Characterization of sludges - Hygienic aspects - Treatments

This CEN Technical Report gives information about principles to be followed in different sludge treatment processes to reach specified hygienic requirements.

Charakterisierung von Schlämmen - Hygienische Aspekte - Schlammbehandlung

Caractérisation des boues - Aspects hygiéniques - Traitements

Le présent Rapport technique du CEN donne des informations sur les principes à suivre dans les différents procédés de traitement des boues pour satisfaire aux exigences spécifiées en matière d’hygiène.

Karakterizacija blata - Higienski vidiki - Priprava

General Information

Status
Published
Publication Date
25-Nov-2008
Current Stage
6060 - Definitive text made available (DAV) - Publishing
Due Date
26-Nov-2008
Completion Date
26-Nov-2008

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SLOVENSKI STANDARD
SIST-TP CEN/TR 15809:2009
01-maj-2009
Karakterizacija blata - Higienski vidiki - Priprava
Characterization of sludges - Hygienic aspects - Treatments
Charakterisierung von Schlämmen - Hygienische Aspekte - Schlammbehandlung
Caractérisation des boues - Aspects hygiéniques - Traitements
Ta slovenski standard je istoveten z: CEN/TR 15809:2008
ICS:
13.030.20 7HNRþLRGSDGNL%ODWR Liquid wastes. Sludge
SIST-TP CEN/TR 15809:2009 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST-TP CEN/TR 15809:2009
TECHNICAL REPORT
CEN/TR 15809
RAPPORT TECHNIQUE
TECHNISCHER BERICHT
November 2008
ICS 13.030.20
English Version
Characterization of sludges - Hygienic aspects - Treatments

Caractérisation des boues - Aspects hygiéniques - Charakterisierung von Schlämmen - Hygienische Aspekte -

Traitements Schlammbehandlung

This Technical Report was approved by CEN on 25 August 2008. It has been drawn up by the Technical Committee CEN/TC 308.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,

France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,

Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36 B-1050 Brussels

© 2008 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TR 15809:2008: 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 and definitions ...................................................................................................................................5

4 Hygienic considerations ...............................................................................................................................6

4.1 General............................................................................................................................................................6

4.2 From concept to good practice ....................................................................................................................6

4.3 Aspects of microbiology, virology and parasitology.................................................................................7

4.4 Aspects of epidemiology ..............................................................................................................................7

4.5 Definition of the hygienic objective of treatment .......................................................................................8

5 General methodologies and tools to define the hygienic effect of treatment, and to

manage the hygienic safety..........................................................................................................................9

5.1 General............................................................................................................................................................9

5.2 Health risk assessment...............................................................................................................................10

5.2.1 Hazard identification ...................................................................................................................................10

5.2.2 Dose-response assessment .......................................................................................................................10

5.2.3 Exposure assessment.................................................................................................................................10

5.2.4 Risk characterisation ..................................................................................................................................10

5.3 Quality Assurance and Hazard Analysis and Critical Control Point (HACCP) for use in

sludge ...........................................................................................................................................................11

6 Treatments available: efficiency and drawbacks .....................................................................................14

6.1 General..........................................................................................................................................................14

6.2 Biological treatment ....................................................................................................................................16

6.2.1 Anaerobic digestion ....................................................................................................................................16

6.2.2 Composting..................................................................................................................................................16

6.2.3 Thermophilic aerobic digestion (TAD) or Aerobic thermophilic stabilisation (ATS)............................17

6.2.4 Long term storage .......................................................................................................................................17

6.2.5 Reedbeds......................................................................................................................................................17

6.3 Chemical treatment......................................................................................................................................18

6.3.1 Treatment with lime .....................................................................................................................................18

6.3.2 Other chemical methods.............................................................................................................................18

6.4 Physical treatment.......................................................................................................................................19

6.4.1 Pasteurisation of sludge .............................................................................................................................19

6.4.2 Thermal drying.............................................................................................................................................19

6.4.3 Thermal hydrolysis......................................................................................................................................19

6.5 Combined treatment and other methods ..................................................................................................19

Annex A (informative) Micro organisms which could be found in sewage sludge ............................................21

Bibliography ..............................................................................................................................................................24

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Foreword

This document (CEN/TR 15809:2008) has been prepared by Technical Committee CEN/TC 308

“Characterization of sludges”, the secretariat of which is held by AFNOR.

