Characterization of sludges - Sludge management in relation to use or disposal

This Technical Report gives guidance for dealing with the production and control of sludge in relation to inputs and treatment and gives a strategic evaluation of recovery, recycling and disposal options for sludge according to its properties and the availability of outlets. This report is applicable for sludges from: - storm water handling; - night soil; - urban wastewater collecting systems; - urban wastewater treatment plants; - treating industrial wastewater similar to urban wastewater (as defined in Directive 91/271/EC; - water supply treatment plants; but excluding hazardous sludges from industry.

Charakterisierung von Schlämmen - Management von Schlamm zur Verwertung oder Beseitigung

Caractérisation des boues - Gestion des boues en vue de leur valorisation ou de leur élimination

Le présent rapport technique donne des recommandations pour la gestion de la production et de la maîtrise
des boues en relation avec les effluents à traiter et le traitement des boues, et fournit une évaluation
stratégique des options de valorisation, de recyclage et d'élimination en fonction de leurs propriétés et de la
disponibilité des débouchés.
Le présent rapport est applicable aux boues provenant :
⎯ du traitement des eaux pluviales ;
⎯ des matières de vidange ;
⎯ des systèmes de collecte des eaux usées urbaines ;
⎯ des stations d'épuration des eaux usées urbaines ;
⎯ des stations d'épuration des eaux industrielles assimilées (telles que définies par la Directive
européenne 91/271/CE [1]) ;
⎯ des stations de traitement de l'eau potable ;
à l'exclusion des boues industrielles dangereuses.

Karakterizacija blata - Ravnanje z blatom glede na uporabo ali odlaganje

To tehnično poročilo podaja smernice za obravnavo proizvodnje in nadzora nad blatom glede na vnose in obdelavo ter podaja strateško vrednotenje možnosti glede predelave, reciklaže in odlaganja za blato v skladu z njegovimi značilnostmi in uporabnostjo za trge. To poročilo velja za blato iz: - ravnanja z vodo ob neurjih; - vsebine greznice; - urbanih sistemov zbiranja odpadne vode; - čistilnih naprav za odpadno vodo; - obravnavanja industrijske odpadne vode na podoben način kot urbane odpadne vode (kot je opredeljeno v Direktivi 91/271/EGS); - čistilnih naprav za sistem oskrbe z vodo; vendar ne iz nevarnega blata iz industrije.

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SIST-TP CEN/TR 13714:2010
SIST CR 13714:2001
Karakterizacija blata - Ravnanje z blatom glede na uporabo ali odlaganje
Characterization of sludges - Sludge management in relation to use or disposal
Charakterisierung von Schlämmen - Management von Schlamm zur Verwertung oder
Caractérisation des boues - Gestion des boues en vue de leur valorisation ou de leur
Ta slovenski standard je istoveten z: CEN/TR 13714:2010
13.030.20 7HNRþLRGSDGNL%ODWR Liquid wastes. Sludge
SIST-TP CEN/TR 13714:2010 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST-TP CEN/TR 13714:2010

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SIST-TP CEN/TR 13714:2010

CEN/TR 13714


June 2010
ICS 77.060; 93.140 Supersedes CR 13714:2001
English Version
Characterization of sludges - Sludge management in relation to
use or disposal
Caractérisation des boues - Gestion des boues en vue de Charakterisierung von Schlämmen - Management von
leur valorisation ou de leur élimination Schlamm zur Verwertung oder Beseitigung

This Technical Report was approved by CEN on 9 February 2010. 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, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland,
Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.



Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2010 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TR 13714:2010: E
worldwide for CEN national Members.

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CEN/TR 13714:2010 (E)
Contents Page
Foreword . 3
Introduction . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions and abbreviated terms . 5
3.3 Abbreviated terms . 6
4 Waste hierarchy . 6
4.1 General . 6
4.2 Context . 7
5 Management of sludge quality - Upstream processes . 7
5.1 General . 7
5.2 Municipal wastewater sludges . 7
5.3 Setting limits for discharges from industrial and commercial premises to municipal
sewers . 8
5.4 Other factors . 9
5.5 Minimising contamination including diffuse sources in municipal wastewater . 9
6 Sludge management .10
6.1 Measures upstream of water and wastewater treatment facilities .10
6.2 Measures at sites of sludge production and processing .10
6.3 Solutions for recycling recovery and disposal.12
6.4 Disposal .14
7 Operational good practices .14
7.1 General .14
7.2 Upstream of the sludge production site .14
7.3 At the sludge production site .15
8 Strategic evaluation of options and links with the other good practice documents.16
8.1 General .16
8.2 Sludge quantity assessment .16
8.3 Sludge quality .17
8.4 Developing a strategy for sludge use/disposal .17
Annex A (informative) Guides of good practice for use and disposal of sludges .19
Annex B (informative) Best Practicable Environmental Option for sludges use or disposal .20
Bibliography .21


