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The Potential of Waterharmonica Concepts in Tanzania

  • Truxor Wetland Equipment, Rekel/water and Rekel Kenya Ltd

Abstract and Figures

Waterharmonica concept is the Dutch initiative which emphasized the use of low technologies that can make bridge or fills the missing links between the quality of water sources and wastewater. It is emphasized the use of natural process “as post treatment ecological engineered” to treat wastewater using low techniques. Therefore Waterharmonica concept can be defined as the embodiment of the ambition to include ecological engineered “linking systems”, such as constructed wetland, as integral part of the design and extension of wastewater treatment plant. The linking system will act as natural post treatment of effluent. The basic principle Waterharmonica concept is to treat or polish and reuse nutrients from wastewater for agriculture and aquaculture activities, consequently to increase the products as well as to conserve and reduce the pollution of water sources.
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Chapter 1
1.0 Introduction
1.1 Waterharmonica Concept
Waterharmonica concept is the Dutch initiative which emphasized the use of low
technologies1 that can make bridge or fills the missing links between the quality of water
sources and wastewater. It is emphasized the use of natural process “as post treatment
ecological engineered” to treat wastewater using low techniques. Therefore
Waterharmonica concept can be defined as the embodiment of the ambition to include
ecological engineered “linking systems”, (Figure 1) such as constructed wetland, as
integral part of the design and extension of wastewater treatment plant. The linking
system will act as natural post treatment of effluent. And might in future be integrated
part of the overall treatment process (Intern. Mels, A. et al 2003).
The basic principle Waterharmonica concept is to treat or polish and reuse nutrients from
wastewater for agriculture and aquaculture activities, consequently to increase the
products as well as to conserve and reduce the pollution of water sources. (Intern. Mels,
A. et al 2003)
Waterharmonica concept is financed by Dutch Foundation for Applied Water Research
(STOWA), Dutch Water Board Holland Noorderwater and Fryslan (two largest water
boards in the Netherlands), and is carried out by the consultancy firm Royal Haskonig
together with the Letting Association Foundation (LEAF) from Wageningen University
and Research Centre. (Intern. Mels,A. et al 2005)
“Waterharmonica concept”
1 Technologies with low or absent energy requirement, easy operation without need highly skilled
personnel, easy to construct with local available raw materials, permanent and continuous operation
without too much maintenance, possibility to produce biomass (e.g. algae, fish, crops etc) by making
beneficial use of available nutrients and applicable both at small and large scale especially feasible in rural
areas e.g. use solar energy..
Figure 1: The “Waterharmonica” as a link between the sewage plant and surface
water, based on Claassen 1996.
One of the examples of Waterharmonica concept is utilisation of constructed wetland as
post treatment to treat human wastes. The constructed wetland enables to improve the
quality of the effluents from conventional wastewater treatment plant. In that way,
constructed wetlands act as the bridge to fill the gap (Figure 2). The effluent from
constructed wetland can be reuse for irrigation or fish farming
Treatment plant” The link “Surface water
Figure 2: The “link” between treatment plant and surface water. Adapted (Intern. Kampf.
et al. 2003).
Also Waterharmonica focus the future on how to use watershed and ecosystem to manage
the wastewater problems; this could be achieved by looking examples of existing of
Ecological Engineering
From Wastewater to Surface water
Waterharmonica cases about the successful and unsuccessful. Also Waterharmonica
focus to provide technical support as well experiences about the design and management
of ecological treatment systems e.g. constructed wetlands etc.
One of the project of Waterharmonica concept is in preparation for the city of Matagalpa
Nicaragua. The aim of this project is to use the concept of Waterharmonica concept to
improve and minimise the water pollution due to contaminants associated with
agriculture and domestic wastewater to the rivers San Francisco and Malino Norte, which
are the source for drinking water source. The research is financed by Novib and Aqua for
All of Netherlands with cooperation with Projecto Cuencas Matagalpa (Joost
1.2 Short history of Tanzania.
Tanzania is developing country situated in eastern of Africa, located on 60 South and 350
East bordering the Indian Ocean. In the south of Tanzania there are Mozambique and
Malawi while in the North one can find Kenya (Figure 3). Tanzania covers 945,087 sq.
km (An area- comparative as twenty times of Netherlands), and is among one of Africa’s
most ecological rich countries, about 40% is covered by forests and woodlands, which
host various types of ecological system. There are several lakes contains fresh water such
as lake Tanganyika (the second world’s deepest lake), lake Victoria (the second world’s
freshwater lake), lake Rukwa, lake Manyara and lake Nyasa (Intern.Factbook,2005).
There are also several big rivers flowing to the lakes and swamps, which contain diverse
types of aquatic life. Tanzania is considered to be a well-watered country with good
rainfall (between November and May). However, in some parts of the country, rainfall is
seasonal and water is not readily available during dry season (long dry spell is
experienced from late May to October), and drinking water quality is general problems.
Tanzania is one of poor countries in the world, with total population of about 36 million
people with income per capita of USD 600. The economy of the country mainly depends
on agricultural activities. (Intern.Factbook,.2005).
Tanzania is emerging from a period of unsustainable and inequitable development. One
cause of that was environmental degradation which caused by pollution from various
sources such as soil erosion, deforestation, land degradation, water pollution etc. which
result a significant health, economically, socially and environmentally troubles. Therefore
the significant challenge which confronting Tanzania is to look for the appropriate
technologies that could solve environmentally troubles.
Figure 3: Map of Tanzania. Retrieved (Intern. Top .2005)
1.3 Wastewater situation in Tanzania
As described early, the economy of Tanzania depends on the agriculture activities.
Therefore wastewater from agriculture activities is the main problem especially in rural
areas whereby farmers use artificial fertilizer (N, P, K, and S), pesticides and herbicides
for farming. As the results, during the rainy season the chemicals from these fertilizers,
pesticides and herbicides are washed away directly to pollute water sources. Also
wastewater from household is big problems especially in the towns of Tanzania. Most of
the wastewaters from household in towns are either untreated or partially treated, as the
result discharged into nearby surface water sources, with eventual pollution of drinking
water sources. An example is the pollution which occurs in Msimbazi river in Dar es
salaam city. The wastewater from industrial activities in Tanzania is minimal. However
some of industries were established without wastewater facilities or partial treatment, as
result discharge their wastewater partial treated to the water sources. In rural areas the
industrial wastewater is almost negligible, because there is not industrial in many areas of
rural areas.
1.3.1 Sanitation situation in Tanzania
The urban and peri-urban areas of Tanzania are among the most polluted and disease -
ridden habitats. Much of human wastes pollutions are caused by inadequate and
inappropriate urban sanitation infrastructure and services. As cities expand and urban
populations increase, the situation is growing worse and becoming even more critical.
Despite the intensive efforts made by the government in trying to privatize human wastes
utilities to improve the service delivery, still many urban areas of Tanzania have not been
able to get adequate human wastes sanitation services because the initial costs are quite high
for the government and users to afford. The human wastes control situations in all urban
areas of Tanzania are comparable to that of Dar es Salaam capital city which is worse one
when compared to rural areas. This is owing to industrialization which is a proliferation
of unplanned and un-serviced plus the accelerated influx of the people. This influx 'pull'
towards the city is the outcome of poverty and lack of adequate paid jobs in the rural areas.
Under these circumstances the human wastes control situation in urban areas gets
worsened particularly in congested unplanned settlements
1.3.2. On-site treatment
In contrast with many other developing countries, like most countries in south-eastern
Asia, people in Tanzania are served by on site sanitation systems, and mostly are pit
latrines which covered about 80 percent (Chaggu.2003) (Table 1). These pit latrines
(Figure 2) “drop–and-store model” consisting of a pit or vaults, a pit cover (slab) and
superstructure fitted in some case with other features like ventilation system or a toilet
seat. They receive excreta that accumulate in the pit over time (2-3 years), then either
flushing them away or burying them in deep pits. The walls of the pit are not well sealed
to prevent penetration (leak) of wastewater thus allowing wastewater to percolate into the
soil representing one of potential source of groundwater contamination. According to
Chaggu, (2003), the Feacal-Coliform count for samples taken from groundwater
(boreholes) in Dar es Salaam capital city at depths between 1.8metres and 6.5metres the
results indicated 3000 FC/100mls and 178FC/100mls respectively. This pollution is
definitely due to seepage from pit latrines and septic tanks.
Figure 4: Pit Latrine and Cross section. Adapted (Intern.RotaryProject.2003)
Solid residue
percolate into
In Tanzania, the use of septic tanks for human wastes treatment is used for individual
resident dwelling. There are various types of septic systems, the most common one is that
which consists of an underground tank of differing sizes, which are connects to a soil
treatment system. Untreated human wastes from a households flows into the septic tank,
whereby the solids are separated from the liquids. Some solids, such as soap scum or fat,
will float to the top of the tank to form a scum layer. Heavier solids, such as human and
kitchen wastes settle to the bottom of the tank as sludge. Self forming bacteria in the
septic tank help the system "digest" these solids or sludge. Baffles built into the tank hold
back the floating scum from moving past the outlet of the tank whilst the remaining
liquids flow out of the tank to a land drainage system or drain field. However, most of
septic tanks system in Tanzania failed to work properly due to various reasons, e.g.
improper location, poor installation and poor regular maintenance by the homeowners as
a result lead to environmental troubles like serious water pollution either ground or
surface waters.
1.3.3. Wastewater treatment
Conventional wastewater treatment processes are widely applied in developed countries.
However, they require high energy inputs, chemicals, skilled man-power and large capital
investments to build and operate. The high per capita costs for wastewater collection and
treatment make these advanced biological processes far beyond the reach of rural
communities and small scale enterprises whose tax-bases and profit margins are low.
This makes the technology expensive for most developing countries, Tanzania included.
