CR 13097:2001

SLOVENSKI STANDARD
01-december-2001
Karakterizacija blata - Dobra praksa za uporabo v kmetijstvu
Characterization of sludges - Good practice for utilisation in agriculture
Charakterisierung von Schlämmen - Gute Praxis bei der Verwendung von Schlämmen in
der Landwirtschaft
Caractérisation des boues - Bonne pratique de la valorisation des boues en agriculture
Ta slovenski standard je istoveten z: CR 13097:2001
ICS:
13.030.20 7HNRþLRGSDGNL%ODWR Liquid wastes. Sludge
65.080 Gnojila Fertilizers
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

CEN REPORT
CR 13097
RAPPORT CEN
CEN BERICHT
August 2001
ICS
English version
Characterization of sludges - Good practice for utilisation in
agriculture
Caractérisation des boues - Bonne pratique de la Charakterisierung von Schlämmen - Gute Praxis bei der
valorisation des boues en agriculture Verwendung von Schlämmen in der Landwirtschaft
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 13097:2001 E
worldwide for CEN national Members.

Contents
Foreword.3
1 Scope .4
2 References.4
3 Terms, definitions and abbreviated terms .5
4 Requirements .5
4.1 General.5
4.2 Preliminary procedures.6
4.3 Quality control (including environmental and agronomic data) .9
4.4 Assuring hygiene when sludges are used in agriculture .12
4.5 Operation .13
4.6 Promotion of agricultural use.18
4.7 Support procedures.19
Annex A Examples of national regulations concerning hygiene.21
Annex B Hazard analysis critical control point (HACCP) .23
Bibliography .24
Foreword
This document has been prepared by CEN /TC 308, "Characterisation of sludges".
This document is currently submitted to the BT for publication as a CEN Report.
The status of this document as CEN Report has been choosed because the most of its content is not completely in
line with practice and regulations in each member state. This document gives recommendations for a good practice
but existing national regulations concerning the sludge utilisation in agriculture remain in force.
1 Scope
This CEN Report describes good practice for the use of sludges in agriculture (where national regulations permit).
It is applicable to all of the sludges described in the scope of CEN/TC 308 (and any of the forms in which they may
be presented - liquid, dewatered, dried, composted, etc.) i.e. 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.
Such sludges can be used on land as a source of plant nutrients, and/or soil improver, and/or liming material for
crop production. Despite differences in the statutory controls between sewage sludge and other sludges, the use of
all types of sludge should follow good practice to maximise benefits for the crops or soils, to minimise potential risks
of environmental contamination and adverse impacts on plant, animal and human health, and to ensure
sustainability and cost-effectiveness.
Sludge producers should be aware that if a sludge is used as a fertilising or liming material, national or EC fertiliser
or liming regulations may apply.
The document assumes that an evaluation has already been made and a decision taken that use of sludge within a
land spreading policy is the best option for the sludge in question.
NOTE For evaluation and decisions for use of sludges, other documents are currently in development (see CR 13174).
Many countries and/or local administrations have regulations and/or standards and/or codes of practice applicable
to the use of some of the types of sludge that are within the scope of this report, however it cannot, and does not,
attempt to summarise or take account of these regulations, etc. because of their very wide range. It is thus
essential that this report is read in the context of the conditions that prevail locally.
2 References
EN 1085, Wastewater treatment – Vocabulary.
EN 12832, Characterisation of sludges – Utilisation and disposal of sludges – Vocabulary.
CR 13174, Characterisation of sludges - Sludge management in relation to use or disposal.
CR 13846, Characterisation of sludges – Recommendations to preserve and extend sludge utilisation and disposal
routes.
3 Terms, definitions and abbreviated terms
For the purposes of this CEN Report, the following terms and definitions given in EN 1085, EN 12832 and EU
Directive 86/278/EEC and the following apply.
3.1
potentially toxic element (PTE)
an inorganic substance which, when present in excess and in forms that are available to the subject in question,
can be toxic
3.2
BPEO
Best Practicable Environmental Option
4 Requirements
4.1 General
The purpose of this CEN Report is to assist sludge utilisation operations to :
a) achieve compliance with 86/278/EEC and/or any other environmental legislation or codes or practice which are
relevant to the type of sludge or to the locality ;
b) gain and maintain the confidence of users, authorities responsible for monitoring regulatory compliance, food
purchasing and/or processing companies and third parties which (amongst others) include members of the
public ;
c) make maximum use of the valuable constituents in the sludge ;
d) have a long term secure future at minimum cost consistent with the above.
