EN 12255-11:2023

Wastewater treatment plants - Part 11: General data required

This document specifies data which is necessary for the planning, design, bidding, performance guarantees, construction, start-up and compliance testing of a wastewater treatment plant or parts of it. This document gives fundamental information about the practices; this document has not attempted to specify all available practices.

Kläranlagen - Teil 11: Erforderliche allgemeine Angaben

Dieses Dokument legt allgemeine Grundlagen für die Planung, Auslegung, Angebotserstellung, Leistungsgarantien, Errichtung, Inbetriebnahme und Abnahmeprüfung von Kläranlagen oder Teilen von Kläranlagen fest. Die Unterschiede bei der Abwasserbehandlung in Europa haben zu einer Vielzahl von Verfahrensweisen geführt. Dieses Dokument enthält grundsätzliche Angaben zu den Verfahrensweisen; es legt jedoch nicht alle Einzelheiten jeder Verfahrensweise fest.

Stations d’épuration - Partie 11 : Informations générales exigées

Le présent document spécifie les données nécessaires pour la planification, la conception, la proposition, les garanties de performance, la construction, la mise en service et le contrôle de conformité d’une station d’épuration des eaux usées ou d’une partie de cette station. Le présent document donne des informations de base sur ces pratiques ; il n’est pas destiné à spécifier toutes les pratiques disponibles.

Čistilne naprave za odpadno vodo - 11. del: Zahtevani splošni podatki

General Information

• Status: Published
• Publication Date: 07-Feb-2023
• ICS: 13.060.30 - Sewage water
• Technical Committee: CEN/TC 165 - Waste water engineering
• Drafting Committee: CEN/TC 165/WG 40 - Wastewater treatment plants > 50 PT
• Current Stage: 6060 - Definitive text made available (DAV) - Publishing
• Start Date: 08-Feb-2023
• Due Date: 29-Jul-2022
• Completion Date: 08-Feb-2023
• Directive: 93/38/EEC - Procurement procedures of entities operating in the water, energy, transport and telecommunications sectors
• Mandate: M/BC/CEN/88/15 - Standardization request to CEN/CENELEC in the field of Water supply, drainage and sewerage
• Ref Project: SIST EN 12255-11:2023 - Wastewater treatment plants - Part 11: General data required

Relations

• Replaces: EN 12255-11:2001 - Wastewater treatment plants - Part 11: General data required
• Effective Date: 04-Apr-2018

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN 12255-11:2023
01-maj-2023
Nadomešča:
SIST EN 12255-11:2001
Čistilne naprave za odpadno vodo - 11. del: Zahtevani splošni podatki
Wastewater treatment plants - Part 11: General data required
Kläranlagen - Teil 11: Erforderliche allgemeine Angaben
Stations d’épuration - Partie 11 : Informations générales exigées
Ta slovenski standard je istoveten z: EN 12255-11:2023
ICS:
13.060.30 Odpadna voda Sewage water
SIST EN 12255-11:2023 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN 12255-11:2023
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SIST EN 12255-11:2023
EN 12255-11
EUROPEAN STANDARD
NORME EUROPÉENNE
February 2023
EUROPÄISCHE NORM
ICS 13.060.30 Supersedes EN 12255-11:2001
English Version
Wastewater treatment plants - Part 11: General data
required

Stations d'épuration - Partie 11 : Informations Kläranlagen - Teil 11: Erforderliche allgemeine

générales exigées Angaben
This European Standard was approved by CEN on 2 January 2023.

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. Up-to-date lists and bibliographical references

concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN

member.

This European Standard exists 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.
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. EN 12255-11:2023 E

worldwide for CEN national Members.
---------------------- Page: 3 ----------------------
SIST EN 12255-11:2023
EN 12255-11:2023 (E)
Contents Page

European foreword ....................................................................................................................................................... 3

Introduction .................................................................................................................................................................... 5

1 Scope .................................................................................................................................................................... 6

2 Normative references .................................................................................................................................... 6

3 Terms and definitions ................................................................................................................................... 6

4 Symbols and abbreviations ......................................................................................................................... 7

5 Requirements ................................................................................................................................................... 7

5.1 Contract strategy ............................................................................................................................................. 7

5.2 Provision of loading data.............................................................................................................................. 8

5.2.1 General ................................................................................................................................................................ 8

5.2.2 Sewerage system ............................................................................................................................................. 8

5.2.3 Population served ........................................................................................................................................... 8

