SIST EN 14702-3:2019

SLOVENSKI STANDARD
oSIST prEN 14702-3:2017
01-december-2017
.DUDNWHUL]DFLMDLQUDYQDQMH]EODWRP'RORþHYDQMHODVWQRVWLXVHGDQMDGHO
'RORþHYDQMHKLWURVWLXVHGDQMD
Characterization and management of sludge - Determination of settling properties - Part
3: Determination of zone settling velocity (ZSV)
Charakterisierung von Schlämmen - Absetzeigenschaften - Teil 3: Bestimmung der
Sinkgeschwindigkeit
Caractérisation et management des boues - Détermination des propriétés de
sédimentation - Partie 3: Détermination de la vitesse de sédimentation
Ta slovenski standard je istoveten z: prEN 14702-3
ICS:
13.030.20 7HNRþLRGSDGNL%ODWR Liquid wastes. Sludge
oSIST prEN 14702-3:2017 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
oSIST prEN 14702-3:2017

---------------------- Page: 2 ----------------------
oSIST prEN 14702-3:2017


DRAFT
EUROPEAN STANDARD
prEN 14702-3
NORME EUROPÉENNE

EUROPÄISCHE NORM

November 2017
ICS 13.030.20
English Version

Characterization and management of sludge -
Determination of settling properties - Part 3:
Determination of zone settling velocity (ZSV)
Caractérisation et management des boues - Charakterisierung von Schlämmen -
Détermination des propriétés de sédimentation - Absetzeigenschaften - Teil 3: Bestimmung der
Partie 3: Détermination de la vitesse de sédimentation Sinkgeschwindigkeit
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee
CEN/TC 308.

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: Avenue Marnix 17, B-1000 Brussels
© 2017 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 14702-3:2017 E
worldwide for CEN national Members.

---------------------- Page: 3 ----------------------
oSIST prEN 14702-3:2017
prEN 14702-3:2017 (E)
Contents Page
European foreword . 3
Introduction . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Principle . 6
5 Interferences . 6
6 Equipment . 7
7 Procedure . 8
8 Expression of the results . 8
9 Precision . 9
10 Test report . 9
Annex A (informative) Settling apparatus . 11
Annex B (informative) Measurement of settling velocity according to different cases . 12
B.1 Measurement of settling velocity by measuring the interface position between
supernatant and sediments . 12
B.2 Measurement of settling velocity in absence of interface . 13
Annex C (informative) Determination of the theoretical area of the thickener by Talmage
and Fitch method . 15
Annex D (informative) Results of validation trials for zone settling velocity (ZSV) and
Compression point . 16
Bibliography . 21

2

---------------------- Page: 4 ----------------------
oSIST prEN 14702-3:2017
prEN 14702-3:2017 (E)
European foreword
This document (prEN 14702-3:2017) has been prepared by Technical Committee CEN/TC 308
“Characterization and management of sludge”, the secretariat of which is held by AFNOR.
This document is currently submitted to the CEN Enquiry.
The EN 14702 series consists of the following parts:
— Characterisation of sludges — Settling properties — Part 1: Determination of settleability
(Determination of the proportion of sludge volume and sludge volume index);
— Characterisation of sludges — Settling properties — Part 2: Determination of thickenability;
— Characterization and management of sludge — Determination of settling properties — Part 3:
Determination of zone settling velocity (ZSV).
3

---------------------- Page: 5 ----------------------
oSIST prEN 14702-3:2017
prEN 14702-3:2017 (E)
Introduction
In wastewater treatment plants sludge thickening occurs in the lower portions of clarifiers and in
separate thickening tanks. Due to wide variation in sludge settling properties both final clarifiers and
thickeners should, if possible, be designed on the basis of pilot plant data. Continuous-flow pilot units
are expensive and difficult to operate so design criteria for the process are mostly based on batch
thickening tests.
A number of parameters have been developed to obtain a quantitative measure of the settleability of
sludge. All of these tests are based on one of two basic approaches.
The first approach uses the volume of the sludge occupied after a fixed period of settlement. In this
approach laboratory tests [1 and 2] are conducted by allowing a sludge to thicken in a small graduated
cylinder, without (SVI: Sludge Volume Index) or with stirring (SSVI: Stirred Sludge Volume Index) and
evaluating the proportion of the sludge volume is recorded. These characterization tests are easily
performed and have a widespread use in routine process control for sludge quality comparison in
settling tanks or by scientists who tried to correlate these indexes to sludge velocity and to aid
thickener design [3]. The use of these indexes for sizing/optimizing decanters and static thickeners
should be done with care as they are influenced by laboratory artefacts (channeling and bridging
effects, turbulences caused by filling, shallow depth by partial support through the solids from the
bottom to the vessel, impact of stirring on sludge) [4].
The second approach uses the subsidence velocity of the solid/liquid interface of the sludge at its initial
concentration calculated from the straight-line portion of the resulting curve. This parameter should be
measured in large-diameter columns having a depth with the same order of magnitude as industrial
thickener. Following the interface between the solid and liquid phase enables the determination of the
(zone) settling (or sedimentation) velocity (SV) of the sludge (initial slope of the curve) and
compression point (intersection of the linear sedimentation zone and the asymptotic falling zone). The
use of sedimentation curve data after the compression point enables to calculate the required time and
theoretical area of the thickener to obtain the desired sediment concentration [5].
The sedimentation velocity and compression point are basic parameter for decanters/static thickeners
sizing [6] and are linked directly to phenomena occurring in the industrial devices. This measurement
can evaluate the impact of sludge chemical conditioning on the size and design of the thickener or on
the process productivity. A decanter/thickener well sized will enable further sludge treatment as lowest
cost for its volume reduction.
4

