Future Projections of urban environmental flows and their impacts in Kampala City, Uganda
Richard O. Oyoo
National Water & Sewerage Corporation, P. O. Box 7053, Kampala, Uganda
Telephone: +256 772 632567
Email: Richard.oyoo@nwsc.co.ug, Richard.oyoo@wur.nl
ABSTRACT
The rapid population growth and changing lifestyles in urban centres are important drivers to
the increasing quantity and changing composition of the urban waste. Generally, only the
business districts and affluent neighborhoods that receives adequate solid waste and sewerage
services. The informal settlements are characterized by heaps of uncollected solid waste, no
sewerage system and poorly operated and maintained on-site sanitation. This pollutes water
sources and poses health risk to the public. This paper quantified the future projection of
urban waste generation and their impacts on Kampala’s environment with plausible urban
waste management scenarios. A dynamic model integrating urban waste flows from
generation to final disposal, and their consequences on the environment. The model is
calibrated and validated on the basis of the available data for Kampala and Dar es Salaam
respectively. Using population projections, technology improvement, policy enforcement and
awareness raising, four scenarios simulated for 50 years. The “proper management” scenario
showed the best implying increased composting, awareness and enforcement reduced urban
waste loads to the environment, but all other scenarios are less effective. Thus, strategy that
maximizes recovery of organic waste would improve the urban environmental quality and as
well as extend the life span of the landfill.
1
1.
Introduction
The increasing quantity of urban waste in urban towns of developing nations coupled with
inadequate sanitation services is of a growing concern to the deteriorating urban environment.
In this case, urban waste refers to the solid waste generated from households, markets, and
commercial establishments, and human excreta from the population. Because of limited
funds, it is only the business districts and affluent neighbourhoods that have adequate solid
waste collection. The slums are characterised by heaps of uncollected solid waste posing a
health risk to the public (Ezron, 2006; Spaargaren et al., 2006). The sewerage coverage is
small and therefore majority of the population uses on-site sanitation system, which is a threat
to groundwater contamination (Gill et al., 2008). Hence it is a challenge to urban authorities
to provide adequate sanitation services to all urban residents including urban poor who lives
in slums.
Kampala in Uganda also faces these urban waste management problems. This is evidence by
heaps of uncollected solid waste along roadsides, and illegal discharge of faecal sludge into
storm water drains. The majority of the on-site sanitation facilities are poorly constructed,
operated and maintained. The operations and maintenance of these facilities are not
institutionally supported by the public sector. The emptying of these facilities is done at fee
by the Kampala City Council (KCC) and the Private Cesspool Operators (PCOs). But KCC is
overwhelmed, and therefore the PCOs are the major players both for the present and in the
future. Due to the cost involved in emptying, the poor households often discharge their faecal
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matter in the storm water drains. Similarly, solid waste collection in informal settlements is
inadequate, probably due to the increased involvement of Private Service Providers (PSPs)
who serves only households that pay.
The changing composition makes waste management complex and difficult as waste
treatment technology need to adapt to new waste material (Brunner and Baccini, 1992). The
quantity and composition of waste generated are the basic information for designing
sustainable waste management systems. A sustainable waste management system must meet
environmental, economical, technical and socio-political goals, and resilient to changes. The
central hypothesis is that waste generation rate in a defined system should be lower than the
rate at which it is absorbed (Simone et al., 2001). Such solutions are designed and assessed
using system dynamic approach. System approach is beneficial for identifying week points of
waste management, and subsequently developing mitigation measures to advert the
environmental problems recognised early (Light, 1990). This paper quantified the future
projections of urban waste and their impacts on the environment of Kampala City with
different plausible waste management scenarios.
The future projections for solid waste and wastewater generation for Kampala City have ever
been done (National Water and Sewerage Corporation, 2004; Kampala City Council, 2006).
Unfortunately, these projections were done using static models that likely underestimated the
increase in urban waste and ignored changes in composition. Such static models are also
inappropriate to study dynamic system as they illustrate trend verifying the inherent
systematic features related to observed data (Dyson and Chang, 2005). Therefore, a new
innovative integrated dynamic model driven by population change and influence by
technology, awareness and enforcement is developed to project the future urban waste
generation and their impacts on the environment. The model applies the “what if” type of
questions to illustrate the future consequences of the different waste management scenarios
(Schwarz, 1997; Pallottino et al., 2005). This help to deal with the uncertainties about the
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urban waste impacts on the environment and better understand how the factors influence the
urban waste flows.