Considerations of treatment, source control of pollutants and preparation of sludges are discussed in CR 13174.
The widely recognised waste management hierarchy recommends that, in general, the use of sludge (e.g. by
spreading on land within an environmental protection programme) as preferable to disposal options such as landfill.
Where agricultural land is available and conveniently accessible, this is usually the Best Practicable Environmental
Option (BPEO).
Sludges usually contain nutrients, organic matter and trace elements, which are beneficial to the growth of crops
(including grass) and to the fertility, structure and/or texture of soils. They are valued by farmers. Sludges may
contain contaminants, and/or pathogens, and may be odorous. Consequently, the whole process (from source
control of potential pollutants, through sludge treatment, to sludge application and the way the land is farmed)
should be controlled to avoid adverse impacts on the environment, or on plant, animal and human health. Such
safe controlled use of sludge on land can be considered a component of sustainable development.
Many European countries have developed guidelines and regulations for the safe use of sewage sludge. These
have been placed on a common statutory basis in the European Union through the implementation of the EU
Directive 86/278/EEC which requires certain limit values for PTEs in soil and sludge. Other EU legislation
encourages the utilisation of suitable industrial sludges on land provided measures are taken to avoid endangering
human health or harming the environment (91/156/EEC amending Directive 75/442/EEC on waste). However,
unlike the situation for sewage sludge, there is little detailed information available and there is less legislative
control for these other sludges. In the past the emphasis has been on preventing chemical pollution, but whilst this
is still essential, the modern agenda also includes hygiene, and the need to demonstrate safety through quality
assurance and independent validation.
In order to establish and maintain cost-effective, safe and sustainable operations using sludge in agriculture,
certain procedures should be established for effective operational management, to meet legal requirements and to
address the concerns of stakeholders.
This document has been written in an order that attempts to reflect the logical steps of a successful (which also
means sustainable) sludge utilisation operation. It starts with the initial steps in designing an operation, and then
considers the quality control, design, etc., before moving on to the day-to-day operations. Although marketing
(finding outlets) and support are also continuing activities they are treated in separate sections because they are
general and not particular to each individual outlet. Despite this linear structure, continuous improvement is
recognised as an important component, which therefore implies the cycle of design, operate, review, refine,
operate, review, etc.
4.2 Preliminary procedures
4.2.1 General
This section discusses the more significant procedures and considerations for setting up a new programme to use
sludge in agriculture or modifying an existing one. These would include understanding the relevant regulations
within which the sludge will be used, the quantity of the sludge, the quality of the sludge, whether there are
programmes for ensuring sludge quality, and whether there would be demand for the sludge; including whether
there are competing materials, e.g. animal manure.
4.2.2 National regulations
In the case of sewage sludge, national regulations set maximum permissible quality standards for the receiving soil
and may set standards for the sludge. The specific values and combinations of control mechanisms vary between
countries, and a combination of sludge, waste management, water and general environmental regulations may
apply. Few if any countries have comprehensive regulations to control all sludges that may have similar
environmental impacts. Those using sludges should make themselves aware of the regulations that apply in the
areas where they are working. CEN/TC 308 has compared and discussed different sludge treatment operating
parameters in CEN Report CR 13846.
4.2.3 Voluntary agreements
In some states some sludge producers have gone beyond national regulations by voluntarily entering agreements
with interested parties (such as food retailers and processors, farmers and landowners). These agreements have
addressed the question of perception and increased the acceptance of using sludge in agriculture. Any applications
of sludge should be consistent with these agreements.
4.2.4 Quality assurance
It is recommended that there should be a quality assurance system for the whole process from source control of
potential pollutants, through sludge treatment and spreading, and finally to how the land is farmed. To prove
transparency and ensure the confidence of stakeholders, it is desirable that this is validated by independent audit.
The principal criteria should include :
a) sludge quality, particularly :

