oSIST prEN 12566-6:2018

SLOVENSKI STANDARD
01-december-2018
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Small wastewater treatment systems for up to 50 PT - Part 6: Prefabricated treatment
units for septic tank effluent
Kleinkläranlagen für bis zu 50 EW - Teil 6: Vorgefertigte Anlagen für die weitergehende
Behandlung des aus Faulgruben ablaufenden Schmutzwassers
Petites installations de traitement des eaux usées pour une population totale équivalente
(PTE) jusqu’à 50 habitants - Partie 6 : Unités préfabriquées de traitement secondaire
Ta slovenski standard je istoveten z: prEN 12566-6
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
October 2018
ICS 13.060.30 Will supersede EN 12566-6:2016
English Version
Small wastewater treatment systems for up to 50 PT - Part
6: Prefabricated treatment units for septic tank effluent
Petites installations de traitement des eaux usées pour Kleinkläranlagen für bis zu 50 EW - Teil 6:
une population totale équivalente (PTE) jusqu'à 50 Vorgefertigte Anlagen für die weitergehende
habitants - Partie 6 : Unités préfabriquées de Behandlung des aus Faulgruben ablaufenden
traitement secondaire Schmutzwassers
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, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey 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
© 2018 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 12566-6:2018 E
worldwide for CEN national Members.

Contents Page
European foreword . 5
3.1 Terms and definitions . 9
3.2 Symbols and abbreviated terms . 9
4.1 Design . 10
4.1.1 General. 10
4.1.2 Inlets, outlets, internal pipework and connections . 10
4.1.3 Ventilation . 10
4.1.4 Access . 11
4.1.5 Extension shaft . 11
4.1.6 Sizing basis . 11
4.1.7 Overall dimensions . 12
4.2 Load bearing capacity . 12
4.2.1 General. 12
4.2.2 Load bearing capacity determined by calculation (See 4.2.1.1, e) . 12
4.2.3 Load bearing capacity determined by testing (See 4.2.1.1, a) to d)). . 14
4.3 Treatment efficiency . 15
4.3.1 Characteristics . 15
4.3.2 Tank selection . 16
4.4 Watertightness . 16
4.4.1 General. 16
4.4.2 Water loss . 17
4.4.3 Pressure variation . 17
4.5 Durability . 17
4.5.1 General. 17
4.5.2 Concrete . 18
4.5.3 Steel. 18
4.5.4 Unplasticized polyvinyl chloride (PVC-U) . 18
4.5.5 Polyethylene (PE) . 18
4.5.6 Glass reinforced plastic (GRP) . 19
4.5.7 Polypropylene (PP) . 19
4.5.8 Polydicyclopentadiene (PDCPD) . 20
4.5.9 Flexible sheets . 21
4.6 Reaction to fire. 21
4.6.1 General. 21
4.6.2 Classification without the need for testing . 22
4.6.3 Classification according to the test results . 22
4.7 Treatment capacity . 22
5.1 Load bearing capacity . 22
5.1.1 Crushing test . 22
5.1.2 Vertical load test . 25
5.1.3 Vacuum test . 26
5.1.4 Pit test . 27
5.2 Treatment efficiency . 29
5.2.1 General. 29
5.2.2 Installation and commissioning . 30
5.2.3 Operation and maintenance procedures during testing . 30
5.2.4 Data to be monitored . 30
5.2.5 Time for biomass establishment . 31
5.2.6 Influent characteristics . 31
5.2.7 Daily flow pattern for testing . 31
5.2.8 Test procedure . 32
5.2.9 Sample analysis . 34
5.2.10 Test report . 35
5.3 Watertightness . 35
5.3.1 Water test . 35
5.3.2 Vacuum test . 36
5.4 Durability . 37
5.4.1 General . 37
5.4.2 Concrete . 37
5.4.3 Steel . 37
5.4.4 Unplasticized polyvinyl chloride (PVC-U) . 37
5.4.5 Polyethylene (PE) . 37
5.4.6 Glass reinforced plastic (GRP) . 38
5.4.7 Polypropylene (PP) . 39
5.4.8 Polydicyclopentadiene (PDCPD) . 40
5.4.9 Flexible sheets . 40
5.5 Reaction to fire . 41
6.1 General . 41
6.2 Type testing . 41
6.2.1 General . 41
6.2.2 Test samples, testing and compliance criteria . 42
6.2.3 Test reports . 48
6.2.4 Shared other party results . 48
