EN 12255-3:2024

SLOVENSKI STANDARD
01-april-2024
Nadomešča:
SIST EN 12255-3:2001
SIST EN 12255-3:2001/AC:2001
Čistilne naprave za odpadno vodo - 3. del: Predhodna obdelava
Wastewater treatment plants - Part 3: Preliminary treatment
Kläranlagen - Teil 3: Abwasservorreinigung
Stations d’épuration - Partie 3 : Prétraitements
Ta slovenski standard je istoveten z: EN 12255-3:2024
ICS:
13.060.30 Odpadna voda Sewage water
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN 12255-3
EUROPEAN STANDARD
NORME EUROPÉENNE
January 2024
EUROPÄISCHE NORM
ICS 13.060.30 Supersedes EN 12255-3:2000
English Version
Wastewater treatment plants - Part 3: Preliminary
treatment
Stations d'épuration - Partie 3 : Prétraitements Kläranlagen - Teil 3: Abwasservorreinigung
This European Standard was approved by CEN on 3 December 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
© 2024 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 12255-3:2024 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, abbreviations and indices . 8
5 Planning . 10
6 Screening . 11
6.1 General. 11
6.2 Design of structures . 12
6.3 Screen design . 13
7 Screenings treatment . 18
7.1 General. 18
7.2 Structural design . 19
7.3 Design of screenings treatment equipment . 19
7.4 Screenings disposal/container loading . 21
8 Grit removal . 22
8.1 General. 22
8.2 Structural design . 23
8.3 Design of grit removal equipment . 23
9 Grit treatment . 24
9.1 General. 24
9.2 Structural design . 25
9.3 Design of grit treatment equipment . 26
10 Grease and oil separation . 27
11 Flow balancing and flow splitting . 27
12 Materials . 27
13 Control and automation requirements . 28
14 Operation and maintenance requirements . 29
15 Health and safety requirements . 29
Annex A (normative) Testing of the washing performance of screenings wash-presses (refers to
7.3.1) . 30
Annex B (informative) Testing procedures . 31
Bibliography . 36

European foreword
This document (EN 12255-3:2024) 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 July 2024, and conflicting national standards shall be
withdrawn at the latest by July 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 12255-3:2000.
3:2000:
a) comprehensive revision and additions in all sections;
b) the addition of design recommendations;
c) adaptation to the current state of the art;
d) updating of the Normative references;
e) editorial revision.
It is the third 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 design and construction principles
— Part 2: Storm water 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 1 Part 2 is under preparation.
NOTE 2 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”.
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
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
Detailed information additional to that contained in this document can be obtained by referring to the
bibliography.
1 Scope
This document specifies design principles and performance requirements for preliminary wastewater
treatment using screens with a mesh size above 50 μm, at plants serving more than 50 PT. It also
includes grit removal and grease separation.
NOTE 1 For micro-screens with a mesh size below 50 microns see EN 12255-16.
NOTE 2 The primary application of this document is for wastewater treatment plants designed for the
treatment of domestic and municipal wastewater. However, it contains information that can also be useful for
commercial and industrial wastewater pretreatment and for combined sewer overflows (CSO).
This document applies in combination with EN 12255-1 and EN 12255-10.
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 12255-10, Wastewater treatment plants — Part 10: Safety principles
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 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
aerated grit separator
structure for separating sand and other mineral matter from wastewater, using air to induce circulation
[SOURCE: Modified from EN 16323:2014, term number 2.3.9.1 “aerated grit chamber”, to recognize that
not all separators are chambers]
3.2
bar screen
device comprising bars to separate objects from fluids
3.3
blocking factor
f
B
ratio of the area of a screen being blocked by withheld matter, to the open area of the clean screen
3.4
grit chamber
grit separating trap with a circular or rectangular footprint
3.5
grit channel
grit separating tank with a rectangular footprint
3.6
grit classifier
equipment for draining water from grit
3.7
grit slurry
wet mineral and organic matter removed from a grit separator
3.8
grit separator
device to separate grit, sand or similar mineral material from wastewater
[SOURCE: EN 16323:2
...