5.2.4 Significant trades and industries .............................................................................................................. 8

5.2.5 Data from existing wastewater treatment plants ............................................................................... 9

5.2.6 Design flows and loads ............................................................................................................................... 10

5.3 Effluent quality, requirements for the disposal of residues and sludge .................................. 10

5.3.1 Effluent quality .............................................................................................................................................. 10

5.3.2 Requirements for storm water overflow discharge ........................................................................ 10

5.3.3 Requirements for the residues from preliminary treatment ...................................................... 11

5.3.4 Requirements for sludge disposal ......................................................................................................... 11

5.4 Site description ............................................................................................................................................. 11

5.4.1 General ............................................................................................................................................................. 11

5.4.2 Plans (maps) of the site .............................................................................................................................. 11

5.4.3 Existing wastewater treatment plants ................................................................................................. 11

5.4.4 Ground geology, groundwater and climate ........................................................................................ 12

5.4.5 Special site constraints .............................................................................................................................. 12

5.5 Additional data required ........................................................................................................................... 12

5.6 Time schedule ............................................................................................................................................... 13

5.7 Start-up and guarantee testing ............................................................................................................... 13

5.7.1 Start-up ............................................................................................................................................................ 13

5.7.2 Guarantee testing ......................................................................................................................................... 14

5.8 Operational cost information .................................................................................................................. 14

5.9 Documents to be provided by a turn-key contractor or the consulting engineer ................ 14

5.9.1 Complete documents .................................................................................................................................. 14

5.9.2 Design options ............................................................................................................................................... 14

5.9.3 Proposed solution ........................................................................................................................................ 14

5.10 Calculation and presentation of costs ................................................................................................... 15

5.10.1 Construction costs ........................................................................................................................................ 15

5.10.2 Operational costs ......................................................................................................................................... 15

5.10.3 Presentation of costs ................................................................................................................................... 17

Bibliography ................................................................................................................................................................. 18

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SIST EN 12255-11:2023
EN 12255-11:2023 (E)
European foreword

This document (EN 12255-11:2023) has been prepared by Technical Committee CEN/TC 165 “Waste

water engineering”, the secretariat of which is held by DIN.

This European Standard shall be given the status of a national standard, either by publication of an

identical text or by endorsement, at the latest by August 2023, and conflicting national standards shall

be withdrawn at the latest by August 2023.

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. CEN shall not be held responsible for identifying any or all such patent rights.

This document supersedes EN 12255-11:2001.

This is the eleventh part of the EN 12255 series 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 construction principles
— Part 2: Storm management systems
— 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 Part 2 is under preparation.
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SIST EN 12255-11:2023
EN 12255-11:2023 (E)

Any feedback and questions on this document should be directed to the users’ national standards body.

A complete listing of these bodies can be found on the CEN website.

According to the CEN-CENELEC Internal Regulations, the national standards organisations of the

following countries are bound to implement this European Standard: 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 the

United Kingdom.
---------------------- Page: 6 ----------------------
SIST EN 12255-11:2023
EN 12255-11:2023 (E)
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 below 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 stabilised 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.

NOTE For requirements on pumping installations at wastewater treatment plants, see EN 752, Drain and

sewer systems outside buildings — Sewer system management 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.
---------------------- Page: 7 ----------------------
SIST EN 12255-11:2023
EN 12255-11:2023 (E)
1 Scope

This document specifies data which is necessary for the planning, design, bidding, performance

guarantees, construction, start-up and compliance testing of a wastewater treatment plant or parts of it.

This document gives fundamental information about the practices; this document has not attempted to

specify all available practices.
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:

— IEC Electropedia: available at https://www.electropedia.org/
— ISO Online browsing platform: available at https://www.iso.org/obp
3.1
relevant plant

new wastewater treatment plant; rebuild, upgrade or extension of an existing wastewater treatment

plant or a part of a new or extended wastewater treatment plant (e.g. sludge handling facilities)

3.2
client

municipality, city or other organization which intends to build a wastewater treatment plant or parts

thereof, or its representative
[SOURCE: EN 12255-1:2002, 3.6]
3.3
functional tender

tender document that contains the design flows and loads, a description of the site where the relevant

plant is to be erected, the relevant discharge limits and any additional requirements

