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STRAUSS MONTANGERO FS 2002 Management Review of Pracitces Problems Initiatives
FS Management Review
Engineering Knowledge and Research Project - R8056
1
Capacity Building for Effective
Decentralised Wastewater
Management
FS Management – Review of Practices, Problems
and Initiatives
Martin Strauss
Agnes Montangero
EAWAG/SANDEC
FS Management Review
2
Contents
Acronyms .................................................................................................................... 5
Abbreviations............................................................................................................... 5
Glossary ...................................................................................................................... 5
Photo credit ................................................................................................................. 5
Acknowledgements...................................................................................................... 6
Preface ........................................................................................................................ 6
1
1.1
1.2
1.3
1.4
Introduction........................................................................................................7
Faecal Sludge Management – Importance and Framework ................................. 7
Scope .................................................................................................................. 8
Report Structure .................................................................................................. 8
The Decentralised Management Paradigm .......................................................... 9
2
Excreta Management – A Great Urban Challenge .........................................10
2.1 Situation and Problems...................................................................................... 10
2.2 Paradigms in Choosing Strategies and Technologies ........................................ 15
2.3 FS Management as A Component of Urban Planning in Environmental
Sanitation........................................................................................................... 16
2.4 Economic aspects.............................................................................................. 17
2.4.1 Integrated Cost Considerations ................................................................... 17
2.4.2 Scale of Treatment Works vs. Haulage Cost ............................................... 17
3
Technical Options (overview) .........................................................................18
3.1 Faecal Sludge Characteristics and Specific Quantities ...................................... 18
3.1.1 Per-capita quantities .................................................................................... 18
3.1.2 FS characteristics ........................................................................................ 18
3.2 Emptying , Collection, Haulage .......................................................................... 21
3.3 Treatment .......................................................................................................... 23
3.3.1 State-of-Development in Treatment Technology.......................................... 23
3.3.2 Treatment Goals and Feasible Options........................................................ 24
- Treatment goals and criteria ................................................................... 24
- Numerical values – at the base of the barrier principle ........................... 25
- Options and component overview (see Annex 7.2 for more details)...... 26
3.3.3 Cost and land requirements......................................................................... 28
3.3.4 How to Select A Treatment Option............................................................... 29
3.3.5 Where FS Treatment Schemes are Being Operated or Planned.................. 30
4
Selected Initiatives for Improving FS Management .......................................32
4.1 General Observations ........................................................................................ 32
FS Management Review
4.2 Rationale for Choosing Vientiane, Nam Dinh, Kumasi and Bamako as
Selected Initiatives ............................................................................................. 32
4.3 Vientiane (Laos) – Plans for improved FS collection and treatment
formulated.......................................................................................................... 33
4.3.1 The City, the Sanitation Situation and Challenges ....................................... 33
4.3.2 Towards Improved FS Management............................................................ 34
4.3.3 Lesson......................................................................................................... 34
4.4 Nam Dinh (Vietnam) – Rapid upgrading of household sanitation calls for
effective FS collection and treatment ................................................................. 35
4.4.1 The City, the FS Management Situation and Challenges............................. 35
4.4.2 Plans for Coping and Improving................................................................... 37
4.4.3 Lesson......................................................................................................... 38
4.5 Kumasi (Ghana) – Managerial and Technical Solutions in Place ....................... 38
4.5.1 Geographical Setting and Developments in Environmental Sanitation......... 38
4.5.2 Stakeholder Involvement ............................................................................. 39
4.5.3 FS Management .......................................................................................... 39
- Sanitary facilities..................................................................................... 40
- Faecal Sludge Collection and Haulage ................................................... 41
- FS disposal + treatment.......................................................................... 41
4.5.4 Wastewater Management ............................................................................ 43
4.5.5 Reuse practices........................................................................................... 44
4.5.6 Lesson......................................................................................................... 44
4.6 Bamako (Mali) – The dynamics of small entrepreneurship ............................... 45
4.6.1 The City and the FS Management Situation ................................................ 45
4.6.2 Recent FS Management Initiatives .............................................................. 46
4.6.3 How to Make Sure That Faecal Sludge Ends up in The Treatment Plant
Rather Than in a Drainage Ditch ................................................................. 47
4.6.4 Lesson......................................................................................................... 48
5
Opportunities and Constraints .......................................................................49
5.1 Case analysis and discussion ............................................................................ 49
5.2 Enabling and Hindering Factors ......................................................................... 52
5.3 Gaps-in-Knowledge on (Faecal) Sludge Management ....................................... 53
6
Conclusions and Recommendations .............................................................55
7
Annexes............................................................................................................56
7.1 About Minimising FS Haulage Cost (see also Chpt. 2.4) .................................... 56
7.1.1 What Speaks Against Large, Centralised Treatment Schemes.................... 56
7.1.2 Calculation of estimated km-dependent haulage costs ............................... 56
7.2 Technical Options for FS Treatment (see also Chpt. 3.3)................................... 58
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7.3 Pathogen Die-off in Faecal Sludge at Ambient Temperatures............................ 69
7.4 References ........................................................................................................ 70
7.5 Documents on FS Management and Treatment Which May Serve for
Training Purposes.............................................................................................. 72
7.6 Selected Institutions and Persons Actively Engaged in FS Management
and FS Management Applied Research............................................................. 73
_______________
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5
Acronyms
CBO
DWWTP
FS
FSTP
GIE
KVIP
OSS
TS
Community-based organizations
Decentralised wastewater treatment plant
Faecal sludge(s)
Faecal sludge treatment plant
Groupe d’intérêt économique
Kumasi ventilated improved pit latrine
On-site sanitation
Total solids
Abbreviations
AIT
CREPA
EAWAG
IWMI
KNUST
SANDEC
UNR
UESP
Asian Institute of Technology (Bangkok, Thailand)
Centre Régional pour l’Eau Potable et l’Assainissement à faible coût
(Ouagadougou, Burkina Faso)
Swiss Federal Institute for Environmental Science & Technology
International Water Management Institute
Kwame Nkrumah University of Science & Technology, Kumasi,
Ghana
Dept. of Water & Sanitation in Developing Countries (at EAWAG)
Universidad Nacional de Rosario (Rosario, Argentina)
Urban Environmental Sanitation Project (World Bank/IDA) in Ghana
Glossary
Faecal sludge
Sludges of variable consistency collected from so-called onsite sanitation systems; viz. latrines, non-sewered public
toilets, septic tanks, and aqua privies
Percolate
The liquid seeping through an unplanted or planted sludge
drying bed and collected in the underdrain
Public toilet sludge
Sludges collected from unsewered public toilets(usually of
higher consistency than septage and biochemically less
stabilised)
Septage
Contents of septic tanks (usually comprising settled and
floating solids as well as the liquid portion)
Wastewater treatment
plant sludge
Sludges produced during wastewater treatment (settled
solids – primary sludge – and excess bacterial biomass –
excess sludge)
Photo credit
All photos by SANDEC except where stated otherwise.
FS Management Review
Acknowledgements
We are particularly thankful to Marc Jeuland, environmental engineer and Peace Corps
Volunteer working with the FS collection and treatment entreprise Sema Saniya in
Bamako, Mali. He has very valuably contributed to this report by making available the
feasibility study on FS treatment for two Bamako districts and by a rather pathbreaking
conceptual note on economic aspects and possible fee structures for FS handling and
treatment. Cordes Towles, predecessor of Marc Jeuland in the same function, has
provided background information FS management in Bamako. The contributions by both
engineers are making up the section entitled “Bamako (Mali) – The dynamics of small
entrepreneurship” in Chpt. 4 of this report (Selected Initiatives for Improving FS
Management).
The authors greatly acknowledge also the input by Anthony Mensah, environmental
engineer and project-in-charge at the World Bank/IDA/Govt. of Ghana co-financed
UESP-Ghana in Kumasi. He significantly contributed to the section entitled “Kumasi
(Ghana) – Managerial and Technical Solutions in Place” in Chpt. 4.
Preface
SANDEC was sub-contracted by GHK to cover aspects of faecal sludge (FS)1
management in the DfID-financed EngKAR R8056 Project entitled Capacity Building for
Effective Decentralised Wastewater Management – Phase I (Review of Existing
Initiatives, Training Material and Decision Support Tools). Although the Project’s prime
focus is on wastewater – the managerial and institutional aspects in particular – it was
recognised that the situation regarding the management of faecal sludges in urban areas
of developing countries is rather dramatic. It was therefore decided to dedicate a
separate study to the issues of challenges and possible improvements in managing the
faecal sludges.
1
Faecal sludges (FS) comprise sludges of variable consistency collected from so-called onsite sanitation systems; viz. latrines, non-sewered public toilets, septic tanks, and aqua
privies
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1 Introduction
1.1
Faecal Sludge Management – Importance and
Framework
While substantial progress has been made in the field of wastewater treatment in
developing countries over the past decades, the management and treatment of sludges
from on-site sanitation systems has been addressed, neither by problem holders nor by
researchers. This is surprising as the absence or insufficiency of adequate excreta
management in many cities of developing countries, particularly so in low-income areas,
continuously leads to serious health and environmental hazards. A reason for this
backlog in dealing with excreta in urban areas is, among others, the paucity of
appropriate managerial and technical measures. This had prompted SANDEC to engage
in R+D on FS management and treatment in 1992.
Fig. 1 shows how faecal sludge and wastewater management stand side-by-side in
urban environmental sanitation and how they might technically be interlinked. FS
management deals with the management of sludges from on-site sanitation systems,
while wastewater management deals with sewered sanitation. FS may be treated in
Fig. 1
Systems Framework for Faecal Sludge and Wastewater Management
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separate treatment works or co-treated with sludges produced in wastewater treatment
plants.
Ideally, responsibilities at municipal level for both sectors should be borne by the same
authority, which deals with excreta management in an integral manner, i.e.
encompassing the aspects of sanitation choices at household level, excreta or
wastewater collection, treatment and use or disposal.
1.2
Scope
SANDEC was mandated to collating information on existing technologies and on
implemented or planned strategic options in the field of faecal sludge (FS) management.
SANDEC also attempted to identify training and decision support documents, which may
have been developed in the specific field of (faecal) sludge management.
The information presented in this report are the outflow of experience, observations and
field research data gathered by SANDEC and its partners upon conducting R+D over
close to ten years. Our experience and accumulated knowledge predominantly pertain to
appropriate technical options for treating faecal sludges. It is more recently, only, that
SANDEC has initiated fieldwork on issues of FS management planning and, hence,
developed some limited expertise in this specific field. Accordingly, SANDEC avails of
limited information only on such important issues as the costing, economics and
management of entire FS systems, which would include all relevant infrastructure
components and services, viz.
-
The on-site, household-level installations
FS collection and haulage
FS treatment
Reuse or disposal of FS or of biosolids produced during treatment
To the authors’ knowledge, there has, in fact, been little in-depth field research and
evaluation of entire FS management systems to date. SANDEC is not aware of
published documentation of comprehensive assessments comprising all of the above
components, based on actual practices.
1.3
Report Structure
The report sets out in Chpt.2 to describe the situation in FS management worldwide and
analysing the relationship between causes, problems (or challenges in more positive
terminology) and consequences in the current, often dramatic situation of FS
management. Chpt. 2 also addresses the fact that FS management is an integral
component of urban environmental sanitation and should be viewed with its linkages to
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all the other components. Further to this, economic aspects are touched upon. An
overview of FS characteristics, options for FS collection and treatment is provided in
Chpt. 3 (Annex 7.2 provides a more extended overview of selected treatment
technologies). The chapter also contains a discussion on treatment standards.
Chpt. 4 provides the reader with accounts of initiatives for improved FS management in
two selected cities in Asia (Vientiane, Laos and Nam Dinh, Vietnam) and in Africa
(Kumasi, Ghana, and Bamako, Mali). Each case is concluded with a short statement on
the lesson learnt. Chpt. 5 contains a synopsis of opportunities and constraints, hindering
factors and gaps-in-knowledge identified by making use of the cases presented in the
preceding chapter. The chapter ends with a preliminary listing of presumed needs for
capacity building in the area of FS management. In Chpt. 6, the authors draw the
conclusions and list recommendations.
1.4
The Decentralised Management Paradigm
The situation and problems associated with FS management are of a nature that – for
achieving sustainable improvements – the need for decentralised management imposes
itself almost without saying. This is being shown implicitly and explicitly throughout the
document. The cases discussed in Chpt. 4 show that stakeholders in various cities have
in fact started – deliberately or not – to rely on strategies, which lean on the
decentralisation paradigm.
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10
2 Excreta Management – A Great Urban Challenge
2.1
Situation and Problems
In urban areas of developing countries, the excreta disposal situation is dramatic. Every
day, worldaround, several hundred thousand tons of faecal matter from either open
defaecation or collected from on-site sanitation (OSS) installations (unsewered family
and public toilets, aqua privies and septic tanks) are disposed of into the urban and periurban environment. The “waste” are either used in agriculture or aquaculture or
discharged indiscriminately into lanes, drainage ditches, onto open urban spaces and
into inland waters, estuaries and the sea, causing serious health impacts, water pollution
and eye and nose sores.
For those urban dwellers having access to a sanitary facility, private and public OSS
systems are the predominant type of installation in Africa and Asia. In Latin America, the
proportion of on-site or unsewered vs. sewered sanitation is also considerable (Table 1
and Fig. 2; Strauss et al. 2000).
On-site sanitation
– predominant in
low and middle
income countries
Sewered sanitation –
predominant in hig-
income countries
City or country
Manila
Philippines
(towns)
Bangkok
Ghana
Bamako (Mali)
Tanzania
Latin America
% of inhabitants
served by on-site
sanitation systems
78
98
65
85
98
> 85
> 50
Table 1 Proportion of urban populations
served by on-site sanitation systems
Fig. 2
Excreta disposal systems
typical of urban areas in low
and high-income countries
The problems and challenges in FS management rest with all the components of the
faecal sludge stream – viz. pit/vault emptying, haulage, storage or treatment, and use or
disposal. All aspects are involved, viz. institutional/managerial, financial/economic,
sociocultural, and technical.
Pit emptying constitutes a major problem in many places, both technically and
managerially. In many countries and cities, both mechanised and manual pit emptying
FS Management Review
services are being offered. Mechanised services are rendered by municipal authorities or
medium to large-size entrepreneurs. Individuals, small groups of individuals or microentreprises, offer manual emptying. It is traditionally done with buckets. Emptiers step
into the vault or pit to evacuate the sludge, which has turned too solid to be scooped.
Hence, the traditional manual emptying is associated with considerable health risks – for
the emptiers in the first place. The general public is at risk, too, as the emptied sludge is
usually deposited into nearby surface drains or into lanes. Manual emptying is often
done at night and is associated with clandestineness. It is common that families have or
want to rely on such a service, either because services for mechanical emptying are not
reliable, too costly, solidified deposits are not removable by suction, or because the pit is
not accessible by emptying vehicles. A mechanised, yet manually operated pit-emptying
technology was developed in the eighties and nineties. It is reported about in Chpt. 3.2
FS collection and haulage are particularly challenging In metropolitan centres with their
often large and very densely built-up, low-income districts: Emptying vehicles may not
have access to pits or suction hoses must be laid through neighbours’ yards and homes
! The fact that metropolitan cities are stretched out causes the haulage routes usually to
be rather long. Traffic congestion further aggravates the problem and renders haulage to
designated discharge or disposal sites uneconomical and financially unattractive, leading
to uncontrolled dumping of collected FS at shortest possible distance from the area of
collection. This shows that the FS management problem may, in most situations, be
solved through decentralised schemes and institutional set-ups, only.
Suitable sites for treatment and use or for final disposal may be found at the outskirts of
cities only. Vacuum tankers discharge their load at shortest possible distance from the
points of collection to save time and cost. In many cities, dumping sites for FS are close
to squatter or formally inhabited low-income areas where they threaten the health of this
ever-growing segment of population. Children, in particular, are at greatest risk of getting
into contact with indiscriminately disposed excreta.
Lack of long-term urban planning and/or enforcement of existing zonal plans have lead
to the situation, whereby feasible landfilling or treatment sites at reasonable haulage
distance are lacking. Emptying services are poorly managed. A minor fraction (< 10 %
?), only, of the faecal sludges accumulating in on-site sanitation installations are formally
collected and discharged or treated. Where treatment schemes exist, charges are
usually levied for each load of FS delivered to the plant by private collectors. As a
consequence, they often prefer to dump the waste in non-designated sites to avoid fee
paying. This may go unavenged due to lack of competition among collection entreprises,
corruption and lack of adequate enforcement. Innovative incentive, fee levying and
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12
licensing procedures might contribute considerably to avoiding such problems and to
rendering FS management more sustainable 1.
In summary, the current situation of what might be designated “the urban shit drama”,
with its causes, problems and consequences related to FS management, can be
described and summarised in Table 2. Photos 1 and 2 illustrate the situation.
Photo 1
Uncontrolled discharge of faecal sludge at
the city’s outskirts
1
Photo 2
Discharge of untreated septage into a
fishpond in Vietnam
In Chpt. 4.6 (FS management in Bamakao, Mali), an innovative model for levying fees based
on balanced incentives for involved stakeholders is presented.