The status of this document as CEN/TR has been chosen because much of its content is not completely in

line with the practice and regulations in each member state.

This document gives general principles about hygienic aspects. Other guides on good practice for the use of

sludge (Guides 2, 4, 5, 6, 7, 8) contain the specific recommendations based on the hygienic aspects

described in this guide.
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Introduction

This Technical Report has been prepared within the framework of CEN/TC 308 on characterization of sludges.

This document concentrates on hygienic aspects for good practice concerning treatment of sludge, but

acknowledges that existing national regulations remain in force.

The use of sewage sludge on land is controlled within the EU by the sludge directive (86/278/EEC [1]) “on the

protection of the environment, and in particular of the soil, when sewage sludge is used in agriculture”.

Regarding the purpose of the directive, it states:

 whereas the aim of this Directive is to regulate the use of sewage sludge in agriculture in such a way as

to prevent harmful effects on soil, vegetation, animals and man, while encouraging its correct use;

Regarding hygiene, it requires:

 whereas sludge must be treated before being used in agriculture; whereas Member States may

nevertheless authorize, on certain conditions, the use of untreated sludge, without risk to human or

animal health, if it is injected or worked into the soil;

 whereas a certain period must elapse between using the sludge and putting stock out to pasture or

harvesting fodder crops or certain crops which are normally in direct contact with the soil and normally

consumed raw;

 whereas the use of sludge on fruit and vegetable crops during the growing season, except for fruit-tree

crops, must be prohibited.
86/278/EEC defines 'treated sludge' as:

 sludge which has undergone biological, chemical or heat treatment, long-term storage or any other

appropriate process so as significantly to reduce its fermentability and the health hazards resulting from

its use;

EU Member States have enacted the directive into their national legislations with conditions that are no less

stringent than the directive. In many cases they have more detailed treatment requirements than those written

in the directive.

The European Commission has said repeatedly that 86/278/EEC, which was the first soil protection directive,

has been a success because there have been no cases of adverse effect where it has been followed.

Sludge treatments and practices that control health risks can also affect odour; in the public’s mind they are

linked.

When making choices in sludge management the hygienic aspects should be considered alongside the

environmental impacts of the treatment such as energy use or emissions and the benefits of the final product.

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1 Scope

This CEN Technical Report gives information about principles to be followed in different sludge treatment

processes to reach specified hygienic requirements.
2 Normative references

The following referenced documents are indispensable for the application of this document. For dated

references, only the edition cited applies. For undated references, the latest edition of the referenced

document (including any amendments) applies.
EN 1085:2007, Wastewater treatment — Vocabulary

EN 12832:1999, Characterisation of sludges — Utilization and disposal of sludges — Vocabulary

CEN/TR 15473, Characterization of sludges — Good practice for sludges drying

EN ISO 22000, Food safety management systems — Requirements for any organization in the food chain

(ISO 22000:2005)
3 Terms and definitions

For the purposes of this document, the terms and definitions given in EN 12832:1999, EN 1085:2007 and the

following apply.
3.1
Critical Control Point (CCP)

step [in a process] at which control can be applied and is essential to prevent or eliminate a hazard or reduce

it to an acceptable level
3.2
HACCP (hazard analysis and critical control point)

system that identifies, evaluates, and controls hazards which are significant for safety

3.3
HACCP plan

document prepared in accordance with the principles of HACCP to ensure control of hazards which are

significant for safety in the segment of the chain under consideration
3.4
hazard
potential source of harm
3.5
hazard analysis

process of collecting and evaluating information on hazards and conditions leading to their presence to decide

which are significant for safety and therefore should be addressed in the HACCP plan

3.6
hygienic safety
intended degree of safety
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3.7
hygienisation

process that leads to reduced levels of pathogens in order to prevent infections, and their spreading in the

exposed human, animal or plant population
3.8
monitor

act of conducting a planned sequence of observations or measurements of control parameters to assess

whether a CCP is under control
3.9
risk

combination of the probability of occurrence of harm and the severity of that harm

