health aspects of nightsoil and sludge use in agriculture and aquaculture

172 Pages·2008·8.17 MB·English

IRCWD Report No. 04/85
3 5 2 .0
8 6 H E ;
HEALTH ASPECTS OF NIGHTSOIL
AND SLUDGE USE IN AGRICULTURE
AND AQUACULTURE
Parti
Existing Practices and Beliefs in
the Utilization of Human Excreta
PIERS CROSS
Part II
Pathogen Survival
MARTIN STRAUSS
[35-2. o
International Reference Centre for Waste Disposal (IRCWD)
Ueberlandstrasse 133, CH-8600 Duebendorf, Switzerland
IRCWD Report No. 04/85
HEALTH ASPECTS OF NIGHTSOIL
AND SLUDGE USE IN AGRICULTURE
AND AQUACULTURE
Parti
Existing Practices and Beliefs in
the Utilization of Human Excreta
PIERS CROSS
Part II
Pathogen Survival
MARTIN STRAUSS
International Reference Centre for Waste Disposal (IRCWD)
Ueberlandstrasse 133, CH-8600 Duebendorf, Switzerland
WASTEWATER REUSE USE OF STORED NIGHTSOIL
Farmers in Tula river basin, Mexico, Removal of decomposed, humus-like
irrigating a chili field with waste- material from a dry-alkaline-fer-
water from Mexico City (Photo by tilizer ("DAF") latrine in Guatemala.
Ursula Blumenthal). This material is used on the fields
as soil conditioner and fertilizer.
NIGHTSOIL FERTILIZATION OF FISH PONDS
This fish pond owner grows fingerlings
Excreta fertilization of small fish or
in his excreta-fertilized pond in Bogor,
vegetable ponds through the use of over-
Indonesia. Others buy the fingerlings
hung latrines is an old tradition in the
and grow them to consumable size in
Indonesian highlands. Fish and vegetables
ponds not receiving any excreta.
are always consumed cooked.
CONTENTS
Page
FOREWORD i
ACKNOWLEDGEMENTS iv
SUMMARY (Parts I, II and III) v
INTRODUCTION 1
1. Purpose and Scope of Review 1
2. Excreta as a Resource 3
2.1 Agricultural Use 3
2.2 Aquacultural Use 6
2.3 Conclusion 7
3. Excreta as a Health Risk 8
3.1 Introduction 8
3.2 Faecal Microflora of Healthy, Non-Infected Persons 10
3.3 Excreted Pathogens, Diseases and Symptoms 11
3.3.1 Overview 11
3.3.2 Viruses 13
3.3.3 Bacteria 15
3.3.4 Protozoa 18
3.3.5 Helminths 18
3.4 Towards an Epidemiologically Useful Classification of
Infections and Sanitation Measures 20
3.5 Pathogen Detection and Interpretation of Results 27
3.6 Excreted Pathogen Levels in Raw Human Wastes 30
4. Development and Sanitation Measures 31
5. Theoretical vs. Actual Health Risks . 33
6. Sources of Information 37
PART I: EXISTING PRACTICES AND BELIEFS IN THE UTILIZATION
OF HUMAN EXCRETA 1-1
1.1 Why Consider Socio-cultural Aspects of Excreta-Re-use? 1-1
1.2 Cultural Variation in Excreta Utilization Practices 1-2
1.3 Case-Studies A: China 1-3
1.3.1 Traditional Beliefs and Practices 1-3
1.3.2 Direct Use 1-4
1.3.3 Indirect Use 1-4
1.3.4 Nightsoil Collection in Cities 1-6
1.3.5 Traditional Hygiene 1-6
1.3.6 Improving Excreta Disposal and Reuse Practices 1-6
CONTENTS (continued)
1.4 Case-Study B: Islamic Cultures 1-8
1.5 Case-Study C: Sub-Saharan Africa 1-10
1.6 Discussion 1-12
1.6.1 Cultures that Use Excreta 1-12
1.6.2 Cultures that do not Use Excreta 1-15