control of potential pollutants from point sources ;

sampling and analysis strategy to monitor sludge quality for the concentrations of specified PTEs, and in
some cases other contaminants such as persistent organics ;

treatment of sludge to significantly reduce its content of pathogens and its fermentability (i.e. potential to
produce bad odours) ;
b) soil quality, particularly :

a soil sampling strategy to monitor soil quality for the concentrations of specified PTEs, often in relation to
certain soil conditions, such as pH soil type and content of organic matter and/or cation exchange
capacity, in order that limit values are not exceeded ;
c) sludge application rate, particularly :

the average quantity of PTEs that can be applied to the land and over what period, usually in terms of kg
PTE/ha/y (or multiple of years), or mg PTE/kg nutrients ;

the amount of sludge dry solids that can be applied per year or multiple of years ;

the quantity of nutrients which can be applied, particularly nitrogen, and phosphorus in accordance with
the types of crop grown ;

the timing of and method of applying the sludge and after-use of the land and crops; these are generally
designed to protect animals and food consumers from pathogen transfer, and/or conserve plant nutrients,
and/or reduce the risk of run-off.
It is a general legal requirement for sewage sludge that appropriate records are maintained which in addition to the
above criteria, should include information on sources and quantities applied and the location of the receiving land.
However most countries do not yet require the same rigour for other sludges, even though they may have
environmental effects similar to sewage sludge.
4.2.5 Strategic evaluation
In order to launch a sludge utilisation programme, a strategic exercise should be undertaken in order to evaluate its
probable viability and sustainability within the area of land that is being considered for sludge recycling. This is
particularly important where there has been no previous experience of using sludge, or when introducing a new
sludge product. A two phased approach should be adopted :
a) firstly, a comprehensive evaluation of the whole sludge strategy should be undertaken, employing Best
Practicable Environmental Option (BPEO) methodologies. This would test the security, practicability and
economic viability of a proposed operation in an objective manner. Such evaluations would cover a wide range
of factors that would probably include many of the following which is neither exclusive nor in an order of priority :

the area of land that might be available ;

the possibilities for temporary storage, if necessary ;

farming practices and other relevant land use information ;

the use of lime and fertilisers ;

what other "competitor" materials are available and their quality and quantity ;

national and local legislation and controls that would affect the operation of the proposed sludge use
programme ;

the reaction of farmers' organisations, the food industry and other stakeholders ;

the management and organisation of the sludge production plant ;

sensitive zones (surface and ground water protection, housing, etc.) ;

soil (type, quality, trafficability, nutrient status and pollutant content) ;

sludge type, sludge quality, sludge quantity ;

climate, e.g. is there a rainy season when trafficability is low or a long frozen period when sludge
application can be prohibited ;

topography, roads, bridges, etc. to evaluate access ;

consultation with a wide range or organisations to check the environmental and practical sustainability of
the proposed sludge use programme ;

the type of sludge that might be produced (e.g. liquid, dewatered, dry, compost, digested, limed, etc.) by
varying the production or treatment process, that is the most appropriate for a sustainable sludge use
programme, bearing in mind the whole life cost of the alternatives ;

the size, structure and location of storage facilities ;