FS Management Review
Table 2
13
Current FS Management Practices – Causes, Problems and Consequences
Causes
FS management component and aspect
Problems
Consequences
Emptying + collection
·
·
Technical
Institutional / financial
·
·
·
Limited or no accessibility to pits
Inappropriate emptying equipment
Manual, non-mechanised emptying
·
·
·
Poor service management
Users’ low affordability for pit emptying
Lack of information (e.g. on how septic tanks work)
·
·
Traffic congestion
Lack of suitable disposal or treatment sites at
short distance from the area of FS collection
·
·
Lack of urban planning à lack of suitable disposal
or treatment sites at short distance from the area
of FS collection
Lack of involvement of private sector service
providers
Lack of suitable incentive and sanctions structure
·
Collectors minimising haulage distance and time
·
Overflowing pits
·
Emptying frequency often very low
·
Informal or emergency emptying of
pits and indiscriminate disposal of
FS
·
Collectors dump FS in an
uncontrolled manner at the shortest
possible distance from where FS
was collected
At neighbourhood level, mainly
Health hazards from openly dumped FS
and through use of contaminated water
· Eye and nose sores
· Non-functionality of infrequently emptied
septic tanksà solids carry-over
·
Haulage
·
Technical
·
Institutional
·
·
Financial/economic
At district or municipal level, mainly:
·
Pollution of surface and (shallow)
groundwater
·
Eye and nose sores
·
Health hazards from use of
contaminated surface water (e.g. for
vegetable irrigation)
Treatment
·
Technical
·
Lack of proven and appropriate treatment options
·
Financial / economic
·
Where FS treatment exists: private collectors /
entrepreneurs avoid the paying of treatment fees
·
Institutional / financial
·
·
·
·
Lack of political will to invest in treatment
Lack of effective cost recovery
Lack of urban planning
Lack of information
· FS is used or dumped untreated
At district or municipal level, mainly:
· Health hazards through use of
· Non-availability of suitable treatment
sites
· Use or discharge of untreated FS
contaminated water sources and water
pollution
FS Management Review
Table 2
14
Current FS Management Practices – Causes, Problems and Consequences (cont’d.)
Causes
FS management component and aspect
Problems
Consequences
Use in agriculture
·
Agronomic /
institutional / financial /
economic
·
Farmers in want of cheap soil amendment + fertilizer (in
many countries, farmers are traditionally accustomed to the
use of untreated or only marginally stored FS (“nightsoil”)
·
Private and public providers of FS collection + haulage
services interested in generating revenue from selling FS to
farmers while avoiding illegal dumping and/or payment of
treatment fees
·
Lack of enforcement of crop restrictions where such exist
·
Soils amended and
vegetables fertilised with
untreated FS
·
Potential health risks to
consumers
·
Institutional
·
Lack of promotion and marketing of biosolids produced in FS
treatment
·
Lack of incentives by
producers of biosolids and
by farmers to trade biosolids
·
·
Health
·
·
Farmers unaware of potential health risks
Lack of hygiene promotion
·
Lack of hygiene and health
protection
·
Actual health hazards to
farmers and consumers
·
Lack of implementation of FS treatment schemes, of town
planning and designation of suitable treatment sites; lack of
adequate fee structure and incentives for haulage of FS to
treatment sites
·
Indiscriminate dumping of
untreated FS
·
Water pollution and risks to
public health
·
Lack of promotion and marketing of biosolids produced in FS
treatment
·
High-quality biosolids
remain unused and need to
be landfilled
·
Depletion of soil organic
fraction and deterioration of
soil productivity
Disposal
·
Institutional
FS Management Review
2.2
Paradigms in Choosing Strategies and Technologies
Sewage and sewage sludge treatment processes and technologies, as are being
routinely and widely applied in industrialised countries, viz. extended aeration, digesters
(with or without gas utilization), mechanically stirred sludge thickeners, centrifuges, belt
presses, and vacuum filter presses, may, in theory, also be used for the treatment of
faecal sludge. However, the high degree of mechanization requires large capital
investment and high cost of operation and maintenance. The concomitant high degree of
sophistication calls for advanced professional skills. In developing countries, such
requirements may be satisfied only in larger cities or in economically more advanced
regions. In the majority of settlings in developing countries, though, the paradigms for
making technological choices as presented in Box 1 must be adhered to:
Box 1
Paradigms for making technological choices
·
Such options should be chosen, whose O+M cost and cost of
repair and replacement will be affordable in the long run to the
municipality or to the entity to which the works have been
entrusted.
(Although capital investments for urban sanitation infrastructure
are financed by external support agencies in full or part in many
cases, recurrent (O+M) cost is not. Hence, politicians and highlevel decision-makers should not give in to the temptation to opt for
the externally-financed high-cost solution, as capital-intensive
infrastructure will entail high recurrent cost. These would unduly
burden the city’s budget for decades to come or lead to
malfunctioning or disuse of infrastructure !)
·
Only such degrees of technical sophistication should be opted for,
which can be matched by adequate skills at all levels, viz.
operating, management + control.
Low-cost, easy-to-operate and sturdy technology alone do, however, not represent a
sufficient pre-requisite for sustained treatment and for the reliable production of effluents
and biosolids meeting stipulated standards. Even the simplest schemes require:
i
ii
regular and minimal operational care
maintenance and occasional repairs, e.g.
- removal of settled and accumulated solids
- cutting of plants growing on embankments
- de-blocking of conduits
- disposal of screenings
Without this, schemes will cease to produce the required level of treatment or may even
fail completely ! Hence, institutional responsibilities in budgeting, supervision and proper
staffing also extend to modest-cost, not so prestigious infrastructure !
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2.3
FS Management as A Component of Urban Planning in
Environmental Sanitation
Current FS management has resulted from the historical development in excreta
handling (which, often, is linked to agricultural practices), general socio-economic
developments and purposeful planning efforts, which indirectly or directly affect the
choice of sanitation systems. Improving on and finding appropriate strategies and
solutions in FS management must, thus, be dealt with in conjunction with both unplanned
and planned urban and peri-urban development, institutional settings, jurisdictional
conditions, and expected future sanitation infrastructure and service provision.
In short, an FS management concept should be based on the assessment of (Klingel
2001; Klingel et al. 2002):
·
·
·
·
·
·
existing sanitary infrastructure and trends
current FS management practices and their shortcomings
stakeholders customs, needs and perceptions regarding FS management and use
environmental sanitation strategy
prevailing socio-economic, institutional, legal and technical conditions, and
the general urban development concept
Based on an FS management concept, FS treatment objectives may then be formulated
and, consequently, feasible treatment options be evaluated.
In most places, a large array of technical, economic and institutional/organizational
measures are required to improve the FS management situation. Given the difficulties in
collecting FS and in hauling it across cities to designated disposal and treatment sites,
devising semi or decentralized FS management options is all-important. The devising of
modest-scale decentralized or “satellite” treatment plants (Fig. 3) and of neighbourhood
or condominial septic tanks (Fig. 4) may contribute significantly to reducing indiscriminate
dumping of FS and, hence, to reducing health and pollution risks. However, every city
has to be taken at its own merits, given the great variability of spatial settings, sanitation
infrastructure and planning mechanisms, which influence sanitation planning and the
allocation of suitable sites for either condominial septage tanks or FS treatment plants.
Also, such solutions call for non-conventional managerial approaches.
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17
What scale for FS treatment:
centralized or semi-centralized ?
Communal instead of individual septic tanks
è
FSTP
Objective:
minimize overall cost for collection, haulage and treatment
while guaranteeing safety in FS handling, use or disposal
Fig.
Fig.23
Semi or decentralized FS treatment – a
strategic tool to minimize cost, indiscriminate
dumping, health risks and water pollution
2.4
Economic aspects
2.4.1
Integrated Cost Considerations
è
Allows to cater for better access to septic tanks
and, hence, for more effective FS management
Fig. 4
The use of communal septic tanks – a
strategic tool to facilitate effective FS
collection
Whenever possible, cost of existing and improved FS management should be viewed not
only from a purely financial viewpoint (e.g., “what are the comparative cost of FS
treatment alternatives”) but also from an economic viewpoint. Hence, it will be necessary
to assess cost and revenue streams over time, to consider direct and social cost incurred
by e.g. not improving FS management. This, in turn, calls for including all components of
FS management, i.e. collection, haulage, treatment, use and disposal, as well as other
areas upon which FS management may impact, such as sanitation planning and
infrastructure (e.g. on-site sanitation vs. sewerage), health care, solid waste
management, agriculture. Such comprehensive assessments are justified for large urban
development projects. For smaller cities or for towns, though, such comprehensive
assessments might go beyond the scope of project budgets. Nevertheless, the direct
cost of FS management alternatives, inclusive of collection, treatment and reuse or
disposal should be assessed to allow a well-informed judgement. Also, potential impacts
on other urban activities such as health, solid waste management and agriculture should
be evaluated in a semi-quantitative or at least a qualitative manner.
2.4.2
Scale of Treatment Works vs. Haulage Cost
Looking at the scale and cost of treatment works and at cost of hauling FS to these
works in an integral is but one yet an important example of looking at cost in an integral
manner. In Annex 7.1, a model for determining per-kilometre cost of FS haulage is
presented. Such calculations are required when devising a concept for FS treatment in a
particular urban setting and to enable setting up contracts with private entrepreneurs in
charge of FS haulage and treatment.
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3 Technical Options (overview)
3.1
Faecal Sludge Characteristics and Specific Quantities
3.1.1
Per-capita quantities
Table 3 contains the daily per capita volumes and loads of organic matter, solids
and nutrients in faecal sludges collected from septic tanks and pit latrines, as well as
from low or zero-flush, unsewered public toilets. Values for fresh excreta are given for
comparative purposes. The figures are overall averages and may be used for planning
and preliminary design. Actual quantities may, however, vary from place to place.
Where nematode infections are not endemic and, hence, eggs may be found at
insignificant concentrations only in excreta and FS, bacterial pathogens (e.g.
Salmonellae spp.) or bacteriophages might be used as indicators-of-choice.
Table 3
Daily per capita volumes; BOD, TS, and TKN quantities of different
types of faecal sludges (Heinss et al. 1998)
Parameter
Septage 1
Public toilet sludge 1
Pit latrine
sludge 2
Fresh
excreta
•
BOD g/cap·day
1
16
8
45
•
TS
14
100
90
110
•
TKN g/cap·day
0.8
8
5
10
•
Volume l/cap·day
1
2
(includes water for toilet
cleansing)
0.15 - 0-20
1.5
(faeces and
urine)
g/cap·day
1
Estimates are based on a faecal sludge collection survey conducted in Accra, Ghana.
2
Figures have been estimated on an assumed decomposition process occurring in pit latrines. According to the
frequently observed practice, only the top portions of pit latrines (~ 0.7 ... 1 m) are presumed to be removed by
the suction tankers since the lower portions have often solidified to an extent which does not allow vacuum
emptying. Hence, both per capita volumes and characteristics will range higher than in the material which has
undergone more extensive decomposition.
3.1.2
FS characteristics
In contrast to sludges from WWTP and to municipal wastewater, characteristics of faecal
sludge differ widely by locality (from household to household; from city district to city
district; from city to city). Fig. 5 shows the vast differences of septage characteristics in
the three cities of Accra, Bangkok and Manila (Montangero and Strauss 2002) and Fig. 6
depicts the differences in solids contents of faecal sludges, WWTP sludges and tropical
wastewater (for wastewater characteristics, see Mara 1978).
FS Management Review
19
Fig. 5
80
Septage characteristics in Accra,
Bangkok and Manila – they are widely
differing !
60
40
Accra
Bangkok
20
0
Manila
CODtot [g/l]
TS [g/l]
Total solids (TS) concentration
Faecal sludge
High-strength FS
(e.g. from unsewered,
low or zero-flush public
toilets)
Low-strength FS
(septage)
WWTP sludge
Wastewater in the
tropics
mg TS/L
Primary and anaerobically
digested sludge
Waste activated sludge
1,000-1,500
0
10,000
20,000
30,000
40,000
Fig. 6 Solids contents of faecal sludges, WWTP sludges and tropical wastewater
A basic distinction can usually be made between sludges which, upon collection, are still
relatively fresh or contain a fair amount of recently deposited excreta (e.g. sludges from
frequently emptied, unsewered public toilets) and sludges which have been retained in
on-plot pits or vaults for months or years and which have undergone a biochemical
degradation to a variable degree (e.g. sludge from septic tanks – septage). Moreover,
varying amounts of water or wastewater are collected alongside with the solids, which
have accumulated in vaults or pits. Based on numerous FS monitoring studies, the
authors found that FS can often be associated with one of two broad categories, viz. high
and low-strength sludge. Table 4 shows typical FS characteristics. It is based on results
of FS studies in Argentina, Accra/Ghana, Manila/Philippines and Bangkok/Thailand. The
characteristics of typical municipal wastewater as may be encountered in tropical
countries are also included for comparative purposes.
Storage duration, temperature, intrusion of groundwater in septic tanks, performance of
septic tanks, and tank emptying technology and pattern are parameters which influence
the sludge quality and are therefore responsible for its high variability. Unlike digested
50,000
FS Management Review
Table 4
20
Faecal sludges from on-site sanitation systems in tropical countries:
characteristics, classification and comparison with tropical sewage
(after Strauss et al. 1997 and Mara 1978)
Item
Type “A”
(high-strength)
Type “B”
(low-strength)
Sewage – for
comparison purposes
Example
Public toilet or bucket latrine
sludge
Septage
Tropical sewage
Characterisation
Highly concentrated,
mostly fresh FS; stored for
days or weeks only
COD mg/l
FS of low concentration;
usually stored for several
years; more stabilised than
Type “A”
20, - 50,000
< 15,000
5 : 1 .... 10 : 1
COD/BOD
2, - 5,000
NH4-N mg/l
500 - 2,500
2:1
<
1,000
30 - 70
TS mg/l
≥ 3.5 %
< 3 %
< 1 %
SS mg/l
≥ 30,000
@ 7,000
200 - 700
20, - 60,000
@ 4,000
300 - 2,000
Helm. eggs no./l
sludge produced in mechanised biological wastewater treatment plants or in other types
of wastewater treatment works (e.g. waste stabilization ponds, oxydation ditches), the
organic stability of FS attains varying levels. This variability is due to the fact that the
anaerobic degradation process, which takes place in on-site sanitation systems, depends
on several factors, among them ambient temperature, retention period, and the presence
of inhibiting substances. The fact that the faecal matter is not being mixed or stirred
impairs the degradation process. The dewaterability is a varying parameter as well,
which is related to the extent that the sludge has undergone biochemical degradation.
Fresh, undigested sludge as is collected from public toilets, e.g., does not lend itself to
dewatering.
Sludge hygienic quality
In many areas of Africa, Asia and Latin America, helminth, notably nematode infections
(Ascaris, Trichuris, Ancylostoma, Strongyloides, etc.) are highly prevalent. Ascaris eggs
are particularly persistent in the environment. The bulk of helminth eggs contained in
faecal or in wastewater treatment plant sludges end up in the biosolids generated during
treatment. Hence, in many places, nematode eggs are the indicators-of-choice to
determine hygienic quality and safety where biosolids are to be used as a soil conditioner
and fertilizer. The concentration of helminth eggs in the biosolids is largely dependent on
the prevalence and intensity of infection in the population from which FS or wastewater is
collected. Where biosolids use in agriculture is a practice or being aimed at, treatment
must aim at reducing helminth egg counts and viability, or solids storage must be long
enough to achieve the desired reduction.
FS Management Review
3.2
21
Emptying , Collection, Haulage
Small, Engine-Driven Emptying Vehicles and Sludge Unloading Systems
Given the great difficulties in some urban areas to access toilet pits and septic tanks
through narrow lanes and backyards, emptying technologies were developed, which
allow pit emptying under such circumstances. Manus Coffey, an Irish manufacturing firm,
developed a 1-m3 vacuum tanker (“mini tanker”) in the 1980’s. The vehicle is widely used
in Eastern and Southern Africa by private and public emptying services. It is uneconomic for such small tankers to haul their load to the designated discharge or
treatment site after each emptying. Hence, the municipal emptying service of the City of
Maseru, Lesotho, e.g., has developed a system of sludge transboarding between the
mini tanker and a conventional-size vacuum tanker on a road nearest to the congested
area served by the mini tanker. Photos 3 and 4 show the mini tanker emptying and FS
transfer 1.
Photo 3
Mini-Tanker Closing Up to A Latrine
for Emptying (Maseru, Lesotho)
Photo 4
Transboarding of FS from a MiniTanker to A Standard-Size Vacuum
Tanker (Maseru, Lesotho)
The Sewer and Drainage Company of Haiphong (N. Vietnam), a public utility entreprise,
is responsible for septage collection. Collection is carried out with vacuum tankers and
small vacuum tugs for areas difficult to access, used together with intermediate-storagetanks mounted on a hook-lift truck. The mini-vacuum-tugs were developed by the
company in collaboration with a local manufacturer. They have a capacity of 350 L and
cost around $ 4,000. The combination of large and small equipment has proven
successful and almost 100% of the houses can be covered. Photos 5 a + b show a mini
tug and a storage tank, which can be hooklifted and hauled away.
