SIST-TP CEN/TR 12566-5:2009

SLOVENSKI STANDARD
SIST-TP CEN/TR 12566-5:2009
01-januar-2009
0DOHþLVWLOQHQDSUDYHGR3(GHO)LOWULUQHQDSUDYH]DSUHGþLãþHQHKLãQH
RGSDGQHYRGH
Small wastewater treatment systems up to 50 PT - Part 5: Pre-treated effluent filtration
systems
Kleinkläranlagen für bis zu 50 EW - Teil 5: Filtrationsanlagen für vorbehandeltes
häusliches Schmutzwasser
Petites installations de traitement des eaux usées jusqu'a 50 EH - Partie 5 : Systemes de
filtration d'effluent prétraité
Ta slovenski standard je istoveten z: CEN/TR 12566-5:2008
ICS:
13.060.30 Odpadna voda Sewage water
SIST-TP CEN/TR 12566-5:2009 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST-TP CEN/TR 12566-5:2009

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SIST-TP CEN/TR 12566-5:2009
TECHNICAL REPORT
CEN/TR 12566-5
RAPPORT TECHNIQUE
TECHNISCHER BERICHT
November 2008
ICS 13.060.30

English Version
Small wastewater treatment systems up to 50 PT - Part 5: Pre-
treated Effluent Filtration systems
Petites installations de traitement des eaux usées jusqu'à Kleinkläranlagen für bis zu 50 EW - Teil 5:
50 EH - Partie 5 : Systèmes de filtration d'effluent prétraité Filtrationsanlagen für vorbehandeltes häusliches
Schmutzwasser
This Technical Report was approved by CEN on 7 April 2008. It has been drawn up by the Technical Committee CEN/TC 165.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,
Romania, Slovakia, Slovenia, 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
© 2008 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TR 12566-5:2008: E
worldwide for CEN national Members.

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SIST-TP CEN/TR 12566-5:2009
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Contents Page
Foreword.3
Introduction .5
1 Scope .6
2 Normative references .6
3 Terms and definitions .6
4 Description of filters.9
5 Design Parameters .9
6 Components.12
7 General requirements for the installation of septic tanks.15
8 Construction.15
9 Filter systems.17
10 Operation and Maintenance.27
Annex A (informative) Preliminary site consideration.29
Annex B (informative) Reeds bed filters comparison.31
Annex C (informative) Selection of suitable sands.33
Annex D (informative) Phosphorus removal .36
Bibliography .37

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Foreword
This document (CEN/TR 12566-5:2008) has been prepared by Technical Committee CEN/TC 165
“Wastewater engineering”, the secretariat of which is held by DIN.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
The standard series EN 12566 "Small wastewater treatment systems for up to 50 PT" contains the following
parts:
 Part 1: Prefabricated septic tanks;
NOTE 1 This part specifies the requirements and test methods for prefabricated septic tank units.
 Part 2: Soil infiltration systems;
NOTE 2 Code of Practice for in-situ constructed soil infiltration systems. No treatment requirements are specified.
 Part 3: Packaged and/or site assembled domestic wastewater treatment plants;
NOTE 3 This part specifies the requirements and test methods used to evaluate packaged wastewater treatment plants
which are required to treat wastewater to a declared quality.
 Part 4: Septic tanks assembled in situ from prefabricated kits;
 Part 5: Pre-treated effluent filtration systems (this Technical Report);
 Part 6: Prefabricated treatment units for septic tank effluent (in preparation);
 Part 7: Prefabricated tertiary treatment units (in preparation).
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to announce this Technical Report: Austria, Belgium, Bulgaria, Cyprus, Czech Republic,
Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden,
Switzerland and the United Kingdom.


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Key
A: Raw domestic wastewater 1: Prefabricated 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 4: Septic tank assembled in situ from prefabricated kit
E: Tertiary treated wastewater 5: Pre-treated effluent filtration system
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
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SIST-TP CEN/TR 12566-5:2009
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Introduction
Filtration systems have effluent collection systems and the effluent quality can be measured. The systems
described are intended to illustrate the main principles of construction and are subject to variation. The
regulatory authorities shall be consulted for suitability. All filtration systems shall be designed to accept the
total daily flow from at least one house.
No treatment efficiencies are indicated in this document for any particular system.
