EN 12255-12:2024

SLOVENSKI STANDARD
01-junij-2024
Čistilne naprave za odpadno vodo - 12. del: Krmiljenje in avtomatizacija
Wastewater treatment plants - Part 12: Control and automation
Kläranlagen - Teil 12: Steuerung und Automatisierung
Stations d'épuration - Partie 12: Régulation et automatisation
Ta slovenski standard je istoveten z: EN 12255-12:2024
ICS:
13.060.30 Odpadna voda Sewage water
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN 12255-12
EUROPEAN STANDARD
NORME EUROPÉENNE
March 2024
EUROPÄISCHE NORM
ICS 13.060.30 Supersedes EN 12255-12:2003
English Version
Wastewater treatment plants - Part 12: Control and
automation
Stations d'épuration - Partie 12 : Régulation et Kläranlagen - Teil 12: Steuerung und Automatisierung
automatisation
This European Standard was approved by CEN on 29 January 2024.

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
© 2024 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 12255-12:2024 E
worldwide for CEN national Members.

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 Instrumentation and control requirements . 8
5.1 General requirements . 8
5.2 Instruments. 8
5.3 Instrumentation systems . 8
5.4 Process control and automation . 10
6 Design and implementation . 11
6.1 Initial design . 11
6.2 Detailed design . 11
6.3 Commissioning, test and take over. 12
Annex A (informative) Guidance for the selection of instrumentation, control and automation
systems . 13
A.1 General. 13
A.2 Instrumentation life cycle . 14
A.2.1 Overview . 14
A.2.2 Stage 1 - Instrumentation purpose . 14
A.2.3 Stage 2 - Instrumentation specification . 14
A.2.4 Stage 3 - Installation . 15
A.2.5 Stage 4 - Operation and maintenance . 15
A.2.6 Stage 5 - Review and replacement . 16
A.3 Examples of basic instrumentation and control systems . 16
A.3.1 General. 16
A.3.2 Simple relay-based control systems . 16
A.3.3 Programmable logic controller (PLC) based instrumentation and control systems . 17
A.3.4 Advanced process control . 18
A.4 The level of instrumentation, control and automation in wastewater systems . 19
A.4.1 Overview . 19
A.4.2 Determination of appropriate instrument and control systems for trickling reactor
plants . 19
A.4.3 Determination of appropriate instrument and control systems for activated sludge
plants . 21
Bibliography . 26

European foreword
This document (EN 12255-12:2024) 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 September 2024, and conflicting national standards shall
be withdrawn at the latest by September 2024.
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 12255-12:2003.
EN 12255-12:2003:
a) comprehensive revision and addition in all sections;
b) adaption to the state of the art;
c) updating of the normative references.
This is the twelfth 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 construction principles
• Part 2: Storm water 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.
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.
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 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 removal of micropollutants) G tertiary sludge
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.
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, Drain and sewer systems outside buildings —
Pumping systems:
— Part 1: General requirements;
— Part 2: Positive pressure systems;
— Part 3: Vacuum systems.
1 Scope
This document specifies general requirements for instrumentation and specific requirements for process
control and automation systems on wastewater treatment plants for more than 50 PT.
NOTE 1 Because of the rapid rate of development of sensor and control equipment, this document is intended as
an overview and uses examples and general requirements, not detailed equipment specifications. Detailed
information additional to that contained in this document can be obtained by referring to the Bibliography.
NOTE 2 Although EC directives become matters of law in member states of the EU and some other situations,
this standard is intended for wider use and hence those directives with clear technical guidance of a type that would
generally be appropriate in a standard are referenced in the text and listed in the Bibliography. The alternative of
listing requirements copied from directives would potentially create unacceptable conflict when directives are
revised.
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 16323:2014, Glossary of wastewater engineering terms
EN 62305-3, Protection against lightning — Part 3: Physical damage to structures and life hazard
(IEC 62305-3)
IEC 60364, Low voltage electrical installations
3 Terms and definitions
For the purposes of this document, the terms and definitions given in EN 16323:2014 and the following
apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
• ISO Online browsing platform: available at https://www.iso.org/obp
• IEC Electropedia: available at https://www.electropedia.org/
3.1
instrumentation
electronic or mechanical devices that are used to either sense or monitor process variables
Note 1 to entry: These can be split into sensors and monitors.
3.1.1
sensor
electrical or mechanical device that communicates the qualitative state of a process variable
Note 1 to entry: Examples of this include a contact probe or switch that outputs a 0 or 1 as an off/on state and
devices which transmit an electrical signal (usually a voltage) that is scalable to a process variable.
3.1.2
monitor
electrical or mechanical device that communicates the quantitative state of a process variable
Note 1 to entry: Examples of
...