1
The Vacutug is a newer devlopment of the mini-tanker produced by Manus Coffey
from Ireland. It is used in a UN-Habitat co-financed waste management project (see
http://www.un-habitat.org/urbsan/9-titleunchs.htm).
FS Management Review
22
The municipal emptying authority of the suburban town of Bharakpur near Calcutta have
procured an India made 2 m3 vacuum tanker, which is able to service pits in the more
densely built up city areas. Haulage distances to the nearest trenching site at the town’s
outskirts are relatively short; hence FS transfer to larger vehicles as is practiced in
Maseru, Lesotho, is not required. Photo 6 shows such a tanker during emptying
operations.
Photo 5 a + b
Haiphong made minivacuum tug (350 L) for
narrow lanes, used
together with a
intermediate-storagetank placed in the
nearest accessible road.
Photo 6
3
2m vacuum tanker emptying a
septic tank in a narrow lane in
Bharakpur (near Calcutta,
India)
Mapet – Hand-Powered Pit Emptying Technology
Mapet stands for Manual Pit Emptying Technology, a low-cost, decentralised emptying
technology developed by WASTE in collaboration with the Dar es Salaam (Tanzania)
Sewerage & Sanitation Department, pit latrine emptiers (scavengers), local leaders and
technicians, and residents in the late eighties/early nineties (Muller 1997). The project
comprised the technical as well as organisational development of a locally adapted and
rooted technology enabling the traditional scavengers to depart from their humiliating and
risky job of having to enter latrine pits for scooping out the faecal sludge. Further to this,
the new emptying option came in response to the inaccessibility of many residential
areas by normal vacuum tankers; the inadequacy of the municipal emptying service
organisation, and the non-affordability of emptying prices charged by the municipality.
MAPET equipment comprises a hand pump (activated by a manually driven flying
wheel), a 200 –litre vacuum tank (both mounted on a pushcart), flexible hose pipes, and
a mixing rod (see also Photos 7 and 8).
FS Management Review
Photos 7 + 8
MAPET equipment in the D.R. of Congo (Photos WASTE, Holland)
In the former pilot area in Dar es Salaam, where the system was developed, a MAPET
team consists or consisted of three workers, all self-employed. The team is autonomous
in organising its work and regulating the sharing of cost and income. The team operates
in a service territory assigned by elected neighbourhood leaders. The neighbourhood or
ward office serves as a booking office for residents who require pit emptying. The
municipality supports the MAPET micro-entrepreneurs by providing technical assistance
for major repairs. The emptiers can turn to local workshops for minor repairs.
The MAPET-based FS handling in Dar es Salaam is reportedly still operational to some
extent, yet with equipment partly dysfunctional. There is, reportedly, a strong demand
from community-based organisations (CBO) to procure equipment and introduce nonformal pit emptying services (Rijnsburger 2002). Meanwhile, MAPET has also been
introduced in the town of Barumbu, D.R. Congo, through a CBO. Informal emptiers paid
by a directly negotiated customer fee operate the system.
It is widespread practice to have pits or vaults emptied at intervals of several years, only.
This leads to solidification of the settled solids preventing removal by suction equipment.
Hence, manual curing of the lower part of the pit is required if the owners wish to utilise
the entire volume of their latrine pit or vault. For curing, emptiers need to step into the pit,
thereby exposing themselves to health hazards (see also Chpt. 2.1 regarding manual pit
emptying and related problems). There exist on the market vacuum tankers, which are
able to evacuate even solidified material, but investments and operating cost and, hence,
emptying fees, are high and affordable to high-income households only.
3.3
Treatment
3.3.1
State-of-Development in Treatment Technology
Contrary to wastewater management, the development of strategies and treatment
options to cope with faecal sludges, adapted to the conditions prevailing in developing
countries, have long been neglected. It is in recent years only (since about 1990) that
authorities in a few cities have pioneered to invest in improved FS management, notably
23
FS Management Review
treatment. This was perhaps in cities mainly, where people have most heavily been
affected by the “shit drama” situation (see Chpt. 2) and where problem holders have
been particularly sensitised to the “faecal film” prevailing in urban areas and impairing
public health, causing pollution and creating nose and eye sores. An amazing and
encouraging number of initiatives for improved FS management, including the devising of
appropriate FS treatment schemes, have cropped up very recently, particularly in several
West African states (Senegal, Mali, Ivory Coast, Burkina Faso, Ghana, a.o.).
Like the urban infrastructure services for FS management, R+D efforts, too, have been
lagging far behind those for wastewater. The authors have themselves been involved in
R+D on FS management since 1993. The prime efforts were thereby laid on developing
treatment options, which appear appropriate for DC. Issues pertaining to management
strategies and planning processes have become a focus more recently, only.
3.3.2
Treatment Goals and Feasible Options
Treatment goals and criteria
For what purpose should FS be treated – for rendering the treatment products (biosolids
and liquids) apt for discharge into the environment (inclusive of landfilling), or for
producing biosolids, which may be safely used in agriculture ? 1 What effluent and plant
sludge (biosolids) quality criteria should be met in treating FS for either of these goals ?
In the majority of less-industrialized countries, effluent discharge legislation and
standards have been enacted. Stipulated standards have usually been copied from those
enacted in industrialised countries, as the political will and the awareness regarding the
need to generating an informed judgement based on the specific conditions prevailing in
the particular developing country is usually lacking. Quite commonly, in DC, effluent
standards or the performance of infrastructure works are neither controlled nor enforced.
In most if not all cases, the standards were enacted having wastewater treatment and
discharge in mind. Faecal sludges and products from their treatment were hardly taken
into consideration. Thus, standards enacted in any particular country usually apply for
both wastewater and faecal sludge treatment. In most cases, the standards are often too
strict to be attained under the unfavorable economic and institutional conditions
prevailing in many countries or regions. For FSTP, the enacted effluent standards would
call for the use of sophisticated and highly capital-intensive treatment. Hence, the
paradigm of opting for modest solutions would be seriously violated.
In industrialised countries, pollution laws have been made more stringent in a stepwise
manner over many decades (see Fig.7; Bode 1998). Concurrently, wastewater and
sludge treatment technology has been upgraded stepwise to cope with an increasing
number of constituents and to reduce pollution loads discharged into the environment
1
Unless diluted by freshwater or effluent from wastewater treatment, the liquid effluents from
FS treatment are too high in dissolved solids, i.e. too salty, to be used for irrigation.
24
FS Management Review
25
(Johnstone and Horan, 1996). A suitable strategy would consist in also selecting a
phased approach, under the paradigm that “something” (e.g. 75 % instead of 95-99 %
helminth egg or COD removal) is better than “nothing” (the lack of any treatment at all or
the often totally inadequate operation of existing treatment systems) (Von Sperling,
2001).
The EU has adopted a rational strategy for public health protection in biosolids use. The
general principle is to define and set up a series of barriers or critical control points,
which reduce or prevent the transmission of infections. Sludge treatment options, which
were found to inactivate excreted pathogens to desirable levels, are the prime element in
this (Matthews 2000). “Barrier points” such as the sludge treatment works, can be easily
200
180
COD (mg/L)
160
140
120
100
80
Fig. 7
Gradual development of
the effluent discharge
standard for COD in
Germany
(Bode 1998)
60
40
20
0
1979
1985
1989
1990
controlled with respect to design and operations, thereby securing the compliance of the
treated biosolids with stipulated quality standards. In contrast to this, the controlling of
numerical quality criteria for wastewater or biosolids requires regular monitoring. In
economically less developed countries, such monitoring is often difficult and very costly
to perform. Results may not be reliable and replicable as adequate routine, quality
control and cross-referencing are lacking.
Numerical values – at the base of the barrier principle
In Table 5, a set of effluent and plant sludge quality guidelines for selected constituents is
listed. The suggested values are based on the considerations outlined below. Following
the principle of defining and setting up barriers against disease transmission, which can
be used as critical control points for securing safe biosolids quality, technically and
economically appropriate options for the treatment of faecal sludges and biosolids must
be defined, which will guarantee a defined quality level. Hence, numerical quality values
need to be used to define process specifications, yet they do not have to be regularly
monitored once the processes are in place.
Xanthoulis and Strauss (1991) proposed a guideline value for biosolids (as produced in
faecal sludge or in wastewater treatment schemes) of 3-8 viable nem. eggs/ g TS. This
recommendation is based on the WHO guideline of £1 nematode egg/litre of treated
wastewater used for vegetable irrigation (WHO, 1989), and on an average manuring rate
of 2-3 tons TS/ha·year.
FS Management Review
Table 5
26
Suggested effluent and biosolids quality guidelines for the treatment
of faecal sludges (Heinss et al., 1998)
BOD [mg/l]
total
filtered
A:
NH4-N
[mg/l]
Helminth eggs
[no./L]
FC
[no./100 mL]
Liquid effluent
1. Discharge into receiving waters:
•
Seasonal stream or estuary
100-200
30-60
10-30
£ 2-5
£ 104
•
Perennial river or sea
200-300
60-90
20-50
£ 10
£ 105
2. Reuse:
•
Restricted irrigation
n.c.
1)
£1
£ 105
•
Unrestricted irrigation
n.c.
1)
£1
£ 103
B:
Treated plant sludge
•
1)
2)
3)
3)
n.c.
n.c.
£ 3-8/ g TS 2)
£ Crop’s nitrogen requirement (100 - 200 kg N/ha.year)
Based on the nematode egg load per unit surface area derived from the WHO guideline for wastewater
irrigation (WHO, 1989) and on a manuring rate of 2-3 tons of dry matter /ha·year (Xanthoulis and Strauss,
1991)
Safe level if egg standard is met
n.c. – not critical
Use in agriculture
Examples for faecal sludge treatment standards are known from China and Ghana. In
the Province of Santa Fé, Argentina, e.g., current WWTP effluent standards also apply to
FS treatment. For biosolids used in agriculture, a helminth egg standard of £ 1 egg p. 4 g
of TS is being stipulated (Ingallinella, 1998).
Options and component overview (see Annex 7.2 for more details)
Fig. 8 provides an overview of options for faecal sludge treatment, which can be
implemented by using modest to low-cost technology, and which therefore carries a high
potential of sustainability. Some of the options were or are currently being investigated
upon by EAWAG/SANDEC and its partners in Argentina, Ghana, Thailand and The
Philippines and will be presented in the following paragraphs.
Proper FS treatment, either in combination with wastewater or separately, has been
practiced in a few countries only to date (e.g. China, Thailand, Indonesia, Argentina,
Ghana, Benin, Botswana, South Africa). The authors are aware of several, very recent
initiatives for improved FS management and treatment, notably in West Africa. Treatment
options used or proposed comprise batch-operated settling-thickening units; unplanted
and planted sludge drying beds; non-aerated stabilization ponds; combined composting
with municipal organic refuse; co-treatment of FS in wastewater treatment plants.
FS Management Review
Fig. 8 Overview of potential, modest-cost options for faecal sludge treatment
Below, a few basic aspects of FS treatment are outlined. A more detailed description of
selected treatment options is contained in Annex 7.2. They include:
·
·
·
·
·
Solids-liquid separation in settling-thickening tanks or in primary
sedimentation/anaerobic ponds
Sludge drying beds (unplanted; planted)
Pond systems for separate treatment of FS and combined treatment with
wastewater
Combined composting with organic solid waste (“co-composting”)
Anaerobic digestion with biogas utilization
In this report, the above core processes are described. For effluent polishing, such as
through pond systems or constructed wetlands, e.g., reference is made to the ample
literature available on the respective options. Biosolids resulting from the core processes
may have to be subjected to further storage or drying to achieve more extensive
pathogen inactivation and allowing their unrestricted use in agriculture. The add-on
treatment is not being elaborated upon in this report. Table 15 in Annex 7.3 shows
pathogen die-off periods in faecal matter at ambient temperatures and may be referred to
for estimating additional storage periods required to render biosolids apt for use.
The fact that faecal sludges exhibit widely varying characteristics, calls for a careful
selection of appropriate treatment options, notably for primary treatment. Primary
treatment may encompass solids-liquid separation or biochemical stabilization if the FS is
still rather fresh and has undergone but partial degradation during on-plot storage and
prior to collection.
27
FS Management Review
Faecal and WWTP sludges may, in principle, be treated by the same type of modest-cost
treatment options.
The separating of the solids and liquids, which make up FS, is the process-of-choice in
FS treatment unless it is decided to co-treat FS in an existing or planned WWTP and if
the FS loads are small compared to the flow of wastewater. Solids-liquid separation may
be achieved through sedimentation and thickening in ponds or tanks or filtration and
drying in sludge drying beds. Resulting from this are a solids and a liquid fraction. The
solids fraction, which may be designated as “biosolids”, is of variable consistency. It may
require post treatment, mainly to meet hygiene requirements for reuse in agriculture as a
soil-conditioner and fertilizer. Additional dewatering/drying might be required for
landfilling. Polishing treatment might be necessary for the liquid fraction, too, to satisfy
criteria for discharge into surface waters and/or to avoid long-term impacts on
groundwater quality, where effluents will be allowed to infiltrate.
3.3.3
Cost and land requirements
Investment and O+M cost of FS collection and treatment must be determined on a caseto-case basis, as local conditions are decisive. The following factors play a role:
·
·
·
·
·
·
·
Economic indicators (land price, labour cost, interest rates, gasoline prices)
Possible income from sales of treatment products (e.g. hygenised biosolids or
compost; biogas)
Site conditions (permeability, groundwater table)
Haulage distances and traffic conditions
Economy of scale (plant size)
Legal discharge standards
Extent of government subsidies and incentive structures (where schemes are
funded by non-government entities, primarily; see also Chpt. 4.6.3)
Further to this, the availability and choice of construction material, whether produced
locally or imported, play a role.
There is no published literature on FS management cost and no systematic search or
review of construction and O+M cost for FS management schemes has been made by
SANDEC to date. Consequently, only scarce information on cost is available.
Klingel (2001), in his FS management planning study for the city of Nam Dinh, Vietnam
(see also Chpt. 4.3), estimated the cost for three treatment alternatives based on bills of
quantities and labour salaries. The treatment schemes were designed to treat 2,500 m3
of septage annually. Table 6 shows capital, O+M, annualised cost per ton of TS, and net
land requirements for FS treatment by constructed wetlands, unplanted sludge drying
beds, and ponds comprising primary treatment in settling/thickening tanks (the figures
pertain to the main treatment units plus post-treatment of biosolids by extended
28
FS Management Review
29
storage/drying, but are exclusive of polishing treatment of the liquid fraction and of land
cost)
Table 6
Capital, operating, annualised cost, and net land requirements for
three FS treatment options planned in Vietnam (Klingel, 2001)
Treatment option
Capital cost
(US $)
1
2
Net land
Yearly O+M
cost
(US $)
Annualised cost
(US $ p. ton of TS)
requirement, m
Constructed wetlands
16,000
1,400
70
200
Unplanted sludge
drying beds
17,000
2,000
85
290
Ponds w. preliminary
settling
15,500
6,000
160
245
1
2
2
Excl. cost for design + construction supervision; depreciation period = 15 years; interest rate = 5 %
3
Comprise annualised capital and O+M cost; treatment for 2,500 m /year @ 20 kg TS/m
3
For small FS treatment works, gross land requirements (comprising land for the
treatment units; space in-between the units and space for corollary installations) are
approximately double the net requirements. Hence, for the options listed in Table 6
above, per-capita gross land requirements amount to 0.02 – 0.03 m2 (based on an
assumed per-capita FS generation of 0.5 L/day and a plant capacity of 2,500 m3/year).
3.3.4
How to Select A Treatment Option
FS treatment objectives may be formulated based on an FS management concept,
which, ideally, will have been developed as an integral component of an overall, city-wide
environmental sanitation plan.
Following this, a pre-screening of options deemed to be unsuitable in the particular
setting, should be performed. For example, if the city does not avail of a sewer system,
the option “co-treatment with wastewater” will be excluded. The option anaerobic
digestion with biogas use must be excluded if, for example, technical expertise is lacking,
and FS originate mainly from septic tanks and other on-site systems, which are normally
emptied at intervals of one or more years, only, and, hence, have undergone substantial
biochemical degradation already.
The second step consists in comparing the potentially feasible options chosen during the
pre-selection step according to selected criteria as shown in Table 7.
FS Management Review
Table 7
Criteria for selecting FS treatment options for Nam Dinh (Klingel et al,
2001)
Performance criteria
·
·
·
30
Process simplicity and
reliability criteria
Achievable consistency and
·
biochemical stability of biosolids ·
Achievable hygienic quality of
biosolids
·
Achievable quality of liquid
effluent
3.3.5
Cost-related criteria
O+M requirements
Skills required for operation and ·
supervision
·
Risk of failure related to
installations or to managerial or
procedural measures:
·
Land requirement.