3.10
safety
freedom from unacceptable risk
3.11
validation
obtaining evidence that the elements of the HACCP plan are effective
3.12
verification

application of methods, procedures, tests and other evaluations, in addition to monitoring to determine

compliance with the HACCP plan
4 Hygienic considerations
4.1 General

Untreated sludge from wastewater treatment may contain different types and species of pathogens for

humans, animals and plants. The occurrence of such pathogens depends on the type and origin of the raw

materials and on the health situation with respect to the presence of diseases in the involved populations. This

does not only apply to sewage sludge, but also to wastewater, biogas residues, animal manure and other

organic fertilisers and compost of human, animal and plant origin. Environment per se is not sterile. Soil is

more than a mineral support on which plants grow, it is an ecosystem with its own indigenous flora and fauna.

Among this microflora are several potential pathogenic as well as toxigenic bacteria and fungi that can be

found in varying concentrations such as Listeria monocytogenes or Clostridium tetani. There are also

competitors and predators of the pathogens with which this guide is concerned. Hygienic considerations

include aspects of microbiology, virology, parasitology and epidemiology.
4.2 From concept to good practice

In the framework of HACCP concept, the intended field of application of sludge has to be defined, followed by

the determination of the existence and the types of pathogens in sludges, as well as the identification of the

possible ways of transmission to humans, animals or plants.

If the interpretation of this analysis (based on the level of risk for health in regard of the uses of sludges)

demonstrates the need for treatment, the process should be capable of reducing the hazard to an acceptable

level of risk by inactivating the selected pathogens to a defined extent. The treatment process should be

validated by a representative indicator organism covering the types of pathogen identified.

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4.3 Aspects of microbiology, virology and parasitology

Besides the indigenous microbiological flora and populations of viruses including protozooic and metazooic

organisms, untreated sewage sludge may contain a variety of pathogens for humans, animals and plants as

well as other undesired organisms which may present an environmental hazard. The species and numbers of

indigenous flora as well as the pathogens and undesired elements depend on the origin and treatment of the

wastewater. Basic data concerning the occurrence of bacterial, viral and fungal pathogens as well as

parasites have been given in the past by several authors [2, 3, 4]. From this variety of bacterial pathogens

Salmonella spp. are the most relevant since they can infect or contaminate nearly all living vectors from

insects to mammals. Amongst the viral pathogens, noroviruses, enteroviruses and rotaviruses are the most

relevant ones from the point of view of environmental risks. Special regard must be paid to the parasitic

pathogens, not only to eggs of round- and tapeworms but to Giardia lamblia and especially Cryptosporidium

parvum. Nearly all gut related pathogens of farm animals could be found in slaughterhouse effluents.

Wastewater from households or industry containing plant material may contain plant-pathogenic viruses,

fungi, bacteria, parasites and undesired weeds. This may cause an additional phytohygienic risk if untreated

material is used in agriculture as a fertiliser [5]. However, in most cases, the concentration of the relevant

pathogens in the sludge is moderate or small. Consequently, risk related treatment, storage and utilisation

basically determines the hygienic safety of the final product.

The health of the population (humans, animals, plants) has to be taken into account both in the risk

assessment and in establishing a HACCP-concept.
4.4 Aspects of epidemiology

The epidemiological aspects of sewage sludge mean that hygienic safety must be considered during all steps

of treatment, transport, storage and utilisation. The right balance between the advantages of organic fertilisers

based on sewage sludge and the requirements to achieve the degree of hygienic safety necessary for the

intended application has to be made. Different European experiences with strategies for proper use of sludge

show that epidemiological risks can be minimized.

Three aspects of hygiene have to be considered related to different epidemiological pathways:

 one aspect concerns the occupational health aspects in transport, storage, treatment and utilisation.

NOTE 1 The occupational health aspects are covered by Directive 2000/54/EC [6] and related national legislation, and

are not covered in this context.

 the second aspect concerns two vectors: transmission of pathogens directly to susceptible hosts or

indirectly via living and non living vectors (e.g. food, animal feed, or contaminated equipment).