6.2.5 Cascading determination of the product type results . 49
6.3 Factory production control . 50
6.3.1 General . 50
6.3.2 Requirements . 50
6.3.3 Product specific requirements . 53
6.3.4 Initial inspection of factory and of FPC . 54
6.3.5 Continuous surveillance of FPC . 54
6.3.6 Procedure for modifications . 54
6.3.7 One-off products, pre-production products (e.g. prototypes) and products produced
in very low quantity . 54
7.1 Marking . 55
7.2 Technical information accompanying the unit . 56
7.3 Installation instructions . 57
7.4 Operation and maintenance instructions . 57
Annex A (informative) Analysis method . 58
Annex B (normative) Mechanical characteristics of test samples used for load bearing
capacity calculation . 59
Annex C (normative) Alternative watertightness assessment methods for FPC (pneumatic
pressure test) . 60
Annex D (normative) Presentation of the microorganism’s test results . 61
Annex ZA (informative) Relationship of this European Standard with Regulation (EU)
No. 305/2011 . 62
Scope and relevant characteristics . 62
System of Assessment and Verification of Constancy of Performance (AVCP) . 82
Assignment of AVCP tasks . 82
Bibliography . 85

European foreword
This document (FprEN 12566-6:2018) has been prepared by Technical Committee CEN/TC 165 “Waste
water engineering”, the secretariat of which is held by DIN.
This document is currently submitted to the CEN Enquiry.
This document will supersede EN 12566-6:2016.
In comparison with the previous edition, the following technical modification has been made:
• mainly changes in AVCP clause and Annex ZA in accordance with the Construction Product
Regulation (CPR) and changes in accordance with the CEN Rules.
This document has been prepared under a mandate given to CEN by the European Commission and the
European Free Trade Association, and supports essential requirements for construction works of
Regulation (EU) No. 305/2011.
For relationship with EU Directive(s), see informative Annex ZA, which is an integral part of this
document.
The series of standards EN 12566 “Small wastewater treatment systems for up to 50 PT” contains the
following parts (see Figure 1):
• Part 1: Prefabricated septic tanks;
• Part 3: Packaged and/or site assembled domestic wastewater treatment plants;
• Part 6: Prefabricated secondary treatment unit (this document);
• Part 7: Prefabricated tertiary treatment unit
For filtration systems, CEN/TC 165 decided to publish the following CEN Technical reports, which are
considered as Code of practices and do not specify treatment requirements:
• Part 2: Soil infiltration systems
• Part 5: Pre-treated Effluent Filtration systems
Key
A domestic wastewater 1 packaged and/or site assembled septic tank
B septic tank effluent 2 soil infiltration system
C treated infiltrated effluent 3 packaged and/or site assembled domestic wastewater treatment plant
D treated wastewater 5 pre-treated effluent filtration system
E tertiary treated wastewater 6 prefabricated treatment unit used for septic tank effluent
7 prefabricated tertiary treatment unit
Figure 1 — Scheme related to the arrangement of the parts of EN 12566
National regulations can specify different arrangements between the products described in the
standard series EN 12566.
1 Scope
This document specifies characteristics and related requirements, assessment methods, the marking
and assessment and verification of constancy of performance (AVCP) procedures for prefabricated
secondary treatment units for populations up to 50 inhabitants.
Prefabricated secondary treatment units in accordance with this document are:
• used for the treatment of effluent from product in accordance with EN 12566-1;
Equivalent septic effluent may come from existing septic tanks.