---------------------- Page: 6 ----------------------
oSIST prEN 14702-3:2017
prEN 14702-3:2017 (E)
1 Scope
This draft European Standard specifies a method for determining the zone settling velocity (ZSV) and
the Compression point.
This draft European standard is applicable to sludge and sludge suspensions from:
— storm water handling;
— urban wastewater collecting systems;
— urban wastewater treatment plants;
— 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 and sludge suspensions of other origins.
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 14742, Characterization of sludges — Laboratory chemical conditioning procedure
EN 16323, Glossary of wastewater engineering terms
3 Terms and definitions
For the purposes of this document, the terms and definitions given in EN 16323 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
settleability
ability of sludge solids to separate from water by sedimentation under gravity
3.2
zone settling (or sedimentation) velocity
ZSV
vertical distance covered by a group of particles per time unit
3.3
compression point
critical time in a gravity sedimentation where the sludge in the thickening zone begins to compress
3.4
theoretical thickener area
required area per unit of solids and time to concentrate sludge according a given factor
5

---------------------- Page: 7 ----------------------
oSIST prEN 14702-3:2017
prEN 14702-3:2017 (E)
4 Principle
The principle of the measurement lies on the sludge introduction in a vertical cylinder and on the
following of the interface between the free supernatant and the concentrated sediment versus time.
The introduction of suspension under vacuum in well adapted for sludge flocs as it limits the shearing
action and consequently the flocs breakage.
ZSV is given by the slope of the straight line part of the interface height versus time curve. The ZSV
decreases as the solids concentration increases. The zone settling curve is composed of two stages: a
constant - rate period, when the interface height versus time curve is a linear function, and a
compaction period when the interface plot is curved (corresponding settling velocity is a variable and is
generally less that the initial zone settling velocity).
The interface height versus time curve gives not only the zone settling velocity but also the compression
point by the graphical construction illustrated in Figure 1 and the theoretical surface unit (Annex A).

Figure 1 — Compression point in a gravity sedimentation (1) clear liquid, (2) uniform
concentration (3) sediment in compression, (4) sediment deposit
5 Interferences
Initially, when following the interface height versus time, there is usually an induction period that is
followed by the linear settling portion, which is supposed to be characteristic of the initial solids
concentration in the column. It is attributed to the formation of the solids structure most appropriate
for settling.
The settling velocity of flocculent suspension depends on the conditions under which the aggregates
were formed. The flocculation step shall be carried out according to EN 14742.
The settling of particles in a fluid generally takes place in a container of finite dimensions that could be
expected to have some effects on the sedimentation velocity. The effect is bound to be related to the size
of the solids relative to the container d/D and it is likely to be more relevant for dilute systems where
particle/particle and particle-wall hydrodynamic interaction effects could be of the same order. The
diameter should be much greater than the particle diameter, generally at least 4 to 5 orders of
magnitude greater.
6

---------------------- Page: 8 ----------------------
oSIST prEN 14702-3:2017
prEN 14702-3:2017 (E)
6 Equipment
An example of the required device is illustrated in Annex A. It includes the following elements:
6.1 Storage/Flocculation tank.
It is used for sludge storage and flocculation according to EN 14742.
An example of appropriated dimensions is:
Height: 40 to 44 cm
Diameter: 25 to 26 cm
Exit pipe at the bottom of the tank, in the middle point, minimum diameter: 25 mm
6.2 Stirrer.
A mechanical stirrer with 3 or 4 horizontal perpendicular blades is set in the storage tank, allowing the
modification and control of mixing speed.
NOTE In case of important sludge volumes, a 3 or 4 staged PVC blades (15 cm to 20 cm x 3cm x 0,5 cm)
impeller could be used with a distance of 10 cm between each blade.
6.3 Feed/Draining valve.
6.4 Measurement cell.
Column in glass or plexiglass.
Internal diameter: 9 to 10 cm
Height: 120 cm for determination of settling velocity, 220 cm for determination of sludge thickening
kinetics (after compression point)
The cylinder could be composed of one part or several parts, gathered by adapted devices. It is closed
with PVC flanges with openings. It is recommended to set different sampling valves with a distance of
20 cm between each valve (the last set up at a distance between 100 mm to 120 mm from the bottom of
the column) to facilitate recovery of the different phases (sediments and supernatants) at the end of the
test.
— Inferior flange: central opening cr
...