Investment costs
Operation and maintenance
cost
Where FS Treatment Schemes are Being Operated or Planned
Table 8 lists a number of countries and cities where, according to the authors’
knowledge, FS treatment schemes have been implemented and are being operated or
where schemes are being planned. The list is not exhaustive. More treatment schemes
might exist elsewhere. The listing shows that efforts are under way in a number of
countries, although several of the schemes might have become partially or fully
dysfunctional, or operate below their design performance. To the authors’ knowledge,
only very few schemes have been investigated upon and monitored to varying levels of
details to date, viz. a full-scale pond scheme in Accra, Ghana; a pond scheme in
Cotonou, Benin, and a pilot co-composting plant in Kumasi, Ghana. The fact that the
majority of the treatment works have never been monitored makes it difficult to judge on
their performance and to make inferences as to their shortcomings. Hence, no lessons
could be learnt from these schemes to date.
The list also comprises the conceived, planned and implemented treatment schemes,
which form part of the FS management cases, described into further detail in the
subsequent Chpt. 4. There exist plans for monitoring one of them in due course, the
Kumasi (Ghana) FSTP, which consists of a series of satbilization ponds.
FS Management Review
Table 8
31
Examples of existing and planned FSTP
Country or city
1
Information and remarks
Asia
-
Approx. 100 plants (pond schemes, some of which are preceded
by Imhoff tanks) implemented; many plants reportedly
underloaded or non-functional
-
2 plants in Jakarta comprising extended aeration followed by
facultative and maturation ponds
Thailand
-
Low-cost schemes (digesters + drying beds + ponds) in provincial
towns; high-tech plants (physico-chemical treatment followed by
act. sludge) in metropolitan Bangkok
Ho Chi Minh City (Vietnam)
-
Drying ponds + sale of biosolids
Nam Dinh (Vietnam)
-
Constructed wetlands planned
Vientiane (Laos)
-
Low-cost treatment planned
P.R. China
-
Anaerobic digestion and other options
-
2 schemes in Accra + 1 in Kumasi + a few smaller FSTP (all
pond-based)
Pilot co-composting scheme in Kumasi
Cotonou (Benin)
-
1 pond scheme
Bamako (Mali)
-
2 FSTP (constructed wetlands and ponds) planned
Ouagadougou (Burkina
Faso)
-
Co-treatment in ponds (under construction)
Botswana, Tanzania
-
Co-treatment with wastewater in ponds
South Africa
-
Co-treatment with wastewater in activated sludge plants
Indonesia
Africa
Ghana
1
A listing based on authors’ observations and collated information
FS Management Review
4 Selected Initiatives for Improving FS Management
4.1
General Observations
The current practice of FS management, i.e. collection, haulage, discharge and use is
extremely diverse among different cities (even of the same country) and countries. While
mostly private entrepreneurs cater for the collection and haulage of FS in some selected
towns and cities (e.g. in Indonesia, Ghana, Burkina Faso, South Africa), other cities are
serviced exclusively by public utilities, i.e. parastatal entities or municipal departments to
date (e.g. Vietnam). In a third category of towns and cities, services are shared among
public utilities and private entrepreneurs. The public sector is likely to dominate the scene
in countries where a socialist political system prevails or has been prevailing until
recently and where private entrepreneuralship is as yet little developed, while the private
sector role tends to be more developed in non-socialist countries. In a few cases, FS
treatment schemes are or are planned to be operated by private entrepreneurs on a
contract or franchise basis (examples reported from Kumasi, Ghana, and Bamako, Mali –
see Chpts. 4.4 and 4.5 below – and from Kalimantan, Indonesia; Pollard 2002).
In many cities, there presumably exist also informal emptying and collection services
rendered by individuals or “mini entrepreneurs” who empty pits manually using buckets
or baskets, with subsequent on-plot burying of FS or haulage to nearby drains or surface
waters (see Chpt. 4.3, example from Nam Dinh, Vietnam; Klingel 2001). Such practices
may fall under the traditional modes of scavenging and should not be considered as
models for replication.
The authors are not aware of any FS management scheme or initiative, where
responsibilities and tasks would have been devolved to community based organisations
(CBO) or individual beneficiaries. Exceptions were reported by Muller (1997) and
Rijnsburger (2002) for places where MAPET, the manual pit emptying technology (see
Chpt. 3.2), has been developed and introduced (in Dar es Salaam, Tanzania, in the early
nineties; in Barumbu, Democratic Republic of Congo, in 2001).
4.2
Rationale for Choosing Vientiane, Nam Dinh, Kumasi
and Bamako as Selected Initiatives
Although the authors are familiar with FS management in a good number of towns and
cities, there are only a limited number of cities on which the knowledge is sufficiently
detailed or where, to the authors’ knowledge, initiatives for improvements are underway.
The four cities Vientiane, Nam Dinh, Kumasi and Bamako were selected because
initiatives comprising elements of decentralisation have been started in recent years and
useful lessons can be learnt from these cases. The authors are familiar with the FS
management situation and plans in these localities or have got at hand documentation
32
FS Management Review
33
allowing presenting a fairly detailed description. In particular, the authors have
themselves familiarised with the FS management situation – to variable degrees, though
– during field visits to Nam Dinh, Kumasi and Bamako. For the description on FS
management in Vientiane, the authors have relied on information provided by Parkinson
(GHK 2001), leader to this EngKAR project. Beside own field observations, Jeuland
(2002) and Mensah (2002) have provided in-depth documentation on the Bamako and
Kumasi initiatives, respectively.
4.3
Vientiane (Laos) – Plans for improved FS collection
and treatment formulated
4.3.1
The City, the Sanitation Situation and Challenges
A planning study for improving sanitation, drainage and wastewater management in the
City of Vientiane, Laos PDR, has been completed in early 2001 (GHK 2001). This forms
a component of the proposed Vientiane Urban Infrastructure and Services Project
(VUISP), which is to be implemented by the Vientiane Urban Development and
Administration Authority (VUDAA) and to be co-financed by the Asian Development Bank
(ADB). The existing sanitation infrastructures, the collection and disposal or use of FS
from the on-plot sanitary installations and the problems associated with the current
practice have been assessed by the study. Proposals for infrastructure improvements,
service enhancement and modes of implementing the plans have been presented.
The City of Vientiane is divided into 112 villages, comprising a total area under VUDAA
jurisdiction of 30 km2 and with a current estimated population of 160,000. The city lies on
low-lying alluvial soils deposited by the Mekong River. The area is flood-prone and
characterised by generally high groundwater table and clayey-loamy soils with low
permeability.
Box 2
Vientiane’s current FS management in a
nutshell (GHK 2001)
·
Sanitary installations:
-
-
·
35 % septic tanks
63 % cesspools and latrines of various kinds
Widespread and frequent failure of toilet and
soakage systems à pollution and health hazards
in neighbourhoods
Collection, haulage, treatment, and disposal:
-
Emptying frequency = 1…5 years
8 out of 10 vacuum tankers privately owned
FS co-treated with wastewater in a WSP
scheme
Fees levied for treatment, hence, substantial
FS quantities are dumped illegally or used
untreated
Photo 9
Pour-flush toilet with
soakage pit in Vientiane,
Laos (Photo J. Parkinson,
GHK)
FS Management Review
34
Photo 10
Emptying of a difficult-toaccess septic tank in
Vientiane, Laos (Photo J.
Parkinson, GHK)
All sanitary installations are on-plot. Their contents overflow directly into surface drains.
Installation design, construction and maintenance are generally very poor, leading to
heavy pollution of soils and water in people’s surroundings, particularly in low-income
areas. The current situation with respect to FS management in Vientiane is summarised
in Box 2. Photos 9 and 10 show the typical situation of household sanitation.
4.3.2
Towards Improved FS Management
The comprehensive sanitation-upgrading plan builds heavily on the decentralization
paradigm; both regarding the development of improved sanitation infrastructure (at
household, neighbourhood and municipal levels) and services, as well as regarding the
procedures through which the plan should be implemented. The collection of FS shall be
enhanced by making provision for increasing truck fleets of entrepreneurs mainly (e.g.
through the City leasing out trucks it may purchase through external funds, or by devising
suitable credit programs), while strengthening the supervisory role of the municipality,
e.g. by enforcing FS delivery to the designated treatment sites. Modest-cost,
decentralised FS treatment facilities shall be constructed. The project for a previously
conceived FS treatment plant to be sited some 18 km from the city shall be given up (a
FS treatment plant located at such a long distance from the area of collection may hardly
ever receive any FS !).
The proposed improvements shall first be tried through pilot projects in selected City
districts with socially stable communities (“villages”), which avail of land tenure. Village
groups shall be formed as the administrative planning foci, whereas appropriate
infrastructure solutions shall be devised based on the City’s sub-catchment (and housing
?) areas.
4.3.3
Lesson
Experience has led to a policy whereby private entrepreneuralship for FS collection and
haulage shall be promoted by the municipality. The need for physical decentralisation of
future FS treatment schemes is being recognised and has been taken into consideration
FS Management Review
35
when formulating the plans for improved FS management. Concurrently, neighbourhood
or city district (“village”) groups shall form the planning foci, hence, there is intention to
devolve specific responsibilities from the municipal authority to the beneficiary level. The
initiative for FS management improvements originated from the municipality. Overall
responsibilities for planning, implementation and future enforcement rest with the
municipality.
4.4
Nam Dinh (Vietnam) – Rapid upgrading of household
sanitation calls for effective FS collection and
treatment
4.4.1
The City, the FS Management Situation and Challenges
The City of Nam Dinh is located in the Red River delta in Northern Vietnam, 90 km SE of
Hanoi. Like Vientiane, it is built on the alluvial, finely divided soils deposited by the river.
Box 3
State-of-practice in sanitation and FS management in
Nam Dinh (Klingel 2001)
·
Sanitary installations (1997):
-
·
Collection, haulage and disposal:
-
·
50 % septic tanks (expected to rise to 85 % by 2005)
20 % bucket latrines (private and public)
10 % dry latrines
16 % toilets directly conmnected to drains
Low frequency of septic tank emptying
à blockage of stormwater drains trhough solids carry-over;
pollution of surface waters
Public utility service poorly managed and equipped
Vehicles not having acces to narrow lanes
Self-employed latrine scavengers provide cheap emptying
service
Discharegh of FS into fish ponds
FS use:
-
-
Traditionally, high demand for bucket latrine sludge; today’s
demand >> supply
Fish pond fertilization
Photo 12
Typical nam Dinh alley; special
equipment is needed to enable
emptying of latrines and septic tanks
at adequate frequencies (see also
Chpt. 3.2 for emptying technology)
FS Management Review
36
Photo 11
Heavily polluted and partially blocked
rainage ditch in Nam Dinh
The City has heavily suffered from flooding until a few years ago. It has substantially
improved the drainage infrastructure and its operations in the course of implementation
of the Nam Dinh Urban Development Project, a joint undertaking of municipal and
provincial authorities wit the support by SDC. The City has a population of 230,000. It is
surrounded by intensely cultivated farmland, where mainly rice and vegetables are
grown. There exist also several natural lakes on the City’s outskirts and constructed
ponds in public recreational areas. Fish are proliferating in both ponds and lakes.
Box 3 contains the relevant information on the current status of sanitation developments
and FS handling. A drainage ditch in Nam Dinh, typically polluted by excreta-loaded
surface runoffs and partially blocked with faecal and other solids in shown in Photo 11.
Sanitation systems in place in Nam Dinh comprise septic tanks, bucket latrines, pit and
double-vault/urine separating latrines (Klingel 2001). Bucket latrines, the contents of
which are collected and used by farmers in peri-urban agriculture are rapidly being
phased out and replaced by pour or cistern-flush toilets connected to a septic tank. Nam
Dinh does not have a sewerage system. Overflows from septic tanks are discharged into
the surface drainage system (when walking through the City, one can clearly see the
pipes crossing underneath the walkway and discharging into the street drains; this is
certainly not unique in Vietnam), which finally discharges into either the Red River or
lakes and fishponds. Hence, there is a lot of excreta-fertilised fish production (natural and
induced). Faecal sludge, which comprises septage (the contents of septic tanks), bucket
latrine sludge (nightsoil in its proper sense) and sludges from other pit or vault toilets, is
formally emptied by URENCO, the City's emptying service (but the service is weak for
several reasons) and informally by municipal workers who render the service in their free
time as micro-entrepreneurs. Their service is cheaper than the one offered by the public
utility. The hand-emptied sludge is discharged into the nearest drains or (fish) ponds.
Bucket latrine sludge is still collected by farmers or sold to farmers by those who collect
it, but this happens at a diminishing rate as bucket toilets are being replaced by septic
tanks at a high pace.
FS Management Review
4.4.2
37
Plans for Coping and Improving
A recently conducted FS management planning study (Klingel 2001) has documented
the problems and challenges based on an in-depth assessment of the current situation,
stakeholder needs and perspectives and expected sanitation developments.
Stakeholders contacted and interviewed are:
·
·
·
Farmers and fishermen (often the same as
many farming families own small domestic fish
ponds)
Farmers’ cooperatives
Provincial Agricultural and Rural Development
Service
·
·
·
·
Municipal Agriculture Department
URENCO
UCMC
Households
The need for emptying increased numbers of septic tanks is imminent, as thousands
have been installed in recent years in the course of the Nam Dinh UDP credit scheme.
They will gradually fill up with solids and, hence, cease functioning. The frequency at
which citizens have their septic tanks emptied remained low to date, like in most
countries, also because of limited willingness or ability-to-pay by the users. The
inadequate frequency of septic tank emptying causes considerable carry-over of
wastewater solids into the surface drainage system, thereby causing public health risks
and silting of drainage canals. As a consequence, canals may not fulfil their function
during periods of increased surface runoff. Flooding will then be aggravated. Hence, the
intensive use of septic tanks for excreta and wastewater management remains
inappropriate unless efforts are undertaken to arrive at increased frequencies of septic
tank emptying. Even with better emptying practices, though, non-negligible loads of
pathogens are discharged from septic tanks into street drains, drainage ditches and
canals via the settled effluent. Devising an emptying management based on efficient and
cost-effective public or private entrepreneurship is therefore needed. In densely built-up
neighbourhoods, septic tanks may often not be accessible due to the narrowness of
lanes. Appropriate equipment needs to be procured and put at use to overcome this.
Faecal sludges collected from septic tanks and bucket toilets remains untreated to date.
Devising appropriate treatment has now become an issue of high priority among the Nam
Dinh authorities, as increasing numbers of septic tanks become due for emptying.
Treatment schemes are required which need to be strategically located to minimise
haulage distances and allow for easy marketing of treatment products to farmers and
fishermen. Experience has shown that identifying areas for treatment of either liquid or
solid waste is difficult due to public resistance from nearby dwellers or from dwellers
living along access roads.
Two FS management improvement options and three potentially feasible FS treatment
options have been proposed by the FS management planning study (Klingel 2001). Box
4 describes the options in a summarised form.
FS Management Review
Box 4
FS management and treatment options for Nam Dinh
·
Management option A
-
·
Improving on public utility’s collection and haulage capacity
Public awareness campaign for enhanced frequency of septic tank emptying
Considering subsidzing of emptying fees
Regulations for and licensing of private entrepreneur involvement in FS collection and
haulage
Devising appropriate FS treatment schemes
Management option B
-
Frequency of septic tank emptying regulated by authorities
Public awaerness campaign
Devising (subsidized ?) empyting fees or introducing a public utility tax covering water,
4.4.3 Lesson
pit emypting, electricity, etc.)
Regulating private entrepreneur involvement
Devising appropriate
FS treatment
FS management
has not kept
up with schemes
the rapid pace at which household-level sanitation
became
upgraded through the installation of septic tanks. Traditionally, most FS was
· Treatment and use
manually collected for use in agriculture. Replacement of bucket latrines by septic tanks
Three low-cost options, producing biosolids safe for use in agriculture, viz.:
calls for a different mode of FS collection, both technically and organisationally, if the
- Constructed wetlands w. effluent polishing in a pond
uncontrolled dumping of septage is to be avoided. The need to devise improved FS
- Drying beds + post-storage of biosolids and effluent polishing in a pond
collection management and appropriate treatment for septage has been recognised by
- Settling/thickening followed by a series of ponds for liquid treatment + drying of
city authorities.
FS treatment
will+ be
based
on physical
biosolids
on drying beds
effluent
polishing
in a pond decentralization, using modestscale -treatment
works
strategically
located
at
the
Demonstration trials for biosolids-manured soilscity
andoutskirts.
crops and marketing through the
traditional outlet channels, viz. farmers’ cooperatives
4.5
Kumasi (Ghana) – Managerial and Technical Solutions
in Place
4.5.1
Geographical Setting and Developments in Environmental
Sanitation
Kumasi, located 300 km Northwest of Accra, covers 150 km2 and counts about 1 million
inhabitants. The city is an industrial centre with formal industries in timber, food
processing (including beer brewing) and soap manufacturing, together with informal
activities in woodworking, light engineering, vehicle repair, footwear, furniture
manufacture and metal fabrication.
Most residents in Kumasi (about 38%) use public toilets for which they pay between ¢20
and ¢1001 per visit depending on the type of facility. Another 26 percent use household
water closet facilities; The unhygienic bucket latrine system caters for around 12% of the
population; 8% rely on sewerage while pit latrines (KVIP/traditional; 10%) and the bush
provide for the rest of the population (Mensah 2002 a).