• made of concrete, steel, Unplasticized Polyvinylchloride (PVC-U), Polyethylene (PE), Polypropylene
(PP), Glass Reinforced Polyester (GRP-UP), Polydicyclopentadiene (PDCPD), PVC and/or EPDM;
• used buried in the ground;
• with or without extension shaft;
• made of prefabricated components that are factory or site-assembled by one manufacturer and
which are tested as a whole.
This document does not cover prefabricated secondary treatment units:
• where vehicle loads apply to it;
• with direct infiltration into the ground (non-watertight);
• made of retrofit kits (see definition in 3.1.5).
The assessment methods specified in this European Standard establish the performance of the
prefabricated secondary treatment unit, needed to verify its suitability for the condition in which it is
normally installed.
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 206, Concrete — Specification, performance, production and conformity
EN 580, Plastics piping systems — Unplasticized poly(vinyl chloride) (PVC-U) pipes — Test method for the
resistance to dichloromethane at a specified temperature (DCMT)
EN 727, Plastics piping and ducting systems — Thermoplastics pipes and fittings — Determination of
Vicat softening temperature (VST)
EN 976-1:1997, Underground tanks of glass-reinforced plastics (GRP) - Horizontal cylindrical tanks for
the non-pressure storage of liquid petroleum based fuels - Part 1: Requirements and test methods for single
wall tanks
EN 978:1997, Underground tanks of glass-reinforced plastics (GRP) - Determination of factor alpha and
factor beta
EN 1992-1-1, Eurocode 2: Design of concrete structures - Part 1-1: General rules and rules for buildings
EN 1993-1-1, Eurocode 3: Design of steel structures - Part 1-1: General rules and rules for buildings
EN 1905, Plastics piping systems - Unplasticized poly(vinyl chloride) (PVC-U) pipes, fittings and material -
Method for assessment of the PVC content based on total chlorine content
EN 10088-1, Stainless steels - Part 1: List of stainless steels
EN 12311-2, Flexible sheets for waterproofing - Determination of tensile properties - Part 2: Plastic and
rubber sheets for roof waterproofing
EN 12566-1, Small wastewater treatment systems for up to 50 PT - Part 1: Prefabricated septic tanks
EN 13369, Common rules for precast concrete products
EN 13501-1, Fire classification of construction products and building elements — Part 1: Classification
using data from reaction to fire tests
EN 14150, Geosynthetic barriers - Determination of permeability to liquids
EN 16323:2014, Glossary of wastewater engineering terms
EN ISO 178, Plastics - Determination of flexural properties (ISO 178)
EN ISO 179 (all parts), Plastics — Determination of Charpy impact properties (ISO 179, all parts)
EN ISO 527-2, Plastics - Determination of tensile properties - Part 2: Test conditions for moulding and
extrusion plastics (ISO 527-2)
EN ISO 899-2, Plastics - Determination of creep behaviour - Part 2: Flexural creep by three-point loading
(ISO 899-2)
EN ISO 1133-1:2011, Plastics - Determination of the melt mass-flow rate (MFR) and melt volume-flow rate
(MVR) of thermoplastics - Part 1: Standard method (ISO 1133-1:2011)
EN ISO 1183 (all parts), Plastics — Methods for determining the density and relative density of non-
cellular plastics (ISO 1183, all parts)
EN ISO 2505:2005, Thermoplastics pipes - Longitudinal reversion - Test method and parameters (ISO
2505:2005)
EN ISO 2555, Plastics - Resins in the liquid state or as emulsions or dispersions - Determination of
apparent viscosity using a single cylinder type rotational viscometer method (ISO 2555)
EN ISO 9967, Thermoplastics pipes - Determination of creep ratio (ISO 9967)
EN ISO 9969, Thermoplastics pipes - Determination of ring stiffness (ISO 9969)
EN ISO 13229, Thermoplastics piping systems for non-pressure applications - Unplasticized poly(vinyl
