CR 13714:2001

SLOVENSKI STANDARD
SIST CR 13714:2001
01-december-2001
Karakterizacija blata - Ravnanje z blati glede na uporabo ali odlaganje
Characterisation of sludges - Sludge management in relation to use or disposal
Charakterisierung von Schlämmen - Management von Schlamm zur Verwertung oder
Beseitigung
Caractérisation des boues - Bonne pratique pour la gestion des boues en vue de leur
valorisation ou de leur élimination
Ta slovenski standard je istoveten z: CR 13714:2001
ICS:
13.030.20 7HNRþLRGSDGNL%ODWR Liquid wastes. Sludge
SIST CR 13714:2001 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST CR 13714:2001

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SIST CR 13714:2001
CEN REPORT
CR 13714
RAPPORT CEN
CEN BERICHT
June 2001
ICS
English version
Characterisation of sludges - Sludge management in relation to
use or disposal
Caractérisation des boues - Bonne pratique pour la gestion Charakterisierung von Schlämmen - Management von
des boues en vue de leur valorisation ou de leur élimination Schlamm zur Verwertung oder Beseitigung
This CEN Report was approved by CEN on 9 June 2001. It has been drawn up by the Technical Committee CEN/TC 308.
CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece,
Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2001 CEN All rights of exploitation in any form and by any means reserved Ref. No. CR 13714:2001 E
worldwide for CEN national Members.

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Contents
Foreword.3
Introduction .4
1 Scope .5
2 References.5
3 Terms and definitions.5
4 Waste hierarchy .6
4.1 General.6
4.2 Measures upstream of wastewater treatment facilities .6
4.3 Measures at sites of sludge production and processing .7
4.4 Measures for recovery and disposals .8
5 Upstream processes.10
5.1 Non domestic effluent control.10
5.2 Setting limits for discharges from industrial and commercial premises.11
5.3 Minimising contamination including diffuse sources.12
6 Operational good practices .12
6.1 General.12
6.2 Upstream of the sludge production site.13
6.3 At the sludge production site .13
7 Strategic evaluation of options and links with the other good practice documents.14
7.1 General.14
7.2 Sludge quantity assessment .14
7.3 Sludge quality.15
7.4 Developing a strategy for sludge use/disposal .15
Annex A Sludges from the drinking water production .19
A.1 General.19
A.2 Reduction.19
A.3 Recycling .20
Annex B.22
Bibliography .24

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Foreword
This CEN Report has been prepared by Technical Committee CEN/TC 308, "Characterisation of sludges", the
secretariat of with is held by AFNOR.
The status of this document as CEN Report has been chosen because the most of its content is not completely in
line with practice and regulation in each member state. This document gives recommendations for a good practice
but existing national regulations remain in force.

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Introduction
The purpose of this CEN report is to assist in finding outlets for sludge which are primarily safe and sustainable but
also secure and cost-effective. The challenge is to manage the quality of the sludge so that it is suitable for the
outlets available. It follows that a sludge of high quality will provide operational flexibility because it is likely to be
suitable for most or all of the outlets available, including those associated with maximum sustainability and
minimum environmental pollution.
Sludge quality is central to the development of good practice for sludge production in relation to use or disposal.
Sludge quality depends on the composition of the wastewater (or other process water) and also from sludge
treatment and the extent of processing it receives during sludge treatment. 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
infectivity ;

chemical properties include :

content of potentially toxic elements (PTEs) which include inorganic (metals, metalloids, and other
minerals), and organic micropollutants ;

concentrations and form (availability) of plant nutrients and main components ;

physical properties include whether liquid, semi - solid (pasty) or solid, which is achieved progressively by
thickening and dewatering, and aesthetic factors associated for instance with removal of unsightly debris by
effective screening. Calorific value will be a quality criterion if the sludge is to be incinerated or used as a fuel.
Others physical properties include, thickenability, dewaterability and conditioners demand.
The constancy of these different properties is also an important aspect of the sludge quality.
Standard methods should be used where these are available to measure the quality parameters of sludge. This
aspect is being addressed by CEN/TC 308 WG 1. 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 purposes.
The option evaluation (clause 7) is intended to indicate which recycling or disposal options are available in any
particular set of circumstances.
The processes to achieve appropriate sludge quality will be those described by the technical committee
CEN/TC 165 "Waste water engineering".
The following abbreviated terms necessary for the understanding of this report apply :
BAT : Best Available Technology
BATNEEC : Best Available Technology Not Entailing Excessive Cost
BOD: Biochemical oxygen demand
BPEO : Best Practicable Environmental Option
COD : Chemical oxygen demand
EQO/EQS : Environmental Quality Objectives/Environmental Quality Standards
PTE : Potentially Toxic Elements