1.7 Conclusions and Recommendations 1-17
References 1-20
PART II: PATHOGEN SURVIVAL II-l
11.1 Principles of Pathogen Survival II-l
11.2 Survival during Storage and Treatment 11-4
11.2.1 Objectives and Boundary Conditions 11-4
11.2.2 Latrines II-5
11.2.3 Aqua Privies and Septic Tanks 11-11
11.2.4 Thermophilic Composting 11-13
11.2.5 Biogas Digesters 11-16
11.2.6 Ponds 11-19
11.2.7 Summary and Evaluation 11-25
11.3 Survival in Soil and on Crops 11-27
11.3.1 Basic Considerations 11-27
11.3.2 Survival of Helminths 11-28
1I.3.3 Survival of Bacteria 11-34
11.3.4 Survival of Viruses 11-43
11.3.5 Survival of Protozoa 11-58
11.3.6 Summary; Pathogen Survival vs. Vegetable Growth Periods 11-59
11.3.7 Patterns of Nightsoil Supply and Demand 11-62
11.3.8 Mulching or Ploughing ? 11-64
11.4 Survival in Fish 11-66
11.4.1 Basic Considerations 11-66
11.4.2 Pathogen Transmission Routes Involving Fish 11-67
11.4.3 Survival 11-70
11.5 Overall Conclusions and Recommendations 11-75
11.5.1 Conclusions 11-75
11.5.2 Recommendations 11-76
References 11-79
Appendix: Survival of Bacteria and Viruses in Fish: Literature A-l
Summaries
LIST OF TABLES Page
Table 2.1 Characteristics of Fresh Human Excreta and
Nightsoil 4
Table 2.2
Nutrient Values of Various Natural Fertilizers 4
Table 3.1
Viable Bacteria Commonly Found in Faeces of
Healthy, Non-Infected Persons 10
Table 3.2
Important Pathogens Excreted in Faeces 12
Classification of Excreted Pathogens Based on
Table 3.3
Epidemiological Features 22
Dominant Transmission Foci of Excreted Pathogens
Table 3.4
and Suggested "Soft" and "Hard" Control Measures 25
Tentative classification model of environmental
Table 3.5
infection categories associated with the relative
importance played by nightsoil in transmitting
certain types of pathogens 26
Table 3.6 Levels of Excreted Pathogens and Indicator
Organisms in Raw Human Wastes 30
Table 5.1 Current Epidemiological Evidence of Excreted
Infection Transmission Risks from Excreta
Utilization in Agriculture 36
Table 5.2 Current Epidemiological Evidence of Excreted
Infection Transmission Risks from Excreta
Utilization in Aquaculture 37
Table I.I Examples of Human Excreta Re-use Practices 1-3
Table I I.I Major Environmental Factors Influencing Pathogen
Die-Off 11-2
Table II.2 Survival of Excreted Pathogens in Nightsoil,
Faeces and Sludge at 20-30 C 11-7
Table II.2a Survival of Trematode (Fluke) Eggs in Faecal
Sludge at 20-30°C 11-8
Table II.3 Pathogen Content Expected in Final Product of
Composting Latrines Operating Anaerobically at
Ambient Temperature in Warm Climates 11-10
Table II.4 Summary: Survival of Excreted Pathogens During
Pre-Application, Storage and Treatment:
IDEAL-World Situation 11-25
Table II.5 Summary: Survival of Excreted Pathogens During
Pre-Application, Storage and Treatment:
REAL-World Situation 11-26
Table II.6
Helminth Development and Survival in Soil 11-30
Table II.7
Helminth Development and Survival on Crops 11-32
Table 11.8
Survival of Excreted Bacterial Pathogens in Soil 11-36
LIST OF TABLES (Cont.)