chloride) (PVC-U) pipes and fittings - Determination of the viscosity number and K-value (ISO 13229)
EN ISO 14125:1998, Fibre-reinforced plastic composites - Determination of flexural properties (ISO
14125)
3 Terms, definitions, symbols and abbreviated terms
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in EN 16323:2014 and the following
apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1.1
end use
condition in which a prefabricated secondary treatment unit is normally installed
3.1.2
extension shaft
component(s) which is part of the prefabricated secondary treatment unit, and allow access from or
slightly above the ground surface
3.1.3
flexible sheet
flexible impermeable liner
3.1.4
product family
group of products in which, for evaluation, the selected property(s) is/are similar for all products
within the group considering at least similar shape, equipment, materials and conditions of end use and
ensures the minimum hydraulic efficiency and minimum structural behaviour for all the products in the
range
3.1.5
retrofit kit
set of components that are provided by a single manufacturer for installation within an existing septic
tank
3.2 Symbols and abbreviated terms
AVCP Assessment and Verification of Constancy of Performance
BOD (or BOD ) Biochemical oxygen demand at 5 or 7 days
5 7
COD Chemical oxygen demand
CPR Construction Products Regulation No 305/2011
CWFT Classified Without Further Testing
DoP Declaration of Performance
EPDM Ethylene Propylene Diene Monomer
FPC Factory Production Control
GRP Glass reinforced plastic
KN Kjeldahl Nitrogen
MFR Melt mass-Flow Rate
NH -N Ammonium nitrogen
P Phosphorus
PDCPD Polydicyclopentadiene
PE Polyethylene
PP Polypropylene
PT Population total
PVC Polyvinyl Chloride
PVC-U Unplasticized Polyvinyl Chloride
Q Nominal hydraulic flow
N
SS Suspended solids
4 Product characteristics
4.1 Design
4.1.1 General
Prefabricated secondary treatment units shall be:
• structurally stable, durable, watertight and corrosion resistant, and
• provided with an alarm to indicate electrical, mechanical or hydraulic malfunction of the system,
and
4.1.2 Inlets, outlets, internal pipework and connections
The hydraulic design of the equipment, the internal pipework and connections shall ensure that no
back-flows, blockage or surcharging occur during normal operation.
Inlet and outlet pipes shall be compatible with pipe systems in accordance with European Standards.
4.1.3 Ventilation
The prefabricated secondary treatment unit and the inlet pipework shall be ventilated to prevent the
accumulation of fermentation gases.
4.1.4 Access
The prefabricated secondary treatment unit shall be designed to provide access to the inlet and outlet
areas; for routine maintenance sampling, removal of sludge, cleaning and/or maintenance.
Access covers shall be fit for purpose.
The access opening shall be a minimum of 400 mm (i.e. width for rectangular section or diameter for
circular section). Where the access is for a person, the minimum dimension of the opening shall be
600 mm.
The prefabricated secondary treatment unit shall be designed to restrict unauthorized access by one of
the following means:
a) mass of the individual covers;
b) securing feature; or
c) locking accessory.
Where a locking accessory or securing feature is used, it shall be designed so that the cover cannot be
easily opened with objects readily accessible by children.
4.1.5 Extension shaft
Extension shaft may be part of the prefabricated secondary treatment unit and shall be fit for purpose.
It may be an extension piece of the prefabricated secondary treatment unit, which is fitted only over
certain points for example to allow maintenance or observation.
The extension shaft shall be constructed to avoid any surface water entering prefabricated secondary
treatment unit. This can be achieved by overlapping the access or fixed to the product or using a gasket.
