CEN/TR 16394:2014

SLOVENSKI STANDARD
01-februar-2015
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Characterization of sludges - Protocol for preparing synthetic suspensions
Charakterisierung von Schlämmen - Protokoll zur Herstellung synthetischer
Suspensionen
Caractérisation des boues - Protocole de préparation de suspensions synthétiques
Ta slovenski standard je istoveten z: CEN/TR 16394:2014
ICS:
13.030.20 7HNRþLRGSDGNL%ODWR Liquid wastes. Sludge
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

TECHNICAL REPORT
CEN/TR 16394
RAPPORT TECHNIQUE
TECHNISCHER BERICHT
November 2014
ICS 13.030.20
English Version
Characterization of sludges - Protocol for preparing synthetic
suspensions
Caractérisation des boues - Protocole de préparation de Charakterisierung von Schlämmen - Protokoll zur
suspensions synthétiques Herstellung synthetischer Suspensionen

This Technical Report was approved by CEN on 18 August 2014. It has been drawn up by the Technical Committee CEN/TC 308.

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

CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2014 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TR 16394:2014 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 Preparation of inorganic synthetic suspensions .5
4.1 General .5
4.2 Materials .5
4.3 Modalities of preparation .6
5 Preparation of organic synthetic suspensions .7
5.1 General .7
5.1.1 General .7
5.1.2 Materials .7
5.1.3 Modalities of preparation .8
5.2 Preparation of organic synthetic suspensions by concentration of synthetic waters .9
Annex A (informative) Example of composition of activated suspension and its evolution over
storage time . 10
Bibliography . 11

