National foreword

This British Standard is the UK implementation of EN 12255‑3:2024. It supersedes BS EN 12255‑3:2000, which is withdrawn.

The UK participation in its preparation was entrusted to Technical Committee B/505/40, Wastewater Treatment Plants > 50 PT.

A list of organizations represented on this committee can be obtained on request to its committee manager.

Contractual and legal considerations

This publication has been prepared in good faith, however no representation, warranty, assurance or undertaking (express or implied) is or will be made, and no responsibility or liability is or will be accepted by BSI in relation to the adequacy, accuracy, completeness or reasonableness of this publication. All and any such responsibility and liability is expressly disclaimed to the full extent permitted by the law.

This publication is provided as is, and is to be used at the recipient’s own risk.

The recipient is advised to consider seeking professional guidance with respect to its use of this publication.

This publication is not intended to constitute a contract. Users are responsible for its correct application.

Compliance with a British Standard cannot confer immunity from legal obligations.

This British Standard was published under the authority of the Standards Policy and Strategy Committee on 29 February 2024.

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 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.

EN 12255‑3:2024 includes the following significant technical changes with respect to EN 12255‑3:2000:

comprehensive revision and additions in all sections;
the addition of design recommendations;
adaptation to the current state of the art;
updating of the Normative references;
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:

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

3 Terms and definitions

4 Symbols, abbreviations and indices

5 Planning

6 Screening

6.1 General

6.2 Design of structures

6.3 Screen design

7 Screenings treatment

7.1 General

7.2 Structural design

7.3 Design of screenings treatment equipment

7.4 Screenings disposal/container loading

8 Grit removal

8.1 General

8.2 Structural design

8.3 Design of grit removal equipment

9 Grit treatment

9.1 General

9.2 Structural design

9.3 Design of grit treatment equipment

10 Grease and oil separation

11 Flow balancing and flow splitting

12 Materials

13 Control and automation requirements

14 Operation and maintenance requirements

15 Health and safety requirements

Bibliography

BS EN 12255-3:2024

Wastewater treatment plants - Preliminary treatment

Current

Published:

29 Feb 2024