The dimensional values and ranges given in the document were agreed as sufficient to provide acceptable
treatment for basic parameters in the majority of simple situations.
Some specific dimensional values and ranges can be found in country’s codes of practice and regulations
given in the bibliography.
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1 Scope
This Technical Report provides details of filtration systems used for applications ranging from a single house
up to and included 50 PT. The filtration systems receive domestic wastewater from septic tanks manufactured
according to the requirements given in EN 12566-1 and EN 12566-4.
This document is a code of practice and gives design parameters, construction details, installation and
component requirements for constructed sand filters and subsurface flow sand or gravel reed beds.
2 Normative references
The following referenced documents are indispensable for the application 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 1085:2007, Wastewater treatment – Vocabulary
EN 12050-2, Wastewater lifting plants for buildings and sites - Principles of construction and testing - Part 2:
Lifting plants for faecal-free wastewater
EN 13252, Geotextiles and geotextile-related products — Required characteristics for use in drainage
systems
3 Terms and definitions
For the purposes of this Technical Report, the terms and definitions given in EN 1085:2007 and the following
apply.
3.1
biological layer
biological film which grows on the top of the filter material when pre-treated effluent from the septic tank
infiltrates the filter material
3.2
buried filter
filter covered with a layer of soil
3.3
collection layer
layer in which collection pipes collect treated waste water that has passed through the filter
3.4
collection pipe
perforated pipe placed at the bottom within the collection layer connected to the collection chamber
3.5
collection chamber
chamber receiving treated waste water from the collection layer and discharging through the pipe to the outfall
NOTE It is designed to enable effluent sampling.
3.6
collection trench
mound of granular fill material on the base of the excavation at the outlet side, in which a collection pipe
collects water which has passed through the filter
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3.7
covered filter
filter usually covered with pebbles or gravel
3.8
connection pipe
non-perforated pipe used to connect the septic tank to the distribution chamber or the collection pipe(s) to an
external collection chamber
3.9
distribution chamber
chamber allowing even gravity distribution of septic tank effluent via the distribution pipes
3.10
distribution layer
layer of the system composed of granular fill material in which pre-treated effluent from the septic tank is
discharged through infiltration pipes
3.11
distribution pipe
non-perforated pipe used to connect the distribution chamber to a single infiltration pipe
3.12
dosing chamber
small tank receiving pre-treated effluent from the septic tank and containing a dosing device (e.g. a pump, a
hydraulic siphon or a tipping trough) which automatically discharges the desired volume
3.13
end connections
perforated and non-perforated pipes and fittings that connect the lower ends of infiltration pipes, and can
enable airflow between infiltration pipes
NOTE The connecting fittings may incorporate ventilation and access provision.
3.14
filter area
surface area of the filter material
3.15
filter material
inert material with various particle or pore sizes used for filtration
NOTE This material, often sand, placed beneath the distribution layer provides both an area for biological growth and
a degree of filtration for the pre-treated effluent from the septic tank.
3.16
filtration system
construction of infiltration pipes, filter material and a collection system used for treating pre-treated effluent
NOTE The infiltration pipes may be located either in trenches or beds which can be singular or multiple.
3.17
granular fill material
inert material in which the infiltration pipes are placed in the distribution or collection layers
Note It may also be used to replace native soil when used as backfill.
3.18
gravel filter
constructed filter using gravel as the filter material
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3.19
horizontal reed bed
open gravel filter planted with macrophytes where the effluent is treated by flowing horizontally from the
distribution to the collection point
NOTE Local practice may dictate the use of specific macrophytes, reeds or plants.
3.20
horizontal filter
filter where the effluent is treated by flowing horizontally from the distribution to the collection point
3.21
impermeable film
inert membrane, which is impermeable to liquid
3.22
infiltration pipe
perforated pipe through which the pre-treated effluent from the septic tank is discharged into the treatment
installation
3.23
installation area
area of septic tank and filtration system excluding the outfall
3.24
land drain
surface or subsurface channel for the transportation of rainwater
NOTE They are used to dewater ground and divert the natural flow of surface and subsurface water away from the
filtration system.