Foreword
This document (CEN/TR 16394:2014) has been prepared by Technical Committee CEN/TC 308
“Characterization of sludges”, the secretariat of which is held by AFNOR.
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.
Introduction
In order to carry out lab-scale tests of suspensions, and interlaboratory validation trials for standardized
methods, it is necessary to have samples with constant characteristics available. When dried suspension
samples cannot be used and testing requires fresh sludge samples, problems arise because:
a) most suspension characteristics change over time, which makes them unfit for storage;
b) some preservation practices (e.g. freezing) are not applicable, or their effects unknown;
c) some suspension characteristics are strongly affected by handling;
d) transporting sludge samples requires special precautions and authorization.
This means that fresh suspension samples cannot be used to guarantee results reliability and reproducibility.
As a consequence, fresh suspension samples should be examined by laboratories very close to wastewater
or waterworks plants and analysed as soon as possible, minimizing their manipulation. As a result, the
circulation of fresh suspension samples to laboratories in several countries is analytically not feasible.
Interlaboratory analysis on these suspensions should be carried out through circulation of analysts, close to
the place where samples are collected according to the Modified Round Robin tests procedure
(CEN/TR 15252).
A valid alternative is the creation and testing of synthetic suspensions.
Synthetic suspensions are prepared on-site on the basis of a defined recipe and specified ingredients. This
will also allow the comparison of results obtained from different places, at different times.
This Technical Report establishes methods for preparing synthetic suspensions, both inorganic and organic,
in repeatable and quantified conditions, able to describe the behaviour of a real suspension with regard to
specific parameters, and suitable for circulation as samples in interlaboratory trials for validation of standards
when fresh suspensions cannot be used. It represents the state of the art of the available knowledge on
synthetic suspensions.
1 Scope
This Technical Report deals with methodologies for preparing synthetic suspensions. Synthetic suspensions
can be used for:
a) evaluating or testing new devices or techniques for suspension treatment;
b) studying the influence of different compounds on suspension behaviour with regard to specific
parameters, e.g. settleability, dewaterability, physical consistency, etc.
The chemical, physical and biological characteristics of suspensions are subjected to changes as soon as
they are collected. Guidance exists on the sampling and handling techniques (see ISO 5667-12 and
EN ISO 5667-13), and on the preservation and storage procedures (EN ISO 5667-15) that help minimize
changes in the composition. This is mainly achieved by suppressing chemical and/or biological activity and by
avoiding contamination.
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 ISO 17353, Water quality - Determination of selected organotin compounds - Gas chromatographic
method (ISO 17353)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in EN 12832:1999 apply.
4 Preparation of inorganic synthetic suspensions
4.1 General
The procedure specified in this Technical Report refers to the preparation of inorganic synthetic suspensions
to simulate the behaviour of real inorganic suspensions. Inorganic suspensions produced by waterworks
plants exhibit wide variations in their physical and chemical properties due to the raw water differences and
the design and operation of each individual treatment plant. Many different products could be used for
preparation of such suspensions depending on the properties to be evaluated.
Quartz sand, calcite and kaolin are the three most commonly used minerals in large industrial sectors. Hence,
a combination of these three minerals is perfectly suited to simulate the behaviour of real inorganic
suspensions. Role and characteristics of such materials have been discussed in [6] and [7].
4.2 Materials
Primary particle properties, such as particle shape, size distribution, specific surface area, density, surface
structure, dry bed porosities, as well as their dispersion properties, for example solid concentration, or pH,
have a strong influence on the physical properties of inorganic suspensions (e.g. compressibility, settleability,
specific resistance), which have to be known and defined for a standardized synthetic suspension.
Table 1 gives an example of the main characteristics of kaolin, calcite, and quartz sand [6].
Table 1 — Characteristics of materials composing inorganic synthetic suspension
Kaolin Calcite Quartz sand
Average particle size (µm) 5 10 20
Crystal structure monoclinic rhombohedric tetragonal
Specific surface area (m /g) 9 3 2
Dry bed porosity (tapped-poured) 0,6 to 0,7 0,5 to 0,6 0,4 to 0,5
Density (g/cm ) 2,60 2,70 2,65
SiO (%) 46 2 99
Al O (%) 39 0,4 0,2
2 3
Fe O (%) 0,2 < 0,1 0,3
2 3
CaO (%) 1 55 0,1
MgO (%) 0,1 2 0,1
K O (%) < 0,1 < 0,1 < 0,1
Na O (%) 0,2 1 0,1
Loss on ignition (%) 13 39 < 0,1
Compressibility range 0,7 to 1,1 0,2 to 0,3 0,1 to 0,2
Only binary mixtures can be used for evaluation of specific parameters. For example, mixtures of kaolin (75 %
to 90 %) and quartz sand were used for rheological measurements [8]. Suppliers of polymers prefer using
mixtures of kaolin (30 g/l to 100 g/l) and calcium chloride (0,5 g/l to 1,65 g/l) to prepare inorganic synthetic
suspensions which easily flocculate both with anionic and cationic polymers.
For ternary mixtures, comparison tests were performed on a 30 g/l industrial suspension sampled at a
granulate extraction plant.
Reasonably good compliance in terms of settleability, capillary suction time (CST), specific resistance,
compressibility and suspension dryness (after compression) was achieved using a synthetic suspension
consisting of 90 % kaolin, 5 % quartz sand and 5 % calcite [9].
4.3 Modalities of preparation
Ingredients are kaolin, quartz sand and/or calcite which can be mixed in different proportions to be fixed for
the development of a standard inorganic suspension.
The suspensions have to be prepared from mineral powders before the start of each set of experiments in
order to avoid modification of surface properties of powders. All samples shall be prepared in the same way
because the preparation has a significant influence on the final state of the suspension (degree of dispersity,
rheological behaviour).
A good preparation of inorganic synthetic suspension usually requires:
— fine particles and narrow particle size distribution to ensure homogeneity;
— a defined proportion of ingredients, whose respective weights should be adjusted to prepare the
suspension of chosen concentration;
— a defined quality (e.g. pH, turbidity, conductivity, alkalinity, hardness) of water for suspension preparation
as defined for example in EN ISO 17353;
— a description of mixing conditions between powder and water. Mixing with a magnetic stirrer at low speed
(250 r/min) for 30 min is generally sufficient to achieve uniform dispersion;
— additives (HCl, HNO ) to adjust pH ≈ 7 to achieve the highest possible suspension stability;
— additives (KCl, KNO ) to adjust ionic strength to prevent possible interference by ions, released by the
surface of the clay.
5 Preparation of organic synthetic suspensions
5.1 General
5.1.1 General
The preparation of organic synthetic suspensions able to reproduce a biological real sewage suspension is a
more complex matter than conventional particulate systems. Sewage suspensions, whichever the treatment,
consist mainly of water (95 % to 98 %), but also contain a high number of organic and mineral matters, such
as colloids, flocs, fibres, micro-organisms, particles with size varying from 1 mm to 1 µm, polymers (proteins,
sugars, fats) and ions. Organic matter represents 50 % to 90 % of total solid matter and has a very complex
composition (mixture of bacteria, cellular wastes and particles). Further, a biological suspension is a complex
system for which the structural stability results from the combination of various interactions; particle charge
density or hydrophobicity play important roles and cannot be summarized by only one compound [10].
Carbohydrates and proteins were found to be the major extracellular polymeric substances components, but
lipids, nucleic acids and humic compounds were also reported. Calcium ions participate in the inter-polymer
binding, forming a very complex bio-flocculated structure [11]. Moreover, micro-organisms interact with
organic matter leading to a composition change in the suspension over time (Figure A.1) [12].
Synthetic suspensions can be prepared by direct formulation
...