Presently, the future projection of the urban waste generation and their impacts on the
environment of Kampala is lacking. Hence, the system boundary and model development are
discussed in section 2. Section 3 discussed model calibration and validation, scenarios
development and their impacts on the environment. The impacts of the different scenarios are
measured by the levels of Biological Oxygen Demand (BOD), total nitrogen (TN) and total
phosphorus (TP). The conclusion is provided in section 4.
2.
Method and Materials
2.1.
Description of the Study Area
Kampala City is the study area with coverage of about 150 Km2. Its population by 2002 was
estimated to be about 1.2 million with an annual growth rate of 3.8% spread in the five
administrative divisions (Uganda Bureau of Statistic, 2006). The present Kampala City
administrative boundary is the system boundary for the 2052 projections of urban waste
production and their impacts on the environment (see Fig. 1). The city is characterised by low
lying flat top hills and valleys covered with papyrus (Kulabako, 2005). This has implication
on the provision of sanitation services, for instance, connecting low lying areas to the
sewerage works would require pumping, thus increasing the costly.
The climate is characterised as tropical with small variations of temperature (27- 29oC)
(Campbell, 2001), moderate humidity and wind throughout the year. The moderate
temperature enhance fast breakdown of readily biodegradable organic solid waste. This
implies that storage of organic solid waste at household cannot be long where solid waste
indoor storage is poor. The mean annual rainfall is 1180 mm (Matagi, 2002). This increases
the moisture content of the solid waste, and subsequently increased solid waste bulk density.
The city is drained by channels and streams passing through slums. The surface water in these
channels and streams transports solid waste and faecal matter discharged into them. The
4
streams flow through wetlands before discharge into the Lake Victoria, Inner Murchison Bay
(IMB). This deteriorates the IMB water quality, which represents the only drinking water
source for the residents of Kampala City, Mukono and Wakiso towns.
2.3.
Data collection
The urban waste data was gathered through literature reviews, field measurements and
existing database. The sanitation coverage and type data obtained from the recent studies
(Uganda Bureau of Statistic, 2006; National Water and Sewerage Corporation, 2008). The
quantity of faecal sludge disposed at the Bugolobi Sewage Treatment Works (BSTW)
estimated from the daily disposal records. The sewage flow into BSTW estimated hourly, and
sewage quality determined by standard laboratory methods (Arnold et al., 1980). The
performances of the sewage treatment plants were determined by balancing mass of the
influent and effluent organic loads. The monthly sewage overflows in the sewer network
established by the product of average time taken to clear the blockage, the number of
blockages and overflow rate.
The amount of solid waste disposed determined from the daily disposal record at the landfill.
The solid waste composition determined based on the American Society for Testing Materials
(ASTM) method (Kampala City Council, 2006). The quantity of solid waste recycled from
the landfill was estimated from the amount of recyclables sold. The fraction of organic solid
waste composted estimated by interviewing the KCC officials and the local communities. The
household solid waste generation rates estimated through household survey randomly selected
and willing to participate. The landfill design obtained from existing literature (Antonio de
Pina et al., 2005), and the performance of the leachate treatment plant estimated by mass
balancing of the influent and effluent loads.
2.3.
Description of urban waste flow model
An Integrated Urban Waste Flow Model (IUWFM) is developed to calculate urban waste
flows in selected geographical region (this case, Kampala City) for a defined time span. The
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computation is based on the principle of mass conservation to balance the waste material
around a process using equation 1.
dm
 I O
dt
(1)
Where I is input, O is output and dm/dt is rate of change of mass with respect to time. The
mass balances are calculated throughout the system giving the opportunity to identify the
environmental improvements related to compartments. The potential impacts of the urban
waste on the environment are assessed by the Life Cycle Assessment (LCA) approach. On the
basis of material flows, the costs and revenues involved to arrive at a defined target can be
calculated.
The IUWFM comprises four subsystems, namely: ‘Population’, ‘Solid waste’, ‘Sanitation’
and ‘Environment’ (see Fig. 2). It aims to analyse the consequences of the different plausible
urban waste management scenarios to determine future trends. This model is developed in
SMILE graphical simulation software (Robert and Jon, 2003) as shown in Fig. 3. The boxes
represent stock variables where urban waste are generated, collected, stored or processed. The
processes in the boxes are described by the empirical relationship between inputs and outputs,
but exclude detailed processes inside the box. The flows from one box to another are
modelled as fractions, and are represented by arrows. The sizes of the flows are determined
by the different variables that mimic the effectiveness of urban waste management via a
combination of environmental, socio-political and economical factors. The total amount of
urban waste entering the environmental compartment is computed, and is the cumulative
environmental burden from other compartments. The environmental subsystem is limited to
the soil, surface water, ground water and wetlands, and is the sink to the waste materials.