Page
Table II.9 Survival of Excreted Pathogens on Crops 11-39
Table 11.10 Virus Survival in Spread-Out, Drying Sludge 11-45
Table 11.11 Survival of Excreted Viruses in Soil 11-47
Table 11.12 Factors Affecting the Survival of Viruses in Soil 11-48
Table 11.13 Effects of Virus Adsorption State on Virus
Survival 11-54
Table. 11.14 Survival of Excreted Viruses on Crops 11-57
Table 11.15 Environmental Factors Influencing Pathogen
Die-Off or Survival 11-60
Table 11.16 Suggested Effects of Mulching and Ploughing on
Pathogen Survival on Nightsoil Fertilized
Fields 11-65
Table 11.17 Tentative Recommendations for Excreta Storage
Periods in Warm Climates 11-77
LIST OF FIGURES Page
Fig. 3.1 The Pathogen-Host Relationship, and Possible
Transmission Routes of Excreta-Related Infections 10
Fig. 3.2 Pathogen Density and Survival Time Outside the
Host 23
Fig. 3.3 Length and Dispersion of Transmission Cycles of
Excreted Infections as Categorized in Table 3.3 24
Fig. II.1 Poliovirus Die-Off in Sludge-Fertilized Soil 11 -2
Fig. II.2 Salmonella Die-Off on Sewage Sludge-Irrigated
Lettuce 11-2
Fig. II.3 Time-Temperature Relationship for Excreted
Pathogen Survival in Nightsoil and Sludge 11 -3
Fig. 11.4 Pathogen Die-Off in Faecal Products and Treatment
Periods Required at Different Temperature Regimes 11 -4
Fig. II.5 Single and Alternating-Pit (or Vault) Latrines 11 -6
Fig. II.6 Aqua Privy and Septic Tank (Schematic) 11-11
Fig. II.7 Pathogen Survival in Privies and Septic Tanks 11-12
Fig. II.8 Inactivation of Ascaris Eggs by Thermophilic
Composting 11-15
Fig. II.9 Biogas Digester 11-17
Fig. 11.10 Waste Stabilization Ponds (Schematic) 11-19
Fig. II.11 Pathogen Removal in Waste Stabilization Ponds 11-24
Fig. 11.12 Pattern of Helminth Infection Cycles 11-28
Fig. 11.13 Survival Periods in Days of Excreted Bacterial
Pathogens in Soils of Tropical Climates 11-37
Fig. 11.14 Survival Periods in Days of Excreted Bacterial
Pathogens on Crops in Tropical Climates 11-40
Fig. II.15a Pathogen Survival in Soil vs. Vegetable Growth
Periods in Warm Climates 11-61
Fig. II.15b Pathogen Survival on Crops vs. Vegetable Growth
Periods in Warm Climates 11-61
Fig. 11.16 Transmission Path of Helminthic Infections
Having Fish as an Intermediate Host 11-68
FOREWORD
Animal and human wastes have been used in all parts of the world and
for many centuries to fertilise fields and ponds where fish and aquatic vege-
tables are grown. No country could afford to waste this important nutrient
source. However, only in the last few decades, after having developed a high
energy consuming technology to produce mineral fertilisers, many industria-
lized countries ceased to recycle the nutrients contained in faecal wastes.
This tendency was probably reinforced mainly by the increasing awareness of
the health risks related to the use of faecal matter in agriculture, and by
the low energy prices. In the United States for instance, where energy prices
were very low until recently, it is still common practice to incinerate the
sludge produced in communal sewage treatment plants, whereas in many European
countries, where energy prices have always been considerably higher, all the
animal manure and most of the sludge generated from human waste is applied to
fields after appropriate treatment. As a result of increasing energy prices.,
the growing awareness of natural resource limitations, and for ecological
reasons in general, the concept of recycling nutrients has recently regained
popularity in the industrialized countries. Unfortunately, these countries are
faced today with a new problem: the contamination of sludge with heavy metals
and other industrial pollutants is limiting sludge use in agriculture.