1
1 US$ = 7,800 cedis (March 2002)
38
FS Management Review
One of the most critical waste disposal problems of the city of Kumasi is the disposal of
nightsoil and septage from public latrines, household bucket latrines, and septic tanks.
The current system of human waste management in Kumasi is inadequate; waste
removed from the public and bucket latrines end up in nearby streams and in vacant lots
within the city limits creating an unhealthy environment. Many government offices,
schools and private institutions require improved sanitation facilities. Industrial effluent
from the breweries, leachate from sawmills and waste oil spillage from the vehicle repair
complex is also discharged into receiving waters without treatment. The storm water
drainage system is essentially an open sewer, which discharges surface water, and as a
result the beneficial uses of these rivers (domestic water supply, irrigation, livestock
watering and recreational activities) are adversely affected for a number of miles
downstream.
The Kumasi Metropolitan Assembly (KMA) with the assistance of the UNDP/World Bank
Water & Sanitation Program (now the World Bank Water & Sanitation Program)
produced a Strategic Sanitation Plan for Kumasi (SSP-Kumasi) for the period 1990-2000.
The Plan was updated for the period 1996-2005. The SSP-Kumasi identifies the facilities
needed to provide comprehensive services; describes the implementation and financing
arrangements for each component; and sets priorities.
Technical options were recommended for each type of housing areas in the city based
on the characteristics of these areas as well as user preference, willingness and ability to
pay. The SSP-Kumasi recommended the use of simplified sewerage in the high-density
area, latrines in the medium-density areas and WC/septic tanks in the high-cost/lowdensity areas. The cost of household latrines would be shared equally by the city and
beneficiaries on a 50:50 basis. The construction of new public sanitation facilities were
encouraged in markets, schools and light industrial areas, while existing public bucket
latrines were phased out. Two faecal sludge treatment plants were planned, one of them
is built and ready to be commissioned, the construction of the second one should start
this year.
4.5.2
Stakeholder Involvement
KMA moved from direct provision of sanitation services, and started promoting and
establishing active involvement of both communities and the private sector in their
delivery. According to the SSP, the private sector should be involved in the faecal
sludge collection and haulage, operation and maintenance of the facilities (public toilets,
sewerage systems, treatments systems for sewer and faecal sludge) including the
collection of user charges (Kumasi Metropolitan Assembly 1995). Holding workshops to
which entrepreneurs as well as service users are convened has meanwhile become
established practice in Kumasi.
4.5.3
FS Management
39
FS Management Review
Sanitary facilities
There are about 400 public toilet facilities in Kumasi, which provide service to 400,000 of
the city’s population. Public toilets are equipped either with flush toilets and a holding
tank or VIP latrines with 2 pits per latrine (used alternatively) or one pit per latrine. The
use of double pit latrine has not proved successful. As the pits were filling faster than
expected the sludge retention time in the unused pit was too short to allow sludge
stabilization.
High maintenance standards at the public toilets have been difficult to achieve over the
years. The introduction of franchise management arrangement involving the private
sector in 1992/1993 saw some significant improvement. During this period, a private
partnership (franchise) approach was carried out. KMA controlled the construction and
had the overall responsibility for the toilet facilities. The private contractors were
responsible for the operation, maintenance and management of the toilets. However,
since January 97, when the Assembly members started managing the toilet sites, the
situation has deteriorated considerably. Users complain about dirtiness, smell and user
fees. Only 10% of the users are satisfied with the quality of the public toilets. According
to Frantzen (1998), the toilets were managed much better and more effectively by private
contractors than by Assembly Members. In a public-private partnership, tasks and
responsibilities are divided between the different actors, the role of the various actors and
the relationship between public and private actors are clearly defined and the various
actors can work in a more accountable and transparent way. Ineffective pubic toilet
management under the Assembly Members is reportedly due to unclear divisions of
tasks and responsibilities between the various actors involved. Frantzen (1998)
concluded that in public-private partnerships, clear rules concerning the division of tasks
and the roles of the different actors can be included in contracts, increasing
accountability, efficiency and transparency and hence quality of provided services.
About 120,000 people use bucket or so-called pan latrines. Due to the unhygienic nature
of this type of toilet and lack of conservancy labourers, WC-septic tanks or KVIP latrines
(home latrine programme) are replacing bucket latrines.
There are several sanitary sites in the city. The sanitary sites consist of a refuse
collection point and a public toilet. In areas where bucket latrines are still in use a holding
tank for bucket latrine sludge is located at the sanitary site. Vacuum trucks empty the
holding tanks
About 260,000 people use WCs linked to septic tanks and seepage pits. Septic tanks
perform well in areas where there is sufficient space for a drain field; however, most of
the existing septic tanks overflow to surface drains due to undersized or non-existent
drain fields.
About 268 (out of 301) secondary schools in Kumasi have sanitation facilities integrated
into the school compound. Most facilities lack organised management, and the aqua
privies and cistern flush systems, which are the most common systems, do not have
drain fields. As a result most school facilities are in serious state of neglect and provide a
40
FS Management Review
41
poor basis for teaching hygiene and environmental awareness to students (Mensah 2002
a).
Faecal Sludge Collection and Haulage
There are currently seventeen haulage trucks (see Table 9), which provide desludging
service in Kumasi. As proposed in the Strategic Sanitation plan, faecal sludge collection
and haulage has been partly privatised. The KMA, the Army, the Police, Prisons and
KNUST own one truck each while the remaining 12 belong to four different private
operators. The 17 trucks haul an average of 84 trips of septage a day, which represents
sufficient capacity to meet the septage haulage needs of the city (Mensah 2002 a).
Table 9
Item
Desludging Service Operators in Kumasi
Company/Organization
No. of
Trucks
Average No.
of Trips/Day
Operating Status
1
KMA-WMD
1
2
Protocol Service
2
Babdako Enterprise
5
35
Commercial Service
3
Albert Joseph & Co.
1
3
Commercial Service
4
Planet Green Enterprise
2
10
Commercial Service
5
Afranie Sanitation Services
4
28
Commercial Service
6
Ghana Prisons Service
1
2
Protocol Service
7
Ghana Police Service
1
1
Protocol Service
8
Ghana Army
1
1
Protocol Service
9
University
1
2
Protocol Service
Total
17
84
Privately owned vehicles transport 76 out of the 84 truckloads. Private contractors are
licensed by KMA. KMA sets a range of collection fees within which the operators are
supposed to operate. KMA’s truck empty tanks/pits belonging to government employees
(protocol service). The service is free. It also provides desludging service for nongovernmental employees, in case KMA’s truck operators are available (besides protocol
service). In this case, KMA’ service is cheaper than the private one, however, clients
have to wait longer. Emptying fee is about $ 10 (the monthly salary of a truck driver was
$ 40 in 1990, for comparison’ sake).
FS disposal + treatment
Faecal sludge (average 500 m3 per day) is currently disposed of at the Kaasi site with
reasonable degree of cooperation in terms of payment of tipping fees and emptying at
the designated site. Private truck operators have to pay a tipping fee of 1.5$. The Kaasi
pond system was built as temporary treatment system in January 2000 (Africa Cup). The
desludging of the system is not feasible; ponds have been filled with solids resulting in
inadequate treatment of the effluent that flows into the Subin River. Ponds will soon be
FS Management Review
taken out of operation as a new treatment facility has been built at Buobai, 14 km north
east of the city centre under the Urban Environmental Sanitation Project (UESP/world
Bank) and is yet to be commissioned.
The Buobai plant consists of two settling ponds followed by facultative and maturation
ponds and is designed to treat about 200 m3 sludge per day. Trucks will have to pay a
tipping fee, probably a bit higher than in Kaasi due to the fact that operational and
maintenance costs will be higher. KMA trucks will not have to pay. According to the
experience gained in Kaasi there is indication that truck drivers will not discharge their
load indiscriminately but transport it to Buobai and pay the discharge fees. The Waste
management and the Environmental Health departments of the KMA have been warning
truck drivers through letters and periodic meetings regarding the need for high
environmental protection standards. Moreover they risk loosing their license if they are
caught discharging at an illegal site. Operation and maintenance will be handled by the
private sector under franchise scheme. However the waste management department will
manage the plant during the first 3 months of operation in order to determine the surtax
to be paid by the private contractor to KMA based on FS inflow and cost for operation
and maintenance. The contractor will also be responsible for biosolids management.
Drying beds were planned to dewater the settled solids desludged from the settling
ponds but could not be built because of shortage of funds (Mensah 2002 b).
The Environmental Sanitation Policy states among others that “recycling of waste for
industrial, agricultural and other uses shall be practiced wherever it produces a net cost
reduction or positive environmental impact” and also that “the promotion of waste
reduction shall be an integral part of waste management”. It is mentioned in Annex 2 that
“composting shall be carried out using simple methods and on decentralised basis, as
near as possible to the point of generation. It shall only be carried out if it results in the
net savings to the Assembly in terms of reduced transport and landfill requirements and
possible revenue (estimated with due regard to the limited market for compost)”. Salifu
(2001) demonstrated that for a 500 houses scheme, a 20% composting of the
biodegradable organic fraction can save up to US$ 100/month in transportation costs as
well as extend the landfill space by nearly 5 years.
A pilot co-composting plant (composting of organic solid waste and dewatered faecal
sludge) has been put in operation at the beginning of 2002. The plant is located at the
Buobai FS treatment site. Investigation of the system just started and will deliver
information on the sustainability (marketability, etc.) of this treatment option in the
Ghanaian context. The pilot project is co-ordinated by IWMI (International Water
Management Institute) in collaboration with the University of Science and Technology in
Kumasi, the Waste Management Department (KMA) and SANDEC. Results of the
investigation will help the WMD (Waste Management Department) develop its biosolids
management strategy.
A new landfill will be built in the South of the city (Dompoase). Another FS treatment
plant will also be built at the landfill site and serve the southern section of the city.
42
FS Management Review
Besides faecal sludge landfill leachate will also be treated in the plant. Construction
works is expected to start in 2002.
4.5.4
Wastewater Management
Overview
Five small-scale sewerage systems with target coverage of about 40,000 people
currently exist in Kumasi. They include:
·
·
·
·
·
The Conventional Sewerage System at KNUST;
Asafo Simplified Sewerage System built in 1994;
Ahinsan Satellite Sewerage System rehabilitated under UESP in 2001;
Chirapatre Satellite Sewerage System rehabilitated under UESP in 2001; and
Komfo Anokye Teaching Hospital (KATH), City Hotel and the central parts of the
4BN Army barracks Conventional Sewerage System.
The treatment facilities to the University (KNUST) and KATH systems are currently not
functioning (Kumasi Metropolitan Assembly 1995).
Asafo Simplified sewerage System
The Asafo simplified sewerage network was built in the high-density area in 1994 as
recommended in the SSP. Sewage is treated in a waste stabilization pond system. The
Asafo scheme has not been as satisfactory as planned. The main problem is the price
the users have to pay. Water fees in Kumasi increase with water consumption. The
inhabitants of this area just fall into a higher price category (commercial price) as they
use flush toilets (9l/flush). They are not able to pay a sewerage fee in addition to this high
water fee. The scheme was supposed to be franchised. A private contractor should
manage the system, operate and maintain the scheme and collect the sewerage fee by
the beneficiaries. The sewerage fee was supposed to cover operation and maintenance
costs of the sewerage and pond system. The actual situation is different: a private
contractor manages the Asafo treatment plant for a fixed monthly fee paid by KMA. KMA
has been paying the fixed fee to the contractor, as the payment of maintenance fee could
not be enforced. 60% of the people who have connections use them. These 60% paid
the connection fees but don’t pay the monthly sewerage fee.
Satellite sewerage networks: Chirapatre and Ahinsan
The two low cost housing estates – Chirapatre and Ahinsan – were built in the late
seventies. They were equipped with networks of sewer collection and communal septic
tank systems for black water. Chirapatre counted 6 communal septic tanks for a
population of 1800 inhabitants and Ahinsan 5 for about 1500 inhabitants. Sewer lines
were blocked and septic tanks were in a bad state of maintenance. Both schemes have
been replaced with 2 sewerage networks for blackwater and waste stabilization pond
systems. Greywater (effluent bathrooms and kitchens) is discharged in the drainage
43
FS Management Review
system. The need for an effective maintenance and management structure was
recognised. The unsuccessful maintenance of the previous schemes is reportedly due to
lack of resources and technical know-how of residents. A management plan was
prepared by the KMA. Private contractors will undertake the operation and maintenance.
The community has been involved in the preparation of the management plan. It will also
be involved in the execution of the scheme, especially in its maintenance. The sharing of
the operation and maintenance costs has also been defined. A steering committee
(community members) will advise the company responsible for operation and
maintenance. The operator will collect the fee (Mensah 2002 b).
4.5.5
Reuse practices
Farmers located along the Subin drain (one of the four main drainage canals) or Subin
River (in which the Subin drain discharges) use the Subin water for irrigation. The
drainage channels are partially covered and transport rainwater as well as greywater,
septic tank overflows and blackwater. Drains and streams are heavily polluted and
exhibit high FC concentrations (Mensah et al. 2001).
Untreated faecal sludge reuse in agriculture as it is practised in Tamale (northern Ghana)
is apparently not common in Kumasi. A preliminary study aiming at assessing farmers
perception with regard to faecal sludge reuse (compost produced with organic solid
waste and faecal sludge) as well as their willingness/ability to pay was conducted among
90 farmers in 2001. The results indicate that 2/3 of the farmers are willing to pay for the
compost. The main factor that could motivate the farmers is field trials (IWMI 2001).
However, the study was carried out before the operation of the co-composting plant
started. The study will therefore be repeated once compost will be available.
4.5.6
Lesson
Efforts to improve on Kumasi’s sanitation are dating back to the late eighties and have in
its nature been a top-down approach with initial decisions taken on the central, municipal
level. Hence, the decision to improve the city’s FS management through an array of
measures comprising the household-level and public toilet installations, FS collection and
FS treatment was taken at the “top”. However, elements of decentralisation were
introduced from the early stages: by devolving parts of the decision-making to local
stakeholders, by promoting private entrepreneurship for public toilet management, FS
collection and FS treatment, and by devising two FS treatment plants to cater for the
sludge loads currently being collected.
44
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45
4.6
Bamako (Mali) – The dynamics of small entrepreneurship 1
4.6.1
The City and the FS Management Situation
The City of Bamako, Mali, is the country’s capital. It straddles the river Niger and has a
population of 1–1.2 million. The City is administratively truncated into 6 districts
(“Communes”), each comprising from 10-12 wards. Sanitation systems in use in Bamako
encompass private and public latrines of various types, septic tanks and a low-cost
sewerage scheme covering a small zone of the City. The emptying of pits and vaults is
accomplished by 25 vacuum trucks and 4 collection vehicles with manual suction pumps
(33 tractor and 1 donkey-drawn). Urban agriculture plays an important role, with some 6
% of the population involved in vegetable, flower and tree growing (Visker 1998; Towles
2001). FS are widely applied in vegetable, cereal and tree growing, usually after some
type of processing (storage upon mixing with organic solid waste, plant residues or cattle
dung). The fact that excreta are traditionally used in agriculture should render it fairly
easy to sell a finished treatment product (biosolids or compost) to farmers.
Photos 13 and 14 show, respectively, a NGO operated public toilet and manually
operated pit emptying equipment.
Photo 13
Photo 14
Bamako (Mali), Lafiabougou market: public toilet
operated by the Women’s Cooperative for
Family Health and Sanitation (COFESFA)
Tractor-drawn suction tank with manual membrane
pump operated by Commune III of Bamako (Mali)
Starting in the early nineties, small entreprises (“groupes d’intérêt économique”, GIE –
economic interest groups) became established in response to the Malian government’s
reduction in hiring for civil posts. In order to help many of the unemployed graduates
affected by this decision, the government offered small loans to these private enterprises.
They started rendering services in the public needs sectors such as sanitation. A group
1
This paragraph is largely based on contributions by Marc Jeuland and Cordes Towles, Peace
Corps Volunteers seconded to Sema Saniya, a Malian micro-entreprise devising FS and solid
waste collection, haulage and treatment services in the City of Bamako.
FS Management Review
or entreprise called “Sema Saniya” was the first of the GIE to be founded in 1991, with
others been established meanwhile. Sema Saniya is currently (April 2002) preparing
plans for a faecal sludge treatment plant (FSTP) to treat FS collected from the City’s
Communes V and VI.
CEK-Kala Saba, an NGO working in the environmental sanitation sector as facilitators,
project co-ordinators and technical-managerial consultants, are developing plans for
another FSTP to treat FS from Commune IV 1.
Sema Saniya started with a few donkey carts to dispose of garbage and has now
advanced to two tractors with a biweekly collection serving over 1,500 families. They
have also acquired two vacuum trucks in the process. The company has reportedly other
satellites in other areas, but due to some governmental regulations is not in direct control
of them. Sema Saniya has built and operates many public toilets in other districts of
Bamako area and is planning to expand on these services. Their main source of
revenue, however, is the removal of faecal sludge from septic tanks (septage) and public
toilet vaults.