NOTE 2 The direct or indirect transmission of zoonotic agents to farm animals is generally regarded as the most

relevant risk factor of agricultural utilisation of untreated or insufficiently treated sludge. This direct relationship between

fertilizing with sewage sludge and infection in cattle fed with forage after sludge spreading was first demonstrated for

Salmonella [7]. The transmission of parasites was observed much earlier. Transmission to humans via products based on

sludge or containing insufficiently treated sludge by applying them to plants in househods or in home-gardens is a

relatively rare event. The risk of infection of persons exposed to salmonellae after sludge application to farmland is

minimal and no different from that of the nonexposed population [8].

Indirect transmission to humans is of special importance, because the introduction of pathogens into the food chain via

contaminated fertiliser leading to contaminated animal feed resulting in infection of farm animals or excretion of pathogens

is of basic epidemiological significance. This is mainly due to contamination of meat and meat products during

slaughtering and processing as well as contamination of plants and plant products by manure of animals excreting the

above mentioned organisms. The risk of transmission of pathogens to human food by living vectors such as insects,

rodents and birds from processing, handling and agricultural utilisation of organic fertilisers is also regarded as a risk

factor [9].

 the third aspect concerns the introduction of organisms in the environment during transport, treatment,

and storage but mainly during utilisation.
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NOTE 3 This may be closely related to health aspects if pathogens are introduced into the biocenosis, and then carried

by birds or rodents. This could include the introduction of resistance genes into the biocenosis, a potential risk that applies

to treated wastewater as well. Antibiotic resistant bacteria may be present in sludge, and therefore could contribute to the

presence of so called “community acquired multiresistant bacteria” in human populations. However, it is likely that other

ways of transmissions are of primary importance [10].

Epidemiological risks arise because pathogens may survive for a considerable period of time in excreta,

manure, sludge and the environment [2]. A compilation of general epidemiological risks due to handling and

the utilisation of organic wastes as fertilisers in agriculture is given in Table A1.

4.5 Definition of the hygienic objective of treatment

The hygienic objective of treatment is to be defined for the treatment. The definition of this objective is on the

authority of each country regulation. The principle is to determine the microorganisms you want to inactivate

and the microorganisms you accept there are remaining.

An example for inactivation of remaining type of organisms is given in Table 1. Suggestions for test organisms

for validation of treatment processes are given in Table 2.
Table 1 — Hygienic objectives

NOTE Pathogenic prions are not covered by this approach, if present in the sludge other treatment options as given

below must be considered.
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Table 2 — Possible test organisms for validation of treatment processes in relation to the intended

hygienic level (informative)

Pathogens inactivated Possible test organisms Minimal reduction to be reached in the

validation

Vegetative bacteria For biotechnological and chemical At least 5 log for all test organisms

treatment: Salmonella senftenberg
W 775, H2S negative
Virus with moderate resistance For thermal or other physical
treatment: Enterococcus faecalis
ATCC 2912

Vegetative bacteria For chemical treatment: Salmonella At least 5 log for Salmonella senftenberg and

senftenberg W 775, H S negative Enterococcus faecalis
and eggs of Ascaris suum

Virus with moderate resistance For biotechnological and thermal or At least 99,9 % inactivation of the eggs

other physical treatment:
Infectious parasitic stages
Enterococcus faecalis ATCC 2912

Vegetative bacteria For biotechnological and chemical At least 3 log for Bovine parvovirus

treatment: Bovine parvovirus strain
Haden

Virus with moderate and high For thermal or other physical At least 5 log for Coliphage T1

resistance treatment: Bovine parvovirus strain
Haden or Coliphage T1
Infectious parasitic stages

If validation is done by input-otput analysis for determining a reduction rate in the indigenous bacteria and/or viruses the parameters

“E. coli”, “Enterococci” or “Coliphages” may be used instead.

Generally, treatments used to stabilise sludge have the effect of enhancing the natural decay in the

indigenous as well as in the pathogenic micro-organisms present and generally to restrict regrowth within

certain limits. The effect depends on their biological properties. The factors leading to the inactivation can be

chemical, physical or biological in nature. Every treatment may have some effect on the beneficial soil

conditioning properties of the sludge (e.g. loss of nutrients, loss of organic matter, loss of beneficial

organisms).

Wastewater treatment results in sludge. Untreated sludge may contain pathogenic vegetative bacteria, as well

as bacterial spores, viruses with different chemo- and thermoresistance, as well as infectious stages of

different parasites (see Tables A2 to A4 in Annex A). This is the material related to the highest epidemiological

risk in this context.

