EN 14701-2:2013

Characterisation of sludges - Filtration properties - Part 2: Determination of the specific resistance to filtration

This European Standard specifies a method for determining the specific resistance to filtration of conditioned and non-conditioned sludges, provided that no sedimentation occurs during filtration (i.e. single phase suspension with particles in suspension).
This European Standard is applicable to sludges and sludge suspensions from:
-   storm water handling;
-   urban wastewater collecting systems;
-   urban wastewater treatment plants;
-   industrial wastewater that has been treated similarly to urban wastewater (as defined in Directive 91/271/EEC);
-   water supply treatment plants.
This method is also applicable to sludge and sludge suspensions of other origins.

Charakterisierung von Schlämmen - Filtrationseigenschaften - Teil 2: Bestimmung des spezifischen Filtrationswiderstands

Diese Europäische Norm legt ein Verfahren zur Bestimmung des spezifischen Filtrationswiderstandes von konditio¬nierten als auch unkonditionierten Schlämmen fest, vorausgesetzt, es erfolgt während der Filtration keine Sedimentation (d. h. einphasige Suspension mit Partikeln).
Diese Europäische Norm gilt für Schlämme und Schlammsuspensionen aus folgenden Bereichen:
-   Behandlung von Regenwasser;
-   Kanalisationssysteme für kommunales Abwasser;
-   Anlagen für die Behandlung von kommunalem Abwasser;
-   Behandlung von industriellem Abwasser, die auf ähnliche Weise erfolgt wie die von kommunalem Abwasser (wie in der Richtlinie 91/271/EWG festgelegt);
-   Aufbereitungsanlagen für die Wasserversorgung.
Dieses Verfahren ist auch auf Schlämme und Schlammsuspensionen anderer Herkunft anwendbar.

Caractérisation des boues - Propriétés de filtration - Partie 2: Détermination de la résistance spécifique à la filtration

La présente Norme européenne spécifie une méthode de détermination de la résistance spécifique à la filtration des boues, conditionnées ou non, en considérant qu’aucune sédimentation n’a lieu pendant la filtration (c’est-à-dire qu’elle s’applique à une suspension monophasique avec des particules en suspension).
Elle s’applique aux boues et aux suspensions provenant :
-   de la collecte des eaux de pluie ;
-   des systèmes de collecte des eaux usées urbaines ;
-   des stations d’épuration des eaux usées urbaines ;
-   des eaux usées industrielles traitées de la même manière que les eaux usées urbaines (telles que définies dans la Directive 91/271/CEE) ;
-   des usines de production d’eau potable.
Cette méthode peut également être appliquée aux boues et aux suspensions d’une autre provenance.

Karakterizacija blata - Filtracijske lastnosti - 2. del: Določanje specifične odpornosti do filtriranja

Ta evropski standard določa metodo za določanje specifične odpornosti do filtriranja predelanega in nepredelanega blata, če med filtriranjem ne pride do sedimentacije (tj. enofazna suspenzija z delci v suspenziji). Ta evropski standard se uporablja za blata in suspenzije blata iz:
– sistemov za zbiranje deževnice;
– zbiralnih sistemov za mestno odpadno vodo;
– čistilnih naprav za mestno odpadno vodo;
– industrijske odpadne vode, ki je bila pripravljena podobno kot mestna odpadna voda (v skladu z Direktivo 91/271/EGS);
– čistilnih naprav v sistemih oskrbe z vodo.
Ta metoda se uporablja tudi za blata in suspenzije blata drugega izvora.

General Information

• Status: Published
• Publication Date: 23-Apr-2013
• Withdrawal Date: 30-Oct-2013
• ICS: 13.030.20 - Liquid wastes. Sludge
• Technical Committee: CEN/TC 308 - Characterization of sludges
• Drafting Committee: CEN/TC 308/WG 1 - Characterization methods
• Current Stage: 9093 - Decision to confirm - Review Enquiry
• Start Date: 04-Jun-2024
• Completion Date: 14-Apr-2025
• Ref Project: SIST EN 14701-2:2013 - Characterisation of sludges - Filtration properties - Part 2: Determination of the specific resistance to filtration

Relations

• Replaces: EN 14701-2:2006 - Characterization of sludges - Filtration properties - Part 2: Determination of the specific resistance to filtration
• Effective Date: 01-May-2013

Overview

EN 14701-2:2013 - "Characterisation of sludges - Filtration properties - Part 2" is a CEN laboratory standard that defines a validated method to determine the specific resistance to filtration (r) of conditioned and non‑conditioned sludges. The method assumes a single‑phase suspension (no sedimentation during filtration) and is intended to assess sludge filterability for wastewater and water treatment applications.

