ISO 5667-13:1997

INTERNATIONAL ISO
STANDARD 5667-13
First edition
1997-12-15
Water quality — Sampling —
Part 13:
Guidance on sampling of sludges from sewage
and water treatment works
Qualité de l’eau — Échantillonnage —
Partie 13: Guide pour l’échantillonnage de boues provenant d’installations
de traitement de l’eau et des eaux usées
A
Reference number
ISO 5667-13:1997(E)

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ISO 5667-13:1997(E)
Contents Page
1 Scope . 1
2 Normative references . 2
3 Definitions . 2
4 Sampling equipment . 3
5 Sampling procedure . 4
6 Storage, preservation and handling . 12
7 Safety . 15
8 Reporting . 16
Annexes .
A Vacuum sampling devices . 17
B Apparatus for samping from pipes under pressure . 19
C Bibliography . 21
©  ISO 1997
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized
in any form or by any means, electronic or mechanical, including photocopying and microfilm, without
permission in writing from the publisher.
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Printed in Switzerland
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ISO ISO 5667-13:1997(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of
national standards bodies (ISO member bodies). The work of preparing International
Standards is normally carried out through ISO technical committees. Each member
body interested in a subject for which a technical committee has been established has
the right to be represented on that committee. International organizations, governmental
and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates
closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
Draft International Standards adopted by the technical committees are circulated to the
member bodies for voting. Publication as an International Standard requires approval by
at least 75 % of the member bodies casting a vote.
International Standard ISO 5667-13 was prepared by Technical Committee ISO/TC 147,
, Subcommittee SC 6,
Water quality Sampling (general method).
International Standard ISO 5667 consists of the following parts, under the general title
Water quality — Sampling
— Part 1: Guidance on the design of sampling programmes
— Part 2: Guidance on sampling techniques
— Part 3: Guidance on the preservation and handling of samples
— Part 4: Guidance on sampling from lakes, natural and man-made
— Part 5: Guidance on sampling of drinking water and water used for food and
beverage processing
— Part 6: Guidance on sampling of rivers and streams
— Part 7: Guidance on sampling of water and steam in boiler plants
— Part 8: Guidance on the sampling of wet deposition
— Part 9: Guidance on sampling from marine waters
— Part 10: Guidance on sampling of waste waters
— Part 11: Guidance on sampling of groundwaters
— Part 12: Guidance on sampling of bottom sediments
— Part 13: Guidance on sampling of sludges from sewage and water treatment
works
— Part 14: Guidance on quality assurance of environmental water sampling and
handling
— Part 16: Guidance on biotesting of samples
Annexes A, B and C of this part of ISO 5667 are for information only.
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Introduction
This part of ISO 5667 should be read in conjunction with ISO 5667-1,
ISO 5567-2 and ISO 5667-3. The general terminology used is in accordance
with the various parts of ISO 6107.
Sampling and the determination of the physical and chemical properties of
sludges and related solids are normally carried out for a specific purpose. The
sampling methods given are suitable for general use but do not exclude
modification in the light of any special factor known to the analyst receiving the
samples or any operational reason dictating the need for sampling.
The importance of using a valid sampling technique cannot be overemphasized
if the subsequent analysis is to be worthwhile. It is important that the personnel
taking and analysing the sample be fully aware of its nature and the purpose for
which the analysis is required before embarking on any work programme. Full
cooperation with the laboratory that will be analysing the samples ensures that
the most effective application of the sampling occasion can be made. For
example, the use of method-specific sample preservation techniques will assist
in the accurate determination of results.
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ISO 5667-13:1997(E)
INTERNATIONAL STANDARD  © ISO
Water quality — Sampling —
Part 13:
Guidance on sampling of sludges from sewage and
water treatment works
1  Scope
This part of ISO 5667 gives guidance on the sampling of sludges from wastewater
treatment works, water treatment works and industrial processes. It is applicable to all
types of sludge arising from these works and also to sludges of similar characteristics,
for example septic tank sludges. Guidance is also given on the design of sampling
programmes and techniques for the collection of samples.
This part of ISO 5667 is applicable to sampling motivated by different objectives, some
of which are to:
— provide data for the operation of activated sludge plants;
— provide data for the operation of sludge treatment facilities;
— determine the concentration of pollutants in wastewater sludges for disposal to
landfill;
— test whether prescribed substance limits are contravened when sludge is used in
agriculture;
— provide information on process control in potable and wastewater treatment,
including:
a) addition or withdrawal of solids;
b) addition or withdrawal of liquid;
— provide information for legally enforceable aspects of the disposal of sewage and
waterworks’ sludges;
— facilitate special investigations into the performance of new equipment and
processes;
— optimize costs; for example for the transport of sludges for treatment and/or
disposal.