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1 Scope
This CEN report gives guidance for dealing with the production and control of sludge in relation to inputs and
treatment and give a strategic evaluation of recovery and disposal options for sludge according to its properties and
the availability of outlets.
This report is applicable for following sludges :

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) ;
but excluding hazardous sludges from industry.
Annex A gives information on sludges from water supply.
2 References
Wastewater treatment – Vocabulary.
EN 1085,
EN 12832, Characterisation of sludges – Utilisation and disposal of sludges - Vocabulary.
Wastewater treatments plants – Part 8 : Sludge treatment and storage.
EN 12255–8,
1)
CR 13097, Characterisation of sludges – Good practice for sludge utilisation in agriculture .
CR 13767, Characterisation of sludges – Good practice for sludge incineration with or without grease and
1)
screenings .
CR 13768, Characterisation of sludges – Good practice for combined incineration of sludge and household
1)
waste
.
prEN 13983, Characterisation of sludges – Good practice for sludge used in land reclamation.
prEN WI 308044, Characterisation of sludges – Good practice for the landfill of sludge and sludge treatment
residue.
3 Terms and definitions
For the purposes of this CEN Report, the terms and definitions which apply are those given in :
Directive 91/271/EC (see 1) (Concerning urban waste water treatment).
Directive 86/278/EEC (see 2) (On the protection of the environment and in particular of the soil, when sewage
sludge is used in agriculture).

1) In preparation.

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Directive 75/442/EEC (see 3) (The Waste Framework Directive) as amended by EU Directive 91/156/EEC
(see 4).
EN 1085 and EN 12832.
4 Waste hierarchy
4.1 General
Sewage sludge is a waste which can be considered as a secondary resource when beneficially reused. The extent
to which the recycling option is available depends on the quality and properties of a sludge and on the availability of
the outlets. The same principles apply to the management of sewage sludge as to any other waste product.
It is not possible to eliminate the production of this particular waste. 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 3) as
amended by 91/156/EEC(see 4)). In order of preference, this hierarchy encourages :
a) firstly, the prevention or reduction of waste production and its harmfulness, in particular by :

the development of clean technologies more sparing in their use of natural resources ;

the 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 ;

the development of appropriate techniques for the final disposal of dangerous substances contained in
waste destined for recovery ;
b) secondly :


the 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.
Three of the stages within the hierarchy can be applied to sludges, namely reduction, 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 reduction and recovery strategies.
The waste hierarchy can be applied equally to activities upstream of wastewater treatment facilities as to the
processes employed within a treatment works. 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.
The demand for prevention and reduction applies to the management of the effluents which contribute to
 
wastewater (EU Directive 91/21/EEC (see 1 ).
4.2 Measures upstream of wastewater treatment facilities
Reduction
As a general rule, sewage sludge comes from three sources in varying proportions:
1) domestic wastewater ;
2) industrial wastewater from large- and small-scale industries ;
3) stormwater containing pollutants washed out of the air and the soil.

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Minimisation of the wastewater load can be achieved by :
a) reduction of industrial wastewater :

minimisation of the volume and waste load of water ;

industrial wastewater pre-treatment ;

internal recycling of water within the industry ;
b) reduction in flow of collected stormwater by using alternative techniques ;
c) reduction of infiltration water ;
d) reduction of domestic wastewater when possible, e.g. by domestic devices better designed.
The control of industrial discharges to the sewer is discussed in Clause 5.
4.3 Measures at sites of sludge production and processing
4.3.1 Reduction
4.3.1.1 Wastewater treatment
When selecting wastewater treatment processes, consideration should be given to the quantity and type of sludge
that will be 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 the biological processes, optimisation of chemical dosages).
4.3.1.2 Sludge treatment
All recommendations have to be adapted to the local context and constraints associated to the outlets :
a) water content reduction.
The reduction in the volume of water present in a sludge by thickening and dewatering is the primary route by
which sludge quantity may be reduced following treatment.
Apart from producing sludge cake, dewatering generates a liquor requiring treatment 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, and most
dewatered sludge (for instance by belt press, filter press, centrifuge, etc.) have dry solids content in the range 15 %
to 40 %.
Thermal drying of sludge will reduce the volume of sludge by evaporating water that cannot be removed
mechanically to as high as 95% dry solids. However, considerable energy is used to dry sludge to this degree and
local circumstances will dictate whether any environmental benefit is gained from thermal drying over the transport
of large volumes of wet sludge for recycling or disposal purposes. It is essential for such factors to be appraised in
the strategic evaluation of options (Clause 7). It is necessary to remember that most of the evaporated water has to
be recycled to the wastewater plant after the condensing step of the exhaust gases. Storage design has to take the
risk of self-ignition into account ;
b) water and organic solids content reduction.
Reduction of sludge mass rate can be achieved through biological stabilisation. Digestion typically achieves a
40 % to 50% volatile matter reduction and aerobic stabilisation will achieve a volatile matter reduction of 30 % to
40 %. These processes partly reduce also the pathogen content of the sludge and its odour potential.
Incineration
(see CR 13767) is in essence a reduction option carried out by a combustion of organics sludge at
high temperature. It produces an ash (about 20 % to 50 % of sludge dry weight) which has to be disposed of unless