In Tanzania, the common wastewater treatment facilities is waste stabilization pond
system, which has been installed in Dar es Salaam city, and towns of Arusha, Morogoro,
Iringa, Tanga, Mbeya, Dodoma, Kilimanjaro, and Mwanza. In either case, these treatment
systems are directed primarily to meet the needs of large towns without considering the
rural community of majority. Nevertheless, these treatment systems have proved
difficulty to maintain because of poor operation maintenances and resources.
Consequently water borne diseases such as cholera, typhoid fever and dysentery are
likely remaining uncontrolled. Also the wastewater problems in Tanzania increasing
with the increased of urbanisation, industrialisation and population while the treatment
services has not been expanded to cope up with the growth or is almost stagnant. The
current treatment systems forms of wastewater control have proved not to offer sustainable
solutions to the massive sanitation problems in the country. As a result, low quality
effluents are being discharged into the environment. In general, this situation cause
Tanzania to spend large amount of money for advanced machineries and technologies
and even chemicals for wastewater control.
Table 1: Tanzania-National Coverage of Human disposal. Adapted (Chaggu.2003.)
Type of Disposal National Coverage (%)
Urban Rural Total
Pit latrines
Traditional Pit latrines
84 (90)2
Ventilated Improved Pit latrines3
Septic tank and Soakage pits
Without access to any type of disposal
2 Some literatures indicates 90% total traditional pit latrines
3 Own toilet
4 Shared toilets
1.4 Summary and conclusion
From the literature described, the Waterharmonica concept is a Dutch initiative aimed to
improve quality of the water using ecological engineering treatment systems such as
constructed wetlands and also a cost effective way of treating human wastes. It also
realised the concept has potential of improving livelihood.
The human wastes controls problems in Tanzania are caused by following situation;
- Population explosion which not cope with sanitation services.
- Rapid pace of industrialisation in unplanned areas.
- Substantial rise of urban population.
- Small population is served by sewer and sewerage systems exists in few
large cities
- Uncontrolled spillage of wastewater
Therefore, different approaches of human wastes control are urgently needed in
Tanzania. The approaches should be affordable, easy to operate and sustainable to
provide safe and decent sanitation, reduce poverty, reduce health risks, contribute to food
security, preserves the environment and maintains natural basis of life on earth.
According to descriptions of Waterharmonica concept could be promising approach in
Tanzania for wastewater control, this is because the approach treat wastewater at cost
effective ways as well improving livelihood. Notably, livelihood issues are of much
concern to most developing countries with Tanzania included.
Therefore, the next chapter illustrate the main objective, main research question and
methodology of the research.
Chapter 2
2.0 Objective and methodology
2.1 Introduction
In this chapter, the main objective of the research, main research question, sub research
question and methodology are described.
2.2 Objective
The main objective of this research report is to presents the potential of Waterharmonica
concept in Tanzania, the concept that could help to solve the current problems of human
wastes control consequently to reduce waterborne diseases and poverty among people of
Therefore to attain the above research objective, the main research question was
2.3 Main Research Question
What is the potential of Waterharmonica concept in Tanzania?
2.4 Sub-Research Questions.
1. What is the current situation of human wastes management in Tanzania?
2. What cause the human wastes control problems?
3. What will be the advantages and disadvantages of Waterharmonica concept in
4. In which ways Waterharmonica concept could help to improve the health of
people as well as to reduce poverty among people living in Tanzania?
5. What are roles of local people should be played in order to implement and
strengthen Waterharmonica concept; given the weak economic status of country?
2.5 Definition of the concepts
Potential: The positive aspects or the abilities (of Waterharmonica concepts) to meet the
need of present and future development or achievements such as food and economic
security through production of crops, safeguard human health and minimise health risks
of people.
Waterharmonica concepts: This is the concept created by Waterharmonica programme
and is defined as the embodiment of the ambition to include ecological engineered
“linking systems”, such as constructed wetland, as integral part of the design and
extension of wastewater treatment plant. The linking system will act as natural post
treatment of effluent. And might in future be integrated part of the overall treatment
process (Mel, A. et al 2003).
Tanzania: Developing African country with population of 36 million people, agricultural
is one of major activities for growth of country economy (refer introduction chapter).
Current problems of human waste control: Conventional forms of centralized and
individual sanitation systems have proved not to offer sustainable solutions to the massive
sanitation problems in the country. The current way of thinking that the human wastes
“wastes products” rather than valuable resources (refer to introduction chapter).
Waterborne diseases: Diseases that associated or link with contaminated water e.g.
Cholera, typhoid fever, diarharrea, dysentery, amoebic etc
Poverty: viewed as encompassing both income and non-income dimensions of
deprivation—including lack of income and other material means; lack of access to basic
social services such as education, health, and safe water; lack of personal security; and
lack of empowerment to participate in the political process and in decisions that influence
someone’s life. (Intern.UNDP.2003).
2.6 Target groups
In this research project, the target groups which are focused are the local communities of
Tanzania and Waterharmonica programme in Netherlands.
2.7 Research methodology
Step model is used in this report research (Figure 3). At initial step the proposal report
was prepared. In the proposal report, main research questions, sub research questions and
objectives of the final research report were proposed. Target groups are also identified in
the proposal report. There is a point of decision for proposal report to be approved. Final
writing report started.
On writing both proposal and final report the information was obtained from text books,
journals, and the internet websites. Interviews were also being conducted from
institutions and individuals in Netherlands e.g. LEAF, Wetland International and Ex
UNICEF consultant. The aim of interview is to collect their experiences regarding
Waterharmonica concept and Tanzania as well as developing countries as the whole.
This followed by the general descriptions of Waterharmonica concept in order to get the
information on the potential of the concept.
Later, the discussions were made based upon the potential of Waterharmonica concept in
Tanzania. The criteria for the discussion were social environmental and economic
Finally, conclusions and recommendation were made based upon the findings obtained.
Figure 5: Research steps model
Set up report
(Proposal report)
Literatures findings
Decision point
General information on
Criteria are social,
environmental and
economic aspects
2.8 Summary and conclusion
The sub research questions were formulated so as to give the answers to the main
research question. In that way the objectives, main research question were formulated
mainly to focus the target group of this research which are local communities of Tanzania
and Waterharmonica programme in Netherlands.
Moreover, the objective of this report is not intended or reflects that Waterharmonica
concept could solve all problems of human wastes in Tanzania. But look for the
possibilities by which the concept be suitable or not in Tanzania.
Chapter 3
3.0 Potential of ecological engineering system for treating human waste5 in Tanzania
3.1 Introduction
Ecological engineered also referred as ecological-technology is emerging a new
interdisciplinary branch of engineered that shares concepts from closely allied disciplines
of environmental engineered, ecology and biotechnology. Ecological engineered uses
either natural ecosystems or constructed systems that imitate natural ecosystems to deal
with environmental and pollution control (Intern. Port of entry. 2002).
Therefore ecological engineered systems for human wastes treatment can be defined as a
"low-technology" above the ground alternative to traditional human wastes treatment
technologies. They are affordable and require little maintenance, and can make an
invaluable contribution to sustainable livelihoods and poverty reduction by increasing
food through the return of nutrients from human waste (human excreta and wastewater)
to the soil, also can reduce health risks due to ability to control water pollution.
Therefore, in this chapter the potential of three types of ecological engineered systems for
human wastes treatment in Tanzania are described, which are constructed wetlands,
source separation systems and oxidation ditch that developed in Netherlands. These types
of human waste treatments systems are described in this chapter because are of
outstanding examples of the development of ecological engineered technologies. They
are cost-effective alternative to more conventional engineered systems to treat potential
polluting substances. They are also part of the natural cycle and provide a ready means of
thinking that treated human wastes are available for reuse. Both developing and
developed countries found economical and ecologically acceptable solutions to the
pollution control through application of these types of ecological engineered treatment
5 Refer also wastes and wastewater
Also in this chapter, the applicability of these three types are described with respect what
has been obtained now in Tanzania (refer the introduction part). Advantages and
disadvantages of each type will also described focus the situation of Tanzania.
3.2 Constructed wetlands
Constructed wetland is a man made wastewater treatment system (Figure 1) that have
been designed and constructed to imitate the natural processes which involving
vegetation, soil, and variety of micro-environmental which all assists in pollutants
removal. The basic features in constructed wetlands are that they have a bed uniformity-
graded sand or gravels with emergent plants grows on in it which are then help in
pollutants removal mechanisms (Roshan, R.2001). Wastewater is evenly distributed on
the bed and flow through it either horizontally or vertically. As the wastewater flows
through the bed it gets treated through natural processes.
Figure 6: Constructed wetland. Retrieved (Intern.IRIDRA.2004).
Constructed wetlands have been found to be effective in treating BOD, TSS, N, K and P
as well as for reducing metals, organic pollutants and pathogens. The removal
mechanisms in the constructed wetlands are complex and interrelated (Annex 1).
However pollutants in constructed wetlands are removed through the following major
settling of suspended particulate matters
Filtration and chemical precipitation through contact of the water with
substrate and litter
chemical transformation
adsorption and ion exchange of the surfaces of plants, substrate, sediment
and litter
breakdown and transformation of pollutant by micro organism and plant
predation and natural die-off of pathogens
Constructed wetlands normally are used to improve the quality of wastewater pollution,
including storm water runoff, domestic wastewater, agricultural wastewater, and coal
mine drainage. Also being used to treat petroleum refinery wastes, compost and landfill
leachates, fish pond discharges, and pre-treated industrial wastewaters, such as those
from pulp and paper mills, textile mills, and seafood processing. One of the most
common applications of constructed wetlands has been the treatment of primary or
secondary domestic sewage effluent. However the constructed wetland system for
wastewater treatment can served other purposes as well. Can served as a wildlife
sanctuary and provide a habitat for wetland animals. The constructed wetland can also be
aesthetically pleasing and serve as an attractive destination for tourists to explore its
environmental and educational possibilities. (Intern.Polprasert, C. at al. 2000). There two
common types of constructed wetland namely as horizontal Flow System and the vertical
Flow System (Annex 2).