The extension shaft shall be constructed to ensure accessibility, access for maintenance work and the
opening / closing of the cover
4.1.6 Sizing basis
Depending on the end use, one or more of the following design criteria shall be taken into
consideration:
a) population load;
b) sizing of the septic tank (in accordance with EN 12566-1) in relation with the total population
loading;
c) declared value of SS settlement (grams of beads) of the septic tank (in accordance with
EN 12566-1);
d) minimum and maximum daily loading that a prefabricated secondary treatment unit can accept;
e) minimum volume criteria;
f) additional design criteria for domestic wastewater flows from sources such as hotels, restaurants
or commercial premises.
NOTE Rules and units (per inhabitant, BOD, SS…) to be used for the determination of the population load are
given by national regulations.
4.1.7 Overall dimensions
The overall dimensions of the prefabricated secondary treatment unit (i.e. height, width, length,
diameters, etc.) shall be measured and recorded.
The measurements shall be within ± 0,5 % of the design dimensions.
4.2 Load bearing capacity
4.2.1 General
4.2.1.1 Characteristics
Performance of the load bearing capacity of the prefabricated secondary treatment unit (i.e. of the tank
of it) with or without extension shaft, shall be established either by testing or by calculations for one of
the following characteristics, as:
a) pit test resistance, as specified in 4.2.3.5, or
NOTE Considered as the referenced one.
Alternatively, this may be as:
b) crushing test resistance, as specified in 4.2.3.2,
c) vertical load test resistance, as specified in 4.2.3.3,
d) vacuum test resistance, as specified in 4.2.3.4,
e) load bearing capacity determined by calculation, as specified in 4.2.2.
4.2.1.2 Performance expression
The performance of load bearing capacity for any of the characteristics referred in 4.2.1.1 shall be
expressed as:
• value of the maximum allowed height of backfill expressed in meters (see H of Figure 6);
b
• possibility to install the prefabricated secondary treatment unit either in wet or dry site, i.e.
expressed as indication either WET together with a value of the maximum height of the water table
measured from the base of the prefabricated secondary treatment unit or DRY.
4.2.1.3 Tank selection
Performance of the load bearing capacity of prefabricated secondary treatment unit shall be established
for the tank which represent the lowest performance within the product family.
NOTE Usually the biggest prefabricated secondary treatment unit is generally considered with the lowest
performance.
4.2.2 Load bearing capacity determined by calculation (See 4.2.1.1, e)
4.2.2.1 General
For determination of performance of load bearing capacity of the prefabricated secondary treatment
unit, calculation method shall apply, either indirectly (see 4.2.2.2) or directly (4.2.2.3), based on an
empty prefabricated secondary treatment unit buried underground with the loads defined in 4.2.2.4 to
4.2.2.6.
The performance shall be expressed as defined in 4.2.1.2.
4.2.2.2 Indirect method
This indirect calculation method shall be used when:
• geometrical data of the prefabricated secondary treatment unit (e.g. wall thickness, distance of ribs,
shape) are provided;
• properties of the materials and components of the prefabricated secondary treatment unit are in
accordance with provisions of 4.5.2 to 4.5.9, as relevant for the respective material;
• mechanical characteristics of test samples used for calculation are in accordance with Annex B.
NOTE For materials not covered in Annex B (i.e. PDPCD and flexible sheets), this calculation method is not
applicable.
4.2.2.3 Direct method
The direct calculation method shall apply, when the prefabricated secondary treatment unit is made of
• reinforced concrete, based on EN 1992-1-1 (Eurocode 2) or
• steel, based on EN 1993-1-1 (Eurocode 3) shall apply.
NOTE For the other materials, this calculation method is not applicable.
4.2.2.4 Loads applied in calculation
4.2.2.4.1 Backfill loads
Calculation of backfill loads shall take account of the effect of ground conditions, backfill materials and
tank shape factors. A vertical and a horizontal component shall be calculated as follows:
• vertical component:
2 3
H × 18 (expressed in kN/m ), where 18 (kN/m ) is the specific weight of the soil and H (m) is the height
of backfill.
• horizontal component:
2 3
K × D × 18 (expressed in kN/m ), where 18 (kN/m ) is the specific weight of the soil, D (m) is the
distance from the ground level to the point where the load applies, and K is the coefficient
depending on the backfill material.
