SIST-TP CEN/TR 15126:2005
(Main)Characterization of sludges - Good practice for landfilling of sludges and sludge treatment residues
Characterization of sludges - Good practice for landfilling of sludges and sludge treatment residues
This CEN Technical Report gives one of a series on sludge management options and describes good practice for the disposal of sludges and sludge treatment residues to landfill where national regulations permit.
This document is applicable to sludges described in the scope of CEN/TC 308 i.e. specifically derived 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/EEC ) ;
- water supply treatment plants;
- water distribution systems;
but excluding hazardous sludges from industry.
Charakterisierung von Schlämmen - Gute fachliche Praxis bei der Deponierung von Schlamm und Rückständen aus der Schlammbehandlung
Caractérisation des boues - Bonne pratique pour la mise en décharge des boues et des résidus de traitement des boues
Le présent rapport technique CEN présente l'une des options envisageables pour la gestion des boues et décrit les bonnes pratiques d'élimination des boues et des résidus de traitement des boues par mise en décharge, lorsque cela est permis par les réglementations nationales.
Le présent document s'applique aux boues décrites dans le domaine d'application du CEN/TC 308, provenant spécifiquement :
- de la collecte des eaux pluviales ;
- des matieres de vidange ;
- des systemes 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 91/271/CEE) ;
- des installations de traitement de l'alimentation en eau ;
- des systemes de distribution d'eau ;
a l'exclusion des boues industrielles dangereuses.
Karakterizacija blata - Dobra praksa za odlaganje blata in ostankov po obdelavi blata
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
SIST-TP CEN/TR 15126:2005
01-december-2005
Karakterizacija blata - Dobra praksa za odlaganje blata in ostankov po obdelavi
blata
Characterization of sludges - Good practice for landfilling of sludges and sludge
treatment residues
Charakterisierung von Schlämmen - Gute fachliche Praxis bei der Deponierung von
Schlamm und Rückständen aus der Schlammbehandlung
Caractérisation des boues - Bonne pratique pour la mise en décharge des boues et des
résidus de traitement des boues
Ta slovenski standard je istoveten z: CEN/TR 15126:2005
ICS:
13.030.20 7HNRþLRGSDGNL%ODWR Liquid wastes. Sludge
SIST-TP CEN/TR 15126:2005 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 15126:2005
TECHNICAL REPORT CEN/TR 15126
RAPPORT TECHNIQUE
TECHNISCHER BERICHT
July 2005
ICS 13.030.20
English Version
Characterization of sludges - Good practice for landfilling of
sludges and sludge treatment residues
Caractérisation des boues - Bonne pratique pour la mise en Charakterisierung von Schlämmen - Gute fachliche Praxis
décharge des boues et des résidus de traitement des bei der Deponierung von Schlamm und Rückständen aus
boues der Schlammbehandlung
This Technical Report was approved by CEN on 24 April 2005. It has been drawn up by the Technical Committee CEN/TC 308.
CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,
Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia,
Slovenia, 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
© 2005 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TR 15126:2005: E
worldwide for CEN national Members.
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Contents Page
Foreword .3
Introduction.4
1 Scope.5
2 Normative references.5
3 Terms, definitions and abbreviations.5
4 Outline of landfill processes.6
4.1 General.6
4.2 Inputs.8
4.2.1 Water.8
4.2.2 Solids.8
4.2.3 Gases.8
4.3 Processes .8
4.3.1 Microbiological activity.8
4.3.2 Solution/precipitation.9
4.3.3 Volatilization.9
4.3.4 Sorption reactions.9
4.3.5 Filtration.9
4.4 Outputs.9
5 Current position and European perspective.12
6 Legislative position.12
7 Economics.13
8 Treatment requirements.13
9 Operational aspects .15
9.1 General.15
9.2 Co-disposal of sludges and baled municipal waste .15
9.3 Co-disposal of sludges and loose municipal waste .16
9.4 Monofills for sludge disposal .18
9.5 Sludge in cover materials .18
9.5.1 Temporary cover .18
9.5.2 Final cover .19
10 Environmental aspects .19
10.1 General.19
10.2 Leachate .19
10.3 Methane generation.20
10.4 Void space and settlement.20
10.5 Other environmental factors.20
10.5.1 Odour.20
10.5.2 Contamination of mobile plant.20
10.5.3 Fire and dust.20
Annex A Current landfill legislation in EU Member States.22
Annex B Composition of leachates.25
Bibliography.27
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Foreword
This document (CEN/TR 15126:2005) has been prepared by Technical Committee CEN/TC 308
“Characterization of sludges”, the secretariat of which is held by AFNOR.