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a use can be found for it. A positive aspect is the opportunity for energy recovery through waste-to-energy facilities
and these should preferentially be employed over incineration with no energy recovery. With the improvement in
sludge dewatering and incineration techniques, modern fluidised bed incinerators are autothermic in operation, only
requiring support fuel at start-up, and when coupled with gas cleaning systems, have very low emissions to the
atmosphere. Co-incineration (see CR 13768) with other organic wastes, such as municipal solid waste, may also
be an option under some circumstances.
Wet oxidation is also a reduction option involving thermal degradation, hydrolysis and oxidation of sludge organic
matter in aqueous phase in a single-stage reaction at high temperature and pressure. The technique does not
require the complex gas cleaning equipment which is needed in many combustion processes. During the process,
some of the organic matter is solubilised and it produces ashes and high COD and BOD liquors that are to be
treated.
Vitrification is a technique for further reducing the volume of incinerator ash and to make an environmentally inert
material. Landfill disposal can be avoided since it is possible to use this technique to make environmentally inert
construction materials. The temperature required for vitrification is much higher than for incineration and
consequently has a high energy cost ;
c) hygienisation.
Appropriate treatment practice should be used to control the pathogen risks. More information are given in the CEN
documents dealing with the application.
4.4 Measures for recovery and disposals
4.4.1 General
There are opportunities for recovery of the resource value of sludge at the site of sludge production (e.g. biogas) or
downstream of the site of sludge production (e.g. nutrients content of the sludge).
Sludge can be used in liquid dewatered, composted or dried or incinerated and even vitrified form. The level of
processing employed should be the optimum necessary to ensure the quality of the sludge for the selected end
use.
All these activities should be conducted according to the relevant legislation in place in the relevant Member States,
and other CEN guidance documents.
4.4.2 Application to land (see CR 13097 and prEN 13983)
The most common method of sludge recycling is application to land. Sludge may be beneficially used to supply
plant nutrients and add organic matter and/or lime to soil in agricultural, land reclamation, forestry operations,
landscaping, amenity horticulture and horticulture.
Detailed information on quality should ensure that each type and source of sludge is used appropriately according
to its quality. For example, the nitrogen release characteristics of a digested liquid sludge differ from those of a
digested dewatered cake, and the manner of their use should reflect this to minimise the risk of nitrate leaching
losses.
Recycling to land involves the processing of waste materials to produce a usable, secondary raw material. Sludge
may be recycled in a range of ways which vary in the degree of processing and energy required.
There are several sludge processing techniques that involve the addition of materials in order to produce a more
stable, easily handled material for land application.
One such technique is lime addition for stabilisation, disinfection, dewatering and storage purposes.
Composting. It is an aerobic controlled process (biological oxidation of organic matters with heat generation) to
produce a stable and disinfected product of value as soil amendment. A composting process can be characterised
by the maximum temperature and duration. The composting of sludge can be optimised by the addition of bulking
agent such as straw, wood chips, bark or garden and park wastes. Selection of the bulking agent should avoid any
negative impact in the quality of the composted product due to the presence of any contaminants in the bulking
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Sludge criteria which should be considered for the composting process include :
a) sludge fermentability ;
b) sludge type and treatment prior composting ;
c) sludge rheology.
Factors which should be considered in the design of a composting plant are listed in prEN 12255-8.
Operated correctly, composting will give rise to a highly stabilised and humus like material which can be beneficially
used in agricultural, land reclamation and forestry operations as well as in horticulture. Composting activities should
be conducted in a manner which complies with the relevant legislation and ensures minimum nuisance to site
neighbours from traffic, noise, and dust and odour.
Extended storage using vegetative processes may also produce aerobically composted material suitable for land
application.
4.4.3 Others uses
Sludge and incinerator ash can be used in the production of construction materials, such as fibre board, bricks,
lightweight blocks, paving blocks, etc. Such processes are high cost but may be the Best Practicable
Environmental Option (BPEO) in some circumstances.
4.4.4 Energy Recovery
Useful energy can be recovered from :
a) methane from anaerobic digestion of sludge :