The sanitation and solid waste sub-models combines in the compost compartment through cocomposting organic solid waste with the human excreta. To enable the elemental mass
balances, the organic solid waste is expressed in terms of wastewater parameters. These
parameters are BOD, TN and TP. A wet organic solid waste contains BOD, TN and TP in the
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ratios of 0.297, 0.003 and 0.002 respectively (National Water and Sewerage Corporation,
2008).
The urban waste flows are influenced by technology, awareness and enforcement, expressed
as in equation (2).
UWt 1  ( FE, FA, FT )UWi
(2)
Where UWt 1 is the urban waste flow at time t, FE, FA and FT are factors due enforcement,
awareness and technology respectively, and UWi is the present urban waste flows. The factors
influence the flows either positively or negatively. A positive influence is when an increase in
one element causes an increase in another, and a negative influence is when an increase in one
element causes a decrease in another. The factors are modelled by simple multiplication
factors ranging from 1 to 5. Level 1 indicates the current situation and level 5 a theoretical
maximum efficiency. Increasing these factors mimics enforcement, awareness and technology
enhancement. For example, by enhancing enforcement by ensuring that households within a
radius of 60 m are connected to sewer will reduce the fraction of the population served by onsite sanitation system, but increases the proportion of those served by centralised sanitation
system.
The inputs data for IUWFM are demographic, solid waste generation rates (capita-1 day-1),
solid waste composition, daily capita-1 human excreta production and proportions of
population served by the different sanitation systems. The BOD, TN, TP and Faecal coliforms
(FC) capita-1 values are assumed constant to mimic the wide variation in socio-economic
status. As household income rises both capita-1 BOD and water consumption increases except
the water consumption rises faster than BOD making the BOD load to remain constant
(Arthur, 1983).
The model outputs are: solid waste disposed in landfill, compost produced, and environmental
organic loads expressed as BOD, TN, TP and FC. The BOD, TN and TP variations
characterises the quality of the environment. The BOD is an indicative of the amount of
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oxygen that will be removed from the water by organic matter (Straskraba and Tundisi,
1999). High BOD in water can deplete the dissolve oxygen (DO) thereby ceasing aerobic
process, and anaerobic process then takes over through the use of anaerobic microbes that
obtain energy from oxygen bound to other molecules like sulphate. The removal of oxygen
from sulphate result in the release of sulphide in water imparting "rotten-egg" smell to the
water affecting its aesthetic quality (Gilbert, 1991). In terms of water quality, the nitrogen and
phosphorus are pollutant if their presence in water is in a concentration sufficient to allow
eutrophication. The eutrophication potential is expressed as PO4 -3 equivalents (Mufide et al.,
2008). Algae add colour, odours and objectionable tastes to water, which greatly reduces its
acceptability as a domestic water source. The FC is an indicator microorganism that indicates
faecal pollution of the water, and provide estimate of risk of pathogens presence (Nalubega et
al., 2001).
2.3.1. Population Subsystem
The growth in population size is assumed to vary exponentially with time as a function of net
growth rate. This may not be realistic for long period, for example 50 years, since birth rate
may change due to improved standard of living, increased confidence of children survival to
maturity, improved girls education and increased use of birth control measures. Nonetheless,
as scenario analysis shows plausible paths not prediction, this assumption is reasonable. The
population of the low-income group will increase due to usually higher birth rate and more
immigration of poor rural people to the city.
Given the present socio-economic status and development levels, the high-, medium- and
low-income groups are assumed to have saturation population densities of 50, 250 and 450
persons ha-1 respectively (National Water and Sewerage Corporation, 2008). The population
densities have implication on the quantity of urban wastes generated and their management.
For example, densely populated areas produce relatively more solid waste than sparely
populated area (Massimiliano et al., 2008). Also in high density area the average solid waste
collection cost can be relatively cheaper than the sparely populated areas due to the
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economies of scale. Similarly, densely populated area, the cost of treating human excreta
using centralised sanitation system is cheaper than on-site sanitation system explained by the
economies of scale (Nalubega et al., 2001). However, densely populated area may imply
greater scarcity of land resources such that more pressure is placed to preserve land to
construct sewage treatment plant (Massimiliano et al., 2008).