This document is voluntarily presented in the form of a CEN Technical Report because most of its content is
not completely in line with practice and regulations in each Member State. This document gives
recommendations for good practice concerning the landfilling of sludges and sludge treatment residues, but
existing national regulations remain in force.
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Introduction
All the recommendations in this document constitute a framework within which the landfilling process can be
proposed as a substitute for field spreading, or in addition to specific or combined incinerations, or any other
process.
This document should be read in the context of the requirements of Directive 1999/31/EC on the landfill of
waste which applies to the landfill of sludge and any other relevant regulations, standards and codes of
practice which may prevail locally within Member States.
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1 Scope
This CEN Technical Report gives one of a series of sludge management options and describes good practice
for the disposal of sludges and sludge treatment residues to landfill where national regulations permit.
This document is applicable to the sludges described in the scope of CEN/TC 308, i.e. specifically derived
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/EEC);
water supply treatment plants;
water distribution systems;
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 1085:1997, Waste water treatment – Vocabulary
EN 12832:1999, Characterisation of sludges – Utilization and disposal of sludges – Vocabulary
EN 13965-1:2004, Characterization of waste – Terminology – Part 1: Materials related terms and definitions
EN 13965-2:2004, Characterization of waste – Terminology – Part 2: Management related terms and
definitions
CR 13714, Characterisation of sludges – Sludge management in relation to use or disposal
3 Terms, definitions and abbreviations
For the purposes of this document, the terms and definitions given in EN 12832:1999, EN 1085:1997,
EN 13965-1:2004, EN 13965-2:2004 and also in the following Directives apply:
Directive 91/271/EC concerning urban wastewater treatment
Directive 75/442/EC the waste framework directive as amended by Directive 91/156/EC
Directive 1999/31/EC on the landfill of waste.
Directive 2001/77/EC on renewable energy.
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For the understanding of this document, these abbreviated terms apply:
BIO: Biomass
BOD: Biological Oxygen Demand
COD: Chemical Oxygen Demand
CSO: Chemically Stabilized Organic
DPM: Decomposable Plant Material
MSW: Municipal Solid Waste
PSO: Physically Stabilized Organic
RPM: Resistant Plant Material
TOC: Total Organic Carbon
VFA: Volatile Fatty Acids
WWTP:
4 Outline of landfill processes
4.1 General
The landfill processes which are of importance for understanding the potential for controlling waste
stabilization are the physical, chemical and microbial activities which lead to the modification of waste, from
often complex substances with significant pollution potential to simpler compounds which can be
environmentally benign. In the case of a landfill containing degradable waste, the principal processes of
interest are those which lead to the breakdown of complex organic compounds found in the putrescible
fraction of non-inert waste, and the influence of the by-products of degradation on the mobility and availability
of other compounds and elements. At a simple conceptual level, a landfill can be viewed as a reactor vessel in
which solid, water and gaseous inputs are subject to a variety of processes which produce solid, liquid and
gaseous waste products. The reactor model for landfill processes is shown schematically in Figure 1, with the
inputs, processes and outputs summarized briefly below.
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Figure 1 - Schematic representation of landfill processes
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4.2 Inputs
4.2.1 Water
The principal water input at modern, managed, cellular landfill sites is rainfall which can gain direct access to
waste during the filling phase for each cell and indirectly by percolation through capping and restoration layers
after each cell is finished. Solid waste contains absorbed water and mixed household waste typically carries
about 25 % water on a wet mass basis. Sludges contain about 10 % to 95 % water according to the extent of
dewatering and drying treatment they have received (for information concerning national regulations about the
water content, see Annex A).