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SIST-TP CEN/TR 13714:2010
CEN/TR 13714:2010 (E)
This document (CEN/TR 13714:2010) 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.
This document supersedes CR 13714:2001.
This document gives recommendations for good practice but existing national regulations remain in force.


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The purpose of this Technical Report is to outline the management of sludges both upstream and
downstream of the treatment process to ensure that it is suitable for the outlets available. Sludge is the
inevitable residue of treating raw potable water and municipal and industrial wastewaters. The Technical
Report refers to all types of sludge covered by CEN/TC 308 including sludges from treating industrial
wastewater similar to urban wastewater and from water supply treatment work plants. In considering the
likely quality of sludges it should be remembered that municipal wastewater sludges are composed of
materials that have already been disposed of and are consequently likely to be more variable than many
industrial sludges that arise from sourced materials or water treatment sludges arising from surface water or
The quality of the sludge should match the requirements of the outlets whether that be to land, thermal
processing or as a last resort landfill. As a general rule a sludge of high quality is likely to be acceptable to a
large range of outlets giving greater operational flexibility. High quality sludges are likely to be suitable for
those outlets associated with maximum sustainability and minimum environmental pollution. The
management of sludges will become increasingly more complex as environmental standards become more
stringent and if outlets become more constrained by legislation and public attitudes.
Sludge quality is central to the development of good practice for sludge production in relation to its
destination (use or disposal). Sludge quality depends on the composition of the upstream materials and the
type of treatment including post treatment storage.
Sludge quality can be characterised by its different properties; biological, chemical and physical:
 biological properties include the microbiological stability of the organic matter in the sludge, odour and
hygienic characteristics;
 chemical properties include:
 content of potentially toxic substances (PTSs) which include inorganic (metals, metalloids, and
other minerals), and organic pollutants;
 concentrations and form (availability) of plant nutrients and the main components of the sludge;
 physical properties include whether liquid, semi-solid (pasty-like) or solid, and aesthetic factors
associated for instance with removal of unsightly debris by effective screening. Calorific value is a
quality criterion if the sludge is to be incinerated or used as a fuel. Other physical properties include,
thickenability and dewaterability.
The consistency of these different properties is a critical aspect of the sludge quality and of the ability to
determine its end destination (use or disposal).
Standard methods should be used where these are available to measure the quality parameters of sludge.
There is a continuing need to develop a full set of standardised and harmonised methods which the manager
and operator can use to evaluate the quality of sludge for treatment process design and operational
This Technical Report considers the management of sludges against the waste hierarchy, the management
of sludge quality and an option evaluation process to determine the options available.

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1 Scope
This Technical Report gives guidance for dealing with the production and control of sludge in relation to
inputs and treatment and gives a strategic evaluation of recovery, recycling and disposal options for sludge
according to its properties and the availability of outlets.
This report is applicable for sludges from:
 storm water handling;
 night soil;
 urban wastewater collecting systems;
 urban wastewater treatment plants;
 treating industrial wastewater similar to urban wastewater (as defined in Directive 91/271/EC [1]);
 water supply treatment plants;
but excluding hazardous sludges from industry.
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 1085:2007, Wastewater treatment — Vocabulary
EN 12832:1999, Characterization of sludges — Utilisation and disposal of sludges — Vocabulary
3 Terms and definitions and abbreviated terms
For the purposes of this document, the terms and definitions given in EN 1085:2007 and EN 12832:1999 and
the following apply:
industrial wastewater
trade wastewater
trade effluent
wastewater discharge resulting from any industrial or commercial activity
urban wastewater
municipal wastewater
wastewater from municipal areas consisting predominantly of domestic wastewater and additionally it may
also contain surface water, infiltration water, trade or industrial wastewater

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3.3 Abbreviated terms
The following abbreviated terms necessary for the understanding of this report apply:
BOD: Biochemical Oxygen Demand
BPEO: Best Practicable Environmental Option
COD: Chemical Oxygen Demand
EQO/EQS: Environmental Quality Objectives/Environmental Quality Standards
PTS: Potentially Toxic Substance
4 Waste hierarchy
4.1 General
In order that the management of waste be conducted in an increasingly sustainable manner, the EU
encourages a waste hierarchy as a framework by which Member States should develop their strategy for
waste management (EU Directive 75/442/EEC (see [2]) as amended by 91/156/EEC (see [3])).