Government currently plays but a minor role in the sector of FS collection and haulage to
date. Emptying, collection and haulage services are largely privatised. There are no
contracts or regulations governing the locations served by a particular company. SemaSaniya frequently empties latrines throughout the city, as it is currently the largest and
most dependable sanitation company.
Citizens of Bamako wait to empty their toilets until they are completely filled, in the
interest of saving money, generally over 2 years though this time depends on the number
of people using the toilet. Public toilets can require evacuation monthly or more
frequently during periods of great population passage. The sludge is being dumped in
fields in and outside of Bamako. Government does not exert any control. Hence, unsafe
handling and dumping of FS goes by unavenged.
4.6.2
Recent FS Management Initiatives
The GIE Sema Saniya and the NGO CEK-Kala Saba are planning two treatment works
for Communes IV and V+VI on their own initiative, i.e. without any involvement of the
government. The search for and purchasing of suitable land for treatment has,
reportedly, been rather difficult and lengthy. A reported reason for this was the lack of
acceptance of the treatment works by local residents.
The treatment works for Communes V and VI will probably be owned and operated by
Sema Saniya, as the government does currently not have the capacity to manage such
1
SANDEC has been asked for advice from both entities and become discussion partner to
them. CEK is receiving support from Waste Consultants in Holland under the umbrella of
UWEP, a Dutch financed capacity building and urban sanitation infrastructure and services
improvement programme.
46
FS Management Review
works. Investment cost, however, will have to be co-financed by tertiary (foreign ?)
sources, which might activate government involvement. Moreover, government’s
responsibility needs to be activated to make sure that FS collected by other companies
will be delivered to the plants and that indiscriminate dumping will be stopped. Also,
authorities may have to play an important role in devising a fee and/or sanitation tax
structure, which will allow rendering the treatment works financially viable for the
companies. Although Sema Saniya is intending to either sell the processed and
hygienized biosolids produced at the two sites to farmers and horticulturists and/or use
the biosolids to produce cash crops in own farms, revenues generated from these
activities may recover cost partially at best1.
4.6.3
How to Make Sure That FS Ends up in The Treatment Plant Rather
Than in a Drainage Ditch
Making sure that FS collected from city districts will actually be hauled to the designated
treatment sites appears to be one of the greatest managerial and institutional challenges.
Numerous examples cited in this report and observed all over the world demonstrate that
FS will continue to be discharged in an uncontrolled manner if 1), FS treatment plants are
too distant from the collection areas and 2) if collection entreprises are compelled to pay
for treatment. Such a rule although being sensible from an economic and cost recovery
viewpoint, is easy to by-pass through illegal dumping or bribing.
As has been repeatedly stipulated in international working groups, guidance documents
and aid agency consultations, sustainable environmental sanitation may be achieved or
enhanced only by applying appropriate incentive and sanctioning structures.
Box 5 shows one of several money flux models developed by Marc Jeuland (2002),
technical advisor to the GIE Sema Saniya, in attempting to devise a sustainable future
management of faecal sludges in Bamako. It is based on the premise that adequate
financial incentives are necessary to make things work, i.e. that FS end up at the
designated treatment works instead of being dumped illegally and untreated without
having to establish an elaborate enforcement and policing system. This calls for novel
ways of pricing and money fluxes.
The most important element of Jeuland’s model is the “reimbursement for dumping”
principle 2. Cost of plant operations would be recovered by the company earning on
subscription fees paid by citizens and/or other companies delivering FS to the site.
Altermnatively, Government would levy FS haulage and treatment taxes, from which it
subsidizes the operations by company owning the plant. Subscription fees would be
required for use of the emptying service and of the treatment plant, and would be
collected according to appropriate rules. The difficulty of this type of money flux model
might come in resistance from citizens to an additional subscription, since they already
1
The intended use of the plants’ effluents for irrigation is not possible due to the salt content of
effluents of FSTP normallly being beyond plant salt tolernace.
2
A similar procedure is being planned for FS management in Ouagadougou (Burkina Faso).
47
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48
pay for refuse collection. However, a well-devised system might also allow reducing the
price of the actual evacuation, which, in turn, would mean people might not wait until the
last minute to evacuate latrines or septic tanks.
Box 5
Proposed incentive and fee structure to enable financially viable FS treatment operations
(Jeuland 2002)
Flow of money
Cost of FS transport
incurred to the plantowning GIE
Company’s revenue
Company’s expenditures
Delivery by trucks from
GIE owning the FSTP
Price paid to
non-owning
GIE for
delivering FS
to the plant
GIE (sanitation
company) owning
and operatimng
the FSTP
Biosolids / compost
sales
-$
(cost of FSTP
operations)
Sale of crops grown
with biosolids
Sanitation tax
(paid to Government by FS collectors or citizens) à government
subsidy to GIE owning the FSTP
or:
Subscription fee paid by citizens or non-owning GIE
to the plant-owning GIE
4.6.4
Lesson
The Bamako case shows that and how, in the absence of government support, initiative
and policy, small entrepreneurs and NGOs can move in and set up FS management in a
largely sustainable and socially and environmentally responsible manner. Contrary to
Kumasi (see 4.5 above), the approach, which developed in Bamako, is bottom-up. Yet,
the two contrasting examples show that, apparently, both the top-down and the bottomup strategies may, in principle, lead to sound and largely sustainable solutions.
FS Management Review
49
5 Opportunities and Constraints
5.1
Case analysis and discussion
An analysis of problems associated with the current practices in FS management was
elaborated upon in Chpt. 2 (Table 2). The four cases presented in Chpt. 4 above
illustrate, how, in selected cities in Asia and Africa, private and public stakeholders have
already devised or are attempting to devise improved strategies and technical options to
improve on FS management. All these attempts, besides aiming at reducing health and
environmental hazards caused by improper FS handling, have as an explicit or implicit
objective to render FS management more sustainable. Table 10 shows whether and
what, in the cases presented above, elements of decentralisation (as defined by the
EngKAR project of which this report is an integral part) are in place or proposed to be put
in place.
Table 10
Elements of decentralisation in the cases described in Chpt. 4
Vientiane
·
Are private
entrepreneurs
involved ?
·
·
1
ü
Nam Dinh
Kumasi
Bamako
Mapet-based
schemes 1
ü
ü
ü
ü
ü
ü
ü
Localized
disposal,
treatment and
use
----
Entrepreneurs’ role
to be enhanced in
future
Entrepreneurship
to be promoted
Are CBO involved ?
CBO to be involved
in district-based FS
management
planning
Farmers’
cooperatives to
be involved in
biosolids
marketing
Physical
decentralization of
collection and
treatment / disposal
Decentralized
treatment being
planned
Decentralized
treatment being
planned
ü
ü
see Chpt. 3.2
In Table 11 below, problems identified in the illustrative examples above and from
authors’ observations on FS management in numerous other towns are listed following
the path of the FS from the pit to the final point of use or disposal (column 1). Attempted
and planned for solutions are summarised in column 2 of the Table. Finally, in column 3,
the authors list their analysis of the attempted solutions.
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Table 11
50
FS management – problems, attempted solutions and solution analysis
Solutions attempted in practice
(cited examples)
Identified problems with ….
·
·
Analysis of attempted solutions
Emptying
-
Pits difficult to access
Inappropriate emptying equipment (size and
performance for complete sludge removal)
-
Manufacturing and increased use of small vacuum
equipment
(MAPET; mini-tug Haiphong; mini tanker Maseru)
-
Poor service management (technically as well as
organisationally) by public utilities
-
-
Low willingness-to-pay for service
Devolvement of public service rendering to private
entrepreneurs through contracting, licensing,
franchising
(Vientiane; Kumasi; Bamako)
-
Devising localised, semi or decentralised treatment
(MAPET-serviced neighbourhoods; Kumasi; Bamako)
-
Technical solutions at hand
Little replication; lack of funding for low-cost
equipment
-
Necessary though not sufficient prerequisite for FS
management improvements; needs to be
complemented by an effective incentive and
sanctioning system
-
Necessary though not sufficient prerequisite for FS
management improvements; needs to be
complemented by an effective incentive and
sanctioning system
Likely to lead to reduced illegal dumping of FS
Haulage
-
Lack of suitable disposal or treatment sites close
to the areas of collection; indiscriminate FS
dumping
-
Traffic congestion
-
Lack of effective long-term urban planning, hence,
lack of suitable, nearby treatment sites kept in
reserve
-
(A common phenomenon in municipal administration
in dev. countries; authors are unaware of exemplary
municipalities)
-
Lack of suitable incentive and sanctioning
procedures
-
Devising a suitable revenue and fee structure for FS
emptying, collection, haulage and treatment
(reversed tipping fee proposed for Bamako)
-
Beside devolvement to private entrepreneurship,
single-most important measure to improve FS
management; models still to be applied and tested
in practice
-
Promoting private entrepreneurship
(partly privatised in Vientiane; largely privatised in
Kumasi and Bamako; planned in Nam Dinh)
-
Improves services to customers
-
Catering for a competitive market in FS collection and
haulage, and linking contracts or licenses to
compliance with rules and regulations
(Kumasi)
-
Contributes greatly to improvements in FS
management if sanctioning procedures are made
to work
-
FS Management Review
·
Treatment
-
-
·
·
51
Lack of proven and appropriate treatment options
Entrepreneurs avoid tipping / treatment fee à
illicit dumping
-
R+D in appropriate treatment options (pilot and fullscale monitoring)
(field research of SANDEC with partners in Latin
America, Africa and Asia)
-
Has started to contributing to close the gap-inknowledge on treatment
-
Preparation of plans for implementing suitable,
modest-cost options
(Kumasi – just completed; Bamako; Vientiane; Nam
Dinh)
-
Several recent initiatives in Asia and Africa; few
experiences and performance data to date
à
see under haulage, above
Use
-
Health risks to farmers and consumers through
the use of untreated FS
-
FS treatment à safe biosolids
(Kumasi – treatment in place at full-scale FSTP, yet
biosolids polishing not established yet; planned
treatment schemes in Vientiane, Nam Dinh and
Bamako; pilot co-composting scheme established in
Kumasi)
-
Technically simple to produce hygienically safe
biosolids
-
Non-use or limited use of potentially usable
biosolids
-
Farmer involvement, promotion and marketing
(through joint efforts of public authorities and private
entrepreneurship)
(planned in Nam Dinh and in Bamako)
-
Considered as expedient and necessary; yet,
authors are not aware of related initiatives and
activities
-
Planning for and implementing semi or decentralized
treatment and introducing effective incentive and
control / sanctioning procedures
(Kumasi – in place; Vientiane, Nam Dinh, Bamako –
planned for)
à
see under haulage, above
Disposal
-
Illicit dumping; health and pollution risks from
dumping at designated sites
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5.2
52
Enabling and Hindering Factors
Table 2 in Chpt. 2 and the above Table 11 summarise problems, consequences, and
solutions attempted in a few selected situations to date. What may be learned from these
? In Table 12 below, the authors summarise how, in their opinion, institutional, financial/
economic and technical factors enable and impair or hinder effective (faecal) sludge
management.
Table 12 Enabling and hindering elements in FS management
Factor
Enabling element
Technical
-
Emptying / collection technology
developed and at hand
-
Tentative solutions and guidance on
treatment technology at hand
Hindering element
-
Institutional,
political
-
(“governance”)
-
-
Devolvement of emptying,
collection and haulage services to
private entrepreneurs
Existence of a competitive market
among FS collection entreprises
Existence of a licensing or
contracting system, which
authorities use also as a
sanctioning instrument
Decision-makers and authorities
dedicated to improve on urban env.
sanitation
Appropriate incentives at all levels
(e.g. appropriate fee structure)
Municipality capable of developing
and exerting control over licenses
and contracts
Appropriate legal code regulating
FS management
-
-
-
-
Financial /
economic /
agronomic
-
-
Farmers aware of manuring value
of biosolids and willing to buy
biosolids produced in FSTP
Fees established enable safe
revenues and profits for
entrepreneurs
Planners and engineers still
unaware of available options
Options have not been developed
sufficiently to become proven stateof-the-art
Stipulation of overly strict standards
for FSTP effluent and biosolids
quality and standards not adapted to
the local situation
Non-existence or non-involvement of
private entrepreneurship
Conventional fee structure for FSrelated services
No or insufficient involvement of
stakeholders (owners and users of
sanitation facilities, farmers, private
entrepreneurs, authorities)
Lack of guidance and documented
experience about networking among
stakeholders and their institutionalised involvement
Responsibilities at municipal level
spread over too many entities
Irrational treatment or discharge
standards; lack of will And/or
capacity to control and enforce
regulations
Lack of knowledge or willingness to
make use of treatment by-products
Responsibilities at institutional level
spread over too many entities
- Unaffordable emptying fees (à pit or
vault blockages; discharge of fresh
excreta and wastewater into the
environment)
FS Management Review
5.3
Gaps-in-Knowledge on (Faecal) Sludge Management
Based on the analyses developed above and on problems identified in Chpt. 2 (Excreta
Management – The Great urban Challenge), major gaps-in-knowledge can be identified
on the issues listed below:
On low-cost sludge treatment options:
·
-
Long-term operational experience
What is “best” or quasi-proven technology ?
Lack of detailed costing data
On sustainable sludge management concepts:
·
-
-
Experience and guidance on stakeholder networking and institutionalising
stakeholder involvement
Sound quality standards for end products of sludge treatment (biosolids and
liquid effluent), suiting local environmental, socio-economic and institutional
conditions
Exemplary, tested and sustainable models for fee structures and money
fluxes in FS management
On the use of biosolids in agriculture:
·
-
Exemplary and sustainable marketing models for biosolids
How to institutionalise networking between farmers and stakeholders in FS
management, treatment in particular
On the needs for capacity building for various stakeholders and
·
stakeholder groups 1:
For engineers and technical personnel:
-
1
FS: definitions; characteristics; sampling and analysis
FS treatment: features of feasible options; pre-selection; basic design,
costing and evaluation; operational guidance
Quantities and characteristics of sludges from decentralised wastewater
treatment systems
Training manuals for unskilled operators
Note: this is but a preliminary listing of suggested capacity building needs; better defined
needs can be identified based on the case-study findings from Phase II of the porject.
53
FS Management Review
For planners and facilitators:
-
Developing tools for stakeholder involvement
Tools for assessing stakeholder needs and perceptions
Principles of (faecal) sludge management planning (as an integral
component of planning in urban environmental sanitation)
For politicians / decision makers:
-
On the need of and basic strategic solutions for improved FS management
and treatment
Awareness-building documentation regarding health risks and cost of not
improving FS management; nuisance impacts; environmental impact
On economic aspects of improved FS management and recycling
Standards for biosolids and treated FS liquid quality: need, objectives and
sensible values
Developing incentive structures and procedures to facilitate sustainable FS
management (innovative models of money fluxes!)
On the roles of municipal authorities vs. private entrepreneurs and NGOs in
FS management: licensing; franchising; controlling and enforcement,
entrepreneuralship
For farmers:
-
Opportunities and constraints of using biosolids produced in FS treatment
Cultivation on demonstration plots
Financial aspects of biosolids use
For private entrepreneurs (operators of treatment works; providers of FS
collection and haulage services):
-
Marketing of biosolids
Financial management for small entrepreneurs
Technical guidance for treatment plant franchisees
On the complementing roles of private and public partners in FS
management: entrepreneurial, management and control aspects
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FS Management Review
6 Conclusions and Recommendations
To the extent that authors have become aware during their R+D work in FS treatment
and FS management planning, only a few projects on sustainable and decentralised
management of (faecal) sludges have become established to date (examples cited from
Kumasi, Ghana and Bamako, Mali). Yet, several promising and laudable initiatives have
emerged very recently (examples cited from Nam Dinh, Vietnam and Vientiane. Laos;
several unquoted initiatives in West and South Africa). There appears to be growing
concern among municipal authorities in Asia and Africa about the dramatic situation in
excreta management. In several places, the need to act has emerged and initiatives
have been started to improve the situation. Hence, the need for guidance and training of
the various stakeholders in sustainable sludge management is rapidly increasing.
Documents, which can serve, in whole or in parts, as training tools for planners and
engineers, mainly, are listed in Chpt. 7.5.
The authors recommend that the focus in a possible Phase II of the Project be equally
laid on wastewater and on (faecal) sludge. The great challenge in FS management
improvement relates to FS collection and haulage, i.e. to actually getting the sludge to
where one would like to have it. This is a problem inherent to FS management, while
wastewater will automatically “find its way” to the points of designation once sewerage is
in place. Hence, it’s mainly the sludges originating from on-site sanitation systems which
form the “faecal film” being spread and maintained through entire city districts. Without
improving on the managerial and financial/economic aspects of FS collection and
haulage, indiscriminate and illicit spreading of untreated faecal matter will continue, even
though adequate treatment schemes may have been put in place !
The initiatives and practices reported about in Chpt. 4 for Kumasi, Bamako, Nam Dinh
and Vientiane are likely to serve as fruitful grounds to identify felt needs of stakeholders
for capacity building and training in the field of decentralised (faecal) sludge
management. A list of presumed needs is contained in Chpt. 5 above.