some countries may require public consultation on the intention to start a sludge utilisation programme
that will involve advertising the intention and consulting with municipal administrations ;
b) secondly, as an extension to a best practicable environmental option (BPEO) study, or as a separate exercise
where sludge use programmes have been initiated or are ongoing, it is crucial to understand the potential
customer base, its business needs, and how the proposed sludge use programme can satisfy these needs.
This should be done using the whole marketing mix to test whether there will actually be a market for the
sludge.
4.2.6 Sludge quality
The preliminary stage should develop a methodology for controlling, monitoring, improving and maintaining sludge
quality. The quality of sludge is crucial for its safe and beneficial use, for its "marketability", and for the sustainability
of sludge use programmes. This will invariably require a rigorous source-control programme. A range of chemical,
physical and microbiological quality criteria is important for compliance with legislation, for providing agronomic
value, and for it to be aesthetically acceptable.
In the case of sewage sludge it is important to ascertain at the preliminary stage whether there is enabling
legislation and an effective system for controlling discharges from factories to the sewerage system or whether
such control at source can be implemented. A wide range of contaminants may be found in some sewage sludges
due to discharges from industries, dwellings and surface drainage into sewers. Soil with an active microflora is
capable of breaking down many organic compounds found in sludges. Experience has shown that, when sewage
sludge has been used in compliance with the current controls over loading rate and use established in 86/278/EEC,
no detrimental impact has been detected. For other sludges comparable systems should be designed to prevent
excessive contamination from entering the sludges. They include animal manures, food processing and abattoir
sludges, industrial residuals (e.g. paper, etc.). They may contain significant concentrations of PTEs (and/or
pathogens) but as most countries impose fewer controls on these materials than sewage sludge, the use of these
materials on land should be taken into consideration when sewage sludge is applied to avoid over-application of
PTEs and nutrients. It is important to recognise that agricultural land receives inputs of potentially harmful
compounds from other sources, such as atmospheric deposition, traffic emissions, animal manures, inorganic
fertilisers and crop protection chemicals.
Some waterworks sludges can be beneficially applied to land to use their contents of organic matter and/or lime, or
even to modify soil texture. However there are some waterworks sludges that have negligible soil enhancement
value. Waterworks sludges generally have a low content of N, P or K. These sludges result from the treatment of
surface or ground waters. Their contents of PTEs and other contaminants are generally low. They are useful when
soil improvement by the addition of organic matter or textural modification (e.g. adding silt to excessively drained
coarse textured soils) or soil pH adjustment (by liming) are required but major plant nutrients are not needed.
In regard to the microbiological qualities, it is not practicable to undertake frequent monitoring for specific
pathogenic organisms because levels present may be extremely low and difficult to detect. As has been adopted
for drinking water microbiology, some monitoring of suitable indicator organisms such as E. coli may be a
preferable way of verifying that the overall processes of treatment and use provides effective microbiological
barriers. For sludges that present a hygiene hazard, it is desirable to identify an indicator organism (not necessarily
pathogenic) that is naturally present in large numbers in the sludge and that has a susceptibility to treatment similar
to the pathogens that are of concern. As an example, in the case of materials with faecal origin, E. coli has proved
an effective indicator because it is always present in large numbers in untreated material and it has similar die-off
characteristics to the pathogenic organisms (such as Salmonella) that are of concern.
An example of a quality control technique is outlined in Annex B.
4.2.7 Sludge type
Dewatering, drying, lime treatment, nutrient addition, composting and other processes may be beneficial to improve
the properties of the sludge for its use in agriculture. Physically the material should be capable of easy storage and
application. It should be treated to minimise the possibility of odour emission so that the farmers’ requirements are
addressed. Sustainability may be enhanced by use of the appropriate treatment and application techniques.
4.2.8 Design of the sludge utilisation programme
Before commencing a sludge utilisation programme, the overall design, infrastructure, procedures and resourcing
should be considered. Many of the components are discussed later in this document. They will include the
capacity, design and siting of storage facilities, with their relevant equipment (stirring, access, recovery, etc.),
vehicles and their servicing, spreading equipment, labour, computer hardware and software. Consideration of these
should take account of the locally prevailing regulations.
4.3 Quality control (including environmental and agronomic data)
4.3.1 Process control
As described in Annex B, rigorous control at certain critical control points in the production and recycling process,
backed up by the verification of independent audit will ensure the safety of sludge recycling and the confidence of
important stakeholders. The control points and their critical values need to be identified and evaluated for each
particular sludge processing and recycling example.
4.3.2 Sludge sampling and analysis
Sludges and sludge products should be sampled and analysed in order to :