The following K coefficient can be used:
• sand, K = 0,33;
• gravel, K = 0,27,
• for other backfill materials, K = 0,5.
4.2.2.4.2 Hydrostatic loads
A vertical and a horizontal component shall be calculated as follows:
• vertical component:
2 3
Hw × 10 (expressed in kN/m ), where 10 (kN/m ) is the action resulting from the specific weight of
water and H (m) is the declared water table level from the base of the prefabricated secondary
w
treatment unit;
• horizontal component:
D × 10 (expressed in kN/m ) where D (m) is the distance from the ground level to the point where the
load applies.
On sites, where highest level of the groundwater table is above the bottom of the prefabricated
secondary treatment unit, the stability conditions in relation to the water pressure shall be indicated in
the installation’s instructions.
4.2.2.4.3 Pedestrian loads
For pedestrian loads a value of 2,5 kN/m shall be considered in calculation only when the height of the
backfill (H) is less than or equal to 1 m.
When the height of backfill (H) is over 1 m, the pedestrian loads do not need to be considered for
calculation, as it is assumed to be negligible against other loads.
4.2.3 Load bearing capacity determined by testing (See 4.2.1.1, a) to d)).
4.2.3.1 General
Performance of the load bearing capacity of a prefabricated secondary treatment unit, determined by
testing, shall be using one of the methods referred in Table 1.
Table 1 — Test methods for the determination of the load bearing capacity
Installation Concrete GRP PE, PP and Steel PVC-U and
condition PDCPD flexible sheets
a a a a a
Dry See 4.2.3.5 See 4.2.3.5 See 4.2.3.5 See 4.2.3.5 See 4.2.3.5
or or or
See 4.2.3.2 See 4.2.3.4 See 4.2.3.3
a
Wet See 4.2.3.5
a
Considered here as the referenced method (in bold text), including with those calculated methods, specified
in 4.2.2.2 and 4.2.2.3.
4.2.3.2 Crushing test resistance
Depending of the shape of the prefabricated secondary treatment unit made of concrete, as indicated in
Table 2, the performance of the crushing test resistance of such tank shall be determined using one of
the following crushing tests methods:
a) type A test (vertical load), as specified for testing in 5.1.1.2 and subsequent calculation in 5.1.1.1;
b) type B test (horizontal load), as specified for testing in 5.1.1.3 and subsequent calculation in 5.1.1.1;
c) type C test (vertical load), as specified for testing in 5.1.1.4 and subsequent calculation in 5.1.1.1.
The performance of the crushing test resistance shall be expressed as defined in 4.2.1.2.
Table 2 — Crushing test methods
Rectangular or trapezoidal shape Vertical cylinder shape Horizontal cylinder shape

NOTE Letters A, B and C correspond to the relevant crushing test method.
4.2.3.3 Vertical load test resistance
The performance of the vertical load test resistance of a prefabricated secondary treatment unit shall be
determined in accordance with test method, specified for the testing in 5.1.2 and for the subsequent
calculation in 5.1.1.1.
The performance of the vertical load test resistance shall be expressed as defined in 4.2.1.2.
4.2.3.4 Vacuum test resistance
The performance of the vacuum test resistance of prefabricated secondary treatment unit shall be
determined in accordance with the test method, specified for the testing in 5.1.3.1 and for the
subsequent calculation in 5.1.3.2.
The performance of the vertical load test resistance shall be expressed as defined in 4.2.1.2.
4.2.3.5 Pit test resistance
The performance of the pit test resistance of a prefabricated secondary treatment unit shall be
determined in accordance with test methods specified in 5.1.4.
After the test the prefabricated secondary treatment unit, made of the respective materials, shall meet
the following requirements:
• For the tank, made of concrete or GRP, with characteristics:
a) Variation of volume: no variation, and
b) Loss of watertightness: no loss.
