Bsi bs en 14701 1 2006 (2007)

EN 14701 1 2006 64 e stf BRITISH STANDARD BS EN 14701 1 2006 Characterization of sludges — Filtration properties — Part 1 Capillary suction time (CST) The European Standard EN 14701 1 2006 has the sta[.]

Characterization of

sludges — Filtration

properties —

Part 1: Capillary suction time (CST)

The European Standard EN 14701-1:2006 has the status of a

British Standard

ICS 13.030.20

This British Standard was

published under the authority

of the Standards Policy and

Strategy Committee

on 30 April 2007

© BSI 2007

ISBN 978 0 580 50510 2

National foreword

This British Standard was published by BSI It is the UK implementation of

EN 14701-1:2006

The UK participation in its preparation was entrusted to Technical Committee EH/5, Sludge characterization

A list of organizations represented on EH/5 can be obtained on request to its secretary

The UK committee has never seen the need to standardize this method at a European level and, as a consequence, has not been actively involved in the development of this standard However, the UK committee is pleased that a classic British method was selected The method has long been used as a valuable operational-control method and is available in existing technical literature (see reference [1] in the bibliography of this standard) Due to the difficulty and cost of sending liquid sludge samples (in such a manner that their properties do not change) to laboratories for international interlaboratory trials of the performance of this method, interested parties convened at a workshop to assess the test Their conclusion was that the results are operationally defined (e.g by the filter paper used) and, as the document does not specify all such operational details, the performance data are not really applicable outside the context of the workshop As a result, the members of EH/5 have no information to offer on the reproducibility of the results

This publication does not purport to include all the necessary provisions of a contract Users are responsible for its correct application

Compliance with a British Standard cannot confer immunity from legal obligations

Amendments issued since publication

NORME EUROPÉENNE

EUROPÄISCHE NORM March 2006

ICS 13.030.20

English Version

Characteri z ation of sludges - Filtration properties - Part 1:

Capillary suction time (CST)

Caractérisation des boues - Propriétés de filtration - Partie

1: Détermination du temps de succion capillaire Filtrationseigenschaften - Teil 1: Bestimmung der kapillarenCharakterisierung von Schlämmen

-Fließzeit

This European Standard was approved by CEN on 3 February 2006.

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 Central Secretariat 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 Central Secretariat has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, 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

C O M I T É E U R O P É E N D E N O R M A L I S A T I O N

E U R O P Ä IS C H E S K O M IT E E FÜ R N O R M U N G

Management Centre: rue de Stassart, 36 B-1050 Brussels

2

Contents

Page

Foreword 3

1 Scope 5

2 Normative references 5

3 Terms and definitions 5

4 Principle 5

5 Apparatus 6

5.1 Standard apparatus 6

5.2 Filter paper 6

5.3 Beakers 6

6 Procedure 6

7 Expression of results 6

8 Precision 7

9 Test report 7

Annex A (informative) Simple automatic instrument for determining the filterability of sewage sludge 8

Annex B (informative) Relation between CST and the specific resistance to filtration 9

Annex C (informative) Relation between CST and solids content 10

Annex D (informative) Table of dynamic viscosity 11

Annex E (informative) Results of validation trials 12

Bibliography 15

Foreword

This document (EN 14701-1:2006) 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 September 2006, and conflicting national standards shall be withdrawn at the latest by September 2006

Other parts of this European Standard are:

 Part 2: Determination of the specific resistance to filtration;

 Part 3: Determination of the compressibility

According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, 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

4

Introduction

The capillary suction time (CST) is a fast and simple way to evaluate the sludge dewaterability by filtration This method gives no information on the obtainable solids content in a dewatering process

The measurement of CST should also make possible the evaluation, although only qualitatively, of other sludge characteristics, including dewaterability by centrifugation

1 Scope

This document specifies a method for the determination of the capillary suction time This document is applicable to sludge and sludge suspensions from:

 storm water handling;

 urban wastewater collecting systems;

 urban wastewater treatment plants;

 treating industrial wastewater similar to urban wastewater (as defined in Directive 91/271/EEC);

 water supply treatment plants

This method is also applicable to sludge suspensions from other origin

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 12832:1999, Characterization of sludges — Utilization and disposal of sludges — Vocabulary

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

filterability

property indicating the amenability of a sludge to be dewatered by a filtration process

3.2

capillary suction time (CST)

measurement of the time for a wetting front in a filter paper to travel between two fixed points