4.2.2 Solids
Sludge, household waste and to a lesser extent commercial and industrial waste, contain putrescible materials
which degrade within the landfill environment, giving rise to potentially polluting liquid and gaseous products.
The process of degradation can create conditions in which other, non-organic compounds can pass into
solution or enter a gaseous phase. About 20 % of household waste is rapidly biodegradable (putrescible) and
a further 30 % more slowly degradable (cellulosic materials such as paper). In the case of sludge, about 30 %
is rapidly biodegradable, 40 % progressively more slowly degradable and the remaining 30 % is
non-degradable, inorganic ash. Articles 5.1 and 5.2 of the Landfill Directive (1999/31/EC) require that the
biodegradable municipal waste deposited in landfill should be reduced progressively so that by 2016 the
amount (by mass) of biodegradable municipal waste should not be more than 35 % of the mass produced in
1995. These targets will be achieved in part by composting and separation and recycling of waste. Sludge for
landfill disposal should be stabilized (for instance, by aerobic or anaerobic digestion or by composting or lime
stabilization or by acid treatment) to remove the rapidly biodegradable fraction and dewatered because liquid
waste is unacceptable according to Article 5.3 of the Landfill Directive. However, under Article 2 (q), liquid
waste is defined as any waste in liquid form including wastewaters, but excluding sludge.
4.2.3 Gases
The pore spaces of inert or slowly reactive solid waste arriving at a landfill normally contain a gaseous mixture
close to that of the atmosphere, that is 79 % nitrogen and slightly less than 21 % oxygen, with the balance
composed principally of carbon dioxide and trace amounts of other gases. The pore gases of putrescible
waste can reflect rapid decomposition, in terms of reduced oxygen and increased carbon dioxide levels before
deposition in the fill. The pore gases in and around sewage sludge will contain some methane and hydrogen
sulfide (and other odorous compounds) as well as carbon dioxide. Sludge addition to an MSW landfill can
accelerate gas production and stabilization of the landfill by a bioreactor effect (see [1]).
4.3 Processes
4.3.1 Microbiological activity
The breakdown of natural organic substances and certain man-made compounds is achieved largely through
the activity of various microorganisms which consume the materials as food sources and, in so doing, release
soluble and gaseous waste products and energy in the form of heat. The organisms can be aerobic, i.e. they
require the presence of free oxygen (O gas) for their metabolic processes or they can be anaerobic, when
2
they gain their energy from the dissociation of compounds in the absence of free oxygen. Some organisms
are strict aerobes or anaerobes and can operate only in one mode, but some microorganisms are able to
switch from one form of respiration to the other. The breakdown processes can release directly into solution
elements and compounds which form part of the original material, whilst waste products of this metabolism
can encourage the dissolution of other materials, for example, by producing acidic conditions.
The incorporation of anaerobically digested sludge into a landfill represents an inoculum of bacteria which
may accelerate anaerobic biodegradation within the landfill. This will be advantageous if the landfill is being
run as a flushing bioreactor and by increasing the rate of stabilization within the landfill, the sludge can shorten
the time to safe closure and completion of the landfill. Some authorities consider that if this concept becomes
reality, the use of sludge will play an integral part in its design and operation (see [2])
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4.3.2 Solution/precipitation
The direction of chemical reactions between the waste components and the liquids moving through the waste
(leachate) is controlled by factors such as the relationship between the solubility of elements and compounds
and the pH value and of their responses to Eh changes, that is the presence or absence of free oxygen
(oxygenated systems have a positive Eh values, reducing systems a negative Eh). As an example, the
solubility of many metals is increased as acidity rises (pH values fall to below 7,0), whilst iron is relatively
soluble when reducing conditions are present (negative Eh value), but far less soluble in oxygenated
environments (positive Eh). The physico-chemical conditions within landfilled waste change during the
breakdown and stabilization process (described below) and elements and compounds which are dissolved at
one stage in the lifecycle of a landfill can become immobilized by precipitation at another stage, and vice
versa.