Key topics and requirements

• Scope and applicability: suitable for sludges from storm water handling, urban wastewater collection and treatment plants, industrial wastewater treated like urban wastewater (Directive 91/271/EEC), water supply treatment plants, and other sludge origins.
• Principle: based on Darcy’s law - flow of liquid through a porous medium - by recording filtrate volume over time and deriving r from the linear part of the t/V vs. V plot.
• Validated pressure ranges: tests validated at 50 ± 5 kPa, 150 ± 10 kPa, and 300 ± 15 kPa (above or below atmospheric pressure as appropriate).
• Apparatus essentials:
  • Filtration cell ~250 ml capacity, filter diameter 60–90 mm.
  • Filtering medium (e.g., ash‑free fast filter paper with 20–25 µm retention, ~0.22 mm thickness such as Whatman 41) or equivalent cloth/metallic media.
  • Vacuum pump or air/hydraulic pressure system; optional piston arrangement with pressure sensor.
• Procedure highlights:
  • Measure dry solids (EN 12880) and assume g/kg ≈ g/L for rapid tests.
  • Typical sample volumes: 100 ± 1 ml for non‑conditioned sludge, 200 ± 2 ml for conditioned/easily filterable sludge.
  • Record filtrate volume vs time after collecting at least 10% of initial filtrate; stop on cake breaking, non‑linearity, or 60 min limit.
  • Measure filtrate viscosity and dry mass of the cake; compute r using the standard formula r = (2·Δp·A·b) / (μ·m).
• Limitations: not suitable where sedimentation occurs during filtration or for extremely compressible sludges unless linear t/V behavior is observed. Results at other pressures require prior validation.

Practical applications

• Estimating full‑scale filter performance and sizing pressure filters.
• Comparing filterability across sludges from different plants or processes.
• Evaluating and optimizing chemical conditioning (coagulant/flocculant) doses (see CEN/TR 14742).
• Supporting process design, dewatering strategy selection, and operational troubleshooting in wastewater and water treatment plants.

Who should use this standard

• Environmental and process engineers
• Laboratory technicians in sludge characterization labs
• Wastewater treatment plant operators and consultants
• Equipment manufacturers and filter designers
• Regulatory and compliance laboratories

Related standards

• EN 14701-1 (Capillary suction time, CST)
• EN 14701-3 (Compressibility)
• EN 14701-4 (Drainability of flocculated sludges)
• EN 12880 (Dry residue and water content)
• CEN/TR 14742 (Laboratory chemical conditioning procedure)

Keywords: EN 14701-2:2013, specific resistance to filtration, sludge characterization, filtration properties, sludge testing, wastewater treatment, filterability, Darcy’s law.

Standards Content (Sample)

SLOVENSKI STANDARD
01-julij-2013
1DGRPHãþD
SIST EN 14701-2:2006
.DUDNWHUL]DFLMDEODWD)LOWUDFLMVNHODVWQRVWLGHO'RORþDQMHVSHFLILþQH
RGSRUQRVWLGRILOWULUDQMD
Characterisation of sludges - Filtration properties - Part 2: Determination of the specific
resistance to filtration
Charakterisierung von Schlämmen - Filtrationseigenschaften - Teil 2: Bestimmung des
spezifischen Filtrationswiderstands
Caractérisation des boues - Propriétés de filtration - Partie 2: Détermination de la
résistance spécifique à la filtration
Ta slovenski standard je istoveten z: EN 14701-2:2013
ICS:
13.030.20 7HNRþLRGSDGNL%ODWR Liquid wastes. Sludge
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN 14701-2
NORME EUROPÉENNE
EUROPÄISCHE NORM
April 2013
ICS 13.030.20 Supersedes EN 14701-2:2006
English Version
Characterisation of sludges - Filtration properties - Part 2:
Determination of the specific resistance to filtration
Caractérisation des boues - Propriétés de filtration - Partie Charakterisierung von Schlämmen -
2: Détermination de la résistance spécifique à la filtration Filtrationseigenschaften - Teil 2: Bestimmung des
spezifischen Filtrationswiderstands
This European Standard was approved by CEN on 1 March 2013.