Fig. 4 is the graphical
representation of the population sub model in SIMILE software. The model computes the
growth in population sizes for different parishes, different population groups based on
socioeconomic status (low, medium and high-income) and aggregated population. This submodel is initialised with the 2002 population census data (Uganda Bureau of Statistic, 2006),
and verified with the population estimates produced by the Uganda Bureau of Statistic
(UBOS) as shown in Table 1. The model projected population figures differ slightly from the
UBOS projection due to the estimation of growth rates for the three groups and application of
the population density in the IUWFM. The presence of the population density in the model
therefore controls the population size increase. For the UBOS model a single population
growth rate was applied for the three population groups, and no control on the population
size.
2.3.2. Solid waste subsystem
The quantity of solid waste generated is estimated by computing the product of population
size and capita-1 waste generation. The computation is started in the generation compartment
and distributed to the different compartments, namely: landfill, recycling, compost and
environment as displayed Fig. 5. The flows are grouped as organic, recyclables (metal,
plastic, paper and board) and other. The organic solid fraction is separated because of its high
fraction (83%). The fraction of solid waste collected is explicitly modelled based on income
levels for the three income groups estimated by their water consumption. The leachate from
the landfill is treated and discharged to the environment.
The quantities of solid waste in the different compartments are controlled by their threshold
limits. The threshold limits are only an indicative of the technical constraints that the
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compartments impose. Table 2 provide the threshold values for some of the compartments.
These values are computed as product of solid waste to be produced in 50 years and fraction
of the waste component in the total solid waste. For example, the threshold limit for
recyclables is the product of the solid waste to be generated in 50 years and proportion of
recyclables in the solid waste stream.
The organic solid waste composted to produce humus by microbial action (Mansoor et al.,
1999) is assumed home composting with negligible leachate production. The degradation of
organic matter is explicitly modelled as first-order kinetic (Mara, 1976). In this case, the
proportion of the readily biodegradable organic solid converted to carbon dioxide (CO2) and
methane (CH4) (Dalemo et al., 1997) is assumed to be 10%, and the fraction of paper and
board degraded is assumed 5% due to their slow breakdown.
2.3.3. Sanitation subsystem
This model initiates the computation process in the generation compartments by multiplying
population projection with the capita-1 human excreta generation rate. This is followed by the
distribution of the generated human excreta to the different compartments (centralised
sewage, sewage ponds, on-site sanitation system and compost) as displayed in Fig. 6. These
flows are explicitly computed as fraction of generated human excreta. The human excreta
flow from on-site sanitation to the centralised sewage treatment system mimics the fraction of
human excreta emptied from the on-site sanitation system by vacuum trucks. The flow of
human excreta from the centralized compartment to sludge compartment mimic the faecal
sludge conversion to manure used as soil conditioner. The amounts of human excreta in the
different compartments are controlled by their threshold limits. At the threshold limit, any
additional quantity of human excreta to the compartment results in an overflow into the
environment. For example, the threshold limit for the BOD load at the BSTW is the product
of the design wet weather flow (34,000 m3 day-1), BOD concentration (430mgl-1) and life time
for BSTW operations (15 years from 2002).
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Since the centralised sewage system is open, about 10% of the organic load is lost into the
atmosphere through conversion to CO2 and CH4. The organic effluent load discharged from
the centralized sewerage, ponds and the fraction of untreated waste entering the environment
directly are further degraded. The breakdown of the organic loads in these compartments is
assumed to be 10%.
This sub-model is initialised with the estimated human excreta
production for 2002 population census (see Table 3). The initial BOD, TN, TP and FC loads
are reduced by 50% to account for the degradation.
3.
Results and discussion
3.1.
Solid data
3.1.1. Solid management
The solid waste generated is stored either on-site or in the immediate neighbourhood in skips1
from where it is collected and transported to the disposal site. In the absence of a reliable
primary solid waste collection service, empty plots, road sides and storm drains are
convenient places. The treatment of solid waste by composting is only about 5%, largely
attributed to the low level of urban and peri-urban agriculture, unsteady compost market, and
increased land use for settlement and industries. The unsteady compost market is explained
by the lower nutrient (phosphorus and nitrogen) level in the compost than chemical fertilizer,
relatively high transporting cost to the rural areas and seasonal demand of compost by
farmers.
