EN 12255-14:2023

SLOVENSKI STANDARD
01-september-2023
Nadomešča:
SIST EN 12255-14:2004
Čistilne naprave za odpadno vodo - 14. del: Dezinfekcija
Wastewater treatment plants - Part 14: Disinfection
Kläranlagen - Teil 14: Desinfektion
Stations d’épuration - Partie 14 : Désinfection
Ta slovenski standard je istoveten z: EN 12255-14:2023
ICS:
13.060.30 Odpadna voda Sewage water
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN 12255-14
EUROPEAN STANDARD
NORME EUROPÉENNE
July 2023
EUROPÄISCHE NORM
ICS 13.060.30 Supersedes EN 12255-14:2003
English Version
Wastewater treatment plants - Part 14: Disinfection
Stations d'épuration - Partie 14: Désinfection Kläranlagen - Teil 14: Desinfektion
This European Standard was approved by CEN on 28 May 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 12255-14:2023 E
worldwide for CEN national Members.

Contents Page
European foreword . 3
Introduction . 5
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 7
4 Symbols and abbreviations . 9
5 Design requirements . 10
5.1 General. 10
5.2 Planning . 11
5.2.1 General. 11
5.2.2 Level of disinfection . 11
5.3 Process design . 11
5.3.1 General. 11
5.3.2 UV radiation . 12
5.3.3 Ozonation . 13
5.3.4 Chlorination . 16
5.3.5 Peracids (Peracetic acid) . 18
5.3.6 Membrane filtration . 18
5.3.7 Effluent maturation ponds . 19
5.3.8 Soil filtration . 19
5.3.9 Hydrogen peroxide . 20
5.4 Process control . 20
5.5 Structures . 21
5.6 Health and safety . 21
Annex A (normative) Ozone system classification . 23
Annex B (informative) Measurement of ozone concentration in water. 24
B.1 General. 24
B.2 Titrimetric determination of the ozone concentration according to the KI method . 24
B.3 Photometric determination within the UV range . 28
Bibliography . 31
European foreword
This document (EN 12255-14:2023) has been prepared by Technical Committee CEN/TC 165
“Wastewater 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 January 2024, and conflicting national standards shall
be withdrawn at the latest by January 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 12255-14:2003.
th
It is the 14 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 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
• 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 below
in Figure 1:
Key
1 preliminary treatment
2 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 stabilized sludge
I digester gas
J returned water from dewatering
Figure 1 — Schematic diagram of wastewater treatment plants
Detailed information additional to that contained in this document can 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 and the
EN 16932 series:
—  Part 1: General requirements;
—  Part 2: Positive pressure systems;
—  Part 3: Vacuum systems.
1 Scope
This document specifies design principles and performance requirements for disinfection of effluents
(excluding sludge) at wastewater treatment plants serving more than 50 PT.
NOTE Sludge disinfection is described in EN 12255-8.
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 12255-1, Wastewater treatment plants - Part 1: General construction principles
EN 12255-5, Wastewater treatment plants - Part 5: Lagooning processes
EN 12255-10, Wastewater treatment plants - Part 10: Safety principles
EN 12255-12, Wastewater treatment plants - Part 12: Control and automation
EN 12255-15, Wastewater treatment plants - Part 15: Measurement of the oxygen transfer in clean water
in aeration tanks of activated sludge plants
EN 16323, Glossary of wastewater engineering terms
ISO 15727, UV-C devices — Measurement of the output of a UV-C lamp
3 Terms and definitions
For the purposes of this document, the terms and definitions given in EN 12255-1, 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/
3.1
residual concentration
concentration of a substance in the final effluent of a treatment stage
3.2
UV dose
product of UV irradiance and specific exposure time along the pathway of an infinitesimal small water
volume
Note 1 to entry: UV dose is expressed in millijoules per square centimetre (mJ/cm ).
3.3
UV intensity
quotient of the energy of the UV radiation received on the surface of an infinitesimal small area divided
by the size of the area
Note 1 to entry: The unit of UV intensity is W/m , measured in accordance with ISO 15727.
3.4
UV-reactor
closed vessel or an open channel section with an assembly of UV-lamps irradiating the water passing
through
3.5
bioassay
measurement of the concentration or potency of a substance by its effect on living cells or tissues
[SOURCE: EN 16323:2014, 2.3.5.4, modified to remove limitations]
3.6
specific ozone demand
required dissolved ozone concentration in the wastewater to achieve a level of disinfection
Note 1 to entry: The unit of specific ozone demand is typically g O /m or g O /l.
3 3
3.7
ozone destructor
device for destruction of residual ozone that has not been consumed in the ozonation process and is
accumulated in the gaseous form in an off-gas stream
Note 1 to entry: The destruction takes place in gas-phase by converting ozone (O3) into oxygen (O2).
3.8
chlorinator
equipment for dosing chlorine into water
Note 1 to entry: Includes in situ generation.
3.9
contact tank
tank for providing the required retention time for certain reactions to take place
3.10
contact time
required retention time at a certain concentration for a specific reaction to occur
3.11
membrane
semipermeable material used as filter media in membrane filtration processes
Note 1 to entry: Membranes normally are flat sheets, tubes or hollow fibres composed of a thin semipermeable
layer on a structural material.
3.12
permeate (noun)
liquid or gas that diffuses through a permeable membra
...