3.25
lining
material used to form a container within an excavation
3.26
mesh
fabric, resistant to decomposition with hole diameters approximately 1 mm, which is permeable to liquid and
air but prevents solid particles from passing through it
3.27
open filter
uncovered filter
3.28
prefilter
device used to protect the treatment system (to prevent clogging of the filtration system, particularly the
infiltration pipes)
3.29
reed bed
open filter planted with macrophytes
NOTE Local practice may dictate the use of specific macrophytes, reeds or plants.
3.30
sand filter
constructed filter using sand as the filter material
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3.31
vertical reed bed
open sand or gravel filter planted with macrophytes where the effluent is treated by flowing vertically
NOTE Local practice may dictate the use of specific macrophytes, reeds or plants.
3.32
vertical filter
filter where the effluent is treated by flowing vertically between the distribution and collection layer
3.33
water table
level below which the ground is saturated with water
4 Description of filters
The systems described in this document are:
 Buried vertical sand filter;
 Covered vertical sand filter;
 Open vertical sand filter with reeds;
NOTE 1 This system is also known as vertical reed bed.
 Open vertical gravel filter with reeds;
NOTE 2 Local practice may dictate the use of specific macrophytes, reeds or plants.
NOTE 3 In some countries, this system is also known as a vertical reed bed.
 Open horizontal gravel filter with reeds;
NOTE 4 Local practice may dictate the use of specific macrophytes, reeds or plants.
NOTE 5 In some countries, this system is also known as a horizontal reed bed.
Filters should be described according to Table 1:
Table 1 — Description of filters
Filter name Buried Covered Open vertical Open vertical Open horizontal
vertical vertical sand filter gravel filter gravel filter
sand filter sand filter with reeds with reeds with reeds
Surface Buried Covered Open with reeds
Flow Vertical Vertical Vertical Vertical Horizontal
Filtration media Sand Sand Sand Gravel Gravel
5 Design Parameters
5.1 General
A filtration system may use watertight or non-watertight construction depending upon the circumstances and
regulations. Depending on the local regulations, non watertight filtration systems may not be acceptable.
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NOTE A system that is not watertight may allow a degree of infiltration into the soil. The soil can provide additional
treatment. When the filter discharges a low volume, more of the discharge infiltrates. At higher volume discharges, more of
the discharge flows to the outfall.
The biological layer may limit the infiltration into the filter material. The layer's properties depend on the filter
material's permeability, the specific hydraulic loading rate, the organic and oxygen conditions.
The permeability of the filter material is determined by grain size distribution (sand type), compaction and
discontinuities.
The correct design of the filter area is crucial in order to avoid blockage.
The design parameters given enable a system to be selected to meet the following pollutant concentration
requirements:
 organic matter;
 suspended solids;
 phosphorus (see Annex D);
 nitrogen;
 pathogens.
Local regulations or guidance may determine acceptable levels for each parameter.
5.2 Site considerations
5.2.1 Climatic conditions
When designing, constructing and locating the filtration system, climatic conditions in the area such as
extremes of temperature, dryness, rainfall and snow should be taken into consideration.
Factors influencing excavation depths include:
 frost cover;
 protection from disturbance;
 depth of the outlet pipe from the septic tank;
 depth to water table;
 depth to bedrock.
5.2.2 Water table or bed rock
Hydrogeological statistics and/or site investigations should be used to determine the seasonally highest
groundwater table.
European countries regulations and practices require depths of unsaturated soil to be present between the
base of a non watertight filtration system and the seasonally highest level of the water table or bed rock.
Depending of the vulnerability of the ground water or bed rock the requirement for the depth of unsaturated
soil can vary between 0,2 m to over 1,0 m.
Where the required dimensions can not be achieved, a watertight filtration system or alternative arrangements
(raised filtration systems, etc.) shall be used.
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5.2.3 Location
5.2.3.1 General
Consider all relevant site features when selecting and locating the system. Annex A lists considerations to be
assessed for infiltration; all or some of these considerations may be required by the local authorities as part of
the site investigation.
In the absence of any regulations or guidance, and to avoid pollution of any water source, the filtration system
should be located according to the following criteria:
 within an area not subject to flooding;
 within an area absent of water supply pipes and underground services other than those required by the
filtration system;
 within an area absent of access roads, driveways or paved sections;
 minimum distance to surface water (lake, pond, flood plain, river, stream) 10 m;
 minimum distance to the nearest point of the closest habitable dwelling 4 m;
 minimum distance to the nearest road boundary or ditch 4 m;
 minimum distance to any tree or plant which develops an extensive root system 3 m;
 minimum distance to the boundary of the adjoining site 2 m.