Moreover, wetland plants (emergent) play great roles in removal mechanisms in
constructed wetland. The most significant functions of wetlands plants in the relation of
wastewaters are the physical effects brought by the presence of the plants. The plants
provide huge surface areas for attachment and growth of microbes.
The physical components of the plants stabilize the surface of the beds, slow down the
water flow thus assist in sediments settling and trapping process and finally increasing
water transparency. Wetland plants play also vital role in the removal and retention of
nutrients and help in preventing the eutrophication of wetland, these plants have a large
biomass both above (leaves) and below (underground stems and roots) the surface of the
substrate. The sub surface plant tissues grow horizontally and vertically, and create
extensive matrix, which binds the soil.
A range of wetland plants (emergent)
has shown their abilities to assist in
breakdown of contaminants in
constructed wetlands. The common
Reed Phragmites karka and Cattail
Typha angustifolia (Figure 2) are good
examples of marsh species that can
effectively uptake nutrients. These
plants have a large biomass both above
(leaves) and below (underground stem
and roots) the surface of the substrate
(Wetlands International, 2003
(a) (b)
Figure 7: Emergent plants Reed Phragmites karka(a) and The
Cattail Typha angustifolia (b) .Retrieved (Intern.Aquaplant. 2004)
3.2.1 Application of constructed wetlands in Tanzania.
According to the descriptions of constructed wetland above, this type of ecological
engineered system to treat human waste could have great advantages in Tanzania,
especially in the big cities whereby wastewaters are treated partial (Waste stabilisation
ponds), consequently discharge directly to the water sources to pollute the drinking water.
Therefore, the implementation of constructed in Tanzania could help to minimise the
pollution rate of Tanzania water sources supplies such lake Victoria, lake Tanganyika,
river Msimbazi to mention a few. However the implementation of constructed wetland
could be difficult especially in rural areas of Tanzania whereby wastewaters are not
treated. Wastewaters from many parts in rural areas of Tanzania are discharge directly to
water sources without treatment.
The good example of possibility application of constructed wetland in Tanzania could be
in “some areas” of Dar es salaam city which consists about 4 million inhabitants equal to
7.2 percent of the total National population, revealed that 79 percent of the inhabitant’s
uses pit latrines, 9 percent use septic tanks and remain 12 percent uses sewerage systems
(Chaggu,2003). The sewerage systems now are operated and maintained by the semi-
autonomous, the Dar es salaam City Water (Previously was called DAWASA means Dar
es Salaam Water Sanitation Authority) The operation maintenance of all these systems
has always been minimal as results the systems have effectively not functioning
appropriately as the result wastewaters are discharge partially treated to the water source
consequently pollute water sources (Table 2). With good maintenance of these sewerage
system as well the implementation of constructed wetland, the pollution load due to
wastewater could be minimise particularly into river Msimbazi. Keep in mind that,
utilisation of constructed wetland for wastewater treatment could be implemented only in
the institutions and not the whole area of Dar es Salaam which consist of 4 million
people. The institution like Dar es Salaam airport, Muhimbili hospital and military
barracks could be possible for install constructed wetland. These institutions have their
own sewerage systems which collect small independent drainage areas rather than a full
integrated network. The wastewater from these areas is partial treated by waste
stabilisation pond before discharge to water source and hence pollute.
Table 2: Water pollution load (kg/day) to water sources at Dar es Salaam capital city.
Adapted (Mgana.2003).
Type of Pollution
load (kg/day)
Surface water sources Ground water sources
Pit latrines Septic tanks Pit latrines Septic tanks
Suspended Solids
Dissolved Solids
Total Nitrogen
Total Phosphorus
Apart from Dar es Salaam capital city, the constructed wetland could be also
implemented in some areas of towns of regions in Tanzania like in Mwanza town, a
middle cost, which contains large, medium and small scale enterprises. These including
breweries, soft drink manufacture, soap factories, dairy producers, meat producers, fish
processor factories, bakeries, metal work and garages. The wastewater from these
enterprises plus wastewater from households are collected through Mwanza municipal
piped sewerage system and treated partial by using waste stabilisation pond before
discharged into lake Victoria, consequently pollute lake Victoria which is the main water
source of drinking water of Mwanza region, Bukoba region as well neighbour countries
of Kenya and Uganda which the also shared the territory of lake Victoria (refer map
chapter one)
Also constructed wetland could have great advantages in the region town of Iringa,
southern area of Tanzania, low cost- low density areas. The wastewater from households
are collected and treated partial through the waste stabilisation pond and discharge to the
river Hoho, which then people downstream use that polluted water for irrigation and even
domestic uses. In this region the implementation of constructed wetland could be possible
because of availabilities of land. Also in this region constructed wetland could be
implemented to the tanneries factory which the wastewater from this industry contain
toxic chemicals are discharge partial to the river Ruhuji.
To mentioned a few, implementation of constructed wetland could be also implemented
in other towns region of Mbeya, Morogoro, Tanga, Kilimanjaro and Kigoma region
where wastewaters are partial treated and discharge to lake Tanganyika.
A successful existing example of constructed wetland in Tanzania could be found in the
campus of University of Dar es salaam whereby wastewater from the university activities
plus surrounding residents are treated by using waste stabilisation pond and polish by
constructed wetland before discharge to the water sources.
3.2.2 Some potential advantages of constructed wetland to Tanzania.
Generally, constructed wetlands could offer several potential advantages for wastewater
treatment system. However below are specific advantages of constructed wetlands to
Constructed wetlands could be implemented in Tanzania at lower costs than other
treatment options. This is because the system relies on renewable energy sources such as
solar and kinetic energy, emergent plants and micro-organisms which are the active
agents in the treatment processes. Also constructed wetlands treatment systems are
cheaper alternative for wastewater treatment using local resources. This system promotes
sustainable use of local resources by utilisation of local products and labour helps to
reduce the operation and maintenance costs. Less energy and raw materials are needed,
Constructed wetland could also tolerate both great and small volume of water and
varying contaminants levels especially in many parts of Tanzania like municipal
domestic wastewater, hospitals wastewater which most discharge the effluent directly in
the water sources, agricultural wastewater and industrial effluents so as top minimise the
pollution of water sources. Beside that, constructed wetlands could served as a wildlife
sanctuary and provide a habitat for wetland animals in Tanzania. Together with existing
treatment plants such as waste stabilisation ponds in some parts (regions) in Tanzania,
constructed wetlands could help to polish the wastewater, and people may reuse the
nutrients for agriculture and aquaculture activities to improve the livelihood by increase
income (agriculture, aquaculture) and minimise the water pollution hence to reduce
waterborne diseases.
The tropical temperature of Tanzania is potential advantages for constructed wetlands,
since the mechanisms of removal of pollutants are also related with temperature. Hot
temperature make the removal efficient more quick while cold temperature little bit
slowly down the contaminant removal rate. There are several constructed wetlands in
Tanzania proved to be efficient in removal pollutants. Constructed wetlands in Tanzania
can be found at University of Dar es salaam, Iringa teacher’s college, in Arusha and
Mwanza town to mentioned a few.
Generally, constructed wetlands require larger land areas than do conventional
wastewater treatment systems. However in Tanzania constructed wetland treatment
could be economical relative because land is available and cheap. Constructed wetlands
could be part of teaching approach regarding environmentally education to general public
in Tanzania.
3.2.3 Some potential disadvantages of constructed wetlands in Tanzania.
The potential of disadvantage of constructed wetlands in Tanzania could be the breed of
mosquitoes, especially horizontal surface flow constructed wetlands type. In Tanzania
malaria is leading diseases that kill most of people especially children. However free
surface type constructed wetlands could implemented to reduce the problems of
mosquitoes breeding
3.3 Systems with source separation.
Besides the extensive piping, a major problem included in the human wastes control
systems common in developing including Tanzania and to most developed countries of
today, is that clean water is used as a transportation media for “human excreta” (urine and
faeces). This heavily polluted water from the toilets is mixed with the less polluted grey
water (from washing, dishing and bathing). These mixtures are let into the sewage
system, which then leads to contamination of fresh surface and ground water quality as
well as wastage of important nutrients which can be used by plants growth etc.
Substantial amounts of plant nutrients and organic matters are present in human excreta
and other domestic waste resources such as organic household wastes. The content of
nitrogen, phosphorus and potassium in human excreta and organic household wastes are
close to an optimum ration for plant growth. (Figure 3). As stated by Janssen, D (1999)
the amount of nutrients in human wastes is sufficient for producing food for the world
population. He made clear that reuse of human excreta by farmers can help secure their
subsistence and enhance agricu1tural production. In addition, provides alternatives to
scarce freshwater sources and helping to reduce surface water pollution.
Nutrients c oncentration in Urine an d
N P K S Bo Ca Mg F e
Figure 8: Faecal and urine concentration
Source separation systems it treats human wastes as a valuable resource. The nutrients
contained in the blackwater and grey waters can be collected separately and reuse to
obtain safe fertilizers for agriculture and aquaculture activities to increase the food
productions (Figure 4) and reduce health risks due contaminated water. Also by using
source separation systems it is possible to avoid the pollution problems associated with
expel of human wastes into the water bodies which used as recipients.
Figure 9: The concept of source separation systems. Adapted (Kampf.R.2005)
However, source separation system relies on isolating human wastes or blackwater and
greywater from wastewater. Mainly there are two source separation systems which are
greywater source separation and blackwater sources separation system.