5 General methodologies and tools to define the hygienic effect of treatment, and

to manage the hygienic safety
5.1 General
An appropriate approach for good health practices should:

a) identify the relevant pathogens and the thresholds that ensure sanitary protection of the exposed

population. This can be done with a health risk assessment;
b) include HACCP with process validation;
c) monitor contamination levels in sludge before use in general.
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5.2 Health risk assessment
The health risk assessment comprises four steps:
a) hazard identification;
b) dose-response assessment;
c) exposure assessment;
d) risk characterisation

Health risk assessment is a scientific tool designed to help regulators, decision makers, risks managers and

industries to identify and quantify the potential hazards linked to a specific human activity. Health risk

assessment is used to determine if a list of selected pollutants (chemical or biological agents) pose a

significant risk to human health and under what circumstances.
5.2.1 Hazard identification

Hazard identification is the first step in health risk assessment. It is the process of determining whether

exposure to an agent could (at any dose) cause an increase in the incidence of adverse health effects in

humans. This hazard identification is carried out for each pollutant selected in the risk assessment protocol.

Hazard identification shall result in the identification of one or more key pathogens known to be present in the

sludge in high numbers and which could be transmitted by the way the sludge is used.

5.2.2 Dose-response assessment

Dose-response assessment defines the relationship between the dose of an agent and the probability of a

specific adverse effect in the exposed organisms.

Dose-response assessment is not as well-defined for pathogens as it is for chemicals.

In the case of pathogens, it is sometimes possible to identify a minimum infectious dose which corresponds to

the level of pathogen likely to cause a pathology (this dose can vary according to the physiological state of the

pathogen and of the host).
There are very few dose-response relationships for pathogens in general.

In addition, the assessment is complicated due to the capability of the pathogens to propagate in the

environment or in vectors.
5.2.3 Exposure assessment

Exposure assessment quantifies the uptake of pollutant (here pathogens) from the environment by any

combination of routes of exposure.

Exposure assessment can take into account the worst-case estimate of exposure (maximum contamination

value calculated or measured x maximum time of exposure x most sensitive population) in order to quantify

the maximum level of risk so as to ensure the safety of the whole exposed population.

5.2.4 Risk characterisation

Risk characterization summarizes and interprets the information collected from previous steps of the method

and identifies the limitations and the uncertainties in risk.
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To evaluate the health risk from an exposure to pathogens, it is either possible to compare the dose of

exposure to the minimal infectious dose, when it exists, or to use the mathematical dose-response relationship

defined to assess a probability of infection.

5.3 Quality Assurance and Hazard Analysis and Critical Control Point (HACCP) for use in

sludge

Quality Assurance (QA) revolutionised manufacturing industry and the reliability of its products by formalising

procedures in order to ensure that operations were performed correctly every time.

QA was first applied to sludge recycling operations in 1989 by the largest sludge recycler in the UK. The result

was 100% auditable compliance with legislation and codes of good practice. Subsequently many others have

adopted QA. For example:

 in Germany there is a co-operative QA scheme involving 35,000 farmers and the use of 250,000 t sludge;

 operators in France launched SYPREA in 2002 as a national QA scheme, which includes sludge

treatment;
 there are independent QA systems in Sweden;
 in Norway QA for sludge treatment is a legal requirement; and

 the National Biosolids Partnership offers EMS with third-party audit in the United States.

One of the criticisms of QA is that it makes sure that you do the same thing every time but that if the process

has not been designed properly the outcome will be wrong every time. This is not really an entirely fair

criticism of QA but a process design paradigm from the food industry provides an ideal complement to QA

because it is a structured approach to analysing the hazards that could affect the product. It is called Hazard

Analysis and Critical Control Point (HACCP) [Codex Alimentarius 1997 [10]]

HACCP systems are used internationally in the food industry to ensure product quality standards (see

EN ISO 22000) and with some modifications it is part of EU legislation on animal by-products

(Regulation 1774/2002 [11] not intended for human consumption). HACCP principles are applicable to sludge

treatment (e.g. in U.K. and in Norway) and utilisation.

In this guide, the aim is to use the applicable principles of HACCP in order to identify all measures to be taken

with respect to safe transport, treatment, storage and utilisation
...

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