Approximately 700 tons day-1 of the solid waste is disposed in the sanitary landfill at Kitenzi,
which is 45% of the total solid waste generated. From these, about 200 tons month-1 of
recyclables such as plastics, metals, and papers and cardboard are scavenged. The solid waste
disposed in the landfill is mainly from the business districts and the affluent residents where
Private Service Providers (PSPs) are actively involved. The low-income residents rarely
1
Skip is a container of capacity about 7 to 15 m3 used for waste collection mainly stationed at the markets and
settlement areas.
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receive full solid waste collection services due to inability to pay for the waste collection
services. This would therefore require the full support of the KCC to work with the
communities in managing the solid waste in the low-income residents.
The solid waste collection in Rubaga, Makindye and Nakawa divisions except areas served by
PSPs is not charged on the residents. The revenue generated from other sources is used to
finance the solid waste collection activity. Thus, about 250,000 US$ month-1 (1US dollar is
2000UGX) is needed to ensure 100% collection. Bearing in mind that the solid waste sector
has limited funds, this arrangement is not sustainable as it requires a lot of money for
effective solid waste management for the all city. The Central Division and parts of Kawempe
Division have a user fee ranging from 0.75 US$ week-1 to 15 US$ month-1 for residential and
35 US$ month-1 for institutions, though the impact of this fee is low due to inadequate
publicity, awareness and enforcement to ensure compliance.
The operations of the landfill is contracted out to OTADA Company Ltd, a private firm at
cost of 4.8 US$ ton-1. This implies that 700 tons day-1 of solid waste disposed in the landfill
cost about 100,000 US$ month-1. Presently, no payment is made at the landfill for dumping
solid waste by the waste generators. The operations funds for the landfill come from the KCC
budget generated from other sources. However, since the PSPs charge a fee to the residents
for the solid waste collection, it would be reasonable for the PSPs to pay dumping fee per
dumping. This would supplement the operational budget for the landfill.
The leachate generated at the treatment plant have high BOD (2100 mg/l) indicating a large
volume of readily decomposable organic solid waste is disposed at the landfill (Kirkeby et al.,
2007). The leachate is treated but the effluent quality discharge into the receiving
environment does not meet the set discharge standard by the National Environmental
Management Authority (NEMA). This standard may be too stringent for a landfill receiving
large quantity of readily biodegradable organic matter. It would be reasonable to set the
standard based on the loads with respect to the receiving environment. As the receiving
environment is a wetland, the load could be slightly higher than that for water environment.
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3.1.2. Solid waste generation and composition
The solid waste generation rates estimated for the low-, medium- and high-income groups are
0.46, 0.63 and 0.68 kg capita-1 day-1 respectively. The estimated overall solid waste generation
rate is 0.59 kg capita-1 day-1, which is in the range of the early estimates of 0.55 kg capita-1day1
(Matagi, 2002) and 0.5-0.8 kg capita-1day-1 (Lake Victoria Environmental Management
Program, 2001) The Kampala Solid Waste Management Strategy estimated the solid waste
generation rate of 1 kg capita-1 day-1 (Kampala City Council, 2006; KCC, 2006), which is
higher than the value obtained in this study. The solid waste generation rate estimated for
markets is 45,000 kg day-1.
Table 4 provides the composition of the solid waste generated in Kampala City indicating
organic solid waste as the highest, followed by plastic, paper and boards, and the textile being
the lowest in the waste stream.
3.1.3. Policy, Legal and Institutional Framework
The Uganda Constitution (1995), Public Health Act (Ministry of Health, 1995), the National
Environmental Act Cap, 153 (1995) (National Environmental Management Authority, 1995),
Local Government Act (1997) and Kampala Solid Waste Management Ordnance are the
principle policy documents governing solid waste management. These legal instruments are
in the various ministries and their implementations are not well coordinated. The National
Environment Act, 1995 recommends waste to be discharged, emitted or deposited into the
environment in such a volume and composition that causes no harm to the environment. This
contradicts the practices where waste items such as metals and plastics are recovered and put
to gainful uses.
The collection and transportation of solid waste lies with the administrative divisions, and is
headed within each division by a Divisional Public Health officer (DPHO). Presently, key
players like community development officers, education and public relation officers are
excluded. This system views solid waste as a health problem rather than an environmental
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concern. Additionally, the Local Councilors 1s (LC1s) in contacts with households are
ineffective on the ground to influence solid waste management issues and to enforce the
existing legal provisions on solid waste management. The LC1s can play a big role in
ensuring solid waste management is effective on the ground as they have demonstrated with
security management among the communities. The policies for incentives intended to
stimulate activities like waste avoidance, reusing and recycling are not practiced. This inhibits
the innovative approaches and voluntary compliance of solid waste management.