3.4
sectional tender

separate tender documents prepared for different sections of work that may be constructed by different

entities

Note 1 to entry: Examples of sections of work can include: earth work, concrete work, mechanical equipment,

electrical installations, buildings, etc.
3.5
consulting engineer

independent engineer or engineering company commissioned by the client designing a wastewater

treatment plant or parts of it and/or supervising the construction

Note 1 to entry: The consulting engineer may assist the client with any work preparing all or part of the tender

documents. The consulting engineer supervises the construction and checks the time schedule and costs. The

consulting engineer has knowledge and experience in planning, design and operational aspects of wastewater

treatment plants. In some countries, a special certification may be required.
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SIST EN 12255-11:2023
EN 12255-11:2023 (E)
3.6
turn-key contractor

builder who agrees to complete a facility so that it is ready for use when delivered to the other

contracting party

Note 1 to entry: The turn-key contractor is typically a company which has knowledge and experience in planning,

design, construction and operational aspects of wastewater treatment plants.
3.7
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: The "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 1990:2002, 1.5.2.8, modified to provide consistency with the terminology in EN 16323]

4 Symbols and abbreviations
COD chemical oxygen demand
BOD biochemical oxygen demand in 5 days
TKN total Kjeldahl nitrogen
NH -N ammonium-nitrogen
NO -N nitrate-nitrogen
COD/N ratio of COD and nitrogen
COD/P ratio of COD and phosphorus
5 Requirements
5.1 Contract strategy

The client may decide whether a functional tender or a sectional tender shall be prepared. The client

may commission a consulting engineer to carry out one or more of the following:
— establish the design loads and data as described in 5.2;
— prepare the tender documents for a functional tender;

— design the plant and estimate the costs and prepare the tender documents for the sectional tender;

— inspect the construction in case of functional tendering;
— supervise and coordinate the construction in case of sectional tendering;

— evaluate the bids on the tenders and to propose which contractor or contractors (in case of

sectional tendering) should be commissioned.
---------------------- Page: 9 ----------------------
SIST EN 12255-11:2023
EN 12255-11:2023 (E)
5.2 Provision of loading data
5.2.1 General

Where applicable the following basic data either measured or estimated shall be provided by the client

or his representative, e.g. consulting engineer.
5.2.2 Sewerage system
The data on the sewerage system should include:
— areas served by combined and/or separate sewers;

— proportions of flows and loads from separate and/or combined sewer systems in dry weather

conditions;

— storage capacity for storm water within the sewerage system and details of flow control systems;

— potential to control and balance flows and loads within the sewerage system;

— infiltration flows in dry weather conditions and their seasonal fluctuations (where appropriate);

— septic and corrosive components of the wastewater.

Dry weather conditions and fluctuations in storm water flow will be impacted by climate change. Local

interpretation of average and worst-case climate change scenarios over the design working life of the

sewerage system should be assessed to determine their potential impact.
5.2.3 Population served
The data on the population served shall include:
— current population connected to the sewerage system;
— population connected at start-up of the plant;

— population connected at design working life of the principal components and the design horizon for

the plant;
— seasonal variations of population (e.g. holiday periods);
— weekly variations of population (e.g. movement of commuting population).
5.2.4 Significant trades and industries

A list of trades and industries which discharge significant loads to the sewerage system should include

the following flows and loads, e.g.:

COD, BOD , TKN, NH -N, NO -N, total phosphorus, total suspended solids, organic suspended solids,

5 4 3
salinity and alkalinity; shown as current, start-up, and design target data for:
— hourly peak (m /h, kg/h);
— daily peak and daily average (m /d, kg/d);
— weekly peak day (m /d, kg/d);
...

SLOVENSKI STANDARD
oSIST prEN 12255-11:2021
01-september-2021
Čistilne naprave za odpadno vodo - 11. del: Zahtevani splošni podatki
Wastewater treatment plants - Part 11: General data required
Kläranlagen - Teil 11: Erforderliche allgemeine Angaben
Stations d'épuration - Partie 11: Informations générales exigées
Ta slovenski standard je istoveten z: prEN 12255-11
ICS:
13.060.30 Odpadna voda Sewage water
oSIST prEN 12255-11:2021 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
oSIST prEN 12255-11:2021
---------------------- Page: 2 ----------------------
oSIST prEN 12255-11:2021
DRAFT
EUROPEAN STANDARD
prEN 12255-11
NORME EUROPÉENNE
EUROPÄISCHE NORM
June 2021
ICS 13.060.30 Will supersede EN 12255-11:2001
English Version
Wastewater treatment plants - Part 11: General data
required