4 Principle

The principle of the method is that dewatering is achieved by the suction applied to the sludge by the capillary action of an absorbent filter paper

A part of the absorbent paper area is exposed to the sludge, while the remaining area is free for absorbing the filtrate The rate at which the paper becomes wetted with filtrate is a measure correlated to sludge dewaterability: it is measured by the time necessary for the filtrate to cover the space between two probes which detect the advancement of the liquid front on the paper (Annex A informative)

The CST measurements are strongly affected by many factors, such as properties of the paper, surface tension, temperature, suspended solids concentration, so they give only qualitative and comparative evaluations which can be correlated to the specific resistance to filtration (prEN 14701-2) for a given type of sludge (Annex B informative)

6

5 Apparatus

5.1 Standard apparatus

Device consisting of:

a) filtration apparatus, including base for supporting the absorbent paper, sludge reservoir and probes;

b) automatic time recording unit, including amplifier and digital electric stop-clock recording in seconds (see Annex A informative)

5.2 Filter paper

Paper suitable for chromatography with grain parallel with the longer side (for instance, Whatman n 17 or Wickam CST Papers 7 cm x 9 cm code 8680841) )

NOTE For comparable results the same filter paper type should be used

5.3 Beakers

Conventional beakers, 50 ml minimum

6 Procedure

6.1 Place a filter paper in the apparatus The filter paper shall always be placed with the same side up

6.2 Mix the sludge to be tested by pouring it off from a beaker to another for 4 times

6.3 Pour immediately the mixed sludge into the reservoir until it is completely full Great attention shall be paid in performing measurements immediately after the sludge mixing to avoid any result unreliability due to sludge settling into the beaker (especially for conditioned sludges)

6.4 When the clock stops, register the time which has been automatically measured

6.5 Repeat steps 6.1 to 6.4 in order to have at least 3 significant values, as stated in Clause 7

7 Expression of results

The CST value is given by arithmetically averaging the measured values If one or more values differ of more than 20% from the calculated mean value, they must not be considered and the average shall be calculated again with remaining values: in any case valid values shall be, at least, 3

The influence of the temperature may be evaluated through the relationship:

where

µ1 and µ2 are the dynamic viscosities of water at the two considered temperatures

1) This information is given for the convenience of users of this document and does not constitute an endorsement by CEN of this product Equivalent products may be used if they can be shown to lead to the same results

If the room temperature is between 12 °C and 30 °C, the influence of the temperature can be neglected Water viscosities as a function of temperature are reported in the table in Annex D (informative)

8 Precision

Results of validation trials are summarized in Annex E (informative)

The repeatability standard deviation ranges from 0,411 s (3,6 %) for activated/thickened sewage sludge, to 0,463 s (4,4 %) for activated sewage sludge, to 1,560 s (3,4 %) for waterworks sludge, and to 7,856 s (5,3 %) for digested sewage sludge

Mean value is 2,573 s (4,9 %) Minimum precision is 5,3 %

The reproducibility standard deviation ranges from 0,643 s (5,6 %) for activated/thickened sewage sludge, to 1,043 s (9,9 %) for activated sewage sludge, to 2,023 s (4,4 %) for waterworks sludge, and to 20,01 s (14,0 %) for digested sewage sludge

Mean value is 5,929 s (11,3 %) Minimum precision is 14,0 %

9 Test report

The test report shall contain the following information:

a) reference to this document;

b) all information necessary for the complete identification of the sludge sample;

c) details of sample pre-treatment, if carried out;

d) information about the size of the reservoir used;

e) results of the determination according to Clause 7;

f) any detail not specified in this document or which are optional and any other factor which may have affected the results

8

Annex A

(informative)

Simple automatic instrument for determining the filterability of sewage

sludge

The CST apparatus by Triton as described in [1] consists of a base supporting a rectangular piece of

7 cm x 9 cm of absorbent filter paper and a block holding probes above it; in the centre of the upper block (which stands clear of the paper by resting on five stainless steel supports) there is a circular hole in which a stainless steel reservoir (18 mm bore/25 mm high or 10 mm bore/50 mm high) loosely fit On the under side of the upper block there are two engraved circles, of 3,2 cm and 4,5 cm in diameter, concentric with the reservoir; two of the supports are specially machined probes in line with the first concentric circle and one with the second circle Both probes are electrically connected to the recording unit