provide reliable information to customers ;

satisfy regulatory requirements ;

confirm that process controls are effective.
The frequency of sludge sampling and analysis should be appropriate to the size of the production plant and any
anticipated fluctuation in quality. Plants producing large quantities of sludge, and plants where there is a variety of
inputs and where varying quality is expected should be sampled more frequently. In general, sludge should be
analysed at least every six months, based on composite samples derived from representative sub-samples.
The method of sampling sludge should be evaluated carefully to ensure that the samples are representative of the
quality of the sludge that is actually applied to land. This is particularly important for accurately measuring dry solids
content, and the sludge should be well mixed prior to sampling.
The quality of certain industrial residuals for land spreading may vary substantially from batch to batch which
should be taken into account in the sampling regime in order to ensure that representative samples are obtained.
The parameters that should be measured routinely in sewage sludge for compliance with regulations and to
provide agronomic advice are :

dry matter ;

loss on ignition (which is used as an approximation of organic matter) ;

pH ;

total nitrogen ;

total phosphorus ;

zinc ;

copper ;

nickel ;

cadmium ;

lead ;

mercury ;

chromium.
Some countries may require additional determinants to be analysed. It may be desirable to monitor the
concentrations of other constituents, where these are known to occur in significant concentrations or would be
useful in evaluating agronomic quality. In some circumstances, or for some sludges, analysis to comply with
national or EU fertiliser or liming regulations may be required in some countries. Whilst control of microbiological
risk is best achieved by critical control point (Annex B), monitoring is also appropriate to prove the continuing
effectiveness of the control. Some examples of these additional parameters are :

ammoniacal nitrogen ;

available phosphorus ;

potassium ;

magnesium ;

calcium ;

sulfur ;

sodium ;

manganese ;

molybdenum ;

boron ;

organic micro-pollutants ;

selenium ;

arsenic ;

fluoride ;

cobalt ;

neutralising value.
Other sludges should at least be analysed for nutrients and organic matter to determine their agricultural benefit.
Whilst the risks have been well characterised for sewage sludges, some other sludges may be less well
understood, the process by which they are produced and the possible contaminants etc. that may be in the sludge
should be assessed to decide on the need for monitoring other parameters.
Standard methods of sampling and analysis should be followed where they are available. A permanent record of
the information should be maintained, and copies should be provided to the recipients of the sludge.
4.3.3 Maintenance of sludge quality
Litter in sludge that is spread on the land should be avoided by effective screening during the treatment process.
Operational parameters (e.g. digester temperature) should be measured and recorded to ensure that appropriate
quality and also traceability is maintained. Aspects of sludge treatment to ensure hygiene are dealt with in 4.4.2.
Personnel involved with sludge utilisation programmes should liaise with the sludge producer (and, in the case of
sewage sludge, those involved in industrial effluent control) regarding the maintenance and/or improvement of
sludge quality for :

sludge stability and odour ;

consistency of analyses with respect to constituents of agronomic benefit ;

the content of PTEs and/or organic pollutants.
4.3.4 Soil sampling and analysis
Many countries require that soils are sampled prior to sewage sludge being applied for the first time to establish
baseline concentrations of PTE's (some require that nutrients are also measured), and then at specified
frequencies to monitor the gradual increase in soil concentrations following repeated applications of sludge. Others
have decided from their soil mapping and inventory that this is unnecessary (at least in certain areas) because the
concentrations in soil are already known to be very low, and/or the PTEs applied do not exceed an amount similar
to that in manure.
When sludge is applied to land repeatedly over many years, PTEs may accumulate in the soil, and if this were
permitted to continue unchecked, concentrations could possibly be reached that could cause adverse effects to
plants, animals or humans eating food produced on sludge treated soils. In the case of sewage sludge, regulatory
limit values have been set for PTEs in Directive 86/278/EEC, these are well below the adverse effect thresholds,
and they should be complied with and confirmed by soil sampling and analysis.
The method of soil sampling should comply with that described by ISO/TC 190 on Soil Quality.
Parameters which require monitoring to comply with 86/278/EEC are :