Unlike the situation in industrialized countries, in most developing
countries animal and human excreta have always been regarded as the most im-
portant and often only affordable nutrient source in agriculture and aquacul-
ture. Due to economic reasons, the concept of recycling nutrients was never
abandoned in these countries. In many countries in Asia, even raw or only
marginally treated human excreta (niqhtsoil) are traditionally and widely used
to fertilise fields and fish ponds. Such practices create potential health
risks to those who consume vegetables or fish grown there. Over the past de-
cades, research has been focused on the potential health risks associated with
the outside-host environment, i.e. in water, wastewater, sludge, soil and on
crops. However, relatively little is known about how and to what extent di-
sease transmission is really associated with the practice of recycling nutri-
ents of human wastes. Nor does one know much about the relative importance of
excreta fertilisation in comparison with other possible routes of pathogen
transmission. Consequently, existing basic concepts and standards relating to
the use of human wastes have been based on potential risks and are therefore
very conservative. However, unduly restrictive standards on human waste reuse
which are not justified on health grounds, can lead - especially in countries
with great economical difficulties - to situations where unregulated reuse
projects become tacitly accepted even if they actually pose real health
risks.
11
In 1982, the International Reference Centre for Wastes Disposal
(IRCWD), in collaboration with WHO, started a project on the actual (as op-
posed to the theoretical or potential) health risks related to the use of
human excreta. A further objective of the project is to highlight sociocultur-
al, technical and institutional aspects of such excreta-use practices. In the
first phase of the project three state-of-knowledge reviews were prepared
based on three types of perspectives. Part I, prepared by Piers Cross, a so-
ciologist presently working in Harare, Zimbabwe, highlights cultural differ-
ences in excreta management practices, discusses beliefs and habits, and sug-
gests ways to strengthen the role of sociocultural persDectives in programmes
dealing with excreta disposal and hygiene-related problems. Part II presents
compiled information reviewed by Martin Strauss, a sanitary engineer working
at IRCWD, on survival of excreted pathogens in excreta and faecal sludges
prior to utilisation (i.e. during storage and treatment), and reports about
the fate of these pathogens in the soil, on crops and in nightsoil-enriched
fish ponds. Part III has been prepared by Deborah Blum and Richard Feachem of
the London School of Hygiene and Tropical Medicine, with the objective of
providing an overview of the existing documented epidemiological evidence
regarding disease transmission through nightsoil and sludge use as a fertili-
ser. It highlights gaps in epidemiological knowledge and outlines possible
epidemiological approaches to field investigations of health risks of excreta
use.
The reviews presented in this publication series focus on the use of
excreta, nightsoil and sludge, and not on the use of wastewater for agricul-
tural purposes. This separation is artificial and was done for practical rea-
sons only. It is even reasonable to assume that the range of pathogens is the
same for both nightsoil and wastewater, and that health risks associated with
their use as fertilisers are of a similar nature. The World Bank as executing
agency for the United Nations Development Programme (UNDP) on the Integrated
Resource Recovery Project, has commissioned a team of consultants headed by
Professor Hillel Shuval to do a parallel review on the health effects of
wastewater irrigation. This report "Wastewater Irrigation in Developing Coun-
tries" has been published as World Bank Technical Paper Number 51.
The project on the "Health Aspects of Nightsoil and Sludge Use in Agri-
culture and Aquaculture" will continue. After field visits to several coun-
tries where use of human wastes is practised, we hope that further epidemiolo-
gical studies will be initiated and conducted in the near future. Based on
these field visits, a further report describing actual case studies will be
prepared and published as Part IV of this publication series. On the same
topic "Wastewater and Excreta Use in Agriculture and Aquaculture", Engineering
and Managerial Guidelines for Health Risks Minimization are presently being
prepared for UNEP/WHO by Professor Duncan Mara and Dr Sandy Cairncross.