3.2.
Sanitation coverage and management
The sanitation system in use in Kampala City is divided into two groups; namely (1) off-site
sanitation system where wastewater generated is carried away from the households and taken
to a treatment plant before discharge into the environment; and (2) on-site sanitation system
such as pit latrines and septic tanks where wastewater generated is stored at the point of
disposal and usually undergoes some degree of decomposition (Nalubega et al., 2001).
Table 5 shows the proportion of population using different sanitation systems in Kampala
City. The number of people served by septic tanks increased due to increased in medium- and
high-income houses constructed across the city. But the proportion of population served by
sewer decreased because of the stable number of households with connection against a
growing population. The proportion of the population without access to decent sanitation
increased due to increased population density and lack of corresponding increase in sanitation
provision.
The main sewerage system covers about 2000 hectares and serves about 100,000 people. The
wastewater collected by this system is treated at the Bugolobi Sewage Treatment Works
(BSTW). Five small sewage systems serving housing estates and institutions with estimated
population of 20,000 also exist. About 200 m3 day-1 of faecal sludge emptied from on-site
sanitation facilities is taken the BSTW co-treated with wastewater. About 400 m3 day-1 of the
faecal sludge is stored on-site and 130 m3 day-1 is illegally discharged to the environment
untreated (National Water and Sewerage Corporation, 2008).
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The practice with full pit latrines is to dig a new one nearby, given there is enough space on
the property. In densely populated areas and/or in situations of high groundwater table
unsuitable for constructing deep latrines, a more or less frequent emptying latrine is
unavoidable. Areas inaccessible by trucks employ the services of scavengers to manually
empty the pit latrines. Sludge removed by scavengers is often dumped in drainage channels or
in the best case buried on the property
3.3.
Model calibration and validation
Model calibration is a very important and time consuming task in modelling project.
According to Wainwright and Mulligan (2004) even if a model is extensively calibrated it
will only generate potential developments because of the inherent uncertainty in the processes
represented in the model. This model was calibrated with cumulative mass of the solid waste
disposed in the sanitary landfill from 2004 to 2006 because the stock variable produces
cumulative output. However, due to incomplete data, the solid waste data for 2002 and 2003
were estimated by multiplying the average monthly solid waste collected by 12 and adding to
the previous year data. The fraction of the solid waste disposed was adjusted to fit the
simulation curve to the measured data. The degradation, recycling and leaching rates at the
landfill were set to zero (0) because the data for the solid waste disposed in the landfill are
taken before the effect of leaching, recycling and decaying.
Fig. 7 shows the plots for the simulated and measured solid waste disposed in the landfill. The
plots show a gentle increase in the cumulative mass of solid waste disposed with time. To
measure the variance given by R2 value, the measured solid waste data was plotted against the
simulated (see Fig. 8). The R2 showed a high correlation value of 0.99, which explained fit of
the simulated results to the measured data.
The model was validated with the urban waste data for Dar es Salaam, Tanzania. Dar es
Salaam is the main industrial, commercial and administrative hub for Tanzania, has an area of
about 1400 Km2 with population of about 2.5 million and an estimated growth rate of 4.3%
year-1 (Tanzania National Website, 2003). The urban waste data for Dar es salaam City used
15
to validate the model are shown in Table 6 and Table 7: Solid waste composition for Dar
es
Salaam,
TanzaniaTable
7.
3,000,000
Waste (Tons)
2,500,000
2,000,000
1,500,000
1,000,000
500,000
2001
2002
2003
2004
2005
2006
2007
Years
Landfill (Tons)
Measured (Tons)
Fig. 9 show the plot for the simulated and cumulative measured solid waste disposed at the
dump site. The plot indicates an increasing trend for both the measured and simulated solid
waste dumped at the designated dump sites. The plot for the measured solid waste collected
against the simulated data produced a good fit as displayed with the R2 value (see Fig. 10).
The R2 obtained is 0.99. However, the observed solid waste data obtained for Dar es Salaam is
based on estimates as there is no weighing bridge at the dump site. Additionally, the solid
waste collection rate put in the model is a fixed over time whereas in reality, there is variation
in the volume of solid waste collected with time. Since the simulation is initialised from 2002,
the initial amount of solid waste already dumped at the landfill also plays a role on the
cumulative mass of the additional solid with regard to the threshold level. All these explain
why the plots for the observed and simulated are not superimposed on each other.