4.3.3 Volatilization
The conversion of liquids (or occasionally solids) to the gaseous state is encouraged by increased
temperatures. Microbiological activity can raise the temperature within a waste mass from the average ground
temperature of about 10 °C to values in the range 30 °C to 40 °C or more if the waste layer is very thick.
Consequently, the gaseous mixture within the waste mass can contain not only the gases produced by the
breakdown or organic matter, but water vapour and volatilized hydrocarbons, solvents and similar compounds
derived directly from waste materials.
4.3.4 Sorption reactions
Two groups of processes can be involved:
absorption, in which liquid is stored in the pores of the solids, but from which it cannot drain under gravity.
The liquid and its dissolved content can be released from the pores if the material is compacted
(squeezed) and the liquid can be removed from the pores by evaporation, leaving behind the originally
dissolved components;
adsorption, in which elements and compounds are immobilized by becoming attached to the surface of
the solids. Many organic compounds in solution or emulsion will attach themselves preferentially to stable
organic solids (humic substances, for example), whilst many clay minerals (and other minerals with layer-
lattice molecular structure) exhibit the property of base exchange in which cations in solution (for example,
metals, ammonium ions) exchange with other cations which form part of the mineral structure. The effect
can be reversible so that a cation which has been removed from solution could be released back into
solution if the physico-chemical conditions change.
4.3.5 Filtration
A landfilled mass of waste is a coarse, heterogeneous, granular deposit in which liquids and gases move
through pore spaces. The liquids can carry particulates in the form of fragments of material detached by decay
processes, precipitates and microbial organisms. Removal of particulates from transport by filtration in pore
throats can take place, more particularly as the waste decays and collapse of the larger voids leads to
compaction and a reduction in the average pore size. The movement of liquids in landfills is predominantly
vertically downwards, in response to the gravitational field, and the blinding of pores in the lower parts of
landfills contributes to the progressive reduction in hydraulic conductivity of waste with age and depth of burial.
4.4 Outputs
The principal outputs for a landfill containing biodegradable waste are summarized in Figures 2 and 3. An
initial aerobic stage (Phase I) is short-lived. Aerobic bacteria begin the breakdown of organic materials and in
so doing consume oxygen and release carbon dioxide and water. Aerobic degradation is metabolically
vigorous and a rapid rise in temperature of the waste mass is possible. Once the free oxygen has been
consumed, anoxic conditions set in (Phases II and III) and organically strong leachates are produced. The
methanogenic bacteria which become active as the wastes move from Phase II into Phase IV are sensitive to
pH and become inhibited at values below about pH 6,4. Waste which has partly degraded retains a significant
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buffering capacity and it is probable that methane generation in landfills involves a two-part process, with
acetogenesis (production of acetic acid which the methanogenic bacteria can convert to methane, carbon
dioxide and water) taking place within the more recently deposited waste and the methane production being
carried out in zones of partially degraded materials with higher buffering capacity. In Phase IV, fully anaerobic
conditions become established and the removal of carbon from the waste as methane and carbon dioxide in
landfill gas becomes at least as important as removal in the form of dissolved organic compounds in the
leachate. Finally, exhaustion of the biodegradable components allows the progressive re-establishment of
aerated conditions (Phase V). At the end of this phase, the production of landfill gas and contaminated
leachate ceases and the site becomes finally stabilized.
At the same time that carbon-based compounds are transformed into dissolved or gaseous components within
the landfill reactor, inorganic materials contribute to the composition of the leachate (Figure 3). The variations
in concentrations with time can be related primarily to their solution coefficients or be governed by changes in
Eh/pH conditions within the waste. These latter conditions are strongly influenced by the microbiological
activity in the waste. Examples of the behaviour of different types of contaminants can be illustrated by:
1) chloride, which is a mobile but persistent element. Maximum concentrations are likely to be reached
during the earlier stages of stabilization as a result of direct dissolution and then to decrease with
time through flushing from the wastes;
2) ammonia, which arises largely from the breakdown of proteinaceous material. High values are likely
to be reached early in the life of the fill, but then decrease relatively slowly compared with chloride.
