet
the relevant requirements according to EN 12255-9 and EN 12255-10;
e) minimization of the danger to operating and maintenance personnel.
f) during the design process reasonable consideration shall be given to the future expansion of the
facility to accommodate:
— inclusion of population growth;
— inclusion of likely changes in environmental discharge requirements (particularly air and
water quality);
— inclusion of the effects of climate change, e.g. increased risk from flooding and droughts;
— potential for change in legislation;
g) achievement of the expected service life and long-term structural integrity, including water and gas
tightness;
h) provisions shall be made for all operation and maintenance to be carried out safely;
i) asset supportability and logistic support considerations shall be integrated into the design of a
system or equipment to ensure the equipment is supported throughout its expected service life and
remains within performance requirements;
j) provision for future extensions or modifications of the plant shall be considered;
k) capability to deliver the requirements for Throughput, Reliability, Availability, Maintainability (T-
RAM);
l) be cost effective in respect of total costs (capital and operating costs);
m) the energy consumption during construction and operation shall be considered;
n) the waste products shall be reduced in quantity and improved in quality as far as reasonably
achievable to allow for reuse or safe disposal.
NOTE National regulations can apply.
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5.2 Design requirements
5.2.1 Resilience
The following requirements shall be considered during the design stage of a wastewater treatment
plant to ensure resilience:
a) all assemblies that are subject to occasional failure (e.g. pumps and compressors) shall be installed
with sufficient stand-by capacity so as to achieve full treatment capacity and efficiency with one
assembly out of service. In the case where stand-by assemblies cannot be practically installed,
provisions shall be made to replace rapidly by another one kept in stock;
b) in order to facilitate maintenance, repair or replacement, upstream and downstream isolation shall
be provided and it shall be possible to bypass every unit or assembly, either by a parallel unit or
assembly, channel or pipe;
c) where necessary the inlet to the treatment plant shall include a facility which limits the flow. Such
facilities may be balancing tanks and/or stormwater overflows as required by the relevant
authorities;
d) where the primary power supply cannot be relied upon the need for a secondary power supply
shall be risk assessed including the likelihood of power interruption and shall consider historical
information and robustness of supply. The assessment of the probability of supply failure shall
include supply interruptions of any duration. The mitigating measures shall consider the
operational time to respond and the criticality of the process e.g. impact on compliance, risk of
pollution or permit failure etc.
Where an application requires a secondary power supply, all other possible points of weakness in
the system (other than just the primary power source) that can impact on the treatment process
shall be identified. The selection of the most appropriate technology/solution to provide secondary
power shall be based on Whole Life Cost;
e) Motor control centres (MCC) that are identified as critical to the process treatment shall be
provided with a mobile generation point for the provision of secondary power under emergency/
maintenance conditions. Mobile generation shall be rated in line with the associated distribution
transformer and shall provide sufficient power directly to the consumer without the need for
temporary distribution equipment;
f) when the power supply is restored after an interruption, the treatment plant shall be designed so
that normal operating status is resumed automatically. This can require an automated sequential
start-up of power consumers;
g) appropriate provision shall be made for the case of malfunction or emergency;
h) due consideration shall be given to providing resilience by designing systems with parallel units or
components, rather than designing large single-stream systems;
i) the number and skill level of available maintenance resources shall be considered when designing
units and defining the associated maintenance requirements. The security of supply for future
maintenance services and spares shall also be considered including the standardization and
updating of software to minimize the impact of operating obsolete equipment;
j) the design shall take into consideration the required operating regime and, in particular, allowance
shall be made for maintenance of equipment that is required to run 24 h a day, 7 days a week. The
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design of equipment shall take into account the spares strategy and incorporate the appropriate
amount of redundancy. In order to permit maintenance, repair and replacement of process
equipment the designer shall consider the need for upstream and downstream isolation methods.
5.2.2 Safety and accessibility
The following requirements shall be considered during the design stage of a wastewater treatment
plant to ensure safety and accessibility:
a) The design shall enable operation, maintenance and cleaning to be carried out easily and safely (e.g.
access, flushing connections to pipes, isolation means).
b) Equipment shall be designed such that it can be easily delivered, installed, maintained, operated
and replaced. Structures shall have sufficient installation openings and lifting equipment (e.g. lifting
hooks or rails or a crane).
Common types of lifting systems are:
— Overhead crane
— Gantry Crane
— Fixed monorail
— 'A' Frame
— Jib crane
— Davit
— Mobile hoist
— Mobile crane
c) Where large covers are used or other plant and equipment require the use of a mobile crane then a
suitable access road will be provided. Sufficient footprint for mobile cranes to park and operate and
an area for placing the covers shall be provided.
Covers shall contain sufficient openings and access hatches for routine operation and maintenance
to be carried out from outside.
The creation of confined spaces that require regular man- entry should be minimized.
Covers should be completely removable to provide the best possible access for personnel and
equipment.
d) A means of providing sufficient ventilation of the areas to be accessed shall be considered in the
design.
e) Instruments and equipment requiring adjustment or routine maintenance shall, wherever possible,
be accessible from ground level because working at height carries an increased risk to safety and
the provision of permanent above-ground access can be costly.
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5.2.3 Other design requirements
The following requirements shall also be considered during the design stage of a wastewater treatment
plant:
a) Provision shall be made for taking representative samples upstream and downstream of each
process unit (including sludge treatment) and of any other flow whose characteristics are
important for operation and supervision e.g. return flows from various treatment processes.
b) The design shall ensure that all information (quantities and qualities) that is important for effective
operation of the plant (or to demonstrate compliance with regulatory requirement) is readily
obtainable e.g. flows, levels, pressures, temperatures, dissolved oxygen concentrations, pH-values.
c) In order to obtain representative data, measurement and sampling points should be located on a
straight length of pipe or channel and located as far as possible from bends. Measurement
equipment should be fitted in accordance with manufactures instructions.
d) Equipment shall, wherever possible, be obtained from manufacturers operating a quality system in
compliance with EN ISO 9001:2015. Materials and manufactured articles shall, wherever possible,
be of EC origin. Recycled materials should be used where appropriate.
e) Off-site manufacturing opportunities shall be explored as alternatives to traditional on-site
construction for all aspects of the design from civil structures through to electrical equipment. Pre-
assembled components, units, pre-cast structures, packaged-plants and skid-mounted, pre-
fabricated assemblies delivered to site, shall be considered. These solutions offer many advantages
including safer construction environments, reduced project durations and reduced customer
impact.
f) Buildings or enclosures to house process units and equipment should only be provided where there
is a requirement to provide security, protect assets against the elements, or where a safe
environment is required in order to carry out frequent or critical operating and maintenance
activities, or where planning constraints dictate or the containment of noise, dust, vibration or
odour is not achievable by other means.
g) The provision of permanent buildings for housing equipment is costly. However, when deciding
whether to provide a building it is necessary to balance cost against the need to ensure that
equipment is protected from the elements, can be attended to and maintained as necessary and
does not represent a source of nuisance from noise, odour or dust.
h) Decisions whether to build structures above or below ground shall be based upon lowest whole-life
cost. Factors such as pumping and waste disposal costs and planning and environmental
constraints shall be taken into consideration.
i) Where designin
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