Figure 1 — The waste hierarchy — Including sludges
This hierarchy encourages:
a) firstly, the prevention or reduction of waste production and its harmfulness, in particular by:
 development and implementation of clean technologies more sparing in their use of natural
 technical development and marketing of products designed so as to make no contribution or to
make the smallest possible contribution, by the nature of their manufacture, use or final disposal, to
increasing the amount or harmfulness of waste and pollution hazards;
 development of appropriate techniques for the final disposal of dangerous substances contained in
waste destined for recovery;

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b) secondly, the best possible use of waste:
 recovery of waste by means of recycling, re-use or reclamation or any other process with a view to
extracting secondary raw materials;
 or the use of waste as a source of energy.
The hierarchy places disposal as the last management choice.
Four of the stages within the hierarchy can be applied to sludges, namely reduction, recycling, recovery and
disposal. Obviously, the latter is the least desirable and efforts should be made to minimise the proportion of
sludge which is disposed of, by the adoption of clean technologies, recycling and recovery strategies.
The waste hierarchy can be applied equally to activities upstream of the sludge production process and to
the processes employed within the treatment process. These are discussed separately below. In considering
what management options should be selected, all stages in the sequence of sludge production and its
ultimate fate should be scrutinised.
4.2 Context
The overall objective of a sludge management strategy should be to find outlets for the sludge which are
safe, environmentally acceptable (carbon foot print), secure and economic. The availability of outlets (see
Clause 8) determines how sludge should be treated.
In order to do this, it is important to address quality (Clause 5) and management processes (Clause 6) and
operational practices (Clause 7).
5 Management of sludge quality - Upstream processes
5.1 General
The significant difference between municipal sludges and industrial sludges and to a certain extent water
treatment sludges is the degree and complexity of control over the inputs.
Industrial sludges usually arise from the processing of sourced materials and control over their content and
consequently on the quality of sludge can often be made by analysis of the materials and in many cases by
the imposition of quality standards on them. This may not always be possible for instance in the amount of
bacteriocides and fungicides in paper waste collected for recycling which could vary from batch to batch.
River waters can carry a range of pollutants which could enter the sludge and operators should be aware of
the potential pollutants that could enter the river upstream.
5.2 Municipal wastewater sludges
For municipal wastewater sludges strict limits should be imposed on industrial and commercial discharges to
the sewer so that the sludge produced from wastewater is ‘clean’ or as free as possible of contaminants of
industrial origin.
Industrial point sources of contaminants discharging to the sewer should be identified and restricted or
stopped. Key factors are careful discharge consent settings (see below) monitoring and inspection backed
by enforcement. Quality assurance in support of the consent requires adequate sampling to check
compliance. The extent of sampling of effluent from industrial premises should be decided on a risk
assessment basis taking account for instance of size of operation and quantity of chemicals in use.
The "polluter pays" principle should be used to oblige industries failing to produce acceptable effluents to
investigate and implement remedial measures. This may entail a change in the production process or the
installation on the industrial premises of effluent treatment plant. Often the cost of this is offset by reduced