3.3.1 Greywater source separation system
Greywater is defined as household wastewater with the exclusion of toilet wastewater,
this mean the greywater is the water from domestic washing, shower, washing dishes and
clothes etc (Staudenmann, J. et a, 1995). Compared to blackwater, greywater contains
only small amounts of plant nutrients (nitrogen, potassium and phosphorus). The
composition of greywater varies greatly with the lifestyle such as family size, age of
Greywater for
Blackwater for soil
Wastes and wastewater
from household
separately and
reusing of black
and greywater
residents, eating habits, detergents used etc. Greywater can contain 1-33% of the total
wastewater nitrogen while phosphorus content varies due to the detergents used. Also
greywater contains more than 50% of BOD in household sewage. Faecal coliforms are
usually found, while virus contents are usually not present unless someone in the house
has an infection. The content of heavy metals and organic micro pollutants in greywater,
however are generally quite low. The source of metals in greywater are normally
considered to be dust of metals extracted from metal-contain materials such as cutlery
and machines, dyes of cloths, some phosphorus-based detergents and some cases building
materials e.g. paints (Bjorn Vinneras.2001).
The need for treatment of the greywater depends upon its final discharge or use e.g. if the
final discharge is to the sea, thus normally no or only primary treatment is sufficient. By
relatively simple treatment greywater can be rendered suitable for irrigation. When the
discharge is to inland lakes, rivers or streams secondary treatment is recommended. This
may be achieved by using simple biological or sometimes only mechanical treatment
methods are sufficient e.g. using sand filter or a combination of a simple biofilter system
and a subsurface flow constructed wetland. Where natural conditions are favourable, soil
infiltration is a cost effective option that gives excellent greywater treatment such that the
greywater is applied to a leach field and treated while percolated through the soil.
Treatment efficiency is dependent on the soil type and depth to groundwater e.g. clay soil
is unsuitable for infiltration (Staudenmann, J. et al.1995). Sometimes greywater which
contains hair, grease and soap hence may cause problems, therefore pre-treatment is
recommended such as septic tank which is very common. In the septic tank material such
as solids can settle down while materials like grease and hair can float. In additional,
anaerobic digestion reduces the organic matter content. After that greywater should be
passed through medium up flow filters that can further reduce soluble BOD and thereby
reduce the clogging potential of the effluent in subsequent soil disposal systems.
3.3.2 Blackwater source separation system.
Blackwater (urine and faeces) contains the majority of the nutrients in domestic
wastewater. Of the blackwater components, the urine fraction contains greatest amount of
nutrients. If the blackwater or the urine fraction is collected and treated separately, the
majority of the nutrients can be removed from the human excreta. This requires the use of
toilets that use little or no water, or urine separating toilets. Therefore system with source
separation offers a variety of alternatives for handling human excreta resources, and
provides also co-treatment of various organic wastes (Janssen, D. 1999).
Blackwater contain valuable nutrients including nitrogen, phosphorus and potassium.
Urine possesses the majority of nutrients, as compared to faeces, containing
approximately 80% of the nitrogen, 55% of the phosphorus and 60% of the potassium
which is available for reuse. The use of human excreta as a fertilizer is beneficial from
environmental, economic and social perspectives. Increasing crop yields through the use
of sanitized urine and faeces is cost effective approach such that requiring only an
investment in the ecological sanitation toilet and secondary treatment system. Urine,
faeces and the combination of both urine and faeces can be processed in a number of
different ways. Regardless of how processing occurs, the goal is to return excreta to soils
One interesting and simple method of nutrients removal from human urine is to use urine
source separation system. An alternative here is to use a urine separating toilet. There are
two principally different urine separating toilets system; dry and wet handling. With wet
handling, the faeces are usually treated in the same system as the greywater. This means
that the greywater treatment facility has to be designed to handle the extra organic and
micro organism load that the faeces represent. Generally, urine itself is sterile, but
contaminations can occur in the toilet. For this reason urine cannot be used directly as a
fertilizer. When urine is collected for a use as fertilizer, it is important to store at least six
months that is sufficient for bacteria to die off prior to agricultural use. Also may prevent
odours due to the loss of nitrogen in the air. Most of nitrogen in urine, which initially in
form of urea, is quickly converted to ammonia within a collection and storage device.
However, ammonia loss to the air can be minimized by storage in a covered container
with restricted ventilation.
Blackwater handling and treatment depends on the toilet type. However, the
infrastructure of the system must be changed. Instead of centralized system sewers where
water and nutrients mainly flow to a treatment plant or discharge point, the blackwater
and/or urine fraction is diverted, collected and recycled to agriculture.
However, the use of human wastes for agriculture activities may pose high risk to human
being especially. Therefore this chapter described and examines the prospective of source
separation system as ecological sanitation that treat human waste (black or grey water) in
Tanzania with respect what have been obtained now in Tanzania especially high
percentages of pit latrine.
3.3.3 Application of sources separation systems in Tanzania.
Based upon the descriptions of sources separation systems as well as what has been
obtained now in Tanzania especially percentages of pit latrine (ecological sanitation
standard). Tanzania could benefit from these pit latrines if proper managements and
design are considered. These pit latrines could produce good fertilizer to be used for
agriculture activities to improve the livelihood of local communities in Tanzania.
However, in order to achieve this objective, urine and faeces in pit latrines should be
separated. The basic idea of how to avoid mixing of urine and faeces is simple; the
defecating person should sit or squat over some kind of dividing wall so that faeces drop
down and urine passes in front. This idea of not mixing urine and faeces is not new. In
china, simple toilets with urine diversion have been used for centuries (Steven, A .et
Use of special collection devices such as squatting pan and seat riser (Figure 5) which
diverting urine for storage in separate container, allow the faeces to be dehydrated fairly
easier. Because urine contains most of the plant nutrients but general no pathogens, it
may be used directly without the need for further processing (Steven, A. et al.1998). This
kind of device could functionally reliable and social acceptance to local communities of
Tanzania especially in rural areas. However, some of the barriers relate to local
community religions, taboos and cultural foundation such that local community may feel
that they are "breaking" their inherited rituals should be seen as a question of awareness,
such that beneficiaries are adequately consulted, informed, educated on urine separation
toilet during the implementation.
Figure 10: Squatting pan latrine (A) and Seating pan latrine (B). Retrieved (Intern.
Alfred Shayo.2003)
Also, if these high percentages of pit latrines which has been
obtained in Tanzania are designed and modified with double
vaults, could help to produce safe fertilizer as well to reduce the
ground water pollution. In this type, the pit latrines are design
with two vaults (Figure 6), each with its own seater rise or
squatting slab. Each vault is used alternative for certain period.
When the switch is made from one vault to another, the contents
of vault which has been dormant are empties, the assumption
being that after several months (three to four months). Chaggu
Figure 11: Double vault pit latrine
A good example sources separation pit latrines
could be found in Dar es Salaam Tanzania at
Majumbasita peri-urban area with 23,000
inhabitants. It is about 11 km. from the city
centre in the western direction and closer to the
Dar-es-Salaam International Airport (DIA). In
this area about 96 ecological sanitation toilets
were constructed under the pilot project which
has been implemented by EEPCO
(Environmental Engineering and Pollution
Control, NGO) with a donor support from
UNICEF and partial contribution by
Two basic types of ecological sanitation pit latrines have been constructed at
Majumbasita. These are squatting and sitting type which both fitted with urine separation
inlets. The urine is led through a pipe to a container (tank) of 60 litres capacity outside
the toilet (Figure 7) filled with gravel and sand (Chaggu.2003).
The faeces are collected in a receptacle straight under the squatting hole. In order to
maintain the principle of having very little water in the faeces, ashes are dropped into the
pit-hole after every single use. The addition of ashes assists in the desiccation process and
raises the pH, which aids pathogen reduction.
Another example of sources separation systems have been constructed in Mlalakuwa area
(double vault) which is located about two kilometers from the University College of
Lands and Architectural Studies (UCLAS) in the Dar es Salaam city.
Figure 12: Pit latrine with urine diversion
In this area, people understand the important of reused the nutrients from human wastes
for gardening. Also pollution due of ground water was avoided, since they are
constructed pit latrines above the ground (Chaggu.2003)
3.3.4 Some potential advantages of source separation systems in Tanzania.
Source separation system could be sustainable system for fertilizer production in
Tanzania, such that nitrogen, phosphorus, potassium and organic matters from urine and
faeces can be recycled and reused for agricultural purposes, in that way could improve
the local economy and strengthen the local communities of Tanzania with food while the
surpluses may be sold at the market.
For example, it was estimated that about 25-50 kg of faeces is produced per person per
year. This contains up to 0.55 kg of Nitrogen, 0.18 kg of Phosphorus and 0.37 kg of
Potassium. Furthermore, an adult may produce approximately 400 litres of urine per year
containing 4.0 kg of nitrogen, 0.4 kg of phosphorus and 0.9 kg. of potassium (Chaggu,
Taking above figures into consideration and through the source separation system for
human wastes treatment, it means that Tanzania per annum with the total population of
about 36 million people could produce much of nutrients from for fertilizer from human
excreta (Table 2) This suggests that, if human wastes are treated properly, Tanzania have
a great potential of "human waste” to be used as fertilizer rather than use commercial
fertilizers. The fertilizer from human waste source separation system consist low
concentrations of heavy metals compared to chemical fertilizers and also require little or
no chemical to treat.
Table 3: Estimated nutrients from human excreta in Tanzania
Minimum nutrient Production per annual in Tanzania with 36 million inhabitants
N (Kg)
(x 107)
Note that, the commercial fertilizers consumption in Tanzania was 53,883 tons in 1972;
142,676 tons in 1991 and 200,000 tons of which 25% was N, P, K in 1994 (Chaggu,
Moreover the economic and environmental advantages of adopting source separation
systems are manifold; smaller, simpler treatment plants; lower nutrient emissions to
rivers, lakes, and oceans; reduced sludge production; reduced use of flocculation
chemicals, which saves money and reduces environmental impacts; natural resource
conservation; lower fertilizer impacts; and greatly reduced toxic impacts of combined
3.3.5 Some potential disadvantages of source separation systems in Tanzania.
If human excreta (faeces and urine) is not treated properly. The risks of transmission
pathogens- causing waterborne diseases will be higher to communities in Tanzania.