pH ;

zinc ;

copper ;

nickel ;

cadmium ;

lead ;

mercury ;

chromium.
Individual countries, regions or areas may require additional parameters.
It may be advisable occasionally to monitor other PTEs, such as molybdenum, arsenic, selenium and fluoride,
particularly in areas that may have naturally high background soil concentrations and where the land is used for
grazing or forage production.
Soil analyses ensure compliance with statutory limit concentrations, but because each application of sludge can
add only very small quantities of PTEs, monitoring over an extended period is advisable and is addressed by
states’ regulations. Frequent sampling may be advisable depending on the concentrations of PTEs in the sludge
and how close soil concentrations are to their respective limit values, or how close they are predicted to be based
on the cumulative loading to date. Some countries, regions or areas may specify a frequency for soil sampling.
Soil analyses should be compared with the theoretical calculation of soil concentrations, based on sludge quality
and rate of sludge application. This information should be used (from time to time) to readjust the model of how
many applications of sludge the land can be permitted to receive before it approaches the limit value of the most
limiting PTE. It can also be used to allow calculations of steady state levels of PTEs to avoid further accumulation
in the long run.
4.4 Assuring hygiene when sludges are used in agriculture
4.4.1 General
When sludges are used in agriculture for their beneficial constituents and effects, consideration should also be
given to the overall hygiene of the process. As has been stated before, Europe has a model for protecting hygiene
in its regulations for the use of sewage sludge in agriculture. This established a dual barrier approach. One barrier
is provided by sludge treatment and another by specifying intervals between sludge application and crop harvest or
grazing. Incorporating sludge into soil can also provide a barrier.
The benefits of an approach (such as HACCP) to designing and operating sludge treatment and use have been
outlined in Annex B. Such approaches place the emphasis on controlling operations rigorously and using the
results of quality control sampling and analysis to confirm that the operation of the control points has been
effective.
The health of people involved in treating and using sludge should be protected by educating them in the need for
relevant hygiene precautions including personal protective equipment (overalls, boots, gloves, etc.).
4.4.2 Hygiene control by treatment
The conditions in wastewater treatment processes are generally not favourable to the survival of many pathogens
and at each step in the process there may be some reduction in numbers. To ensure a large reduction in pathogen
content to guarantee it generally requires that the sludge is subjected to elevated temperature for a specific period
(e.g. 70C for 30 min), and/or the sludge is subjected to a pH that is lethal to pathogens (e.g. pH<4 or pH>12),
and/or the moisture content is reduced to a specified value (e.g. 10%).
Some treatment processes minimise the pathogen content of sludge prior to, or in combination with, biological
stabilisation; this ensures that there is an active population of competitor organisms that would prevent
recolonisation if there were subsequent pathogenic contamination. Two examples of this type of treatment are
composting and thermal treatment prior to anaerobic digestion. Treatments such as drying or lime stabilisation
create conditions that are chemically or physically unfavourable to recolonisation.
CEN/TC 308 has compared and discussed different sludge treatment operating parameters in CEN Report
CR 13846. See also Table B.1, which compares the sewage sludge treatment operating standards that have been
adopted in UK and USA.
4.4.3 Hygiene control by application and relating sludge type to land use
Application techniques and timing of application are both barriers to the possible transfer of pathogens.
Incorporating sludge into soil may provide a barrier. Directive 86/278/EEC stipulates that grass or forage crops