Stations d'épuration - Partie 11: Informations Kläranlagen - Teil 11: Erforderliche allgemeine

générales exigées Angaben

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 12255-11:2021 E

worldwide for CEN national Members.
---------------------- Page: 3 ----------------------
oSIST prEN 12255-11:2021
prEN 12255-11:2021 (E)
Contents Page

European foreword ...................................................................................................................................................... 3

Introduction .................................................................................................................................................................... 4

1 Scope .................................................................................................................................................................... 5

2 Normative references .................................................................................................................................... 5

3 Terms and definitions ................................................................................................................................... 5

4 Symbols and abbreviations ......................................................................................................................... 6

5 Requirements ................................................................................................................................................... 6

5.1 Contract strategy ............................................................................................................................................. 6

5.2 Provision of loading data ............................................................................................................................. 7

5.2.1 General................................................................................................................................................................ 7

5.2.2 Sewerage system ............................................................................................................................................. 7

5.2.3 Population served ........................................................................................................................................... 7

5.2.4 Significant trades and industries .............................................................................................................. 7

5.2.5 Data from existing wastewater treatment plants ............................................................................... 8

5.2.6 Design flows and loads .................................................................................................................................. 8

5.3 Effluent quality, requirements for the disposal of residues and sludge ..................................... 9

5.3.1 Effluent quality ................................................................................................................................................ 9

5.3.2 Requirements for storm water overflow discharge ........................................................................... 9

5.3.3 Requirements for the residues from preliminary treatment ......................................................... 9

5.3.4 Requirements for sludge disposal ............................................................................................................ 9

5.4 Site description .............................................................................................................................................. 10

5.4.1 General.............................................................................................................................................................. 10

5.4.2 Plans (maps) of the site .............................................................................................................................. 10

5.4.3 Existing wastewater treatment plants .................................................................................................. 10

5.4.4 Ground geology, groundwater and climate ......................................................................................... 10

5.4.5 Special site constraints ............................................................................................................................... 10

5.5 Additional data required ........................................................................................................................... 11

5.6 Time schedule ................................................................................................................................................ 12

5.7 Start-up and guarantee testing ................................................................................................................ 12

5.7.1 Start-up ............................................................................................................................................................. 12

5.7.2 Guarantee testing .......................................................................................................................................... 12

5.8 Operational cost information ................................................................................................................... 13

5.9 Documents to be provided by a turn-key contractor or the consulting engineer ................. 13

5.9.1 Complete documents ................................................................................................................................... 13

5.9.2 Design options................................................................................................................................................ 13

5.9.3 Proposed solution ......................................................................................................................................... 13

5.10 Calculation and presentation of costs ................................................................................................... 14

5.10.1 Construction costs ........................................................................................................................................ 14

5.10.2 Operational costs .......................................................................................................................................... 14

5.10.3 Presentation of costs ................................................................................................................................... 15

Bibliography ................................................................................................................................................................. 16

---------------------- Page: 4 ----------------------
oSIST prEN 12255-11:2021
prEN 12255-11:2021 (E)
European foreword

This document (prEN 12255-11:2021) 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 12255-11:2001.

This document has been prepared under a mandate given to CEN by the European Commission and the

European Free Trade Association, and supports essential requirements of EU Directive(s).

This is the eleventh part of the EN 12255 series 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 construction principles
— Part 2: Storm management systems
— Part 3: Preliminary treatment
— Part 4: Primary settlement
— Part 5: Lagooning processes
— Part 6: Activated sludge processes
— 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
— Part 14: Disinfection

— Part 15: Measurement of the oxygen transfer in clean water in activated sludge aeration tanks

— Part 16: Physical (mechanical) filtration
---------------------- Page: 5 ----------------------
oSIST prEN 12255-11:2021
prEN 12255-11:2021 (E)
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 below.
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.

NOTE For requirements on pumping installations at wastewater treatment plants see EN 752, Drain and

sewer systems outside buildings and EN 16932, Drain and sewer systems outside buildings — Pumping systems:

— Part 1: General requirements;
— Part 2: Positive pressure systems;
— Part 3: Vacuum systems.
---------------------- Page: 6 ----------------------
oSIST prEN 12255-11:2021
prEN 12255-11:2021 (E)
1 Scope

This document specifies data which is necessary for the planning, design, bidding, performance

guarantees, construction, start-up and compliance testing of a wastewater treatment plant or parts of it.