However, this can be avoided by educate people to use safe human excreta.
Also the use of human waste may face difficulties especially in the areas of Islamic
people in Tanzania, because Islamic cultures insist the avoidance of all contact of human
excreta and water that used by mankind (wastewaters). Faeces, urine and any specified
substances are regarded as spiritual pollutant by Koran edict, and Islamic custom demand
that Muslim should minimize or avoid contact with these substances. However awareness
and education will help Islamic people to understand the potential of human excreta.
Examples could be found in Muslim societies in Muscat where people reuse human
wastes for agriculture and aquaculture to improve livelihood.
3.4 Oxidation ditch
An oxidation ditch is one of ecological engineered system for treating human waste
modified activated sludge biological treatment process that utilizes long solids retention
times to remove biodegradable organics and other nutrients. The oxidation ditch was first
developed in the Netherlands by A.Pasveer, born 1909 – 2001 (Intern. Mels, .A et
al.2005) This type of treatment is just normal ditch with oval shape. Aerator or
recirculating device can be installed on one side of the ditch at the depth of 1.0 – 3.0 m
(Figure 8). The function of the aerator is to provide enough mixing of influents in the
ditch. This mixing process entrains oxygen into the mixed liquor to foster microbial
growth and the motive velocity ensures contact of microorganisms with the incoming
wastewater, hence enable the removal of suspended solids, BOD and some of the
nutrients by bacteria degradation and sludge growth (activated sludge).
Preliminary treatment, such as bar screens and grit removal, normally precedes the
aerated oxidation ditch. Primary settling prior to an aerated oxidation ditch is sometimes
practiced, but is not typical in this design.
Figure 13: Oxidation ditch. Adapted (Kampf, R. et al.2005.
Nitrogen concentration in oxidation ditch can be removed either by nitrification or
denitrification mechanisms, this can be achieved by controlling the oxygen concentration
in the systems. Normal oxidation ditch has capacity of sludge load between 0.05 kg and
0.2 kg BOD per population per day but depend upon the wastewater temperature and
volume of approximately 250 litres to 300 litres per population equivalent (Intern.Mels, al.2005).
Table 4: Expected quality of treated wastewater from oxidation ditch Adapted (Intern.
Mels,A. et al.2003).
Constituent Max.average (%)
BOD 85 - 99
Suspended solids 80 – 95
Nitrogen 70 (Almost complete nitrification)
Electrical aerator
Recirculate sewage
Recirculate sewage
3.4.1 Application of Oxidation ditch in Tanzania.
As the literature described, this technology is still new in Tanzania, also require energy
(electricity) to operate the aerator. In that ways implementation of this technology in
Tanzania could be relative difficult take account the cost of electricity in Tanzania is high
and some parts of the country do not have accessibility of electricity especially in rural
areas of Tanzania. However, this technology could be applied in rural areas if people get
assistance (help) of the initial cost of solar system devices that could generate electricity.
3.4.2 Some potential advantages of oxidation ditch in Tanzania
This technology could be very effective in small installations, small communities, and
isolated institutions where energy is available in Tanzania such in hospitals and schools
in urban areas of Tanzania.
3.4.3 Some potential disadvantage of oxidation ditch in Tanzania
This system could not be applicable in the most parts of rural areas of Tanzania where
there is lack of electricity, this is because aerator device installed in the oxidation ditch is
operated by energy (electricity). Apart from that, this system could be even relatively
difficult in the areas where there is electricity because still the cost of electricity in
Tanzania is relatively high for people to afford.
3.4.4 Summary and conclusion
The ecological engineering systems for human waste treatment could be outstanding
example in Tanzania, because are affordable and require less maintenance. In Tanzania
the implementation of constructed wetlands could be mainly implemented in urban towns
of regions whereby wastewaters are partially treated and disposal to the water sources.
Tanzania could produce huge amount of safe fertilizer to improve crops production if pit
latrines are proper managements and designed. Also could help to reduce water pollution.
The implementation of oxidation ditch is relative difficult in Tanzania, this is because
many areas of Tanzania are not able to access electricity, Also the cost of electricity in
Tanzania is relative high. Oxidation ditch can utilise in Tanzania with the help of solar
power, especially in rural areas.
However, the implementation of source separation systems (ecological toilets) and reuse
of nutrients from human excreta is more complex than other systems especially on
individual families and local communities in Tanzania for appropriate functioning.
Therefore individual families and local communities must become aware that, despite
potential health and income benefits, improper use of sources separation systems
(ecological toilets) may turn into troubles, threaten public health, and pollute the
environmental in Tanzania. These problems can best be avoided by adopting the
appropriate behaviours from the outset. Individual families and local communities must
understand how this source separation system works (ecological toilets), what can go
wrong and have the commitment and skill to manage it correctly. In additional special
care is required to take full advantages of significant resources potential of recycled plant
Chapter 4
4.0 The links Waterharmonica concept and poverty reduction in Tanzania
4.1 Introduction
Poverty is widely viewed as encompassing both income and non-income dimensions of
deprivation—including lack of income and other material means; lack of access to basic
social services such as education, health, and safe water; lack of personal security; and
lack of empowerment to participate in the political process and in decisions that influence
someone’s life. The dynamics of poverty also are better understood, and extreme
vulnerability to external shocks is now seen as one of its major features
It is now widely appreciated that the so called poverty gap is a fact and persistent in many
developing countries. Lack of sufficient food, improper sanitation, improper
management, war and other factors contribute with poverty situation in many developing
countries, Tanzania included. These factors are interrelated. Aquaculture and agriculture
activities are receiving increasing attention in developing countries as potential aspects
that could reduces the gap of poverty. In many rural areas of developing countries
especially in Asia the use of wastewater for irrigation and fish farming are a fact of life
and not a matter of choice. In arid or semi arid areas, the use of wastewater is the only
water sources that support the livelihood of many poor people. The application of treated
wastewater has considerable potential in a cyclical approach to increase crops and fish
productions, provided that health risks are taken into consideration. Public health is the
most critical issue regarding reclaimed wastewater.
Therefore, the links Waterharmonica concept and poverty reduction in Tanzania focus on
the use of ecological wastewater treatment as a buffer to control waste water, which
could contribute to alleviation of poverty in Tanzania. By safely recovering the nutrients
found in wastewater through Waterharmonica concept could be possible to achieve the
needs and demands of the local communities of Tanzania. In that case, wastewater should
be considered a resource, and forms part of nutrients flow, wastewater management and
integrated resources management. However, wastewater reuse also has negative effects on
humans and ecological systems, which need to be identified and assessed early.
Based upon the concept of Waterharmonica, poverty reduction in Tanzania could be view
in two dimensions (Figure 1); these are;
- Income opportunities (Agriculture and Aquaculture), and
- Environmental aspects (Water quality and water quantity)
Figure 14: Links Waterharmonica concept with poverty reduction
Wastes and
Income opportunities
- Crop production
- Fish production
Environmental aspects
- Water quality
- Water Quantity
Combined collection
-Sewage systems
-Sewage treatment
4. 2 Agriculture aspects
With increasing global population, the gap between the supply and demand for water is
widening and is reaching such alarming levels. In certain parts of the world this poses a
threat to human existence. It is the appropriate time, to focus on one of the ways to
recycle water—through the reuse of wastewater, for irrigation. This could release clean
water for use in other sectors that need fresh water and provide water to sectors that can
utilize wastewater e.g. for irrigation and other ecosystem services. On the other hand,
wastewater is a resource that can be applied for productive uses, since wastewater
contains nutrients that have the potential for agricultural activities, and thus could
contribute to farm-based income generation and food security. Take into considerations
that wastewater contains broad groupings of constituents, such as Organic matters,
nutrients (Nitrogen, Phosphorus, Potassium), Inorganic matter (dissolved minerals) etc.
This technology of reuse wastewater for agriculture is not new; it was applied in many
countries around the world (Table 5).
Table 5: Example of the countries utilizes wastewater for agriculture (Intern. ETC SIDA)
America Asia
Mexico - Cereal, vegetable, fodder
Peru - Vegetable, fodder, cotton
Chile - Vegetable, grapes
Argentina - Vegetable, fodder
USA - Vegetable, cereals, fodder
Kuwait - Cereals, fruit, fodder
Jordan - Vegetable
Israel - Cotton
Saudi Arabia - Cereals, fodder
India - Cereals, vegetable
German - Cereals, sugar beet, potatoes
S. Europe - Non food crops
Tunisia - Citrus, fodder
Morroco - Vegetable, food
Around 70 percent of Africans depend on agriculture for a living (Intern.DFID.2003),
Tanzania included. Agriculture is critical issue to Tanzanian economy. At local levels
most cash earnings for rural populations are derived from agricultural activities.
Therefore it would be essential to promote actions that will lead to improvement of
agricultural productivity and ensure cash earning and availability of access to food that
will contribute to improve the livelihood. The need of new approaches in agriculture is
highly required for small and medium scale in Tanzania.
Therefore the links Waterharmonica concept and for poverty reduction with respects to
agriculture is mainly focus extensively on the reuse of safe wastewater for irrigation
agriculture (crops); this is because safe wastewater is rich in nutrients (Table 6) and
provides all the moisture necessary for crop growth. Most crops give higher than
potential yields with wastewater irrigation, and hence reduce the need for artificial
fertilizers, resulting in net cost savings to farmers.