should not be harvested or grazed until at least 3 weeks after land has been treated with sewage sludge. It also
states that fruit and vegetable crops that are normally in direct contact with the soil and normally eaten raw should
not be harvested for at least 10 months following treatment of the soil with sewage sludge. These are minimum
standards for members of the EU. Countries have set their own protocols for relating types of sewage sludge to the
ways that land may be safely farmed appropriate to their local climatic and farming conditions See also annex A
which states some national regulations exemplary. As it is shown in Annex A it is usual to combine timing or
prohibition of application and quality control of the sludge with special cultures. To protect people, animals and
plants of disease transmission, controls have to be operated correctly. There have been no proven cases of
disease transmission as long as these controls have been operated correctly.
It is also very important that the information about farming, harvest intervals, etc. are effectively communicated to
the farmers whose land has been treated.
As CEN members may have set more stringent or more detailed standards for sewage sludge, it is strongly
recommended that these protocols are adopted for all sludges.
4.5 Operation
4.5.1 General
This section discusses the day-to-day operation of a sludge utilisation programme. It is useful to develop a
"beneficial use culture" amongst everybody involved with sludge utilisation as opposed to a "disposal culture".
Adopting a beneficial use culture means that people think about sludge as a material to be used (not disposed)
which in turn militates for environmental protection and against pollution.
4.5.2 Communication strategy and public relations
Communication is an important part of any successful sludge utilisation operation so that customers can make best
use of the beneficial constituents and avoid any adverse effects and to satisfy the requirements for information by
other people. This communication strategy is partly day-to-day and partly a more strategic activity (see also 4.6).
4.5.2.1 Communication with farmer-customers
Farmers who are well informed about the benefits of sludge and receive the quality of service promised, are more
likely to be regular customers. Establishing "repeat business" should be a priority for operational security and cost-
effective operation. The provision of sound and objective agronomic advice should be an integral part of efficient
sludge use programmes and ensuring customers' satisfaction. To achieve this, marketing and quality control staff
involved in customer contact should be well trained in agronomy and/or specialist schemes where they are
available.
Before spreading, and within the framework of a forecast programme, local regulations may require the sending of
documentation to customers informing them on the agronomic quality of the sludge to be applied, as well as the
quantities to be made available for their application.
After the sludge has been applied, local regulations may require that information is sent to customers about the
sludge with which they have been supplied. The directive (86/278/EEC) requires sewage sludge producers to
regularly provide users with all the information referred to in Annex II A (i.e. the sludge analysis).
4.5.2.2 Consultation with others
In some countries and locations, prior to the application of sludge to an area of land, consultation with various
organisations responsible for the environment, waste management, infrastructure, etc., and other interest groups
may be necessary or desirable. The necessity depends on the locality and is intended to ensure compliance with
any restrictions placed on the land, or transport routes to the land, and that there are no conflicts with local
inhabitants. Where it is found to be desirable, consultation should be part of routine operations as and when
needed.
The types of responsible organisations to be consulted will depend on national and local conditions, and legislation,
and therefore will vary between countries and possibly even between local areas or regions. The following are
examples of possible constituents of a consultation programme (written in no order of priority) :