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, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United
Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2013 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 14701-2:2013: E
worldwide for CEN national Members.

Contents Page
Foreword .3
Introduction .4
1 Scope .5
2 Normative references .5
3 Terms and definitions .5
4 Principle .5
5 Apparatus .6
6 Procedure .6
6.1 General .6
6.2 Reduced pressure (Figure B.1) .6
6.3 Under pressure (Figure B.2 a)) .7
6.4 Under pressure with a piston (Figure B.2 b)) .7
7 Expression of results .8
8 Precision . 10
9 Test report . 10
Annex A (informative) Supplementary information to Darcy's law . 11
Annex B (informative) Filtration apparatus . 13
Annex C (informative) Table of viscosity . 15
Annex D (informative) Result of validation trial . 16
Bibliography . 20

Foreword
This document (EN 14701-2:2013) has been prepared by Technical Committee CEN/TC 308
“Characterization of sludges”, the secretariat of which is held by AFNOR.
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 October 2013, and conflicting national standards shall be withdrawn at
the latest by October 2013.
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.
This document supersedes EN 14701-2:2006.
Other parts of EN 14701 are:
 Part 1: Capillary suction time (CST);
 Part 3: Determination of the compressibility;
 Part 4: Determination of the drainability of flocculated sludges.
Most significant changes made since the latest edition:
 “Part 4 …” added to Foreword;
 Introduction modified;
 CEN/TR 14742 added to Normative References;
 Clause “Principle” modified and better specified;
 List Entry 5.1.3 modified and better specified;
 List Entry 5.8 added;
 Clause 6 better specified;
 In Formula (1), “m” instead of “C ”;
o
 Table 1 simplified;
 text added in Clause 7;
 List Entry c) added in Clause 9;
 former Annex A deleted;
 bibliographical references added.
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, Former Yugoslav Republic of Macedonia, France, Germany, Greece,
Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,
Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom.

Introduction
The specific resistance to filtration is a parameter which indicates the suitability of sludge to be filtered. The
value of the specific resistance to filtration has great importance in filtration processes as it can be useful for
estimating the performance of full-scale filtering devices, mainly pressure filters, and comparing filterability
characteristics of sludges produced in different plants. Specific resistance measurements can also give
indications on both the optimal type and dosage of conditioner to be used (CEN/TR 14742).
This revised version only includes editorial changes that do not influence the original, validated method.

1 Scope
This European Standard specifies a method for determining the specific resistance to filtration of conditioned
and non-conditioned sludges, provided that no sedimentation occurs during filtration (i.e. single phase
suspension with particles in suspension).
This European Standard is applicable to sludges and sludge suspensions from:
 storm water handling;
 urban wastewater collecting systems;
 urban wastewater treatment plants;
 industrial wastewater that has been treated similarly to urban wastewater (as defined in
Directive 91/271/EEC);
 water supply treatment plants.
This method is also applicable to sludge and sludge suspensions of other origins.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
EN 12832:1999, Characterization of sludges — Utilization and disposal of sludges — Vocabulary
EN 12880, Characterization of sludges — Determination of dry residue and water content
CEN/TR 14742, Characterization of sludges — Laboratory chemical conditioning procedure
3 Terms and definitions
For the purposes of this document, the terms and definitions given in EN 12832:1999 and the following apply.
3.1
specific resistance to filtration
property representing the resistance to filtration of a layer of particles having a unit mass of dry solids
deposited on a unit filtering area
4 Principle
This method is based on the flow of a liquid through a porous medium in accordance with Darcy's law
(see Annex A). The specific resistance to filtration is determined by pouring a suitable volume of sludge into a
filtering device, allowing the liquid to be filtered under constant vacuum or pressure, whilst recording the
amount of filtrate over time.
Considering that for sludges this parameter is affected by pressure value, this standard has been validated for
the determination of specific resistance to filtration at pressure values (50 ± 5) kPa, (150 ± 10) kPa and
(300 ± 15) kPa, as specifically indicated in Clause 6.
If necessary, as in the case of tests intended to size or optimise industrial filters, tests may be carried out at
different pressures, provided results have been validated in advance.
5 Apparatus
5.1 Filtration apparatus with a capacity of 250 ml, and filter diameters between 60 mm and 90 mm
(see Annex B).
5.1.1 Apparatus for filtration under reduced pressure (see Figure B.1).
5.1.2 Apparatus for filtration under pressure up to 1 MPa (see Figure B.2 a)).
5.1.3 Apparatus for filtration under pressure up to 1 MPa with a piston (see Figure B.2 b)) equipped
with a pressure sensor under the piston to measure the actual applied pressure.
If this set-up is not given, piston friction is not taken into account in the pressure measurement and air filtration
is preferred.
5.2 Graduated cylinders with a capacity of 100 ml and 250 ml.
5.3 Vacuum pump, or air pressure system, or hydraulic system for pressure application, including pressure
adjustment system (regulator or reducer) and pressure gauge.
5.4 Chronometer, e.g. stopwatch, computer.
5.5 Beaker with a capacity of 500 ml.
5.6 Pipettes.
5.7 Filtering medium, filter paper (extra fast, ash-free), with a particle retention between 20 µm and 25 µm ®
1)
and a filtration flow rate of about 100 ml/min and a thickness of 0,22 mm (e.g. Whatman 41 ).
Synthetic, or stainless metallic cloth may also be used if they can be shown to lead to the same results.
5.8 Filtering medium support.
5.9 Apparatus for determining sludge dry residue and water content (see EN 12880).
5.10 Thermostatic cell, for determinations at non-ambient temperatures.
6 Procedure
6.1 General
Measure the dry residue of the sludge, C , in accordance with EN 12880 and assume that the dry residue
o
measured in g/kg is equivalent to the concentration measured in g/l. Prior to measuring, ensure the sludge is
at room or test temperature.
If sludge has to be conditioned, this operation shall be carried out according to CEN/TR 14742.
6.2 Reduced pressure (Figure B.1)
6.2.1 Keep the valve between filter (5.1) and vacuum/pressure system (5.3) closed during the procedure,
maintaining the system at an absolute pressure of (50 ± 5) kPa.