Table 6: Major constituents of typical domestic wastewater (Intern.Pescod.B.1992)
Parameters Concentration (mg/l)
Strong Medium Weak
Total solids 1200 700 350
Dissolved solids 850 500 250
Suspended solids 350 200 100
Nitrogen (as N) 85 40 20
Phosphorus (as P) 20 10 6
Chloride 100 50 30
Alkalinity (as CaCo3 200 100 50
Grease 150 100 50
BOD5 300 200 100
For example, the wastewater from households in Tanzania could be used for crops
irrigation particularly in arid and seasonal arid areas of Tanzania such as in the regions of
Dodoma, Singida and Shinyanga where the have shallow rainfall per year. By utilization
of wastewater for irrigation purposes could increase crops yield, reducing the need of
artificial fertilizer, reduces pollution of water sources and decrease scarcity of alternative
waters for irrigation. This means could conserve or more rationing usage of freshwater
resources especially in arid and semi-arid areas of Tanzania e.g. fresh water for drinking
purposes. Wastewater could equally be used in other areas in Tanzania for high crops production
and net profit compared to the use of commercial fertilizers, which are relatively expensive.
With respect to the fact that Tanzania imports commercial fertilizers from other countries,
this result too much money (income) being spent for buying commercial fertilizers.
Therefore, the use of wastewater for crops production could help the local communities
of Tanzania as well as government to utilise the money for other purpose such as
education, health, roads etc.
However, communities of Tanzania must take great care when reusing wastewater,
because waste water contains chemical substances and biological pathogens with
potentials to threaten public health as well as accumulate in the food chain when used to
irrigate crops. This means inhabitants, most specifically agricultural field workers and
their families, crop handlers, consumers, those living near the fields should be careful
with wastewater reuse. In addition, reuse of wastewater could pose side effect to crops
and environmental as follows:
Public health: Wastewater contains pathogenic microorganisms such as bacteria,
viruses, intestinal nematodes, and parasites. Waterborne diseases such cholera, typhoid,
dysentery could be effectively transmitted by irrigation of crops if wastewaters are not
treated proper. Thus, proper treatment of wastewater, crops restriction and control of
wastewater application are highly effective method of safeguarding public health. Public
health risk is an important decision variable in wastewater irrigation, both adult
population as well as children should be considered as potential exposure group. Second,
the entire population, living within and outside the wastewater irrigation zone, should be
considered as the potential exposure groups for economic valuation purposes.
Crops: Most crops give higher than potential yields with wastewater irrigation; reduce
the need for chemical fertilizers, resulting in net cost savings. But if the total nitrogen
delivered to the crop via wastewater irrigation exceeds the recommended nitrogen dose
for optimal yields, it may stimulate vegetative growth, but delay ripening and maturity,
and in extreme circumstances, cause yield losses.
Soil: Impact from wastewater on agricultural soil, is mainly due to the presence of high
nutrient contents (Nitrogen and Phosphorus), high total dissolved solids and other
constituents such as heavy metals, which are added to the soil over time. Wastewater can
also contain salts that could accumulate in the root zone with possible harmful impacts on
soil health and crop yields. The leaching of these salts below the root zone could caused
soil and groundwater pollution (Intizar Hussain), which may lead to transport of heavy
metals to crop contamination and final affecting soil flora and fauna. The irrigation
wastewater should consider the standards maximum concentration of metals in irrigation
waters as shown (Table 7)
Groundwater resources: Wastewater application has the potential to affect the quality of
groundwater resources in the long run through excess nutrients and salts found in
wastewater leaching below the plant root zone.
Table 7: Standards Maximum Concentration of Metals in Irrigation Wastewaters.
Adapted (Intern. Environmental Act. 1999)
Element Conc. Mg/l Element Conc. Mg/l
4.3 Aquaculture aspects
As defined by the United Nations Food and Agriculture Organization (FAO).
Aquaculture is the “farming of aquatic organisms including fish, molluscs, crustaceans
and aquatic plants. Farming implies some sort of intervention in the rearing process to
enhance production, such as regular stocking, feeding, protection from predators, etc.
Farming also implies individual or corporate ownership of the stock being cultivated.
Because of the increasing demand for animal protein and limitations in the capacity of
capture fisheries (Saber Abdel.2004), the importance of aquaculture as a source of
fisheries products is growing. Therefore aquaculture appears a promising protein source
besides marine fishing which contributes about 12% of the current fish production (Saber
Abdel.2004). Wastewater aquaculture is an old technique which has been used
extensively in Asia and Europe. However, historically wastewater aquaculture is
relatively recent in Africa compared to Asia countries; it is not familiar to the majority of
African countries. The vast majority of aquaculture takes place in Asia. For example in
China fish culture using wastewater is regarded as a traditional form of agriculture. In
1985 the total area of waste-fed aquaculture in China was 8000 ha, with a total fish
production of 30,000t/year. Most of the waste-fed aquaculture in China is located near
the cities and contributes fish products to city markets (Martin Kumar, et al 2003). In
2002, over 70% of worldwide aquaculture production was in China alone (Saber
Abdel.2004) and most farmed fish and shellfish are grown in traditional small-scale
systems that benefit local communities and minimize the environmental impact.
After aquaculture was introduces from European and Asia countries in various African
countries this development started to spread and the main farmed species is tilapia.
Developing countries increasingly direct effort towards fish aquaculture to provide
people with sufficient amount of protein, essential for healthy growth. The net
contribution of these traditional aquaculture systems can be great as they offer many
benefits, including food security in developing nations.
Therefore the link Waterharmonica concept and aquaculture with poverty reduction in
Tanzania is focuses on ecological fish farming and other aquatic organisms or biomass by
utilise wastewater nutrients to develop the fish farming systems, which increase the
production of fish. This ensures that nutrients from the wastewater are not discharged as
pollutants. By recycling wastewater nutrients (organic wastes) for fish farming
(aquaculture) represents could be an attractive alternative in fish production and
safeguard the Tanzania environments from pollution and simultaneously generates
valuable marketable biomass.
Based on upon the concept of Waterharmonica and aquaculture, If local communities in
Tanzania especially in rural areas of majority are encourage to use safe wastewater it will
help to keep the price of the fish food low so that fish food will be affordable to both poor
people, it will also provide income and employment that could help poor people to access
food, and final it will help tax base to support service delivery that will help poverty
However again, fish farming by reuse of wastewater may also impose health risks to the
consumers of the products if not properly treated (Table 8). Therefore the link
Waterharmonica concept and aquaculture with respect poverty reduction should
implemented on - line with education to the users or consumers to avoid risks of diseases
that associated with human waste such as pathogens or toxic chemicals.
Table 8: Relative Health Risks from Use of Untreated Excreta and Wastewater in
aquaculture. Adapted (Martina Strauss .2002)
Class of pathogen Relative amount of excess frequently of
infection of diseases
1. Intestinal nematodes High
- Ascaris
- Trichrus
- Ancylostoma
- Necator
2. Bacterial infections Lower
- Bacterial diarrhoeas
(e.g. cholera, typhoid)
3. Viral infections Least (but not insignificant under
specific circumstances)
- Viral diarrhoeas
- Hepatitis A
4. Trematode and cestode infections
- Schistosomiasis From high to nil, depending upon the
particular excreta use practice and local
- Chlonorchiasis
- Taeniasis
4.4 Environmental aspects
In this part involved the quality and quantity of the water, such that properly planned and
managed wastewater reuse could have a positive environmental impact in Tanzania. By utilize
proper the concept of Waterharmonica, the environmental in Tanzania could be improve in the
way that avoiding of surface water pollution, which may occurs if unused wastewaters are
discharged into rivers or lakes. Major pollution problems such as waterborne diseases (typhoid,
cholera, dysentery etc), dissolved oxygen depletion, eutrophication, foaming and fish kills could
be avoided in many of Tanzania water sources, such as in lake Victoria and river Msimbazi. Also
conservation or more rational usage of freshwater resources, especially in arid and semi-arid
areas: fresh water for urban demand, wastewater for agriculture and aquaculture. Also through the
reuse of wastewater for irrigation crops could help the deterioration of soil nature in Tanzania
which may caused by long run of use chemical fertilizers
4.5 Summary and conclusion.
The links Waterharmonica concept with poverty reduction in Tanzania could be achieved
through ecological wastewater treatment and reuse of nutrients from wastewater. In that
way wastewater should be considered a resource to be used in Tanzania, but should be
used safely. If Tanzanians are encouraged to utilise properly the nutrients from
wastewater for irrigation purpose and fish farming, then it could be possible that poverty
levels could be reduced especially for rural areas where communities depend entirely on
crops farming by using commercial fertiliser. Also by utilising wastewater for irrigation
and fish farming water pollution could be avoided.
However, reuse of nutrients from wastewater should have consideration for health risk to
local communities especially in rural areas. Local communities should be educated on the
safe use of wastewater; crop restriction and fish farming with adequate treated
wastewater. The use of treated waste water does not lead to transmission of waterborne
diseases. Also crops restriction and proper cooking food or fish are suitable ways of
health protection.
Chapter 5
5.0 The roles of local communities on Waterharmonica concept in Tanzania
5.1 Introduction
In order for the Waterharmonica concept to be successfully implemented in Tanzania,
local communities would have their roles to ensure sustainable management of the
concept. This chapter will examine the issues relating to promote and support sustainable
management of Waterharmonica concept in Tanzania. Therefore it is of utmost
importance to take the followings into account:
5.2 Education
It is important to educate local communities about the main purpose of Waterharmonica
concept, which is to treat the wastewater in ecological engineering ways, in the least cost
efficient manner compared to other methods. Education should emphasise on the reuse of
nutrients from wastewater for irrigation and fish farming. In additional, they should be
equally informed on the benefit of the concept to their communities. Some of which are
increase in agriculture and aquaculture output, reduction of waterborne diseases. Above
the benefits mentioned, education could facilitate acceptability of the Waterharmonica
concept within communities.