groundwater and surface water are protected. The consultation should establish whether the proposed land for
sludge application lies within an exclusion zone or sensitive area, that would prevent or restrict either the
quantity or timing of sludge use ;

agricultural organisations, farmers' unions, etc. ;

sites of special scientific or environmental interest are protected - this could prevent or restrict sludge
applications ;

appropriate routes for sludge transport are selected, avoiding weight restricted bridges,

built-up areas, narrow roads, etc., as necessary. Sludge transfer points are selected to avoid obstructing the
highway or creating a hazard ;

the proposed method of delivery, storage and application of sludge does not conflict with local waste
management and environmental health plans and policies ;

there are no conflicts with neighbouring sludge recycling programmes ;

local authorities are kept informed of sludge spreading operations.
4.5.3 Operational planning
A method of planning the work is necessary to ensure that there is a balance between the rate of sludge production
and the demand created amongst customers. There should also be a balance between the spreading resource, the
time available for spreading, the quantity to be spread, and the storage facilities.
4.5.4 Storage
Storage of either liquid or dewatered sludges is often required as a part of the sludge treatment process. Storage
may also be a strategic necessity in areas where the availability of agricultural land is not continuous, due to
legislated restrictions of spreading periods, local cropping practices, adverse weather, etc. Where storage forms
part of the treatment process, adequate assurance (supported by monitoring) should be put in place to ensure the
required level of treatment is achieved. The individual countries, regions or localities may have different regulations
on storage.
Liquid sludge is generally stored in tanks or lagoons at the production plant, or may be stored in on-farm lagoons,
or at some other site. Stirring or some other form of homogenisation of sludges may be required. Permission to
construct a lagoon may be required from local regulatory authorities, and this will generally require an impermeable
liner to prevent egress of sludge liquors into the soil. Lagoons should be securely fenced and should meet
standards for health and safety. Liquid sludge can be temporarily stored in mobile transfer tanks, to facilitate the
transfer of sludge from road transport to field application equipment (and should not be considered as storage).
This generally does not require any specific permission for use as a storage container. A device to warn against or
prevent over-filling is desirable.
Dewatered sludge may be stored on treatment plants on prepared hard-standings and is also commonly stored on
farmland (on a short-term basis) prior to application.
When choosing/evaluating a site for storage of sludge, consideration should be given to the risk of possible
leaching to groundwaters and run-off to surface waters. Consideration should also be given to the existence of field
drains, slopes that might result in the stockpile slumping (down slope) or being flooded (if it is in a valley bottom)
and other safety considerations. The possibility of odours should be taken into account and storage sites should be
chosen with regard to the level of stabilisation of the sludge.
The nutrient content of a sludge (especially nitrogen) and the availability of nutrients, may change during storage
and it may be necessary to evaluate this in the interests of giving good agronomic advice.
4.5.5 Delivery
Adequate supervisory methods should be put in place to ensure transport is undertaken responsibly.
Liquid sludges should be transported in enclosed tankers, usually fitted with an integral pump, or vacuum/pressure
system for efficient filling and discharge. Vehicles should be well designed and maintained to avoid spillages of
sludge on the highway and escape of odours.
Dewatered sludges are transported in lorries or skips, these should be fitted with covers, particularly if the sludge is
odorous or semi-fluid, and to prevent spillage.
All vehicles should be kept clean and well presented to avoid adverse public reaction, etc. The chosen route and
time should be those most likely to limit inconvenience to the population and damage to the road system. After
delivering sludge to a farm, any mud or sludge should be cleaned off the vehicle to avoid contaminating the road.
4.5.6 Application techniques
There are several techniques for applying sludge to land, and there are a very large number of manufacturers
supplying a wide range of equipment specifications. Liquid sludge can be applied to the surface of the land by
tanker or irrigation equipment, or may be applied sub-surface by injection. Dewatered sludges are applied by
manure spreaders. Dried sludges may be spread using bulk fertiliser, lime or manure type spreaders depending on
the quantity, target application rate and flowability of the dried sludge. Application equipment can be specialised
self-propelled units, conventional tractor-drawn tankers or manure spreaders, or liquid sludge may be supplied by
flexible pipe to an applicator or injector mounted directly to a tractor (umbilical system) or to a retracting reel
irrigator. Surface application of sludge is generally less expensive and technically less demanding than injection,
however spreading sludge on the surface may give rise to complaints, particularly if there is offensive odour. There
are several techniques for reducing odours to an acceptable level, the more important ones are:

increasing/changing the extent of treatment so as to reduce the odour to an acceptable level ;

cultivating the land as soon as practicable after application. If odorous sludge is left on the surface, particularly
during hot weather, a smell and/or fly nuisance may be created that may last for several days, and the
operator could risk prosecution ;

avoiding surface application of sludges with a high odour risk close to housing (or other sensitive areas) ;

using sub-surface injection for liquid raw sludge and near to dwellings, etc. ;

not using high trajectory sprayers, these could cause aerosols or mists that could drift for several kilometres.
Low trajectory splash-plate, boom spreaders and trailing hose applicators give rise to less odour during the
spreading operation.
For liquid sludges, subsurface injection into soil has a number of potential operational and agronomic advantages
over surface application of sludge, but the extra draught required can result in more wheel slip in wet conditions,
disruption to plant roots can cause die-back in dry conditions, and in stony ground rocks may be brought to the
surface. Apart from avoiding odour, loss of ammonia to the atmosphere is reduced, which increases the fertiliser
value of the
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