SIST EN 12255-1:2002

SLOVENSKI STANDARD
SIST EN 12255-1:2002
01-december-2002
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Wastewater treatment plants - Part 1: General construction principles
Kläranlagen - Teil 1: Allgemeine Baugrundsätze
Stations d'épuration - Partie 1: Principes généraux de construction
Ta slovenski standard je istoveten z: EN 12255-1:2002
ICS:
13.060.30 Odpadna voda Sewage water
SIST EN 12255-1:2002 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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EUROPEAN STANDARD
EN 12255-1
NORME EUROPÉENNE
EUROPÄISCHE NORM
January 2002
ICS 13.060.30
English version
Wastewater treatment plants - Part 1: General construction
principles
Stations d'épuration - Partie 1: Principes généraux de Kläranlagen - Teil 1: Allgemeine Baugrundsätze
construction
This European Standard was approved by CEN on 9 November 2001.
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 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 Management Centre has the same status as the official
versions.
CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece,
Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2002 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 12255-1:2002 E
worldwide for CEN national Members.

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EN 12255-1:2002 (E)
Contents
page
Foreword.3
1 Scope .5
2 Normative references .5
3 Terms and definitions.6
4 Requirements .7
4.1 General requirements.7
4.2 Design requirements .8
4.3 Structural requirements .8
4.3.1 General.8
4.3.2 Dimensional tolerances.9
4.3.3 Concrete tracks.9
4.3.4 Fixings and connections between equipment and structures.9
4.3.5 Access.9
4.3.6 Building ventilation.10
4.3.7 Water supply and drainage.10
4.3.8 Lifting equipment.10
4.3.9 Storage for hazardous chemicals and fuels .10
4.4 Requirements for equipment.10
4.4.1 Principles for mechanical design.10
4.4.2 General design requirements .11
4.4.3 Environmental impact .15
4.4.4 Safety .15
4.4.5 Documentation.15
4.4.6 Spare parts, special tools .15
5 Test methods.15
5.1 Function and performance.15
5.2 Tightness testing of concrete structures .16
5.3 Tightness testing of earthen basins .16
5.4 Tightness testing of other structures and equipment .16
Annex A (informative)  Explanatory notes .17
Annex B (normative)  Structural tolerances.19
B.1 Circular tank .19
B.1.1 Circular tank with scraper.19
B.1.2 Circular tank with a scraper bridge travelling on the side wall (track).19
B.2 Rectangular tank.19
Bibliography .20
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EN 12255-1:2002 (E)
Foreword
This European Standard 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 July 2002, and conflicting national standards shall be withdrawn at the latest by
December 2002.
It is the first part prepared by the Working Groups CEN/TC 165/WG 42 and 43 relating to the general requirements
and processes for treatment plants for a total number of inhabitants and population equivalents (PT) over 50. The
parts of the series are as follows:

Part 1: General construction principles

Part 3: Preliminary treatment

Part 4: Primary settlement

Part 5: Lagooning processes

Part 6: Activated sludge processes

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
)
1

Part 16: Physical (mechanical) filtration
NOTE For requirements on pumping installations at wastewater treatment plants, provided initially as part 2 "Pumping
installations for wastewater treatment plants", see EN 752-6 "Drain and sewer systems outside buildings — Part 6: Pumping
installations".
The parts EN 12255-1, EN 12255-3 to EN 12255-8 and EN 12255-10 and EN 12255-11 were implemented
together as a European package (Resolution 232/2001 taken by CEN/TC 165).

