prEN 12255-7

SLOVENSKI STANDARD
01-september-2023
Čistilne naprave za odpadno vodo - 7. del: Biološki reaktorji s pritrjeno biomaso
Wastewater treatment plants - Part 7: Biological fixed-film reactors
Kläranlagen - Teil 7: Biofilmreaktoren
Stations d’épuration - Partie 7 : Réacteurs biologiques à cultures fixées
Ta slovenski standard je istoveten z: prEN 12255-7
ICS:
13.060.30 Odpadna voda Sewage water
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
EUROPEAN STANDARD
NORME EUROPÉENNE
EUROPÄISCHE NORM
July 2023
ICS 13.060.30 Will supersede EN 12255-7:2002
English Version
Wastewater treatment plants - Part 7: Biological fixed-film
reactors
Stations d'épuration - Partie 7: Réacteurs biologiques à Kläranlagen - Teil 7: Biofilmreaktoren
cultures fixées
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 12255-7:2023 E
worldwide for CEN national Members.

Contents Page
European foreword . 4
Introduction . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 7
4 Symbols and abbreviations . 9
5 Planning . 9
5.1 Planning principles . 9
5.2 Design principles . 10
6 Biological fixed film reactors . 11
6.1 Types of fixed film reactors . 11
6.2 Selection of support media . 12
6.3 Biological trickling reactors (BTR) . 12
6.3.1 General. 12
6.3.2 Support media . 15
6.3.3 Dimensioning . 15
6.3.4 Flow distribution . 16
6.3.5 Ventilation . 17
6.3.6 Structures . 17
6.3.7 Mechanical equipment . 17
6.3.8 Control and automation . 17
6.4 Rotating biological contactors (RBC) . 17
6.4.1 General. 17
6.4.2 Structural requirements . 18
6.4.3 Mechanical requirements . 19
6.4.4 Support media . 19
6.4.5 Dimensioning . 20
6.4.6 Flow distribution . 22
6.4.7 Oxygen supply . 22
6.4.8 Control and automation . 22
6.5 Submerged medium reactors (SMR) . 22
6.5.1 General. 22
6.5.2 Dimensioning . 24
6.6 Submerged medium filter (SMF) . 25
6.6.1 General. 25
6.6.2 Support media . 26
6.6.3 Dimensioning . 27
6.6.4 Flow distribution . 27
6.6.5 Air and oxygen supply . 27
6.6.6 Structural requirements . 28
6.6.7 Backwashing . 28
6.6.8 Control and automation . 29
6.7 Moving bed biological reactors (MBBR) . 29
6.7.1 General. 29
6.7.2 Support media . 31
6.7.3 Mechanical requirements . 31
6.7.4 Dimensioning . 31
6.7.5 Control and automation . 32
Annex A (informative) Dimensioning of reactors for biological wastewater treatment . 33
Bibliography . 35

European foreword
This document (prEN 12255-7:2023) has been prepared by Technical Committee CEN/TC 165
“Wastewater”, the secretariat of which is held by DIN.
This document is currently submitted to the CEN enquiry.
This document will supersede EN 12255-7:2002.
The main changes in comparison with the previous edition are:
a) comprehensive revision and additions in all sections;
b) addition of design recommendations;
c) addition of moving bed reactors (MBR);
d) adaptation to the current state of the art;
e) updating of the Normative references;
f) editorial revision.
It is the seventh Part prepared by the 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 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.
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 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
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.
1 Scope
This Part 7 of the EN 12255 series specifies design principles and performance requirements for
secondary and tertiary treatment of wastewater in biological fixed-film reactors at wastewater treatment
plants for more than 50 PT.
Its primary application is for wastewater treatment plants for the treatment of domestic and municipal
wastewater. It can also be applied for biodegradable industrial wastewater.
Biological fixed film reactors include rotating biological contactors (RBC), biological trickling reactors
(BTR), moving bed biological reactors (MBBR), submerged medium reactors (SMR) and submerged
media filters (SMF). Membrane Bioreactors (MBR) and anaerobic processes are not within the scope.
Some of the systems using fixed film bacteria are enhanced activated sludge systems (hybrid systems).
For such systems, EN 12255-6 also applies.
This docume
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