NOTE  When designing a sludge sampling programme, it is essential that the objectives of the study be
kept in mind, so that the information gained corresponds to that required. In addition, the data should not
be distorted by the use of inappropriate techniques, such as inadequate storage temperatures or the
sampling of unrepresentative parts of a treatment plant.
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2  Normative references
The following standards contain provisions which, through reference in this text,
constitute provisions of this part of ISO 5667. At the time of publication, the editions
indicated were valid. All standards are subject to revision, and parties to agreements
based on this part of ISO 5667 are encouraged to investigate the possibility of applying
the most recent editions of the standards indicated below. Members of IEC and ISO
maintain registers of currently valid International Standards.
Water quality — Sampling — Part 2: Guidance on sampling
ISO 5667-2:1991,
techniques.
ISO 5667-3:1994, Water quality — Sampling — Part 3: Guidance on the preservation
and handling of samples.
ISO 5667-12:1995, Water quality — Sampling — Part 12: Guidance on sampling of
bottom sediments.
1
Water quality — Sampling — Part 14: Guidance on quality
ISO 5667-14: — ,
assurance of environmental water sampling and handling.
2
ISO 8363: — , Measurement of liquid flow in open channels — General guidelines for
selection of method.
ISO 10381-6:1993, Soil quality — Sampling — Part 6: Guidance on the collection,
handling and storage of soil for the assessment of aerobic microbial processes in the
laboratory.
3  Definitions
For the purposes of this part of ISO 5667, the following definitions apply:
3.1  grab sample
discrete sample taken randomly (with regard to time and/or location) from a body of
sludge
[Based on ISO 6107-2]
3.2  composite sample
two or more samples or subsamples, mixed together in appropriate known proportions
(either discretely or continuously), from which the average value of a desired
characteristic may be obtained
NOTE  The proportions are usually based on time or flow measurements.
[Based on ISO 6107-2]

1
To be published.
2
To be published. (Revision of ISO 8363:1986)
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3.3  flow-related sampling
samples taken at varying time intervals governed by material flow
NOTE  This usually applies to liquid sludges; further guidance can be drawn from ISO 5667-10.
3.4  proportional sampling
technique for obtaining a sample from flowing sludge in which the frequency of
collection (in the case of discrete sampling), or the sample flowrate (in the case of
continuous sampling), is directly proportional to the flow rate of the sampled sludge
4  Sampling equipment
4.1  Materials
The sampling of sludge from fixed points can require the installation of permanent
equipment, even if this is only an additional pipe and valve to the processing plant. It is
important to verify that any such equipment is regularly cleaned and that it is free from
corrosion. In addition, it will be necessary to assess the potential for interference on
any test results that the equipment may have. For example, the use of aluminium
extension pipes to a sampling valve would be inappropriate if the samples were being
taken for the analysis of an aluminium flocculation assister. In general, the laboratory
performing the sludge examination should be consulted before installation of any fixed
point equipment or at the implementation of a new sampling scheme.
Tools should be chosen to avoid contamination by substances of interest. They should
be kept clean and corrosion free. Plastics utensils and polytetrafluoroethylene pallet
knives may be used if they prove to be robust and the absence of any contaminating
influence can be demonstrated. High alloy steels should be avoided if trace metals are
to be determined. The use of stainless steel tools is routinely adopted but the
possibility of contamination needs to be recognized and tested for if analyses for
elements such as chromium are to be performed on the sludge sample. Old, rusty
tools or those with chipped or flaking surface coatings and painted surfaces should not
be used, as they may contribute to random contamination of samples.
Polyethylene, polypropylene, polycarbonate and glass containers are satisfactory from
the point of view of chemical stability when sludge sampling (see also 6.1). However,
caution should be exercised since containers can become pressurized due to gas
production in wastewater sludges and explosive situations may occur. Guidance on
overcoming this problem is given in clause 7.
Glass containers should be used when organic constituents, such as pesticides, are to
be determined whereas polyethylene containers are preferable for sampling
parameters of general interest such as pH and dry matter. Polyethylene containers
may not be suitable for collecting samples to be subjected to some trace metal
analysis (for example mercury); these containers should only be used if preliminary
tests indicate acceptable levels of interference.
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The introduction of aged material from the dead space in sample lines can also
contribute to contamination of samples due to corrosion, see 5.3.3, and can prove to
be a serious potential source of error if not eliminated.