1)
in preparation
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EN 12255-1:2002 (E)
This European standard is limited to general construction principles. Separate standards for special construction
principles for elements of wastewater treatment plants are covered in other parts.
Safety principles and general data required are covered in EN 12255-10 and EN 12255-11.
Annex A is informative, annex B is normative.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to implement this document: Austria, Belgium, the Czech Republic, Denmark, Finland, France,
Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, Spain, Sweden,
Switzerland and the United Kingdom.
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EN 12255-1:2002 (E)
1 Scope
This European Standard specifies general requirements for structures and equipment as they relate to wastewater
treatment plants for a total population of more than 50 PT.
The primary application is designed for wastewater treatment plants for the treatment of domestic and municipal
wastewater.
Requirements for structures which are not specific for wastewater treatment plants are not within the scope of this
European Standard. Other ENs can apply.
Equipment which is not solely used in wastewater treatment plants is subject to the applicable product standards.
However, specific requirements for such equipment when used in wastewater treatment plants are included in this
part.
General principles of building construction, mechanical and electrical engineering are not subject of this standard.
This European Standard does not cover the design of treatment processes.
Differences in wastewater treatment throughout Europe have led to a variety of systems being developed. This
standard gives fundamental information about the systems; this standard has not attempted to specify all available
systems.
Detailed information additional to that contained in this standard may be obtained by referring to the Bibliography.
2 Normative references
This European Standard incorporates by dated or undated reference, provisions from other publications. These
normative references are cited at the appropriate places in the text, and the publications are listed hereafter. For
dated references, subsequent amendments to or revisions of any of these publications apply to this European
Standard only when incorporated in it by amendment or revision. For undated references the latest edition of the
publication referred to applies (including amendments).
EN 752-6, Drain and sewer systems outside buildings – Part 6: Pumping installations.
EN 809, Pumps and pump units for liquids – Common safety requirements.
EN 1085, Wastewater treatment – Vocabulary.
EN 12255-9, Wastewater treatment plants — Part 9: Odour control and ventilation.
EN 12255-10, Wastewater treatment plants – Part 10: Safety principles.
prEN 12255-12, Wastewater treatment plants — Part 12: Control and automation.
EN 60034-1, Rotating electrical machines – Part 1: Rating and performance (IEC 60034-1:1996, modified).
EN 60529, Degrees of protection provided by enclosures (IP code) (IEC 60529: 1989).
ISO 3506-1, Mechanical properties of corrosion-resistant stainless-steel fasteners – Part 1: Bolts, screws and studs.
ISO 3506-2, Mechanical properties of corrosion-resistant stainless-steel fasteners – Part 2: Nuts.
ISO 3506-3, Mechanical properties of corrosion-resistant stainless-steel fasteners – Part 3: Set screws and similar
fasteners not under tensile stress.
ISO 4200, Plain end steel tubes, welded and seamless – General tables of dimensions and masses per unit length.
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EN 12255-1:2002 (E)
3 Terms and definitions
For the purposes of this European Standard, the terms and definitions given in EN 1085 and the following apply.
3.1
structure
any construction and its components built for the accommodation of equipment
3.2
equipment
any component which is installed in, mounted on, attached to, or operated on structures, in the performance of their
intended function
3.3
unit
any structure including any related equipment which is used as a process stage and which can be isolated from
other parallel, upstream or downstream structures
NOTE Examples for a unit are a grit chamber, a clarifier, an aeration tank, a thickener, a digester.
3.4
assembly
mechanical equipment that can be removed and replaced as a whole
NOTE Examples for an assembly are a pump, a compressor, a gas engine, an aerator.
3.5
wastewater treatment plant
system for the purification of wastewater including structures and equipment
3.6
client
municipality, city or other organisation which intents to built a wastewater treatment plant or parts thereof, or its
representative
3.7
Bidder
company or other organisation which offers to built a plant, or to built or supply parts thereof
3.8
contractor
company or organisation which received a contract to built a plant, or to built or supply parts thereof
3.9
tracks
those parts of a structure on which wheels run
3.10
design loading Y
N
effective average loading in continuous operation under full load
NOTE It is greater than or equal to the value of the operating loading which, for example, fluctuates as a function of the
given load.
3.11
continuous load bearing capacity Y
C
load bearing capacity in continuous operation under full load
3.12
maximum loading Y
max
peak loading which is taken as the switch-off value to which, for example, overload circuit breakers are adjusted
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EN 12255-1:2002 (E)
3.13
maximum load bearing capacity Y
B
highest possible load bearing capacity limited to short-term load peaks, such as occur on switching on and off
NOTE In addition, alarm loadings Y , lying between the design loading Y and the switch-off loading Y , can be agreed
S N max
as required, Y and Y being stated by the equipment supplier.
N max
3.14
utilisation factor K
A
parameter for the effects on drive units etc., intrinsic to their operation
NOTE Usually K includes either directly or indirectly information on the loading, running time and temperature and is an
A
overall value of the relationship between load bearing capacity and loading.
3.15
2)
design service life
operating time until break-down of a machinery element under design loading, which is reached by a certain
percentage of the elements tested
NOTE