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56
7 Annexes
7.1
About Minimising FS Haulage Cost (see also Chpt. 2.4)
7.1.1
What Speaks Against Large, Centralised Treatment Schemes
The average haulage distance from the houses where FS is collected to the FS
treatment plant and with this the actual size of the plant is a very decisive variable for the
total cost of the disposal system as well as for its efficiency and sustainability. A
commonly observed practice is the uncontrolled dumping of FS by the driver of the
emptying truck although a treatment plant, which should receive the FS, is in operation.
The reason for such behaviour is that the distance to the plant is often excessively long.
Hence, collection service providers and vacuum truck drivers are tempted to cut haulage
time and cost. The haulage of relatively small faecal sludge volumes (5-10 m3 per truck)
through congested roads over long distances in large urban agglomerations is unfeasible
also from an environmental viewpoint as it is associated with excessive fuel consumption
end hence air pollution. It is therefore of key importance to minimise overall FS haulage
volumes and mileage. This means that small to medium-size plants, semi-centrally or
decentrally located, must be aimed at whenever possible.
While the economy-of-scale factor for the treatment works must also be taken into
consideration, there is no clear-cut tendency that larger plants will entail lower cost.
Large plants may require a more sophisticated technology to save on land requirements.
This would, in turn, increase capital and operating cost.
7.1.2
Calculation of estimated km-dependent haulage costs
Overall haulage cost depend on the size of the area from which the FS is collected.
Assuming a circular collection area with an FS treatment plant in the centre, the average
distance from a sanitary installation to the plant amounts to:
D (average distance) =
(maximal distance from the plant)
2
2
The maximal distance from the plant determines the served area (A) and, with a given
population density, the served number of people. Assuming again a nearly circular area,
the average distance from the sanitary installation to the treatment plant may also be
written as:
D=
served population (SP)
2P o population density (PD)
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57
The collection costs per m3 collected FS can then be calculated as:
man - hour cost
æ
ç truck - km cost +
average speed
C collection US $ 3
= D [km ] o ç
ç
m FS
truck capacity [m 3 ]
ç
è
[
]
ö
÷
÷
÷
÷
ø
The calculations and diagram presented in the Box below show the ratio of kmdependent cost per ton of TS and haulage-km as a function of population served, based
on information from Thailand and Ghana.
Haulage cost as a function of total population served and population density
Standard
conditions
(curves A and B in
the diagram)
Unfavourable
Conditions
(curve C in the
diagram)
Truck km-cost (fuel, wear of tyres etc.):
US$ 0.30
Truck capacity:
7m
US$ 0.30
Average speed:
30 km/h
20 km/h
Man hour (driver + worker):
US$ 3
US$ 4.00
Average TS:
18 g/l
18 g/l
3
5m
3
14
12
100 inh./ha
10
5m
20 km/h
US$ 4/h
C
US$/t TS
3
8
100 inh./ha
B
6
4
200 inh./ha
A
2
0
0
5 10
4
1 10
5
1.5 10
5
2 10
5
2.5 10
5
3 10
5
Served population
The Diagram shows that for the chosen standard conditions, the km-dependant haulage cost for
served population ranging from 50,000 to 300,000 are in the range of US $ 2 to 7 per t TS and per
km, depending on population density. For a population of 20,000, e.g., specific haulage cost
would amount to $ 4.2 / t TS×km under the assumed standard costing conditions. Hence, for a
treatment plant located 10 km outside the settlement area, the haulage cost would amount to $
42 / t TS×km. Under unfavourable conditions (unpaved roads, higher salaries and smaller trucks),
haulage cost per km as per this model may be as high as $ 10.5 per t TS.
FS Management Review
7.2
58
Technical Options for FS Treatment (see also Chpt. 3.3)
Screening and energy dissipation/stilling
Faecal sludges usually contain considerable quantities of non-degradable, coarse
objects, such as plastic bags, rags, small glass or metal containers. Hence, screening
the sludge prior to actual treatment is desirable and expedient.
Further to this, installations are required at the receiving end of FSTP, which cater for
energy dissipation of the FS upon discharging from the vacuum tankers. Stilling
chambers or channels will serve this purpose, thus helping to avoid excessive turbulence
in settling units or scouring of sand layers in sludge drying beds.
Solids-liquid separation
Settling-thickening tanks or primary ponds can be used for solids-liquid separation (Fig.
9). Settling tanks provide a liquid retention time of a few hours (enough to ensure
quiescent settling of settleable solids), while settling ponds cater for several days or a
few weeks of liquid retention and, hence, also allow for anaerobic degradation of
organics. Both types of units are designed based on the storage volume required for a
desired depth and quantity of accumulating solids. At least two parallel units need to be
provided to allow for batch operation comprising adequate loading and resting/emptying
cycles.
Fig. 9
Non-mechanised settlingthickening tanks and
sedimentation/anaerobic ponds
for solids-liquid separation
(schematic)
Non-mechanised, batch-operated settling tanks as well as settling ponds must be
designed such as to enable easy removal of partly or fully dewatered accumulated solids,
by either manual means or by front-end loaders (in larger plants). The solids can be
further processed by drying on so-called sludge drying beds or upon further surface
spreading in thin layers, by co-composting with organic solid waste, or by in-pond
storage in the case of settling ponds. The liquid effluent or supernatant needs to be
further treated in e.g. waste stabilisation ponds prior to discharge into surface waters or
infiltration beds.
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59
Table 13 shows the removal rates, which may be expected in settling-thickening tanks
and in settling ponds, respectively:
Table 13
Expected removal rates in settling-thickening units 1
Settlingthickening tanks
Settling
ponds
60 %
> 95 %
BOD and COD
(unfiltered)
30 – 50 %
70 – 95 %
BOD (filtered)
18 %
45 %
Susp. solids, SS
1
Based on actual performance of investigated installations running at
sub-optimal conditions
The rate of accumulation of settleable solids, hence, the required solids storage
volume, is the decisive design criteria for preliminary settling/thickening units or for solids
storage compartments in primary ponds. The specific volume occupied by separated
solids may vary from 0.02 (thin septage) - 0.15 septage mixed with high-strength sludge
from unsewered public toilets) m3/m3 of raw FS, depending on FS type and composition
and on the period allowed for solids consolidation and thickening (Heinss et al., 1998;
Ingallinella et al. 2000).
Unplanted Sludge Drying Beds
Sludge drying beds, if suitably designed and operated, can produce a solids product,
which may be used either as soil conditioner or fertiliser in agriculture, or deposited in
designated areas without causing damage to the environment. In most cities, the solids
removed from the drying beds after a determined period (several weeks to a few months)
require further storage and sun drying to attain the hygienic quality for unrestricted use.
Where dried sludge is used in agriculture, helminth (nematode) egg counts should be the
decisive quality criterion in areas where helminthic infections are endemic. A maximum
nematode (roundworm) egg count of 3-8 eggs/g TS has been suggested by Xanthoulis
and Strauss (1991).
Gravity percolation and evaporation are the two processes responsible for sludge
dewatering and drying. Sludge drying beds are schematically illustrated in Fig 10.
Evaporation causes the mud to crack; thereby leading to improved evaporative water
losses and enhanced drainage of the sludge liquid and rainwater.
FS Management Review
Fig. 10
60
Unplanted sludge drying beds (schematic)
From 50 - 80 % of the faecal sludge volume applied to unplanted drying beds will emerge
as drained liquid (percolate). The ratio between drained and evaporated liquid is
dependent on type of sludge, weather conditions and operating characteristics of the
particular drying bed. Drying bed percolate tends to exhibit considerably lower levels of
contaminants than settling tank supernatant. This liquid will, nevertheless, also have to
be subjected to a suitable form of treatment (e.g. in facultative ponds) in most cases.
Pescod (1971) conducted experiments with unplanted sludge drying beds in Bangkok,
Thailand. According to the experiments, maximum allowable solids loading rates can be
achieved with a sludge application depth of 20 cm. To attain a 25 % solids content,
drying periods of 5 to 15 days were required depending on the different bed loading rates
applied (70 - 475 kg TS/m2·yr). Results from pilot sludge drying beds obtained by the
Ghana Water Research Institute (WRI) in Accra/Ghana indicate their suitability for
septage/public toilet sludge mixtures and primary pond sludge (TS = 1.6 - 7 %).
Experiments were conducted during the dry season with sludge application depths of £
20 cm. At loading rates equivalent to 200 kg TS/ m2·yr and 8 days of drying, TS contents
of 40 % were attained, whereas at 600 kg TS/ m2·yr, TS contents of 20 % only could be
achieved. The fresh, non-stabilised public toilet sludge was not conducive to drying within
drying periods lasting from 10-20 days.
Dried biosolids dewatered to £ 40 % TS in the Accra/Ghana experiments still exhibited
considerable helminth egg concentrations.
When the contaminant levels in the drained liquid of the pilot beds in Accra were
compared with the levels in the raw sludges applied, the following average removal rates
were calculated from 12 bed loadings:
•
•
•
•
Susp. solids:
COD:
Helminth eggs:
NH4:
³ 95 %
70-90 %
100 %
40-60 %
Constructed Wetlands (planted sludge drying beds)
Constructed wetlands (CW) for treating sludge consist of a gravel/sand/soil filter planted
with emergent plants such as reeds, bulrushes or cattails. The advantage of planted over
FS Management Review
61
unplanted sludge drying beds is that the root and rhizome system of the plants used in
CW create a porous structure in the layer of accumulated solids and thus enables to
maintain the dewatering capacity of the filter during several years. In contrast to CW
treating wastewater, CW for sludge are equipped with a freeboard. This allows
dewatered solids to accumulate over several years. As a consequence removal of
accumulated biosolids is required at a much lower frequency than unplanted sludge
drying beds. Operating cost are thus considerably reduced. The extended storage of
biosolids allows for biochemical stabilisation. The plants pass through repeated cycles of
growth and wilting. Sludge is due to be removed from the filters only after 5 to 6 years.
The biosolids may be dried to a limited degree only – to 65–60 % water content at the
most – in order to ensure sustained plant growth. CW percolate will require posttreatment as per local conditions and discharge regulations.
Three pilot constructed wetlands – planted with cattails – have been investigated since
early 1997 at the Asian Institute of Technology (AIT) in Bangkok. The 3x25 m2 pilot plant
is equipped with a drainage and ventilation system (Fig. 11) and it treats the septage
from approximately 3,000 people. It was first acclimatised with wastewater and gradually
fed with Bangkok septage in a vertical-flow mode of operation. The percolate was treated
in a waste stabilisation pond system at first, and in a constructed wetland bed planted
with ornamental plants in the later project stage. The objectives of the project are to
assess the suitability of this option for the treatment of septage and establish design and
operational guidelines.
cattail
vent pipe
Outlet
pipe
septage
soil
screen
Filter
substrata:
10-cm layer of fine
sand, 15-cm layer of
small gravel, and
40-cm layer of large
gravel from top to
gravel / sand
hollow bloc
ks
bottom
Fig. 11
Pilot constructed wetlands fed with septage since 1997 (AIT, Bangkok)
The system was monitored under different operating conditions. Parameter tests
comprised variations in solids loading rate, sludge loading frequency and percolate
ponding period. Ponding of the percolate water in the beds’ underdrain system was
FS Management Review
62
initiated to reduce the plant wilting observed especially during the dry season (Koottatep
and Surinkul 1997-2001). Optimum operating conditions under which maximal removal
efficiencies were measured and cattails didn’t show any wilting symptoms are the
following (Koottatep et al. 2001):
·
·
·
Solids loading rate …………… 250 kg TS/m2*a
Loading frequency ……………1 x per week
Percolate ponding…………….. 6 days
Fig. 12
Percolate concentration and
removal efficiency of the
constructed wetlands
(average data based on 12
composite samples)
90 cm of dewatered and stabilised solids had accumulated in the CW beds by the end of
4.5 years of septage loading, equivalent to a column of 75 m of raw septage loaded onto
the beds. Fig. 12 depicts contaminant concentrations and related removal efficiencies
across the CW beds.
Table 14
Agronomic characteristics of the biosolids accumulating in the AIT
constructed wetland plant treating septage (Kost and Marty, 2000). Nutrient
levels in matured compost are also included for comparison’s sake (FAO 1987)
Dried sludge layer
Matured compost
TS [%]
TVS
[% of TS]
Total N
[%TS]
Total P
[%TS]
Total K
[%TS]
35-45
60-65
3
0.4-3.5
1.2
0.1-1.6
0.2
0.4-1.6
Table 14 illustrates the characteristics of the accumulated sludge layer, as it was
determined after three and a half years of operation. Nitrogen and phosphorus contents
of the sludge accumulating on the planted drying beds compare very favourably with the
ones found in matured compost.
Helminth eggs analysis showed that the use of the accumulated biosolids in agriculture
would not result in a risk to public health. Nematode concentrations found in raw septage
were approx. 40 eggs/g TS. The number of nematode eggs counted in the solids
FS Management Review
63
accumulated over several years was still high (170 g/TS on avg.). However, only a small
fraction (2/g TS on avg. or 1.2 %) was found to be viable (Schwartzbrod 2000). Average
viable nematode egg concentrations are thus below the suggested quality guideline of 38 eggs/g TS (see chapter 3).
Mass balance calculations across the CW beds have shown that of the entire solids load
discharged onto the beds, in the order of 50 % are retained on the bed surface as
biosolids, 10 % are contained in the percolate and 40 % are “lost” through degradation of
organic material yielding water and CO2 and possibly through accumulation in the bed’s
underdrain system. Of the water brought onto the beds with septage, in the order of one
third is evapotranspirated and two thirds are drained. Some 2 % only are retained in the
accumulating solids. Of the nitrogen loaded onto the CW beds, 50 % are accumulated in
the biosolids and 25 % each leave the system through volatilisation and in the percolate.
Non-Aerated Stabilization Ponds for the Separate Treatment of FS
Fig. 13 shows a WSP system suitable to treat low to medium-strength faecal sludges. It
comprises pre-treatment units (tanks or ponds) for solids-liquid separation followed by a
series of one or more anaerobic ponds and a facultative pond. This allows producing a
liquid effluent apt for discharge into surface waters. Effluent use in agriculture is not
possible due to its high salinity. Biosolids produced during pre-treatment and in the
anaerobic ponds, however, constitute a valuable resource and may easily be treated to
satisfy safe hygienic standards.
Faecal sludge
delivery
AP
FP
AP
Pre-treatment
(Solids-liquid
separation, batchoperated)
Anaerobic
ponds
(1 or more in series
2 in parallel)
Facultative
pond
Solids, to dewatering
and hygienisation
Fig. 13
Schematic Drawing of a WSP System Treating Low to MediumStrength Faecal Sludges (Strauss et al. 2000)
Where FS are made up by critical proportions of sludges from unsewered public toilets
with zero or low-flush installations or in latrines with so-called watertight pits, ammonia
levels might be high. Excessive ammonia (NH3) contents will impair or suppress
anaerobic degradation and/or algal growth. The critical toxicity level of NH3 for anaerobic
degradation is in the order of 70 mg NH3-N/L, while that for toxicity to algae is around 40
FS Management Review
mg NH3-N/L (being equivalent to approx. 400 mg (NH3 + NH4-N)/L at 30 ° C and pH 7.8,
conditions typical of FS in warm climate).
Faecal sludges from unsewered public toilets emptied at intervals of 1-3 weeks only, are
often little conducive to solids separation due to their biochemical instability. Primary
treatment in anaerobic ponds might be the method-of-choice in developing countries to
render such FS conducive to further treatment, viz. solids-liquid separation (in the
primary unit itself), dewatering/drying of the biosolids and polishing of the liquid fraction.
Problems encountered when co-treating FS and wastewater in waste stabilisation
ponds
Where waste stabilisation ponds exist to treat municipal wastewater, and where these
are used to co-treat FS, a number of problems may arise. In many cases, the problems
are linked to the fact that the wastewater ponds were not originally designed and
equipped to treat additional FS load. Common problems are:
·
Excessive organic (BOD) loading rates may lead to overloading of the anaerobic
and facultative ponds. This overloading causes odour problems and prevents the
development of aerobic conditions in the facultative pond.
·
Ponds may fill up with solids at undesirably fast rates due to the high solids
content of FS. The high rate of solids accumulation calls for a higher frequency
of solids removal and handling than with wastewater alone.
·
Fresh, undigested excreta and FS contain high NH4 concentrations. These may
impair or even prevent the development of algae in facultative ponds.
Preventative measures, such as the addition of a solids separation step ahead of the first
pond, and the consideration of a maximum admissible FS load can avoid the
aforementioned problems. Like in pond schemes exclusively treating FS, the (NH4+NH3)N concentration in the influent to a pond supposed to work in the facultative mode, may
not exceed 400 mg/l.
The Combined Treatment of FS and Wastewater in a Pond System
To avoid the above-mentioned problems when co-treating FS and wastewater and to, FS
may be pre-treated in primary settling-thickening ponds. Their effluent can then be cotreated with wastewater in follow-up facultative and maturation ponds (Fig. 14). The FS
settling ponds, which will also allow for anaerobic degradation of dissolved organics,
enables to separate off the bulk of solids ahead of the main WSP system proper.