gas from anaerobic digestion contains about 2/3 CH by volume, 1/3 CO by volume and small amounts
4 2
of N , H , H S, water vapour and other gases. Total gas production can fluctuate over a wide range,
2 2 2
depending on the volatile solids content of the sludge feed and the biological activity of the digester.
3 3
Typical values vary from 0,75 m /kg to 1,12 m /kg of volatile solids destroyed. Because digester gas is
3
typically about 65 percent methane, the low calorific value of digester gas is about 22400 kJ/m (by
3
comparison, methane has a low calorific value of approximately (37300) kJ/m ). Combined heat and
power plants make efficient use of methane for digester heating, air compression, and electrical power for
use on the treatment plant or for export. As digester gas contains hydrogen sulphide, particulates, and
water vapour, the gas frequently has to be cleaned in dry or wet scrubbers before it is used in internal
combustion engines ;
b) dedicated or co-incineration with other wastes (see CR 13767 and CR 13768) :

energy may be recovered as heat to be used for space heating or raising steam for power generation. The
energy value of sludge ranges widely depending on the type of sludge, water content and the volatile
solids content. The energy value of untreated primary sludge is the highest. Because of the water content,
this value is low if there is no drying ;
c) co-combustion with other fuels in power stations ;
d) use as a fuel in an industrial process, such as cement and asphalt production. Conventional fuel can be
supplemented by substituting sludge to fuel.
For the c) and d) uses, the level of sludge addition depends of the particular application, the quality of the gas
being produced during incineration, and the specific atmospheric emission standards to be achieved :
e) other high temperature treatment options exist such as gasification with or without wastes to produce fuels.

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4.4.5 Component recovery
Recovery processes of sludge components have only been applied experimentally because, until now, they are not
commercially viable.
4.4.6 Disposal
Waste disposal is the least desirable management option and should be avoided where environmental benefit can
be derived by an alternative outlet.
Landfill can be cheaper than other options, but costs are increasing through the introduction of environmental
taxes. A carbon limit value for wastes disposed of to landfill is likely to be introduced (already in place in some
countries) and this will encourage reuse options or energy recovery through incineration prior to landfill disposal of
ash.
Sewage sludges unless appropriately treated may not be allowed into landfill under EU Directive 99/31/EC (see
10).
As seen in Clause 7, the main parameters to be considered for sludge landfilling are :
a) sludge rheology (important for the transport and incorporation to the other wastes) ;
b) odours ;
c) dry matter content (important for the water balance of the landfill).
5 Upstream processes
5.1 Non domestic effluent control
5.1.1 General
Strict limits should be imposed on industrial 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 setting (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 will be offset by reduced
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 Potentially Toxic
Elements (PTEs).
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.

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Conventional wastewater treatments will treat most of the degradable polluting load of the wastewater; this is
known as the treatable fraction and is measured in terms of BOD or COD. The process will 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 contained 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. Most of the metal contained in an untreated
wastewater will be found in the sludge after treatment. The percentage of the wastewater load of heavy metals
transferred into sludge will depend on many parameters, such as the wastewater and sludge treatment, pH, solids
content, metals content.
Additional factors to sludge quality have to be considered in setting limits for chemicals in industrial discharges to
the sewer. These are given below :
5.1.2 Protection of biological wastewater treatment processes
This can be the second stage of conventional wastewater treatment by percolating filters, activated sludge or other
biological processes and depends on the action of bacteria and other micro-organisms working in an aerobic or
anaerobic environment. The chosen threshold values for individual contaminants should be protective enough to
avoid biological wastewater processes failure.
5.1.3 Protection of biological sludge treatment processes
This will normally apply to anaerobic digestion but sludge may also be treated by aerobic processes such as
composting. Heavy metals and organic contaminants such as pentachlorophenol have been found to inhibit
anaerobic digestion of sludge
...