as an example, the percentage for rolling bearings is 90 %;

the design service life is different from both the warranty time and an average service life of use, as used for cost efficiency
calculations.
3.16
mode of operation
characteristic value related to the effects on motors and other electrical components intrinsic to their operation (e.g.
frequency of starts, temperatures)
3.17
degree of protection
characteristic value related to the effects on motors and other electrical components intrinsic to their environmental
conditions (e.g. effects of water or dust)
4 Requirements
4.1 General requirements
Wastewater treatment plants shall meet the following requirements:
a) national regulations shall be observed;
b) the discharge limits shall be met;
c) be capable of satisfactory treatment of the full range of flows and loads;
d) personal safety;
e) nuisance, odour, noise and toxicity, aerosols and foam shall be considered and shall meet the relevant
requirements according to EN 12255-9 and EN 12255-10;
f) danger to operating personnel shall be minimized;

2)
Explanatory note see annex A
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EN 12255-1:2002 (E)
g) the required service life and long term structural integrity shall be achieved, including water and gas;
h) tightness;
i) provisions shall be made for case of operation and maintenance;
j) provision for future extensions or modifications of the plant shall be considered;
k) the reliability of operation shall be high and risk of danger and the impact of malfunctions shall be limited;
l) be cost effective in respect of total costs (capital and operating costs);
m) the energy consumption during construction and operation shall be considered;
n) the waste products shall be reduced in quantity and improved in quality as far as reasonably achievable to
allow for reuse or safe disposal.
4.2 Design requirements
The following requirements shall be considered during the design stage of a wastewater treatment plant:
a) All assemblies that are subject to occasional failure (e.g. pumps and compressors) shall be installed with
sufficient stand-by capacity so as to achieve full treatment capacity and efficiency with one assembly out of
service. In the case where stand-by assemblies cannot be practically installed, provisions shall be made to
replace rapidly by another one kept in stock.
b) Where practicable and necessary for maintenance work it shall be possible to bypass every unit or assembly,
either by a parallel unit or assembly, channel or pipe.
c) Where necessary the inlet to the treatment plant shall include a facility which limits the flow. Such facilities may
be balancing tanks and/or stormwater overflows as required by the authorities.
d) Where power supply is subject to prolonged interruption, wastewater treatment plants shall have emergency
power generation or an equivalent facility to provide a sufficient power supply during power failure of the
network, e.g. a terminal for easy connection with a readily available mobile power generator. Connected to the
emergency power supply shall as a minimum include the measuring and control system, the pumps for waste
water and return sludge and any aeration equipment (at a designed minimum capacity).
e) When the power supply is restored after an interruption, the treatment plant shall be designed so that normal
operating status is resumed automatically.
f) Provision shall be made for taking representative samples upstream and downstream of each unit and of any
flow whose characteristics are important for operation and supervision.
g) The design shall ensure that all information (quantities and qualities) that is important for effective operation of
the plant is readily obtainable (e.g. flows, levels, pressures, temperatures, dissolved oxygen concentrations,
pH-values, other concentrations).
h) The design shall enable cleaning, maintenance and repairs to be carried out easily and safely (e.g. access,
flushing connections to pipes, isolation means).
i) Appropriate provision shall be made for the case of malfunction or emergency.
4.3 Structural requirements
4.3.1 General
Structures shall be
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EN 12255-1:2002 (E)