• For other materials:
c) Variation of volume: variation lower than 7,5 %, and
d) Loss of watertightness: no loss.
The performance of the pit test resistance shall be expressed as defined in 4.2.1.2.
4.3 Treatment efficiency
4.3.1 Characteristics
The prefabricated secondary treatment unit shall be tested in accordance with 5.2 and the following
parameters performances shall be expressed:
• Treatment efficiency ratio (%) on BOD , COD, SS, nitrogen parameters and total phosphorus.
• Tested daily load in terms of:
• BOD , COD and SS (in g/d) or
• characteristics (hydraulic efficiency, nominal capacity, etc.) of the septic tank used during the
test expressed in accordance with EN 12566-1.
• The number of desludging procedure carried out.
• The number of microorganism for influent and effluent, expressed in cfu/100 ml or MPN/100 ml
and the microorganism reduction between influent and effluent, expressed in logarithmic unit;
• The power consumption (in kWh/d) under normal operating conditions (nominal sequences of the
test). Assessment of power consumption shall be done by measurement with accuracy of ± 5 % of
the result.
For each the parameters (COD, BOD, SS, nitrogen parameters and total phosphorus) the declared
treatment efficiency ratio shall be the mean value of the 20 treatment efficiency ratios obtained during
the nominal sequences. The treatment efficiency ratio calculation method shall be as provided in 5.2.8.5.
The expressed tested daily load shall be the mean value of the 20 organic daily loads measured during
the nominal sequences.
The number of microorganism for influent, effluent and the respective reduction shall be expressed in a
specific document as described in Annex D.
In addition to the treatment efficiency ratio (%) declaration, another way of expression may be added
for the same parameters (i.e. the minimum and the maximum concentrations in mg/l for the effluent
and the influent).
4.3.2 Tank selection
Performance of the treatment capacity of prefabricated secondary treatment unit shall be established
for the tank which represent the lowest performance within the product family.
NOTE For treatment efficiency, usually the smallest prefabricated secondary treatment unit is generally
considered with the lowest performance.
4.4 Watertightness
4.4.1 General
4.4.1.1 Characteristics
The performance of watertightness of the prefabricated secondary treatment unit, with or without
extension shaft, shall be dealt with characteristics and determined by testing using one of the methods,
all as referred in in Table 3, depending on the material, the tank is made of.
Table 3 — Test methods for the determination of the watertightness
Characteristics Test Concrete GRP PE, PP and Steel PVC-U,
methods PDCPD flexible
sheets
a a a a a
Water loss Water See 4.4.2 See 4.4.2 See 4.4.2 See 4.4.2 See 4.4.2
test
Pressure Vacuum  See 4.4.3 See 4.4.3 See 4.4.3
variation test
a
Considered here as the referenced characteristic or test method (in bold text).
4.4.1.2 Performance expression
The performance of watertightness of the prefabricated secondary treatment unit, when any of the two
characteristics, referred in Table 4 applies, shall be expressed as “compliant”, if the respective
requirement(s) in either 4.4.2 or 4.4.3 are met.
The nominal capacity test may be done in conjunction with the water test.
4.4.2 Water loss
Water loss shall be determined by water test in accordance with 5.3.1.
After the test, the result of water loss shall be evaluated for prefabricated secondary treatment unit
made of:
• Concrete:
a) water loss shall be < 0,1 l/m of the internal wet surface of the external walls.
• Other materials:
b) no water loss (leakage) shall occur.
4.4.3 Pressure variation
Pressure variation shall be determined by vacuum test in accordance with 5.3.2.
Within the test period, the value of pressure variation shall not be higher than 10 %.
4.5 Durability
4.5.1 General
4.5.1.1 Materials
Prefabricated secondary treatment unit, including all internal components, shall be manufactured from
materials, in accordance with 4.5.2 to 4.5.9, that make them suitable and durable for use in a
wastewater environment.
4.5.1.2 Performance expression
Where the material of the prefabricated secondary treatment unit meets:
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