Refer to standard analytical procedures for detailed guidance on the type of sample
container to be used. For guidance on the cleaning of sample containers, see
ISO 5667-3.
4.2  Equipment
In general, sludge sampling equipment is usually most practical if it is as simple in
design and construction as possible. The characteristics of a sludge can vary
according to type and solids content, and therefore the manner of handling in a
sampling device is dependent upon the physical properties; no general
recommendations can therefore be given but some specific examples of equipment for
liquid sludges under particular circumstances are given in annexes A and B.
5  Sampling procedure
5.1  Sampling regime
The most appropriate way of sampling in any situation will depend on several factors:
a) access to the sampling point by personnel;
b) the practicality of installing and maintaining automatic equipment if appropriate;
c) the practicalities of interrupting safely a stream of moving liquid sludge or cake
when manually sampling; and
d) the nature of the chamber or tank design with respect to stratification of liqiud
sludges.
On a fixed plant, when planning a sampling exercise, it is recommended that a review
of the practicalities of the site location is undertaken prior to establishing the safest and
most practical position for manual sampling. The representative nature of the resultant
sample will also play a key role in the final choice of position.
Where sludge is passing in an accessible stream, either continuous or intermittent
sampling should be considered. The greater the number of samples taken, the greater
the degree of confidence in the representativeness of the sludge sample. For further
information see ISO 5667-1 and ISO 5667-14. There may be a requirement to
consider the representative nature of solid sludges. For this purpose further guidance
on the statistical assessment of bulk loads of solid materials can be found in ISO 1988.
Nevertheless, it is often desirable to take daily or shift samples for control purposes,
since definitions of batches and periods will vary from plant to plant. Continuous
sampling is more likely to be practicable where a fixed conveyer discharge can be
sampled automatically. Intermittent sampling is more suited to manual sampling from
the discharge of a wagon or tanker.
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5.1.1  Sample type
The basic types of sample which may be required are:
a) a composite sample which may be generated from either continuous or grab
samples from stockpiles, sampling of liquid or cake sludges;
b) a grab or spot sample, which is taken at random from a liquid or conveyer flow of
cake or from a single sample point in a stockpile. A programmed series of grab
samples analysed individually, which may be liquid or cake samples, is a
refinement of this technique.
To calculate the maximum sampling interval, t, in minutes, between taking samples
when using time-based sampling, equation (1) should be used;
60 Q
  t = . . . (1)
Gn
where:
  Q is the mass of the batch (in tonnes);
  G is the maximum flowrate (in tonnes/hour);
  n is the number of samples.
5.1.2  Composite sampling
5.1.2.1  Continuous sampling
In continuous sampling at regular intervals, the samples are taken uniformly throughout
the whole supply of sludge, but are then grouped together in composite samples.
5.1.2.2  Intermittent or consignment sampling
For this type of sampling, samples are not normally taken at uniform intervals
throughout the whole supply of sludge before being composited. Instead, the sludge is
regarded as a series of batches and only a proportion is selected for sampling. The
selected batches are spread uniformly throughout the whole supply of sludge, and the
samples are taken uniformly from each batch selected for sampling. For example,
sample by randomly picking tankers irrespective of the source of the sludge or the
mass transported.
With this type of sampling scheme, it is necessary to allow for the fact that the time-
interval average will be influenced by the variation between batches, which cannot be
predicted. More samples will be required over the time interval to achieve a given
confidence than if continuous sampling had been carried out, since the error of
sampling a batch is now only a portion of the total error.
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5.1.2.3  Flow-related sampling
This is accomplished by extracting at the end of each time interval a mass of sludge
proportional to the flowrate at the sampling point. This can either be added to a
composite sample or to a partial composite sample. This method is applicable when
sampling primary sludge at the time of draw-off; i.e. as the draw-off head falls, the
discharge rate will drop and the flow proportionality will change. If there is a
requirement for mass transfer information, it is prudent to measure the associated
flowrate and/or batch size of the sludge. For example, daily metals-loading information
may be required for sludge pumped to agricultural land. For further guidance see ISO
8363.
5.2  Replicate sampling
In a situation where automatic sampling is to be installed, for example on a conveyor
belt, it is preferable to establish that the point at which the samples are being taken is
representative of the output from that particular part of the plant. Under these
circumstances replicate sampling should be used to assess the variability of the output
stream at the proposed sampling point. This technique can be applied to liquid as well
as cake sludges.