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payments for effluent discharge and the recovery and reuse of valuable chemicals that would otherwise have
been discharged to the sewer. Experience has shown that by progressively identifying and controlling point
source discharges, the quality of sludge can be substantially improved by reducing its content of PTS.
Emergency planning should make provision to deal with accidental discharges of large amounts of polluting
chemicals to the sewer so that contamination of sludge is minimised, and the biological treatment processes
of wastewater and sludge are protected.
Conventional wastewater treatments remove most of the organic polluting load of the wastewater; this is
measured in terms of BOD or COD. These processes also transfer much of the non-treatable polluting load,
consisting of non-degradable or persistent residues, out of the wastewater and into the sludge. This is
advantageous for the production of clean effluent but if the wastewater contains significant levels of
contaminants of industrial origin then these contaminants are likely to be found in the sludge at levels, which
affect its environmental suitability for use and disposal outlets. Some of the PTS contained in an untreated
wastewater is found in the sludge after treatment. The percentage of the wastewater load of PTS transferred
into sludge depends on many parameters, such as the wastewater and sludge treatment process, pH, solids
content, and PTS content.
5.3 Setting limits for discharges from industrial and commercial premises to municipal
The use of public wastewater systems is regulated by the operators according to the relevant legislation in
place in all the EU Member States and through by-laws, public law agreement or private law operating
The EU legislation covering the control of potentially toxic substances in discharges to the aquatic
environment is Directive 2006/11/EC [4] and Directive 2000/60/EC [5] known as the Water Framework
Directive (WFD). These directives should therefore be the springboard for controlling the discharge of toxic
and harmful materials from industry and commercial activities. There should be an effective control of the
discharge from the wastewater treatment process and the quality of the sludge emanating from it.
Directive 2006/11/EC introduces two lists of 132 dangerous substances to limit discharges from industrial
and commercial premises:
List 1 Substances (e.g. mercury, cadmium, organophosphorus compounds and organochlorine
compounds) should be removed as completely as possible from all industrial wastewater discharges using
the best available technology (BAT). Whenever possible, List 1 substances should be replaced by more
benign and less toxic alternatives.
List 2 Substances (e.g. copper, chromium, zinc, and nickel) should be reduced in discharges by the
application of the «Best Available Technology Not Entailing Excessive Cost» with respect to the level of
environmental risks. A cost/benefit analysis is therefore an essential element in deciding the appropriate
level of treatment.
Annex 10 of Directive 2000/60/EC sets out a list of 33 priority substances or group of substances selected
amongst those which present a significant risk to or via the aquatic environment. For those pollutants,
specific control measures are required that aim for the progressive reduction and for 11 priority hazardous
substances the cessation or phasing-out of discharges, emissions and losses.
Directive 2008/105/EC [6] amending the Water Framework Directive 2000/60/EC (WFD) establishes
environmental quality standards for priority substances and other substances from Directive 2006/11/EC.
Reduction of the pollution by these substances must be assessed through inventories of their discharges,
emissions and losses. This text also proposes a list of 13 substances for their identification as priority or
hazardous priority substances. Directive 2006/11/EC is repealed by the WFD as from the end of 2013.
Requirements for these dangerous substances are the subject of varying national regulations. In all cases,
dangerous substances should be reduced at source as far as possible by suitable pre-treatment of the
industrial waste stream prior to discharge to sewer.

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Improvements in environmental protection as regards both sludge recycling or disposal, and discharges from
treatment plants to the watercourse, require the periodic review of industrial and commercial discharge
permit conditions.
5.4 Other factors
5.4.1 General
Factors additional to sludge quality have to be considered in setting limits for chemicals in industrial
discharges to the sewer. These are given below.
5.4.2 Protection of biological municipal wastewater treatment processes
Biological processes depending on the action of bacteria and other micro-organisms include biofilm
processes and activated sludge. The chosen threshold values for individual contaminants from industrial and
commercial discharges should be protective enough to avoid damage to the biota with the consequent failure
of the biological wastewater processes.
5.4.3 Protection of biological sludge treatment processes
This normally applies to anaerobic digestion but also to sludge treated by aerobic processes such as
composting. Heavy metals and organic contaminants such as pentachlorophenol have been found to inhibit
anaerobic digestion of sludge.
It is not easy to designate threshold values for individual contaminants above which biological wastewater or
sludge treatment processes may fail because this depends also on the composition of the wastewater,
operating conditions and whether the plant is acclimatised to the contaminant. It is now the case that in order
to meet sludge quality requirements for use or disposal, concentrations of PTS in wastewater must be
restricted to levels below those which would be expected to adversely affect biological wastewater or sludge
treatment processes.
5.4.4 Protection of environmental quality in the receiving watercourse
The maximum permissible concentrations of substances discharged to the wastewater given by the national
regulations have to be related to the standards set for the final discharge effluent from the wastewater
treatment works including storm water overflows from the sewerage system, and those for the receiving
5.4.5 Protection of sewer fabric
This is usually controlled by limits for the acidity, alkalinity and temperature of discharges and their content of
sulphate and sulphide.
5.4.6 Protection of sewer maintenance workers
Personnel should observe the normal rules of hygiene and it is necessary that chemicals which could
generate toxic fumes in the sewer are strictly controlled.
5.5 Minimising contamination including diffuse sources in municipal wastewater
There are sources of contamination of municipal wastewater and sludge other than industrial and
commercial discharges to the sewer. These are inputs among others from domestic sources and from runoff
from roads etc. and they are diffuse and less readily controlled than point source inputs.
A programme of public education to minimise discharge of unsuitable substances and materials into
domestic wastewater can advantageous.