For this apparatus, the CST values of raw sewage sludge generally range 60 s to 300 s, using the 18 mm reservoir and the kind of papers reported before (see 5.2)

The 18 mm reservoir is more suitable for low-dewaterable sludges: significant values range 10 s to 900 s The use of the 10 mm reservoir is necessary for easily filterable sludges: significant values range 20 s to

1 200 s

For high filterable sludges, having very low CST, 2 overlapped filter papers could be used

The 10 mm reservoir can be difficult to fill, especially with thick sludges The 18 mm reservoir has been found

to be suitable for use with most sewage sludges, but other dimensions may be more suitable for other types of suspension

Annex B

(informative)

Relation between CST and the specific resistance to filtration

The variation of CST with specific resistance to filtration for 18 mm and 10 mm diameter reservoirs for sewage sludges is reported in Baskerville and Gale (1968) [1]

The relationship between CST and the specific resistance, measured through the Buchner procedure, was also studied by Smollen (1986) [2], and Spinosa et al (1991) [3]

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Annex C

(informative)

Relation between CST and solids content

The variation of CST with solids content is discussed in Vesilind (1988) [4]

Annex D

(informative)

Table of dynamic viscosity

Table D.1 — Dynamic viscosity of water from 0 °C to 40 °C

T

(°C)

Viscosity

(10-3 Pa · s)

T

(°C)

Viscosity

(10-3 Pa · s)

0 1,7921 26 0,8737

1 1,7313 27 0,8545

2 1,6728 28 0,8360

3 1,6191 29 0,8180

4 1,5674 30 0,8007

5 1,5188 31 0,7840

6 1,4728 32 0,7679

7 1,4284 33 0,7523

8 1,3860 34 0,7371

9 1,3462 35 0,7225

10 1,3077 36 0,7085

11 1,2713 37 0,6947

12 1.2663 38 0,6814

13 1,2028 39 0,6685

14 1,1709 40 0,6560

15 1,1404

16 1,1111

17 1,0828

18 1,0559

19 1,0299

20 1,0050 20,2 1,0000

21 0,9810

22 0,9579

23 0,9358

24 0,9142

25 0,8937

NOTE 1 10-3 Pa · s = 10-2 g/cm · s = 1 centipoise

NOTE 2 It is assumed that filtrate viscosity is equal to water viscosity

12

Annex E

(informative)

Results of validation trials

Because the circulation of samples of real sludge high in organic content is not possible due to problems associated to changes in their physical characteristics during handling and transportation, the “Modified Round Robin Tests” procedure, developed by TG 3 of CEN/TC 308/WG 1, and reported in doc CEN/TC 308

N 822, was followed With this procedure, the round robin tests are carried out through “circulation of

analysts”, i e operators coming from the laboratories participating to the exercise meet in a common location,

close to the place where samples are collected, and work there on same samples, each using own apparatus Validation trials were carried out at LUA, Düsseldorf, on 28 September 2004

Trials involved a total of 11 Operators from the following 9 Laboratories/Institutions in 3 Countries: ARPA

Puglia (Bari, I), CEMAGREF (Montaldre, F), CNR-IRSA (Bari, I), Comm Env Emerg in Puglia Region (Bari, I), DIN (Berlin, D), LUA-NRW (Düsseldorf, D), STUA (Lippstadt, D), UBA (Berlin, D), University of Lecce (I) The following 4 different sludge types were tested:

 Sample 1: Sewage sludge – activated

Solids concentration (g/l): 2,81

 Sample 2: Sewage sludge – digested

Dry residue (%): 2,22

 Sample 3: Waterworks sludge

Dry residue (%): 3,62

 Sample 4: Sewage sludge – activated/thickened

Dry residue (%): 0,71

(analyses for measuring solids concentration and/or dry residue were carried out at the Chemical-biological Laboratory of Landeshauptstadt in Düsseldorf)

Test results have been statistically analysed for the evaluation of precision according to ISO 5725-2 In

particular, the repeatability standard deviation sr (for cells containing more than one figure), and the

reproducibility standard deviation sR were calculated

The tables of results which follow contain the following symbols:

i is the operator number;

j is the level (sample) number;

k (= 1, 2, , n) is the test number;

n are the replicates;

nij is the number of test results in the cell for operator (i) at level (j);

p is the total number of operators (i) (i = 1, 2, …, p);

q are the total testing levels (batches of materials) (j) (j = 1, 2, …, q);