stable to bear all loads during construction, operation and maintenance periods, e.g. water pressures, static
and dynamic forces being induced by the equipment,

resistant against chemical and biological attack from wastewater, sludge, air and gas components and against
temperatures and temperature changes as appropriate,

protected against flotation.
4.3.2 Dimensional tolerances
The permissible dimensional tolerances for structures which are required for the function of the equipment are
specified in the relevant specific standards or annex B. Other dimensional tolerances shall be agreed with the supplier
of the equipment.
4.3.3 Concrete tracks
Tracks shall be identified in the drawings.
Tracks shall be level and free of ridges.
Particular requirements in regard of the quality and placing of the concrete shall be met in order to reinforce the tracks
against the effects of

compression and shear forces,

frost and de-icing salt.
The strength of concrete shall not be less than 35 N/mm². The thickness of the concrete covering of the reinforcement
on the wall crest if exposed to de-icing salt shall be at least 1 cm more than normal.
The maximum pressure on the wheels shall be limited to:
2

rubber wheels 2,5 MN/m ;
2

polyurethane wheels 5,0 MN/m .
In the latter case, protection of the track with steel plates or other suitable material may be necessary.
4.3.4 Fixings and connections between equipment and structures
The possibility of differential settlement between structures, and between structures and equipment (such as
pipelines) shall be taken into account. Sufficient flexible joints and flexibility in the equipment itself or in its connections
to the structures shall be provided.
Reinforcement in the structure shall not be used for securing equipment.
Where different metals are in contact, measures shall be incorporated to prevent corrosion by galvanic action.
Where metallic fixings might be in electrical contact with the reinforcement of the structure appropriate electrical
insulation shall be provided, e.g. insulating, chemical anchor with threaded rod.
4.3.5 Access
Safe access in the form of paths, gangways, bridges, stages and the like shall be provided to allow supervision,
operating, servicing, cleaning and maintenance. Openings shall be provided which allow easy replacement of
equipment.
The location of operating and maintenance points shall allow for adverse weather conditions and other hazards (e.g.
handling of gases, vapours, sludge, oil and grease) and possibility of collapse, squeeze and sheer points.
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EN 12255-1:2002 (E)
The buildings and access shall be sufficiently large to allow all erecting and dismantling, maintenance and repair
operations and replacement of assemblies in an easy manner.
Appropriate means shall be provided to deter access by unauthorised persons.
4.3.6 Building ventilation
In enclosed rooms, the possible existence of damp atmospheres, foul air and the risk of explosions shall be
considered according to EN 12255-10. Adequate ventilation shall be provided according to EN 12255-9. If necessary,
treating for frost protection shall be provided.
4.3.7 Water supply and drainage
Where occasional flushing is required, a water supply shall be installed. Process water shall preferably be used for
this purpose. Appropriate means shall be provided to prevent process water from contaminating the drinking water
network. Any national regulations for the quality of process water used for flushing shall be observed. This may be
particularly important when water is pressurised.
Appropriate drainage shall be installed where water accumulation may occur due to overflow, leakage or flushing. In
such locations, all floors shall be sealed and sloped towards a pit from where the water drains by gravity or is
automatically pumped away.
All tanks should be constructed to allow emptying.
4.3.8 Lifting equipment
Lifting equipment or adequate provisions for removal shall be provided where necessary in order to allow all
maintenance work and replacement of all assemblies.
4.3.9 Storage for hazardous chemicals and fuels
Where hazardous liquid chemicals or fuels are stored or conveyed, provisions must be made to prevent
environmental impact in case of leakage. National regulations and any requirements in EN 12255-10 shall be
observed. The required safety provisions (e.g. double tank walls, tanks in bunds, leak sensors) will depend on the
volumes stored and potential risks.
Tanks containing chemicals that would interact to form a hazardous mixture or could attack the material of other tanks
shall not share a single bund.
4.4 Requirements for equipment
3)
4.4.1 Principles for mechanical design
The use and requirements of the equipment shall be specified.
A general description and the following information shall be provided:
a) loads (e.g. traffic loads, wind loads, snow loads, operating loads and travelling single loads);
b) loadings (e.g. design loading, maximum loading, alarm loadings);
c) load bearing capacities (e.g. continuous load bearing capacity, maximum load bearing capacity);
d) utilisation factor K ;
A

