ISO 19654:2025
(Main)Sludge recovery, recycling, treatment and disposal — Laboratory chemical conditioning procedure
Sludge recovery, recycling, treatment and disposal — Laboratory chemical conditioning procedure
This method gives a standardized procedure for the conditioning operation when selecting a conditioning product at laboratory scale and also for the production of flocculated thickened sludge for subsequent dewatering tests. This document provides a method for laboratory chemical conditioning of sludge. The method applies to sludges and suspensions from: — storm water handling; — urban wastewater collecting systems; — urban wastewater treatment plants; — industrial wastewater that has been treated similarly to urban wastewater; — water supply plants. This document is applicable to all sludge that can have similar environmental or health impacts, or both, with exclusion of hazardous sludge from industry and dredged sludge.
Valorisation, recyclage, traitement et élimination des boues — Mode opératoire de conditionnement chimique en laboratoire
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Standards Content (Sample)
International
Standard
ISO 19654
First edition
Sludge recovery, recycling,
2025-11
treatment and disposal —
Laboratory chemical conditioning
procedure
Valorisation, recyclage, traitement et élimination des boues —
Mode opératoire de conditionnement chimique en laboratoire
Reference number
© ISO 2025
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Apparatus . 2
6 Procedure . 3
7 Test report . 4
8 Precision . 4
Annex A (informative) Results of validation trials . 6
Annex B (informative) Examples for mixing devices for chemical conditioning procedure.10
Annex C (informative) Example of table summarizing the operating conditions and the results
of the characterization tests .12
Bibliography .13
iii
Foreword
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This document was prepared by the European Committee for Standardization (CEN) (as CEN/TR 14742:2006)
and was adopted, without modifications other than those given below, by Technical Committee ISO/TC 275,
Sludge recovery, recycling, treatment and disposal.
— The second sentence was added in the Scope;
— informative references were moved from Clause 2 to the Bibliography;
— the term “sludge” was added in Clause 3;
— in Clause 5, the reference to Annex B was replaced by reference to Figure B.1.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv
Introduction
The laboratory assessment of flocculated sludge dewaterability is sensitive to the operating procedure
adopted for the conditioning step. No generalized ranking of products in order of effectiveness can be given
since the ranking changes with the sludge type, dosage of conditioning agent (inorganic coagulant, polymer),
degree of shearing and dewatering device.
v
International Standard ISO 19654:2025(en)
Sludge recovery, recycling, treatment and disposal —
Laboratory chemical conditioning procedure
1 Scope
This method gives a standardized procedure for the conditioning operation when selecting a conditioning
product at laboratory scale and also for the production of flocculated thickened sludge for subsequent
dewatering tests.
This document provides a method for laboratory chemical conditioning of sludge.
The method applies to sludges and suspensions from:
— storm water handling;
— urban wastewater collecting systems;
— urban wastewater treatment plants;
— industrial wastewater that has been treated similarly to urban wastewater;
— water supply plants.
This document is applicable to all sludge that can have similar environmental or health impacts, or both,
with exclusion of hazardous sludge from industry and dredged sludge.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
chemical conditioning
mixing of a chemical product with the sludge in order to increase its thickenability and dewaterability
3.2
sludge
accumulated settled solids separated from various types of water as a result of natural or artificial processes
[SOURCE: ISO 6707-1:2020, 3.8.27]
4 Principle
Sludge conditioned in accordance with the procedure outlined in Clause 6 can subsequently be used in
specific characterization tests in order to determine the most suitable operating conditions for each
particular sludge or suspension; these tests determine particularly the required nature of the reagent, the
dosage, and the sequence of adding the reagent.
Each test is performed as a batch process.
Variables and/or parameters that can have significant effects on the conditioned sludge are either chemical
or physical.
Chemical parameters are:
— characteristics of the sludge, e.g. pH, dry residue, loss on ignition;
— characteristics of the conditioning product, e.g. charge density, molecular weight, chemical structure;
— concentration and dosage of the chemical product;
— water used for on-site product preparation when polyelectrolytes are added.