Differences in wastewater treatment throughout Europe have led to a variety of practices being

developed. This document gives fundamental information about the practices; this document has not

attempted to specify all available practices.
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 terminological databases for use in standardization at the following addresses:

— IEC Electropedia: available at https://www.electropedia.org/
— ISO Online browsing platform: available at https://www.iso.org/obp
3.1
relevant plant

new wastewater treatment plant; rebuild, upgrade or extension of an existing wastewater treatment

plant or a part of a new or extended wastewater treatment plant (e.g. sludge handling facilities)

3.2
client

municipality, city or other organization which intends to build a wastewater treatment plant or parts

thereof, or its representative
[SOURCE: EN 12255-1]
3.3
functional tender

tender document that contains the design loads, a description of the site where the relevant plant is to

be erected, the relevant discharge limits and any additional requirements
3.4
sectional tender

separate tender documents prepared for different sections of work that may be constructed by different

entities

Note 1 to entry: Examples of sections of work can include: earth work, concrete work, mechanical equipment,

electrical installations, buildings etc.
---------------------- Page: 7 ----------------------
oSIST prEN 12255-11:2021
prEN 12255-11:2021 (E)
3.5
consulting engineer

independent engineer or engineering company commissioned by the client designing a wastewater

treatment plant or parts of it and/or supervising the construction

Note 1 to entry: The consulting engineer may assist the client with any work preparing all or part of the tender

documents. The consulting engineer supervises the construction and checks the time schedule and costs. The

consulting engineer has knowledge and experience in planning, design and operational aspects of wastewater

treatment plants. In some countries a special certification may be required
3.6
turn-key contractor

builder who agrees to complete a facility so that it is ready for use when delivered to the other

contracting party

Note 1 to entry: The turn-key contractor is typically a company which has knowledge and experience in planning,

design, construction and operational aspects of wastewater treatment plants.
4 Symbols and abbreviations
COD chemical oxygen demand
BOD biochemical oxygen demand in 5 days
TKN total Kjeldahl nitrogen
NH -N ammonium-nitrogen
NO -N nitrate-nitrogen
COD/N ratio of COD and nitrogen
COD/P ratio of COD and phosphorus
5 Requirements
5.1 Contract strategy

The client may decide whether a functional tender or a sectional tender shall be prepared. The client

may commission a consulting engineer to carry out one or more of the following:
— establish the design loads and data as described in 5.2;
— prepare the tender documents for a functional tender;

— design the plant and estimate the costs and prepare the tender documents for the sectional tender;

— inspect the construction in case of functional tendering;
— supervise and coordinate the construction in case of sectional tendering;

— evaluate the bids on the tenders and to propose which contractor or contractors (in case of

sectional tendering) should be commissioned.
---------------------- Page: 8 ----------------------
oSIST prEN 12255-11:2021
prEN 12255-11:2021 (E)
5.2 Provision of loading data
5.2.1 General

Where applicable the following basic data either measured or estimated shall be provided by the client

or his representative e.g. consulting engineer.
5.2.2 Sewerage system
The data on the sewerage system should include:
— areas served by combined and/or separate sewers;

— proportions of flows and loads from separate and/or combined sewer systems in dry weather

conditions;

— storage capacity for storm water within the sewerage system and details of flow control systems;

— potential to control and balance flows and loads within the sewerage system;

— infiltration flows in dry weather conditions and their seasonal fluctuations (where appropriate);

— septic and corrosive components of the wastewater.
5.2.3 Population served
The data on the population served shall include:
— current population connected to the sewerage system;
— population connected at start-up of the plant;
— population connected at design horizon;
— seasonal variations of population (e.g. holiday periods);
— weekly variations of population (e.g. movement of commuting population).
5.2.4 Significant trades and industries

A list of trades and industries which discharge significant loads to the sewerage system should include

the following flows and loads e.g.:

COD, BOD , TKN, NH -N, NO -N, total phosphorus, total suspended solids, organic suspended solids,

5 4 3
salinity and alkalinity; shown as current, start-up, and design target data for:
— hourly peak (m /h, kg/h);
— daily peak and daily average (m /d, kg/d);
— weekly peak day (m /d, kg/d);
— maximum weekly average (m /d, kg/d);
— annual average (m /a, kg/a);
— annual average and 85 %-percentile (m /a, kg/a).
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oSIST prEN 12255-11:2021
prEN 12255-11:2021 (E)
In addition, for trades and industries with seasonal fluctuati
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