For example, when duplicate sampling is in progress, two samples should be taken by
placing samples alternately in two containers labelled A and B. After a number of
samples have been collected in duplicate, the results should be examined and the
number of samples or the number of batches sampled should be changed to reflect
the guidance given in ISO 5667-1 and ISO 5667-14. After carrying out this exercise, it
may be found that fewer samples can be taken in the future than were at first
estimated to achieve the required confidence defined by the need for sampling. ISO
1988 gives details on the calculation of the number of samples if the material can be
likened to a mineral.
If an occasional confirmation of the sampling performance is required, replicate
sampling is ideal. It is recommended that this is achieved by taking a run of 10
samples in duplicate (i.e. 20 samples) after every 40 ordinary samples. It is not
possible to assess whether there has been a change in sampling behaviour until two
sets of 10 duplicate results have been obtained and compared. If at any time there is
reason to believe that sampling conditions have changed, it is recommended that a
further set of 10 duplicate samples be collected and statistically tested before any
decision to alter the regime is made.
It is important to ensure that the confirmation samples are not taken with more than
ordinary care. One way of ensuring this is always to sample in duplicate, but to
amalgamate the two subsamples together and prepare the combined sample when
duplicate results are not required.
5.3  Methodology
There is no definitive guidance that can be given on the need to sample sludges as
cakes or liquids. For example, it may be necessary to sample sludge in both forms on
any particular plant in order that the process can be optimised and the quality of the
final output monitored for disposal purposes
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5.3.1  Sample size
Little guidance can be given as to the size of samples. This is because this criterion is
dependent on the variability of the sampled material and the type of analysis to be
carried out.
a) Liquid sludges
It should be noted that thin liquid sludges (of low solids content) will require the
preparation of relatively large volumes of the sampled material to provide sufficient dry
matter to allow for a truly representative analysis of constituents such as metals. The
analyst should always be consulted as to the quantities of sludge required, and the
sample reduced accordingly in the field before returning to the laboratory. Large
volumes of sample accrued by the combination of representative samples will need to
be homogenized before subsampling. The mixing process should preferably be tested
to ensure efficacy of mixing. The homogenization can be achieved in a container such
as a plastics dustbin using a suitable paddle to prevent settlement.
b) Sludge cake
To obtain a representative sample of sludge cake, the mass accumulated will always
be too large for laboratory manipulation at the bench. Sample size reduction is,
therefore, best carried out in the field in accordance with procedures described in 6.4.
5.3.2  Sampling from tanks and road tankers
The performance of tanks used for sedimentation or consolidation of wastewater or
sewage sludges, digesters and other vessels, cannot always be gauged from samples
taken from the inlet and outlet pipelines. The segregation of solids likely to occur can
be detected by sampling different sections and depths of a tank. Access to different
strata is often provided by a design feature such as stepped draw-off pipework.
Inspection of the tank concerned will usually reveal the presence of these facilities if
they have been built in. Examples of equipment that could be used when this is not the
case are given in annex A.
Usually a composite sample of the sludge is required and the sludge in the tank
should, where possible, have been thoroughly mixed before sampling. This practice
minimizes the need for sampling stratified material, since the whole sludge production
is treated as a composite. When this cannot be achieved, interpretation of analytical
data will need to be carried out with caution.
A grab sample can be taken from a road tanker by sampling the discharge using a
long-handled ladle. A valuable procedure for obtaining a composite sample from a
tanker discharge is to divert the flow at random intervals into a separate container such
as a barrow to allow separate mixing and subsequent sampling. This technique assists
in removing some of the problems of stratification that may occur when some sludges
are left standing in tanks or tankers, for example with easily settleable sludges.
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5.3.3  Sampling from pipes
If pumping is taking place, correct sampling can be achieved with samples being taken
at appropriate intervals at the pump outlet or a similar convenient place. (see 5.1.1).
However, factors such as the nature of the sludge, the flowrate, the diameter of the
pipes and the roughness of the pipe can affect the tendency of the dynamic system to
allow streaming of the flow. Minimizing the influence of this potential problem can be
achieved by allowing the flow to equilibrate before collecting a portion from which to
take a subsample after mixing. Any sidearms or valves utilized in the sampling
arrangement should be flushed with at least three times the standing volume to ensure
that any stagnant material is removed from the pipework. When taking the sample in
this manner, visual checks should be made to ensure that the flowrate and consistency
remain constant. Blockages in pipes due to fibrous materials will often influence the
nature of the sludge by a filtering action, thereby giving spurious results. This may go
undetected at the time of sampling, necessitating repeating the exercice to assess the
reliability of results.