Physical parameters are:
— method of preparing the solution and its storage;
— intensity and duration of stirring;
— characteristics of the stirrer, i.e. type, dimensions, position;
— method of injecting the conditioning product into the sludge;
— (separation) time between the end of mixing and the dewatering procedure itself.
The method of mixing the conditioning product into the sludge is particularly important since inadequate
mixing, leading to poor initial dispersion or strong floc shearing, can result in very poor test performances:
a large portion of the product can react instantly with particles upon first contact, without dispersing
throughout the mixture.
Inorganic coagulants are generally injected into a reactor with a short residence time (1 min to 5 min)
in a high shearing condition. For this purpose, the reactor is equipped with a high rotating speed stirrer
that enables an instantaneous dispersion of the product and brings the high energy needed (e.g. 80 W/m
to 100 W/m ).
Polyelectrolytes are injected into a reactor with a residence time of a few seconds to a few minutes. As far
as mechanical degradation can occur, the shearing rate is 4 to 10 times lower than for coagulants and the
3 3
energy needed lower (e.g. 40 W/m to 50 W/m ).
The conditioning procedure can concern the addition of more than one product. In that case, the addition
sequence is another parameter that requires careful instructing.
5 Apparatus
5.1 Device with control and measurement of physical parameters (variable stirrer/mixer speed and
time, position of mechanical stirrer depending on sludge volume, see Figure B.1). A magnetic stirrer should
not be used, as it does not ensure homogenous and reproducible mixing. A mechanical stirrer with 4
horizontal perpendicular blades should be used for proper polymer dispersion and floc maturation. In case
the formed flocs are very sensitive to shearing, a tilted 3-blade stirrer (see Figure B.1) should be used. The
characteristics of mechanical stirrer shall be the same in comparative tests. Length of each impeller blade
should be between 1/4 and 1/3 of the beaker diameter.
5.2 Beakers, volume 200 ml to 1 000 ml.
5.3 Volumetric pipettes or syringe or automatic polymer injection system at constant flow rate.
5.4 Analytical balance with a precision of at least 0,1 mg.
5.5 pH-meter.
5.6 Chronometer, e.g. stopwatch, computer.
5.7 Apparatus for evaluation of flocculation drainability, (e.g. drainage cell, see EN 14701-4).
6 Procedure
The procedure is as follows:
6.1 The pH of the sludge shall be measured according to validated standards. For example, the method
specified in EN 15933 can be used. If necessary, adjust the pH to meet the requirements of the conditioning
agent to be used.
6.2 The dry residue of the sludge shall be measured according to validated standards. For example, the
method specified in EN 12880 can be used.
NOTE The loss on ignition can be determined for additional information. For details, see validated standards (e.g.
see EN 15935).
6.3 Put a defined amount of sludge into a beaker. The amount of sludge should be between 25 % and 50 %
of the capacity of the beaker to avoid loss of sludge during mixing and sludge height should be between 0,5
and 1 of the diameter of the cell to ensure proper mixing. It should be taken into account that the whole
flocculated sludge will be transferred in a drainage cell and the quantity of dry matter deposited on the
2 2
filter cloth should be between 0,25 kg/m and 1,5 kg/m .
6.4 Adjust the position of the stirrer to the sludge volume (the stirrer should be positioned from the beaker
bottom at 1/3 of the sludge volume).
6.5 About polymer addition and dispersion:
6.5.1 Add a precise amount of conditioning agent using a volumetric pipette or syringe before stirring.
Ensure proper distribution of the polymer, across the level surface of the sludge.
6.5.2 If the conditioning agent injection is prepared during the stirring of the sludge, add it in the shortest
amount of time possible at a controlled and constant flow rate. The time of the beginning of the injection
(T ) and the time at the end of the injection (T ) should be reported.
B1 E1
6.5.3 The solution of conditioning agent should be prepared according to the recommendations of
suppliers and should be used within 3 h of preparation on the same d
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