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3.4.
Urban waste management scenarios for Kampala city
Many economic, social and environmental processes unfold over long time spans. They often
require assessments that look ahead for 50 years or more to seek a new insight on how
decisions taken today may affect the future. This is done by using scenario analysis. Scenarios
are plausible and often simplified descriptions of how the future may develop based on a
coherent and internally consistent set of assumptions about key driving forces and
relationships. They are also plausible descriptions of how the future may unfold based on
‘what-if’ questions (Monika and Henrichs, 2007). Scenarios helps to navigate the future
impacts of the urban waste on the environment just like a set of maps describing a landscape.
The IUWFM was simulated for 50 years with four plausible urban waste management
scenarios, namely: business as usual”, “more enforcement”, “more collection” and “proper
management”. These scenarios are defined with varying levels of technology, awareness and
enforcement to mimic the socio-political, economical and environmental standards as
summarised in Table 8.
3.4.1.
Business as usual
This scenario assumed no action is put in place to target waste reduction, reuse,
indiscriminate dumping of solid waste and illegal discharge of wastewater. The current level
of solid waste collection is maintained. The flow of organic solid waste into city through
packaging materials still continues. The on-site sanitation facilities in densely built up areas
poorly operated and maintained. The performances of the urban waste treatment facilities not
improved. Additionally, the LC1s are not active in enforcing the existing sanitation
regulations. More so, the community based organisation (CBOs) and the local Non
governmental Organisation (NGOs) are inadequately facilitated in terms of logistic and
financial support. The level of awareness on proper urban waste management is low. Thus,
this scenario continues the current status quo as shown in Fig. 11.
3.4.2.
More enforcement
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This scenario assumed the existing ordinance on solid waste management and sanitation
regulation are enforced by about 70%. In this case, 30% of the enforcement is to boost the
number of enforcement officers on the ground to ensure compliance of solid waste
management at households, access to toilets and households within the radius of 60 m to
sewer are connected. More so, the officers are to ensure that on-site facilities are emptied in
time when never filled up. This enforcement will be expected to reduce the quantity of solid
waste flowing into the environment by about 45%, and human excreta discharged illegally
and open defecation by about 15%. Subsequently, this will reduce the BOD load into the
environment as organic solid waste fraction comprises about 83% of solid waste generated. It
is further assumed that LC1s are empowered by 30% through provision of the necessary tools
to enable them execute their duties to ensure all households access sanitation facilities, and
solid waste are sorted. The LC1s are also to ensure prompt payment or physical participation
of the communities in the urban waste management within their areas. The regulating of the
packaging of fresh food stuffs into the city is assumed 10%.
The awareness on good practice on urban waste management practices such as composting,
waste reduction at source, recycling, and use of appropriate technology that reduces faecal
contamination and promotes good public health is raised by about 15%. As the volume of
urban waste to dispose in designated areas will increased, it is assumed that waste collection
skips and transportation are increased by 5%. The skips are accessible by the residents and
collection trucks. The light tools for emptying on-site sanitary facilities are introduced to
enhance the collection of the faecal sludge in densely built-up areas. This scenario is
summarised in Fig. 12.
3.4.3.
More collection
This scenario puts more effort on the collection and transportation of the urban waste. It
assumed that urban waste collection and transportation is enhanced by 70%. In this case, the
solid waste collection skips are increased by 30% and put in location accessible by the
residents and collection trucks. The skips are emptied in time to prevent solid waste overflows
18
to the environment. The PSPs are to increase the solid waste collection coverage by 20% to
cover residents for the medium- and high-income. The current 30% collection by KCC is to
be concentrated to low-income residents and public places. Additionally, the CBOs capacity
to collect solid waste is assumed enhanced by 10% through provision of light tools such as
wheel barrows and carts. The households pay for solid waste collection or physically
participate in the collection.
The human excreta collection increased by addition of vacuum trucks of appropriate size, and
construction of three additional faecal sludge treatment plants at Lubigi, Nalukolongo and
Kinawataka for population of about 150,000 as per the Kampala Sanitation Master Plan
(National Water and Sewerage Corporation, 2008). Given the high organic strength in the
faecal sludge, anaerobic pond is the assumed treatment option rather than facultative pond
affected by high ammonia level that suppress algal growth (Montangero and Strauss, 2002).