3) Explanatory note see annex A
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EN 12255-1:2002 (E)
e) mode of operation according to EN 60034-1;
f) degree of protection provided by enclosures (IP Code) according to EN 60529. All gears and drives which are
located above water, but near a place where water jet flushing may take place, shall be protected against
spray water according to class IP 54 of EN 60529; gears and drives which may be directly cleaned with water
jets shall be protected according to class IP 55 of EN 60529; gears and drives which may be submersed in
water shall be protected according to class IP 67 of EN 60529;
g) service life classes: Design service life, as defined in 3.15, is divided in service life classes (see Table 1).
Table 1 — Design service life
Service life class
1 234 5
Design service life undefined 10 000 20 000 50 000 80 000
h
Selection of the service life class shall take account of the real loading which can differ from the design loading (see
informative Annex A for additional information).
NOTE Additional information in respect to specific equipment are included in the appropriate specific standards
EN 12255-3 to EN 12255-8, prEN 12255-13, prEN 12255-14 and prEN 12255-16 (in preparation).
Other relevant regulations and standards (e.g. for cranes) have to be observed.
4.4.2 General design requirements
4.4.2.1 Walkways, stairs, platforms and gratings
2
Irrespective of the design traffic load, the load-bearing capacity of walkways shall not be less than 3,5 kN/m . In
addition, the maximum deflection of a walkway shall not exceed 10 mm or the span divided by 200.
4.4.2.2 Covers, assembly openings, cleaning openings
The design and arrangement of covers, assembly openings and cleaning openings shall be consistent with the
operational requirements of the plant. Openings shall be fitted with secure covers which cannot shut accidentally.
Where frequent access is required, the covers shall be easily opened and closed.
4.4.2.3 Cable drums with spring motors
Spring motors used for cable drums may be employed only where the number of cycles does not exceed 1 000 per
year and the path length does not exceed 30 m.
4.4.2.4 Pumps and pipelines
All pumps shall be appropriate to the conveyed medium and its condition. They shall conform to EN 809 and
EN 752-6.
The minimum nominal diameter of pipes and pumps shall be specified appropriately to the medium conveyed.
Generally, the minimum nominal diameter shall be DN 80 if mixtures of water and grit or sludges are conveyed.
Smaller minimum nominal diameters may be agreed if upstream comminution or sieving is incorporated or where
there is no risk of blockage.
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EN 12255-1:2002 (E)
Pumps shall be provided with individual isolating valves and check valves, if not otherwise specified. Positive
displacement pumps shall be equipped with a sensor and a pressure switch to detect lack of liquid inflow and prevent
damage.
Isolating and check valves shall be tight when closed and be appropriate for the medium and its condition (e.g.
pressure, temperature, composition). If not otherwise specified, there shall be no internal obstruction to the flow when
opened.
The forces and vibrations arising in pipe systems shall be taken into account in the design.
Where freezing may cause damage or interfere with operation of the wastewater treatment plant, or where heat
losses are to be minimised, tanks and pipe systems shall be thermally insulated and underground pipelines shall be
frost protected if necessary.
For pipelines conveying wastewater, sludge or digester gas, the pipe arrangement, the profile and the velocity shall be
such that sedimentation (and condensation accumulation in gas or air pipes) and gas accumulation are avoided.
Where this is not possible, means for the removal of sediment, condensate and gas accumulation shall be provided.
Branches shall not be made in such a way that obstructions are likely to be formed. If not otherwise specified, the
radius of bends shall be minimum three times the nominal diameter.
Plastic pipes shall have a m
...