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The public should be advised of those substances, which are not permitted for discharge down drains or the
lavatory and given instructions as to how they can be safely disposed of. Such substances include waste oil,
solvents, paint residues, medicines and pesticides.
The public should be encouraged not to put non-degradable litter items down the lavatory; some countries
have instigated campaigns therefore (e.g. ‘bag it and bin it’ campaign in the UK). The message should be
that collective individual action can make a major impact on the environmental problems.
Organic contaminants in sludge include detergent-derived compounds and other compounds that are widely
used by industry or in the home. It is important to test chemicals before they are put into products for
widespread domestic and other use to ensure that they do not cause a hazard to the environment or man
with respect to sludge use or disposal and to receiving waters. Whether this is done or not is usually beyond
the control of those responsible for sludge quality and safe disposal. There should be more accountability of
the manufacturers of these compounds to ensure treatability. This would be in accordance with the "polluter
payer" principle. To some extent this problem is addressed by Directives 67/548/EEC [7] and 82/242/EEC
[8] and 82/243/EEC [9].
6 Sludge management
6.1 Measures upstream of water and wastewater treatment facilities
6.1.1 Source prevention
Prevention at source of contaminants and quantity of discharges to sewer is a preferable policy when new
industrial or commercial premises are connecting to the sewer or when processes are being redesigned.
6.1.2 Source reduction
Reduction of sludge by reducing the input to treatment processes is the most difficult of the hierarchy levels
to achieve. This often requires industry and commercial activities to pre-treat their effluents often producing
their own sludge but reducing the amount and/or pollutants at the municipal wastewater treatment works. A
large proportion of the sludge from municipal wastewaters is derived from domestic wastewater and this is
difficult to control although a public relations programme to indicate to the public what should not be put
down the sewer is advisable.
Sludge quantities from industry and water treatment are related to the rate of production and demand.
Potable water sludge can be reduced by ensuring that water is not taken from rivers when they are carrying
large loads of silt.
6.2 Measures at sites of sludge production and processing
6.2.1 Water and Wastewater treatment processes
When selecting water and wastewater treatment processes, consideration should be given to the quantity
and type of sludge that is produced and its characteristics relative to the proposed ultimate use or disposal of
the sludge.
Proper operating procedures can help to keep sludge production at a low level (e.g. operation at high sludge
residence time in biological processes, optimisation of chemical dosages).
Volumes of industrial sludges have been reduced by reducing inputs into the process. In the Tannery
industry, average chemical consumption has been reduced from 400 kg/t hide to 250 kg and lime input from
5 % to 2 % to 3 % of hide weight.
Water treatment sludges can be reduced by choosing the optimum flocculant, pH, energy input and retention
time in the mixing and flocculation steps. Where iron and manganese are to be removed the amount of

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sludge produced may be minimised by consideration of the oxidant used. There is also an opportunity to
reduce the amount of dry solids in sludges (Tons of Dry Solids, tDS), if chemical softening is employed by
using caustic soda instead of calcium hydroxide though in this last case there are other drawbacks related to
the drinking water quality and to the dewatering of sludge.
6.2.2 Sludge treatment General
All recommendations have to be adapted to the local context and constraints associated to the outlets.
Appropriate treatment practice should be used to control the pathogen risks. More information on hygienic
aspects is given in the CEN/TR 15809 [10]. Water content reduction
The reduction in the volume of water present in a sludge by thickening, dewatering and drying is the primary
route by which sludge quantity may be reduced following treatment.
All sludge concentration processes in water and wastewater treatment generate a liquor requiring treatment
by a separate process or with wastewater sludge by recirculation through the wastewater treatment works.
There is a limit to the amount of water that can be removed from sludge by mechanical means,

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