Civil constructed barriers can modify these distances.
5.2.3.2 Groundwater protection
Groundwater, in particular any water intended to be used for drinking shall be protected. The installation shall
either be watertight or hydraulically down slope of any groundwater source.
Distances are based on the geological and hydro-geological factors, the type and depth of soil, the depth to
the water table, all of which should be assessed as part of the detailed site investigation.
Where non water tight systems are used, it is not possible to specify with certainty the minimum safe distance
between the filtration system, its outfall and any system that collects drinking water. As a guide for places
where no local regulations or guidance exists, a distance of 30 m may be used, however, local conditions may
require a far greater distance.
5.3 Influent parameters
Filtration systems are intended to receive only domestic wastewater (without any other water such as
rainwater) pre-treated by a septic tank.
Systems to treat wastewater with characteristics outside of domestic wastewater require a different design e.g.
restaurants may have higher BOD, fat, oil and grease levels.
In the absence of local regulation or guidance or other reliable data, a value of 150 l per day per inhabitant
should be used for loading calculation.
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5.4 Selection of filtration system
The selection of specific types and the respective sizing for pre-treated effluent filter systems depends on the
efficiency of the system, site conditions and local requirements for effluent quality.
NOTE 1 Operation, maintenance and checking frequencies should be taken into consideration. These frequencies are
considered as low for buried and covered vertical sand filters, medium for open vertical sand filters with reeds and open
horizontal gravel filter with reeds, and high for open vertical gravel filters with reeds.
Various publications (e.g. scientific, standardization paper, guidelines) indicate performance levels for
parameters (e.g. BOD, COD, SS, P, N). However, due to differences in available information from the various
CEN countries, typical performance parameters are not listed.
NOTE 2 A co-normative research project for clarification and comparison of several types of pre-treated effluent
filtration systems is requested.
6 Components
6.1 General
In the absence of any local regulation or guidance the following requirements apply.
6.2 Pipes
6.2.1 General
All pipes shall be manufactured in accordance with the requirements of the relevant EN, if available or in their
absence with the specifications valid in the place of use.
6.2.2 Distribution pipe
The following specific requirements shall be complied with:
 nominal diameter of the distribution pipe located between the septic tank and the distribution chamber
shall at least be equal to the diameter of the outlet of the septic tank;
 for distribution pipes from the distribution chamber, the minimum internal diameter (ID) shall be 75 mm for
gravity systems and 32 mm for pumped systems.
6.2.3 Infiltration and Collection pipes
Local regulations or guidance may specify the size, perforation and spacing.
The perforations shall be dimensioned and spaced to ensure that granular fill material cannot enter and that
water can flow easily through the perforations without clogging, see Table 2.
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Table 2 — Infiltration and Collection pipe - Characteristics
Type of pipe Infiltration pipes Collection pipes
Purpose Even distribution of effluent over Collects treated water from filter
filter area
Pipe internal surface Shall have a constant diameter and Shall be smooth but may be of
be smooth irregular diameter or corrugated
Perforation type and Holes only, usually downwards Holes or slots, downwards or all
orientation around the circumference
a
Non dosed Dosed
Pipe diameter ≥ 75 mm ≥ 32 mm ≥ 80 mm
a
Perforation separation 0,3 m to 0,5 m 1,0 m  0,1m to Up to 30 % of
distance 0,5 m pipe surface
Perforation size 8 mm 6 mm to 8 mm 2 mm to 2 mm x 8 mm
10 mm (hole) to 8 mm x
200 mm (slot)
a
Hydraulic head of 0,7 m to 1 m is required at the end of the infiltration pipes.

6.3 Sand
The sand sizes shall be in accordance with the descriptions given for each system.
As there is no common specification for sand throughout Europe, information regarding several specifications
for sands is given in Annex C.
6.4 Granular fill material
The granular fill material sizes shall be in accordance with the descriptions given for each system. Granular fill
material shall be inert, washed and graded.
6.5 Protection and separation layer
Infiltration pipes when buried with soil should be covered, with geotextile T (see Table 3) to prevent
contamination of the granular fill material by fine particles of soil. Where air permeable insulation materials are
used, geotextile T may not be necessary.