5.3 Participatory involvement
The effective use of participatory involvement can be of vital important to the success of
Waterharmonica concept in Tanzania. This approach will involve the local community in
the overall identification of problems and the needs, planning decision making and
finding solutions. Participatory involvement could also improve communication within
and between communities, and support agencies. Also participatory involvement could
stimulate the self confidence and creativity within community.
5.4 Summary and conclusion
Waterharmonica concept in Tanzania should not be implemented for their own sake, but
rather than empowering the local people, in particular, to take charge of their own
development. Awareness is required to change the behaviour of individuals, group and
most specifically at local levels.
Chapter 6
6.0 Discussion
Carrying out a research on the potential of Waterharmonica concept in Tanzania can be
quite challenging; Tanzania spends large amount of money to buy advanced machineries,
technologies and chemical to treat wastes and wastewater. However, these have been
difficult to maintain and eventually failed due to higher energy consumption and human
resources. The existing wastewater treatment facilities such as wastes stabilisation ponds
can only be found in some towns, but not in rural areas. Population explosion,
industrialisation in unplanned areas and lack of proper maintenance are some of the
problems encountered by the existing wastewater treatment facilities in Tanzania.
Proper management and design of the high percentage of pit latrines in Tanzania could
provide huge amounts of fertiliser and reduction in water pollution. As a result, this could
improve crop productivity and environmental quality.
The Waterharmonica concept could be a promising approach to treat wastewater in
Tanzania, especially in some towns where wastewaters are treated partially. This is
because Waterharmonica concept relies on natural processes for wastewater treatment.
However, the Waterharmonica concept has some advantages and disadvantages.
Directing these advantages to Tanzania, the Waterharmonica concept could help reduce
poverty and waterborne diseases (See chapter 4). As concern the disadvantages, failure in
proper management could result to the spread of waterborne diseases in Tanzania.
The role of local communities is to ensure the sustainability of the concept. In order for
local communities to play their role, it is important first to understand the main purpose
of the Waterharmonica concept for treat wastewater, and should be involved in
Chapter 7
7.0 Conclusion
This research had centred to reduce waterborne diseases and poverty among the local
people of Tanzania with respect to the potential of Waterharmonica concept in Tanzania;
therefore the followings are summary of the conclusions:
i) Waterharmonica concept could provide sustainable solution of wastewater
management in Tanzania.
ii) This means, it could to help to protect and reduce the pollution to water
sources such as rivers, stream etc. consequently to minimise waterborne
iii) Reuse of nutrients from safe wastewater for irrigation and fish farming, result
to less or no chemical fertilizer will be required by the farmers. Therefore
could help to increase income and food security. The effort of national
government to reduce poverty among local people could be achieved.
iv) Utilising safe wastewater for irrigation and fish farming could help to
minimise the degradation of soil help to conserve the water (water quantity).
Thus, the above aspects could only be achieved if proper management of the
Waterharmonica concept is maintained accordingly.
Chapter 8
8.0 Recommendation
8.1 Recommendation to local communities of Tanzania
Achievements or failures of the Waterharmonica concept is on the hands of local
communities of Tanzania, this means they should be key players in the sustainability
of the concept, thus proper management of the concept will lead to the achievements.
However, Tanzania government (politicians) should also give support to the local
communities for the sustainable development of Waterharmonica concept. If the
government (politician) works against it, it will not go far. It is therefore necessary
that, adequate encouragement is given to the local people so that they can see the
suitable areas of intervention instead of interfering.
8.2 Recommendation for further research
1. The potential of Waterharmonica concept should be also involve neighbors “East
Africa Countries” of Tanzania, which are Uganda and Kenya. These countries
share or have the same social, economical and environmental problems. A good
example is the water pollution which occur in the Lake Victoria, the world’s
second largest fresh water lake which is shared by both countries; Tanzania by
51%, Uganda by 43% and Kenya by 6% (Simon Ndumu. 2002). Therefore there
is need for further research about the potential of Waterharmonica in East Africa
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Agricultural University of Norway, 1432 Aas Norway.
Joost Jacobi (2004). The Potential of Eco-Technology Wastewater Treatment for
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Engineering Group, Sub department Environmental Technology. Wageningen
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sustainable solution as an alternative for separate drainage and treated. Presentation
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Annex 1: Pollutants removal mechanisms
Parameter Mechanisms
- Nitrification, denitrification, violation, sediments,
Suspended solids
uptake by wetland plant.
- Adsorption, precipitation, uptake by wetland
- Sedimentation, filtration.
- Deposition, filtration.
- Filtration
Annex 2: Type of constructed wetlands
Surface flow type Subsurface flow type
- Water level is above ground surface
- Vegetation is rooted and emergent above
the surface.
- BOD removal is believed to occurs
rapidly through settling and entrapment
of particulates matters.
- Suspended solids is effective, most of
removal occurs within the first few meter
of travel distance from the inlet zone.
- Require large area.
- Provide great available surface area for
- Provide wild wife habitat and aesthetic
- Water level is design to remain below the
top of the substrates.
- The floe path is horizontal.
- Best for low relative solid concentration
- Possible, greatly assimilation of land area
compare to surface flow type.
- Have had problem with clogging.
- Breeding place for mosquitoes
Annex 3: Guideline for Wastewater quality for Irrigation
Parameters Unit Degree of restriction on use
None Slightly to moderate Severe
A. Salinity
µs/ m < 0.7 0.7 - 3.0 >3.0
TDS Mg/l <450 450 - 2000 >2000
SAR2 = 0.3 and EC > 0.7 0.7 - 0.2 < 0.2
3-6 > 1.2 1.2 - 0.3 <0.3
6-12 > 1.9 1.9 - 0.5 < 0.5
12-20 > 2.9 2.9 - 1.3 < 1.3
>5.0 5.0 – 2.9 <2.9
C. Specific ion toxicity
Sodium (Na)
Surface irrigation SAR <3 3-9 >9
Sprinkler irrigation Me/l <3 >3
Chloride (Cl)
Surface irrigation Me/l <4 4-10 >10
Sprinkler irrigation Me/l <3 >3
Boron Mg/l <0.7 0.7-3.0 >3.0
D. Miscellaneous effects
Nitrogen (NO
Mg/l <5 5-30 <30
Bicarbonate (HCO
) Me/l <1.5 1.5 – 8.5 >8.5
pH Normal range 6.5 – 8.0
EC means Electrical Conductivity in deciSiemen per metre at 250C
SAR means Sodium Adsorption ration.
NO3-N means Nitrate Nitrogen
Source: Pescod.B (1992), FAO
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Full-text available
During the last decennium separation of wastes has matured into practical use. Separation not only reduces the amount of drinking water spilled in toilets, but makes reuse of nutrients attractive. The main drawback of separation is that it is rather expensive, especially in areas with an existing sewage system. Large centralised sewage treatment plants discharge waste water from large areas on one spot, with a considerable effect on surface water quality. It results in an ambivalent situation. Drinking water is becoming more and more expensive. After use in households and industry this water, collected together with rain water, is considered as a waste. It is transported in sewer systems and treated at huge costs in sewage treatment plants. But after discharging in surface water ecologists consider this cleaned water, originating from drinking water, as "dead water" compared with healthy surface water, not complying with the ideas about natural water quality, as described in the latest directives on ecological water quality of the European Union. To bridge the gap between these two "worlds" (producing drinking water, transporting waste water on one hand and on the other hand the caretakers of surface waters) the Waterharmonica have been postulated. It is a low-tech concept based on ecological engi-neering, using food-chain approach to transfer well treated waste water into "healthy and useable" surface water. The main function is converting treated waste water into a usable natural surface water, but aspects like water buffering, recreation, buffer zones, nature development, water buffering during floods, creating fish spawning areas, growing fish for stocking wild populations are getting more and more important. In this paper the development of the concept is described. The Waterharmonica concept has resulted in a research and implementation programme (2003-2004) of two of the main Waterboards in The Netherlands, supported by the Dutch Foundation for Applied Water Research. This paper describes the development of the concept within integral water management.
Full-text available
To create a sustainable society, the nutrients in household biodegradable solid waste and wastewater have to be recycled to agriculture. lf the nutrients present in wastes from society were recycled, the use of fossil resources would decrease and so would the undesirable effects arising from discharge of nutrients to water recipients. The main proportion of nutrients in the waste is to be found in the urine, faeces and the biodegradable solids. If all of these fractions are collected and recycled, 92% of the nitrogen, 85% of the phosphorus and 63% of the potassium out of the total flow of nutrients in the biodegradable fractions (urine, faces, greywater and biodegradable solids) would be recycled. An easy way to collect the urine, which contains the majority of the nitrogen and a lot of the phosphorus and potassium originating from households, is to use a urine-diverting toilet system. So far, it has proved possible to collect up to 80% of the urine excreted using such a system. In the collected urine mixture (urine and flushwater), there is a tendency for three layers to form. The middle layer, consisting of more than 90% of the total volume, has a composition comparable to the urine mixture if it were homogenized. The top layer, which is less than 5% of the total volume, has a lower concentration of nutrients than the middle layer while the bottom layer, also less than 5% of the volume, has a higher nutrient concentration than the other two layers. When using a water-flushed toilet, it is possible after a short transport to capture the faecal nutrients by separating the faecal particles from the flushwater. High disintegration of the faecal particles, such as may occur in long or vertical transport, results in extraction and suspension of the nutrients, which decreases the amounts of nutrients it is by particle separation possible to separate and recycle. Currently, faecal separation can be performed by Aquatron or filtration. The nutrient separation efficiency of the techniques depends on several factors. Aquatron separation was investigated in the laboratory with a short soil pipe transport and in the Ekoporten block of flats with a long transport through up to four floors to the separation in the basement. The investigation in Ekoporten showed that it was possible to separate about 60% of both nitrogen and phosphorus but only 45% of the potassium. In the laboratory study, 70% of all the nutrients were successfully separated. This indicates that the pipe transport distance should be as short as possible, especially the vertical drops, to enable as many of the faecal nutrients as possible to be collected. One of the separation systems available on the market today is based on filtration with filters that are emptied every six to twelve months. Investigations in the laboratory of biological and chemical activity when faeces are submerged into water showed a rapid degradation of the faeces and extraction of the faecal nutrients, which indicates the importance of fast removal of the filter cake after separation. The laboratory study of filtration with immediate removal of the filter cake on average separated 70% of the faecal nutrients in to the separated solids. If 80% of the urine is diverted and 70% of the faecal nutrients are separated and collected together with the biodegradable solids, 67%, 66% and 48% of the nitrogen, phosphorus and potassium respectively can be collected locally in an easily recycled fraction. Urine diversion and faecal separation are simple and effective methods for collecting recyclable and unpolluted nutrients from wastewater. This increases the sustainability of society and decreases the degree of pollution resulting from nutrients being discharged to the water recipients.