1) This information is given for the convenience of users of this document and does not constitute an endorsement by
CEN of the product named. Equivalent products may be used if they can be shown to lead to the same results.
6.2.2 Put the filtering medium (5.7) in the funnel, moisten it with water and avoid any air entrance into the
filter.
6.2.3 Measure the temperature, put (100 ± 1) ml of non-conditioned sludge or (200 ± 2) ml of conditioned,
or of easily filterable sludge into the funnel after gentle homogenisation by pouring the sludge 3 times to
4 times from one beaker to another (only in case of non-conditioned sludge), open the valve and start
filtration.
6.2.4 Record filtrate volumes, V, and corresponding times, t, only after collecting at least 10 % of the initial
filtrate volume. Recording depends on flow rate and could range from every 5 s at the beginning until every
60 s or more (for sludge of low filterability) at the end. Stop the filtration when one of the following conditions
occurs:
 pressure drops down (breaking of cake);
 filtrate flow rate instantaneously drops down;
 plot t/V vs. V deviates from linearity;
 filtration time exceeds 60 min.
6.2.5 Measure the dry mass of the cake after filtration in accordance with EN 12880, and measure the
dynamic viscosity of the filtrate at test temperature.
6.3 Under pressure (Figure B.2 a))
6.3.1 While keeping the valve between the filter (5.1) and the air pressure system (5.3) closed, adjust the
system to (50 ± 5) kPa, or (150 ± 10) kPa, or (300 ± 15) kPa above atmospheric pressure. The pressure shall
be constantly maintained during the whole procedure.
6.3.2 Put the filtering medium (5.7) into the filtration cell, moisten it with water and avoid any air entrance
into the filter.
6.3.3 Measure the temperature and put 100 ml of non-conditioned sludge or 200 ml of conditioned, or of
easily filterable sludge into the apparatus after gentle homogenisation by pouring the sludge 3 times to 4 times
from one beaker to another (only in case of non-conditioned sludge).
6.3.4 Close the sludge inlet, open the valve of the air pressure system and start the filtration process.
6.3.5 Record filtrate volumes, V, and corresponding times, t, only after collecting at least 10 % of the initial
filtrate volume. Recording depends on flow rate and could range from every 5 s at the beginning until every
60 s or more (for sludge of low filterability) at the end. Stop the filtration when one of the following conditions
occurs:
 pressure drops down (breaking of cake);
 instantaneous filtrate flow rate drops down;
 plot t/V vs. V de
...