To avoid sand from being washed into the collection layer, a coarser granular material than the sand or mesh
shall be used. The separation layer comprises particles of sizes between those of the layers above and below.
The mesh shall not puncture or tear.
Geotextile T should meet the requirements of EN 13252; Mesh B should be suitable for wastewater conditions
and meet the requirements of the relevant standard.
Table 3 — Geotextile and mesh properties
Characteristics Geotextile T (Top) Mesh B (Bottom)
Pore size 0,4 mm to 1 mm
≤ 120 µm

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6.6 Impermeable lining
Impermeable lining may be used on the sides and base of the filtration system to create a watertight
construction.
This lining shall not puncture or tear, either during installation or operation. Large single sheets should be
used if available.
Local regulations may describe how to achieve water tightness. In the absence of such a recommendation,
the following guidance gives the minimum thickness of the impermeable lining:
 high density polyethylene linings shall have a minimum thickness of 200 µm; or
 for rocky soil, a layer of at least 750 µm polyethylene or butyl, sandwiched between two layers of
geotextile for protection.
Sheets of impermeable lining can be laid, overlapping by at least 0,2 m and sealed. Where pipes penetrate
the lining appropriate seals shall be used.
Impermeable linings shall be used to achieve a watertight lining of the excavation. Water tightness may be
achieved by using a ready-made watertight container.
NOTE Where watertight installations are required, a water tightness test may be performed after construction of the
filter.
6.7 Pumping systems
Pumping systems may be used to dose filtration systems, to raise pre-treated septic tank effluent and to
transport it to a remote filtration system. Pumps shall be installed in a separate pumping chamber. Suitable
wastewater pumps with a minimum free passage of 10 mm should be used. When using a pumping system, it
is to be in accordance with EN 12050-2 and shall include an alarm.
6.8 Dosing system
To provide efficient distribution of the effluent all the way through the full length of the infiltration pipes, the use
of a dosing system is highly recommended. The perforation size and density will determine the dosing
distribution over the filter area.
Parameters to be considered are:
a) For a Buried vertical sand filter, Covered vertical sand filter, Open vertical sand filter with reeds, Open
vertical gravel filter with reeds:
 Typical values are 3 l/m² to 15 l/m² per dose in a maximum time of 5 minutes;
 Each dose volume must be adapted to the pipe network volume.
b) For an Open horizontal gravel filter with reeds:
2 2
 Typical values are 3 l/m to 6 l/m per dose in a maximum time of 5 minutes;
 Each dose volume must be adapted to the pipe network volume.
6.9 Chambers
Chambers shall be watertight and be fitted with a removable cover to facilitate maintenance and inspection.
Such covers should prevent unauthorised access.
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To prevent backflow and enable sampling, the inlet of the chamber should be at least one pipe diameter
above the crown of the outlet pipe.
The outlets from the distribution chamber shall be adjustable to enable even flow to the distribution pipes.
There may be optional outlets when the filtration system effluent is discharged alternatively onto different parts
of the filtration surface.
NOTE Dosing and distribution chambers may be combined into a single structure.
7 General requirements for the installation of septic tanks
7.1 General
Septic tanks shall be installed in accordance with national regulations or guidance and manufacturers
instructions.
Provision shall be made for removing the sludge from the septic tank. This is usually removed using a vacuum
tanker.
The outlet pipe from the septic tank shall have a fall of at least 0,5 %. Prior to installation, the use of a grease
separator shall be considered.
The use of a pre-filter after the septic tank shall also be considered. When installed it shall be fitted upstream
of the dosing chamber.
7.2 Ventilation
Generally, a ventilating stack provides an air outlet to the septic tank. Local requirements may specify either a
separate ventilation stack or the building’s ventilating stack (see EN 12056-2). An independent ventilation pipe
may be required in certain circumstances. The ventilating stack shall not be fitted with an air admittance valve.
8 Construction
8.1 General
A border of at least 1 m is recommended around the edge of a filtration system. Excavating beds or trenches
should avoid disturbing the border.
Before selecting the method of effluent supply to the filtration system, check the site contours and where
possible orientate system to use gravity.
8.2 Land drains
Surface channels or land drains shall be installed when it is required to prevent the migration of surface water
into the filtration system.
8.3 General precautionary measures for excavation works
If necessary, the sides and ba
...