After sampling, the samples may be bulked to provide a composite sample or analysed
separately to determine a profile, for example the withdrawal of sludge from a blanket
clarifier or a primary tank. Sampling the discharge from road tankers can be achieved
by using a long-handled ladle.
A special case is the sampling of conditioned sludge from a high-pressure line prior to
plate filter pressing. In this case, if sludge were to be sampled in a conventional
manner allowing rapid decompression, its filtration properties would probably
deteriorate markedly due to shear in the sampling valve. To sample a conditioned
sludge with the minimum of shear, the simple apparatus shown in annex B can be
used to reduce this problem. This type of sampling is usually required if testing for
specific resistance to filtration has been requested to assess the potential efficacy of
chemical dosing on press performance.
5.3.4  Sampling from open channels
A weighted bucket or a pump should be used, depending on the solids content of the
sludge. A solids content of up to 5 % can be sampled from an open channel provided,
when using a pump, the velocity in the suction pipe is sufficient to keep all the
particulates in suspension. This velocity will have to be established on a site-specific
basis using a transparent section of the pump uptake tube to visually assess the
performance of the suction. Samples should be taken across the width and depth of
the channel to ensure that a representative composite sample is obtained after mixing
individual samples. It should be borne in mind that the physical characteristics of the
sludge may change on passing through a pump, due to shear of the particulate matter.
The practice of sampling from open channels is probably only likely to occur when
dealing with wastewater activated-sludge plants, and therefore a weighted bucket is
often more appropriate.
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5.3.5  Sampling of sludge cake from heaps and stockpiles
In general, this is often not required and safety requirements usually prohibit routine
sampling in this manner. However, if it is necessary to sample from heaps and
stockpiles, the following guidance applies. When sampling heaps of air-dried sludge
lifted from drying beds or stockpiles of sludge cake, it is important to obtain portions of
sludge from throughout the mass and not just from the surface layer. The sludge taken
off drying beds should be free of the bed media, since inclusion of grit or sand will
distort measurements of dry matter content. The inclusion of any grit or sand is only
applicable if it is representative of the whole mass of sludge being processed. A
mechanical excavator may be the most practical tool, but care is particularly necessary
to ensure representative sampling.
If after assessment of safety requirements and the availability of equipment, core
sampling can be considered as a means of obtaining samples. Samples should be
taken through the depth of the heap/stockpile, and a composite sample prepared from,
nominally, n such cores,
sp
V
n =  [given to the nearest whole number]
sp
2
where V is the nominal volume of the stockpile, in cubic metres.
n
It is recommended that the value of lie between 4 and 30. Further guidance on core
sp
sampling can be obtained from ISO 5667-12.
Major variations in data throughout stockpiles can be found, particularly old ones, in
which the top layers desiccate to form crusts which allow anaerobic activity to increase
below and aerobic activity to proliferate in the upper near-surface layers. The migration
of nutrient species due to leaching in these situations can also cause difficulty when
attempting to take representative samples and/or use analytical results. The surface
layers may therefore give rise to misinterpretation when coring to the centre or full
depth of the heap, due to surface area-to-volume ratio inconsistencies dependent on
the stockpile shape. In certain circumstances, accessing the cross-sections of a heap
with a mechanical excavator should be considered if it can be safely undertaken to
enable representative sampling.
5.3.6  Sampling from wagons
The only method considered satisfactory for sampling from wagons is to take samples
in such a way that they are representative of all parts of the sludge in the wagon.
Normally, most of the sludge in a wagon is inaccessible and methods usually involve
sampling after unloading. The method to be adopted depends upon the method of
handling wagon-borne sludge and upon the types of wagons concerned. Sampling
from wagons is not recommended as routine practice, but where circumstances dictate
it is necessary, for example on delivery to a landfill, then the guidance given in 5.3.6.1
will apply.
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5.3.6.1  Sampling from the tops of wagons
It is evident that samples of sludge taken from the tops of wagons cannot be
representative of its moisture content if the sludge has been exposed for some time to
rain or snow, or to the drying effects of exposure to the open air during transport.
Consequently, sampling from the tops of wagons for moisture or ash content is not
satisfactory. In addition, appropriate safety precautions for regular access make this
practice an unlikely routine measure.
If sampling is for the purpose of determining the dry solid or ash content, then
a homogenized intermittent sample should be taken at the point of discharge from the
wagon after unloading, if it is judged safe to do so, i.e. not at the tipping face of a
working landfill.
5.3.7  Sampling from belt conveyors
5.3.7.1  General
Fragments of pressed or otherwise consolidated sludge tend to segregate by size and
density when agitated, fin
...