EN 12255-13:2023

SLOVENSKI STANDARD
01-september-2023
Nadomešča:
SIST EN 12255-13:2003
Čistilne naprave za odpadno vodo - 13. del: Kemijsko čiščenje odpadnih vod z
obarjanjem/kosmičenjem
Wastewater treatment plants - Part 13: Chemical treatment - Treatment of wastewater by
precipitation/flocculation
Kläranlagen - Teil 13: Chemische Behandlung - Abwasserbehandlung durch
Fällung/Flockung
Stations d'épuration - Partie 13: Traitement chimique - Traitement des eaux usées par
précipitation/floculation
Ta slovenski standard je istoveten z: EN 12255-13:2023
ICS:
13.060.30 Odpadna voda Sewage water
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN 12255-13
EUROPEAN STANDARD
NORME EUROPÉENNE
July 2023
EUROPÄISCHE NORM
ICS 13.060.30 Supersedes EN 12255-13:2002
English Version
Wastewater treatment plants - Part 13: Chemical
treatment - Treatment of wastewater by
precipitation/flocculation
Stations d'épuration - Partie 13: Traitement chimique - Kläranlagen - Teil 13: Chemische Behandlung -
Traitement des eaux usées par Abwasserbehandlung durch Fällung/Flockung
précipitation/floculation
This European Standard was approved by CEN on 24 April 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 12255-13:2023 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 . 8
4.1 Symbols . 8
4.2 Abbreviations . 8
5 Requirements . 9
5.1 General. 9
5.2 Regulation . 9
5.3 Phosphorus removal strategies . 9
5.4 Design considerations . 10
5.5 Chemical background and process options . 11
5.6 Storage preparation and dosing of chemicals . 15
5.7 Dosing equipment . 15
5.8 Silos, tanks and pipes . 16
5.9 Mixing . 17
5.10 Control systems for dosing of chemical . 17
5.11 Flocculation reactors . 19
5.12 Sedimentation tanks . 20
5.13 Flotation . 20
5.14 Physical filtration . 20
5.15 Sludge . 20
Annex A (informative) Precipitation chemicals . 22
Bibliography . 24

European foreword
This document (EN 12255-13:2023) 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 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 12255-13:2002.
This is the thirteenth 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 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 stabilized 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.
1 Scope
This document specifies the requirements for chemical treatment of wastewater by
precipitation/flocculation for removal of phosphorus and suspended solids.
The application of polymers is not described in this document.
This document has not attempted to specify all available practices.
NOTE Chemical treatment can be performed in combination with primary and more commonly with
secondary treatment, but it can also be performed as separate tertiary treatment, usually in combination with
filtration (see EN 12255-16). Chemical treatment can provide a potential contribution to the circular economy
through the recovery of materials, such as phosphorus, from wastewater or sludge.
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 12255-11, Wastewater treatment plants - Part 11: General data required
EN 16932-1, Drain and sewer systems outside buildings - Pumping systems - Part 1: General requirements
EN 16932-2, Drain and sewer systems outside buildings - Pumping systems - Part 2: Positive pressure
systems
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
chemical treatment
process involving the addition of chemicals to achieve a specific result
Note 1 to entry: For wastewater, typical chemical treatments comprise: coagulation/precipitation with metal
salts (including lime) or organic polymers in order to remove inorganic and organic phosphorus compounds or
suspended solids and colloids.
[SOURCE: ISO 6107:2021, definition 3.108 modified – Note 1 to entry added]
3.2
chemical precipitation
conversion of components dissolved in water into an undissolved form by chemical reaction with a
precipitant
[SOURCE: EN 16323:2014, 2.3.5.8]
3.3
precipitant
chemical used to bring about precipitation
[SOURCE: EN 16323:2014, 2.3.5.45]
3.4
coagulation
destabilisation of undissolved and colloidally dispersed matter to allow aggregation, usually by addition
of coagulants
[SOURCE: EN 16323:2014, 2.3.5.9]
3.5
coagulant
chemical added to destabilise suspensions or emulsions
[SOURCE: EN 16323:2014, 2.3.1.21]
Note 1 to entry: A coagulant is normally based on an aluminium or iron salt (inorganic
coagulant) but could also be a polymer (organic). In water treatment, the coagulant always has a
positive charge
3.6
flocculation
formation of separable flocs by aggregation of small particles
[SOURCE: EN 16323:2014, 2.3.5.19]
Note 1 to entry: Micro-flocculation can be achieved by destabilization and coagulation/aggregation, macro-
flocculation can be achieved by addition of bridge building polymers.
3.7
destabilisation
compensation of negative charges on the surfaces of particles by addition of positively charged bivalent
or trivalent metal ions to achieve particle aggregation
Note 1 to entry: Destabilization is performed by reduction of the zeta-potential.
3.8
tertiary treatment
additional treatment processes which result
...