In Alcorta (Prov. of Santa Fé, Argentina), A series of two stabilisation ponds was put in
operation in 1987 to co-treat both wastewater and septage. A monitoring program of the
system (93-95) revealed that the capacity of the first pond had been reduced in half due
to the high solids content of septage. Based on these investigations conducted by the
64
FS Management Review
65
Raw wastewater
FS pre-treatment (settling)
Fig. 14
Co-treatment of FS
and wastewater in
ponds (schematic)
Biosolids to storage or
further treatment and to
agricultural use
University of Rosario, a septage pre-treatment consisting of two sedimentation ponds
was constructed in July 98 (Fig. 15). The two ponds are operated alternatingly: one pond
is loaded while the sludge accumulated in the other one is drying. The ponds are
designed to allow for in-pond dewatering/drying of the accumulated solids during the
resting period. The idea is that the settled sludge should be spadable and partly
mineralised/hygienized at the end of the resting/drying cycle. The effluent of the
sedimentation ponds is co-treated with wastewater in a series of two waste stabilisation
ponds.
Fig. 15
Se p ta g e
Se wa g e
C1
C2
L1
Co-treatment of septage and wastewater
(schematic)
L2
Efflu e n t
C1, C2: Septage ponds
L1, L2: Ponds treating septage liquid
(supernatant) and municipal
wastewater)
The sedimentation ponds were designed based on the following criteria:
·
·
·
The accumulated sludge layer should be less than 0.5 m
The sludge accumulation rate amounts to 0.02 m3/m3
6 months loading + 6 months in-pond resting/drying of accumulated biosolids
The results of three-years of monitoring show that the efficiency of the ponds treating
septage (sedimentation and degradation) is such that the effluent quality is similar to the
wastewater quality, both under low as well as high BOD loading rates. Raw septage,
sedimentation pond effluent and wastewater quality are illustrated in Fig. 16.
FS Management Review
66
Fig. 16
Raw septage, effluent of
the sepatge pond and
raw sewage
concentration measured
in Alcorta during the first
monitoring cycle (14
campaigns). (Ingallinella
et al., 2000)
Analyses of the dewatered sludge show that the level of humidity reached at the end of
the drying cycle enables an easy handling of the sludge through spading. The final plant
effluent, which is composed of treated septage supernatant and wastewater satisfies
conventional discharge standards.
Composting with Organic Solid Waste (“Co-Composting”)
Co-composting, i.e. the combined composting of faecal matter and organic solids waste
is practiced all around the world, usually in small, informal and uncontrolled schemes or
on a yard scale. Presumably, most of this proceeds at ambient temperatures, with
concomitant inefficient inactivation of pathogens. In contrast to this, thermophilic
composting, i.e. the composting at 50-60 °C, is an effective process for pathogen
destruction while stabilising organic material and creating a valuable soil conditionercum-fertilizer. Co-composting of sewage treatment plant sludge with organic solid waste
is widely practiced in industrialized countries. The authors are not aware, though, of any
thermophilic co-composting scheme treating FS and organic waste, except for one
scheme in South Africa, which was operational from 1992-96, and in which bucket latrine
sludge was co-composted with municipal waste. The scheme was closed down when the
bucket latrines were replaced by a sewerage system.
SANDEC, in collaboration with IWMI-West Africa and the Municipality of Kumasi (Ghana)
have recently started investigating FS and organic solid waste co-composting on pilot
scale. FS, which is composed of high-strength sludge from unsewered public toilets and
of septage, is dewatered to the required solids content by sludge drying beds or,
alternatively, thickened in a primary settling pond. The FS-organic waste mixture is
windrow-composted for a period of 1 month (thermophilic phase) followed by a maturing
phase of 1-2 months. The raw mixture is composed of 1 part dewatered FS vs. 3 parts
sorted waste. Matured compost, produced at a rate of 1 ton/month, will be tested in
comparative planting trials to ascertain its marketability. First results on the treatment
FS Management Review
67
process are expected by June 2002. Fig. 17 is a schematic representation of the Kumasi
pilot scheme.
Co-composting process as used in the Kumasi,
Ghana, pilot plant
Fig. 17
Co-Composting Flow Chart – the faecal sludge needs to be
dewatered or thickened to enable the treatment of inhabitantequivalent quantities of FS and solid waste
Anaerobic digestion with biogas utilization
This option may, in theory, be perfectly suited to treat higher-strength FS, which have not
undergone substantial degradation yet. Such sludges may comprise the contents of
unsewered public toilets, whose vault contents are emptied at relatively high frequencies
of but a few weeks. Fig. 18 is a schematic sketch of FS-based anaerobic digestion with
biogas utilization and Photo 15 shows a cooking stove fuelled with FS-base biogas.
There exist, in practice, two types of digestors, viz. fixed and floating dome units.
Photo 15
Public toilet caretaker in
his quarter, cooking with
biogas produced from FS
(Nagpur, India)
Fig. 18 FS-fed anaerobic digester w. biogas recovery (schematic) and biogas
fuelled cooking stove in a public toilet caretaker’s quarter
FS Management Review
Although, where urine is mixed with faeces, the C:N ratio of the FS is too low to generate
maximum gas yields, the option might nevertheless proof technically and economically
feasible under specific local conditions. The only biogas systems known to the authors,
which are operated on FS as exclusive organic feed are plants attached to public pourflush toilets operated by Sulabh, an Indian NGO, for municipal authorities. There are,
reportedly, approx. 70 such plants in operation. NEERI (India) conducted applied
research on FS-fed biogas plants in the sixties and seventies. Biogas plants processing
FS mixed with cattle dung are presumably being operated in many developing countries
as small, decentralised schemes serving one or several households or institutions. Yet,
the authors do not avail of and have not collated information on such schemes. Gaps-inknowledge pertaining to FS-fed anaerobic digestion pertain to supernatant posttreatment, settled solids evacuating and hygienization; costing and affordability, mainly.
Although anaerobic digestion with gas utilization has been an option widely proposed for
sludge treatment and energy recovery, the number of respective schemes implemented
in developing countries has remained rather low. A possible reason might consist in the
relatively high investment cost of such plants and the concurrent low affordability by
target users. Further to this, removal of accumulated solids from the digestors appears to
be a difficult task, which has caused many such plants to turn unused.
68
FS Management Review
7.3
69
Pathogen Die-off in Faecal Sludge at Ambient
Temperatures
Table 15
Pathogen survival or die-off periods in
wet faecal sludge
Average Survival Time in Wet Faecal Sludge
at Ambient Temperature 1
Organism
•
Viruses
•
Bacteria:
-
•
Salmonellae
Vibrio cholerae
Faecal coliforms2
In temperate climate
(10-15 °C)
[days]
In tropical climate
(20-30 °C)
[days]
< 100
< 20
< 100
< 30
< 150
< 30
< 5
< 50
< 30
< 15
2-3 years
12 months
10-12 months
6 months
Protozoa:
-
•
Amoebic
cysts
Helminths:
-
Ascaris eggs
Tapeworm
eggs
1
When exposed to the drying sun, the survival periods are much shorter
2
Faecal coliforms are commensal bacteria of the human intestines and used as
indicator organisms for excreted pathogens
FS Management Review
7.4
References
Bode, H. (1998). Anmerkungen zu den Kosten der Abwasserreinigung (comments on
wastewater treatment costs). Korrespondenz Abwasser 1998 (45) Nr. 10.
FAO (1987). Soil management: compost production and use in tropical and subtropical
environments. Soils Bulletin No. 56. FAO, Rome.
Frantzen, A. (1998). Public-private partnerships as a solution to the improvement of
public toilet facilities? The case of Kumasi, Ghana. Catholic University of Nijmegen
(July).
GHK (2001). Sanitation, Drainage and Wastewater Management – Final Report.
Vientiane Urban Infrastructure and Services project, Asian Dev. Bank and Vientiane
Urban Dev. and Administration Authority (TA No. 3333 – Lao). GHK International
Ltd., London. Unpublished.
Heinss, U., Larmie, S.A., Strauss, M. (1998). Solids Separation and Pond Systems for
the Treatment of Septage and Public Toilet Sludges in Tropical Climate - Lessons
Learnt and Recommendations for Preliminary Design. EAWAG/SANDEC Report No.
05/98.
Ingallinella, A.M. (1998). Personal communication.
Ingallinella, A.M., Fernandez, R.G., Sanguinetti, G. (2000). Co-Treating Septage and
Wastewater in Ponds – Results of Field Research Conducted at Alcorta, Argentina.
Sanitary Engineering Centre, University of Rosario, Argentina and SANDEC.
EAWAG/SANDEC, P.O. Box 611, CH-8600 Duebendorf, Switzerland.
IWMI (2001). Internal report.
Jeuland, M. (2002). Economic Aspects of FS Management in Bamako, Mali. Unpublished
project report, March.
Johnstone, D.W.M., Horan, N.J. (1996). Institutional Developments, Standards and River
Quality: An UK History and Some Lessons for Industrialising Countries. Water
Science and Technology, 33, No. 3, pp. 211-222.
Klingel, F. (2001). Nam Dinh Urban Development Project. Septage Management Study.
Nam Dinh, Vietnam, November 1, 2001. EAWAG/SANDEC and Colenco (Vietnam).
Klingel, F., Montangero, A., Strauss, M. (2001). Nam Dinh (Vietnam) – Planning for
Improved Faecal Sludge Management and Treatment. Paper presented at the
Annual Conference of the Water Supply & Sewerage Association of Vietnam, Dec. 67, 2001.
Klingel, F., Montangero, A.., Strauss, M. (2002). Guide on Faecal Sludge Management
Planning. EAWAG/SANDEC, drafted.
Koottatep, T. and Surinkul, N. (1997-2000). AIT – EAWAG/SANDEC field research on
septage treatment in planted sludge drying beds. Field reports, unpublished.
Koottatep, T., Polprasert, C., Oanh, N.T.K., Montangero, A., Strauss, M. (2001). Sludges
from On-Site Sanitation – Low-Cost Treatment Alternatives. Paper presented at the
IWA Conference on Water & Wastewater Management for Developing Countries,
Kuala Lumpur, Malaysia, Oct. 29-31.
Kost, M. and Marty, P. (2000). Septage Treatment by Constructed Wetlands. Report on
practical training, AIT/SANDEC, unpublished. September.
70
FS Management Review
Kumasi Metropolitan Assembly (1995). Strategic Sanitation Plan for Kumasi, 1996-2005.
Mara, D. D. (1978). Sewage Treatment in Hot Climates. Chichester: John Wiley & Sons.
Mensah, A. (2002a). Sanitation, Solid Waste Management and Storm Drainage
Component in: Afranie, K., et al (2002). Medium term plan for Kumasi. In
preparation.
Mensah, A. (2002b). Personal communication.
Mensah, E., Amoah, P, Drechsel, P, Abaidoo, R.C. (2001). Environmental concern of
urban and peri-urban agriculture: case studies from Accra and Kumasi. Waste
composting for urban and peri-urban agriculture: closing the rural-urban nutrient
cycle in sub-Saharan Africa, (Drechsel, P. and Kunze, D., eds.). Cabi Publishing.
Montangero, A. and Strauss, M. (2002). Faecal Sludge Treatment. Lecture Notes, IHE
Delft, February 14.
Muller, M.S. (ed.) (1997) The Coillection of Household Excreta – The Operation of
Services in Urban Low-Income Neighbourhoods. Urban Waste Series 6. Waste,
2801 CW Gouda, The Netherlands).
Pescod, M. B. (1971). Sludge Handling and Disposal in Tropical Developing Countries. J.
Water Pollution Control Federation, 43, 4, pp. 555-570.
Pollard, R. (2002). Personal communication.
Rijnsburger, J. (2002). Personal communication.
Salifu, L. (2001). An integrated waste management strategy for Kumasi. Waste
composting for urban and peri-urban agriculture: closing the rural-urban nutrient
cycle in sub-Saharan Africa, (Drechsel, P. and Kunze, D., eds.). Cabi Publishing.
Schawrtzbrod, J. (2000). Consultancy report on helminth egg analyses. Unpublished.
Strauss, M., Larmie S. A., Heinss, U. (1997). Treatment of Sludges from On-Site
Sanitation: Low-Cost Options. Water Science and Technology, 35, 6.
Strauss, M., Heinss, U., Montangero, A. (2000). On-Site Sanitation: When the Pits are
Full – Planning for Resource Protection in Faecal Sludge Management. In:
Proceedings, Int. Conference, Bad Elster, 20-24 Nov. 1998. Schriftenreihe des
Vereins fuer Wasser-, Boden- und Lufthygiene, 105: Water, Sanitation & Health –
Resolving Conflicts between Drinking – Water Demands and Pressures from
Society’s Wastes (I.Chorus, U. Ringelband, G. Schlag, and O. Schmoll, eds.). IWA
Publishing House and WHO Water Series. ISBN No. 3-932816-34-X.
Towles, C. (2001). Faecal Sludge Management in Bamako, Mali – an Introductory Note.
August.
Visker, C. (1998). The Use of Human Excreta in Urban and Peri-Urban Agriculture in
Bamako, Mali (in French). Royal Tropical Institute, Amsterdam, The Netherlands.
Von Sperling, M. and Fattal, B. (2001). Implementation of Guidelines – Practical Aspects
for Developing Countries. In: Water Quality – Guidelines, Standards and Health.
Assessment of risk and management of water-related infectious disease. Eds.:
Fewtrell, L. and Bartram, J.. IWA. In press.
WHO (1989). Health Guidelines for the Use of Wastewater in Agriculture and
Aquaculture. Report of a Scientific Group. World Health Organisation Technical
Report Series 778.
Xanthoulis, D. and Strauss, M. (1991). Reuse of Wastewater in Agriculture at
Ouarzazate, Morocco (Project UNDP/FAO/WHO MOR 86/018). Unpublished mission
reports.
71
FS Management Review
7.5
Documents on FS Management and Treatment Which
May Serve for Training Purposes
Heinss, U., Larmie, S.A., Strauss, M. (1998). Solids Separation and Pond Systems for
the Treatment of Septage and Public Toilet Sludges in Tropical Climate - Lessons
Learnt and Recommendations for Preliminary Design. EAWAG/SANDEC Report No.
05/98.
Klingel, F., Montangero, A.., Strauss, M. (2002). Guide on Faecal Sludge Management
Planning. EAWAG/SANDEC, drafted.
Montangero, A. and Strauss, M. (2002). Faecal Sludge Treatment. Lecture Notes, IHE
Delft, February 14.
72
FS Management Review
7.6
73
Selected Institutions and Persons Actively Engaged in
FS Management and FS Management Applied
Research
Institution and postal address
AIT
Asian Institute of Technology
School of Environment, Resources &
Development
Environmental Engineering Program
P.O. Box 4, Klong Luang
Pathumthani 12120
Thailand
Persons-in-charge;
contact persons
Links
Prof. Chongrak Polprasert,
Dean and principal
investigator
Tel. +66-2-524 60 69
Fax
524 60 71
[email protected]
Dr. Thammarat Koottatep,
D.Eng. Research Associate
Tel. +66-2-524 56 30
Fax
524 56 25
[email protected]
Mr.Narong Surinkul, M. Eng.
Tel.: +66-2-524 55 81
Fax: +66-2-524 56 25
[email protected]
UNR
Universidad Nacional de Rosario
Centro de Ingeniería Sanitaria
Riobamba 245 bis
2000 -Rosario (Sta. Fe) / Argentina
Mrs. Ana María Ingallinella
Tel.: +54-341-480 85 46
Fax: +54-341-480 85 46
[email protected]
IWMI
International Water Management Institute
Ghana Office
c/o University of Science & Technology
Kumasi, Ghana
Dr. (Ms) Olufunke Cofie
Tel.: +233-(0)51-6 02 06
Fax: +233-(0)51-6 02 06
[email protected]
UESP
Urban Environmental Sanitation Project IV
(IDA), Ghana
Kumasi Metropolitan Assembly
P. O. Box 1916
Kumasi, Ghana
Mr. Anthony Mensah
Project-in-charge
Tel. Office: +233-51-3 21 58
Fax: +233-51-3 11 54
Mob. +233-20-816 55 07
[email protected]
CREPA
Centre Régional pour l’Eau Potable et
l’Assainissement à faible coût
03 BP:7112
Ouagadougou 03
Burkina Faso
Dr Klutsé Amah
Chargé de la recherche
Tél.:serv.(00226) 366 210 / 11
mobile: (00226) 831990
Fax : (00226) 366 208
[email protected]
or:
[email protected]
Sema
Saniya
Bamako
Mali
Mr. Marc Jeuland
Corps de la Paix
BP 85
Bamako, Mali
[email protected]
Martin Strauss
Tel. +41-1-823 50 20
[email protected]
Agnès Montangero
Tel. +41-1-823 50 74
[email protected]
SANDEC EAWAG/SANDEC
P.O. Box 611
CH-8600 Dubendorf
Switzerland
Fax +41-1-823 53 99
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