"The objective of this paper is to provide a review of the characteristics of wastewater used for irrigation, and the reasoning behind the international guidelines presently used in regulating wastewater reuse for agriculture.This paper presents various systems of wastewater treatment available and discusses their benefits and shortcomings.Finally, the paper provides the review of environmental valuation techniques for analyzing impacts of wastewater uses in agriculture, and suggest a framework for application of some of these techniques. This framework will be applied to a developing country case study (Faisalabad area in Pakistan), in the ongoing IWMI research program."
In most developing countries commonly practiced domestic wastewater treatment systems predominantly constitute anaerobic treatment process. The anaerobic treatment units mostly installed are on-site at residential dwellings.However the commonly installed units, viz., traditional pit latrines and septic tanks are in fact 'low-rate' anaerobic pre-treatment units and are associated with inefficiency, poor maintenance and groundwater pollution. Moreover since most poor communities, who constitute the majority in the developing countries' populations could afford these types of anaerobic pre-treatment units, their numbers have also grown to unmanageable proportions. Consequently the demand for effective but low cost wastewater treatment facilities for developing countries is indisputably great.On the basis of already available technical information concerning the Upflow Anaerobic Sludge Bed (UASB) reactor performance a wastewater treatment system based on the UASB reactor can lead to a compact, effective and low cost community on-site pre-treatment unit for tropical wastewaters. However the performance of these systems in an actual community on-site situation has so far not been investigated. This thesis therefore investigates the performance and feasibility of using the UASB reactor for the pre-treatment of wastewater under the conditions that arise at community level in tropical regions, viz. highly varying organic and hydraulic loads, but low variation in temperature.On-site pilot scale UASB reactors were configured and operated in parallel at community level for the purpose of acquiring performance data. All the reactors were operated in gravity flow mode at ambient tropical temperature of 25 - 34 ºC. The wastewater in the study area - community level - was highly biodegradable with an average ratio COD:BOD <sub>5</sub> of 1.52 at a standard deviation of 0.13. The wastewater characteristic was highly variable. A 1277-day monitoring duration of the wastewater grab samples has shown that the values of organic loads (with standard deviation in brackets), in terms of COD <sub>tot</sub> , and COD <sub>ss</sub> , were 529.4 (544.6) and 264.4 (448.4) mg/L respectively.A conventional pilot single-step community on-site UASB reactor (volume: 1.5 m <sup>3</SUP>, height: 1.7 m) was operated over three and a half years at an average hydraulic retention time of 6.2 (4.92). The performance data obtained via regular monitoring of the treatment unit showed a declining removal efficiency over time with respect to COD <sub>total</sub> , which likely can be attributed to the increasing rate at which biogas was produced along with the growth of sludge bed and the presence of floating sludge. As a result the removal of dispersed sludge particles becomes poorer, which likely is reinforced by the possible 'less' optimal dimensions and design of the Gas-Solids-Separator (GSS) device. The average removal efficiency on COD <sub>tot</sub> basis was 64 percent. However a study of a parallel pilot two-step community on-site UASB reactor configuration gave more promising results. The two-step UASB pre-treatment unit in this research refers to two UASB reactors connected in series, viz. a first 2m high 1.8m <sup>3</SUP>UASB reactor put in front of a second 1m high 0.852 m <sup>3</SUP>UASB reactor. The second-step UASB reactor is a recipient of effluent including washouts from the first-step UASB reactor The average organic loads of the wastewater imposed to the system with respect to COD fractions COD <sub>tot</sub> , COD <sub>ss</sub> , COD <sub>col</sub> and COD <sub>sol</sub> were 537.2 (165.3), 189.9 (109.5), 127.4 (75) and 223.4 (108.8) respectively. The investigations were conducted over a period of 630 days. The overall removal efficiency obtained on the basis of the distinguished COD fractions was far better than for the individual reactors, i.e efficiencies for COD <sub>tot</sub> , COD <sub>ss</sub> , COD <sub>col</sub> and COD <sub>sol</sub> , were respectively 68.7 (16.7), 51.2 (41.8), 62.1(38.2), and 71.8 (30.5) %. The imposed overall HRT was 7.4 (1.6) (i.e. 5 + 2.4) hours. The advantages of the two-step UASB reactor configuration include 1) the distinct higher overall removal efficiency of the anaerobic pre-treatment system 2) the higher sludge age 3) the higher reliability of the anaerobic pre-treatment process 4) the two reactors can separately be operated in case of technical problems.
Pit-latrines are on-site excreta disposal facilities widely used as anaerobic accumulation system for stabilizing human wastes like excreta, both in rural and urban settlements of developing countries. Flooding of pit-latrines is often a common phenomenon, especially in situations of high water table (HWT) conditions and during the rainy season, causing a health jeopardy to residents. The pits are not water-tight, the (ground )water can freely flow in and out of the pit, especially in HWT areas. This results in groundwater (GW) pollution and even surface water pollution in the neighbourhood and pits that are filling up far too quickly. With a growing concern of public health, GW pollution and the reuse of nutrients from human waste, there is a serious need to study and improve the pit latrines, especially those in HWT areas. Specifically, the scope of this thesis was to study the socio-cultural aspects of excreta disposal in Dar-es-Salaam City , to improve the understanding of the biological stabilization processes in anaerobic accumulation systems and to come up with proper operational guidelines for emptying practices. A literature research and the results of a survey on excreta handling amongst 207 households in 9 of the 52 wards of Dar es Salaam (Dsm.) presented in this thesis shows that 50% of the filling up of pits in Dsm. city is the result of HWT. Moreover almost 16,131 kgCOD/day from pit-latrines reach GW sources (Haskoning and M-Konsult, 1989). In this study an improvement of the pit-latrine was proposed using a plastic tank as pit. A 3000-liter experimental improved pit-latrine without urine separation (IMPLWUS) was constructed and monitored at a 10-person household in Mlalakuwa settlement in Dsm. , Tanzania . The influent to the reactor merely consisted of urine and faeces in the ratio of 1.3:1. The results obtained revealed that, after 380 days of use as a daily pit-latrine, the reactor content was not yet stabilized. 8000 mg/l dissolved COD (but only 100mg COD/l volatile fatty acids) were still present. Part of this dissolved COD was shown to be biodegradable signifying the need for further stabilization of the reactor content. It was hypothesized that the slow conversion of dissolved COD was due to the fact that the reactor was started with sludge that was not adapted to the resulting high ammonia concentration of 3000 mg N/l, i.e. the system in fact was still under start-up, and in subsequent runs of the reactor the conversion of dissolved COD would be much faster. For further evaluation of the conversion processes proceeding in the improved pit-latrine a simple mathematical model was used. The model results for the course of the concentration of the different COD components in the accumulating sludge in improved pit latrines receiving black water or night soil reactors, revealed that under tropical conditions 97% sludge stabilization is achievable within 1 year of reactor use. If 99% or more stability is desired, an accumulation period of 2.5 years is required or closing the reactor without adding any new materials for at least two weeks before desludging is necessary. When assuming Monod kinetics with k <sub>m</sub> = 1 gCOD × gCOD <sup>-1</sup> × d <sup>-1</sup> (Batstone et al,. 2003) it was calculated that for a latrine receiving black water as influent the specific methanogenic activity of the sludge after reactor closure will be about 0.12 g COD/g VSS/day. At a sludge concentration of 30 g VSS/l the volume to be left in the reactor as seed sludge for the subsequent runs is about 250 litres. Finally a short survey was done of existing composting latrines of the type of Ecosan toilets installed in Dar-es-Salaam. The survey revealed that high pH values occur (up to 10.4) in Ecosan toilets due to addition of charcoal ashes. High pH assist in the reduction of E-Coli and Ascaris eggs , but on the other hand could not allow biological degradation of waste. The separated urine in Ecosan toilets showed on average E-coli counts of 1525 no ./ 100 ml. indicating that urine was not adequately separated. In the light of sustainable development and in view of cost and economy, simple sanitary systems like Ecosan and IMPLWUS is the correct approach in Dar-es-Salaam and other tropical regions of developing countries. Sludge drying beds can be used for further stabilization of emptied sludge since they are cheaper than mechanized ones. Correct separation of urine in Ecosan toilets is necessary with the assistance of user health education. Comparing the Ecosan toilets to the improved pit-latrines it has to be concluded that both systems are promising alternatives to the conventional pit-latrine systems. However, both systems are still at their developing stage and require further work to provide a genuine sustainable solution for the disposal of human excreta in Dar-es-Salaam. The wealthy developed countries need to work with the developing countries in implementation of public sanitation aspects in low cost manner instead of advocating the expensive systems that will fail anyway.
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