The ammoniacal nitrogen forms an essential building block of the microbiological protein and is
conserved and cycled within the waste. In Phase V, the ammonia concentrations decrease finally as
a result of the extinction of anaerobic microbial activity. Residual ammonia is likely to oxidize to
nitrate.
3) heavy metals, which are of generally low solubility in neutral or alkaline solutions. Maximum
concentrations are likely to be recorded during the Phases II and III when high rates of fatty acid
production lead to low pH (acid) conditions.
The composition of leachates is such that they can be both polluting and toxic. The principal environmental
pollution threat in the short term arises from the high levels of dissolved organics which can deoxygenate
waters and lead to the destruction of fauna and flora. The high concentrations of ammoniacal nitrogen pose
specific threats to fish life. The processes and reactions that produce leachate are progressive and,
consequently, the composition and strength of leachates change with time. The organic strength of leachate
from fresh waste is greater than that from aged waste, and the ratio of total dissolved carbon to degradable
carbon increases as waste ages and moves into phase III of degradation (Figure 2). However, many modern
landfills evolve rapidly to phase IV in which a high proportion of the dissolved carbon is converted to gaseous
components, with the result that the organic strength (measured as COD, BOD, TOC or Fatty Acids - (TVA or
VFA)) decreases very significantly with levels of ammoniacal nitrogen remaining high.
All micro-organisms require water for metabolic purposes. Although some micro-organisms present within
landfills are able to move actively through the waste mass, many forms are attached and only able to migrate
through, and to colonize the waste mass, via water films. The distribution of bacterial populations in waste, as
delivered to landfills, is non-uniform and heterogeneous. If the flux of water through the wastes is not sufficient
to allow migration and general colonization by the micro-organisms, degradation can be only partial, with
zones of waste remaining in an undegraded state for prolonged periods, but retaining a potential to degrade at
some future time. Incorporation of sewage sludge, with its large population of microorganisms and its moisture
content, can counter this effect.
NOTE A nationwide survey of landfills for the UK Department of the Environment (see [3]) considered sites which
included significant proportions of industrial waste and at which leachates from different parts of sites (and thus of different
age) could mix. Very detailed analyses of leachates were made at selected sites and the results are summarized in
Table B.1.
Compared with leachate and landfill gas, the data set describing the way in which residual solids change as
the landfill processes progress to their end points is practically non-existent. However, it can be postulated
that the end product of the process is likely to be a material similar in overall composition to that which forms
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naturally when inorganic and organic materials are deposited together. If that is the case, then the final
material would be expected to comprise a compacted framework of resistant minerals (silicates, oxides,
carbonates and sulfates) containing resistant organic residues (humic material). In the natural analogue, the
resistates could be gravel, sand silt and clay grade minerals and rock fragments, including limestones
(carbonates) with the organic material present as disseminated or aggregated peat or lignite. In the case of a
landfill, the resistates could comprise natural (soils, sediments and rock included in the waste streams) and
artificial (glass, brick/pottery, persistent plastics, rusted iron) forms. The biodegradable components of the
waste are likely to show a range of rates of decay similar to those found for organic materials entering soils.
Compared with soil organic matter, studies by Jenkinson and Rayner (1977) (see [4]) indicate that there are
few data on the biodegradability of the components of Municipal Solid Waste (MSW – household and
commercial waste streams). However, research at the Polytechnic of East London (1992) (see [5]) suggested
that the components of MSW could be classified in terms of biodegradability into:
readily degradable – vegetable and putrescible and part of the fines < 20mm fractions ~18 % by mass;
moderately degradable – parts of the vegetable, paper and card and fines < 20mm fractions ~12 % by
mass;
slowly degradable – textiles, most paper and card ~31 % by mass.
The remaining 39 % (unclassified, metals, plastics, glass, non-combustibles, fines < 20mm) were classed as
inert. There is no formal direct correspondence between the classifications of soil organic material and MSW,
but it is suggested that the readily degradable fraction of MSW can be considered equivalent to DPM, the
moderately degradable to RPM and the slowly degradable part to PSO.
Key
x Time
y Percent by volume/maximum value
P Phase
L Landfill gas production
S Settlement
Figure 2 — Schematic representation of the evolution of organic components of landfill leachate and
gas
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