The adoption of small-scale technologies for faecal sludge emptying like vacutug and manual
pit emptying technology (MAPET) accounts for 10%.
The 20% is to enhance the capacity of the PSPs to provide incentives by discounting on the
fee charge on customers, for example, by exempting them from commercial tax. The
treatment of organic solid by composting is increased by 10%. The level of awareness on
waste sorting and reuse increased by 10%, and enforcement through facilitation of LCs and
Public health officers (PHOs) increased by 10%. The summary of this scenario is shown in
Fig. 13.
3.4.4.
Proper management
Fig. 14 shows the urban waste flows in the proper management scenario. This scenario
assumed an integrated approach to the waste management, where by enforcement, awareness
raising and technology enhancements are applied equally. The organic solid waste is cocomposted with human excreta to produce compost, which is subsequently used in urban
agriculture or transported to rural areas is assumed 60%.
19
The level of enforcement and awareness are each increased by 20%. The enforcement is
geared towards facilitating the LC1s with the basic requirements such as wheel barrows,
furniture for record keeps, vactugs and marpets to ensure compliance of urban waste
management at community level. For example, ensuring waste sorting at source, households
have access to toilets and toilets are emptied on time when never filled up. More so, the
communities are paying for the services offer by the PSPs or physically participating in the
operation of the waste facilities.
The awareness enhancement is to focus on recycling by linking the low-income to the
medium- and high-income groups in collecting recyclables at source. Part of the awareness is
to focus on the training of the communities on public health in relation to waste management.
The current level of transport is assumed maintained.
3.5.
Scenarios results
Table 9 provides the simulation outputs for the four scenarios quantifying the global BOD,
TN and TP loads into the environment, organic solid waste composted, solid waste disposed
in landfill and global warming potential. The loads are measured as wet weight, and the
global warming potential of the solid waste disposed in landfill is computed based on the
volume of solid waste land filled. The “business as usual” scenario showed the highest
organic load followed by the “more management”, “more enforcement”. The “proper
management” scenario produced the best result with low BOD load to the environment. The
global warming potential was indicated high in the “more enforcement” scenario due to the
increased volume of solid waste dumped in the landfill. The “proper management” scenario
produced had the lowest global warming potential attributed to the increased compost
production resulting less volume of solid waste taken to the landfill.
The “business as usual” scenario estimated a BOD load to the environment to increase by
370% by 2052 using 2008 as the baseline. This has negative consequences to the receiving
water environment. The scenario showed that the accumulated solid waste disposed in landfill
will be less than the landfill designed capacity (2000 Mtons). This is largely explained by the
20
rapid breakdown of readily biodegradable organic solid disposed in the landfill, which
accounts for 83% of the solid waste disposed in landfill. More so, only about 45% of the
solid waste generated are collected and disposed in the landfill. This scenario estimated
accumulated organic load in the environment by 2052 to increase with increasing population
growth as shown in Fig. 16. These high loads are largely attributed to indiscriminate dumping
of MSW coupled with inadequate collection particularly in the low-income residents found in
slums. The high organic load is also partly contributed by the leachate generated at the
landfill as huge amount of readily biodegradable organic waste is disposed in the landfill.
Although the public health Act (1964) clearly stipulates that everyone who plans to construct
a dwelling unit must first provide the facilities for human excreta, but this is not strictly
observed. Many dwelling unit without toilets facilitate are never demolished as provide for in
the public health Act. This laxity has made the enforcement of the public health act week.
More so, unscrupulous landlords continued without toilet facilities, and consequently many
households do not have access to appropriate toilet facilities.
The spatial distribution of the BOD surface load in parishes varies from about 0.5 Tons ha-1 to
110 Tons ha-1 (Fig. 15). Kololo and Nakasero parishes occupied by the high-income society
portrayed low BOD loads attributed to the effective solid waste collection and centralized
sewage treatment. Some parishes also showed low BOD load because of low population
density, which translates to less waste generation than the densely populated parishes. The
parishes with high organic loads, is attributed largely to indiscriminate disposal and
inadequate collection of solid waste, and illegal discharge of faecal matter from on-site
sanitary facilities.
Some parishes, for example Bwaise have high water table and are
frequently flooded affecting the performance of the on-sites sanitation system contributing to
the BOD loading to the environment. The high organic loads to the environment in densely
populated areas calls for increased provision of sanitary facilities and effective solid waste
collection.
21
If human excreta and solid waste continues to flow into the environment as the case now, then
level of BOD in the environment will be beyond the acceptable level. This will consequently
impact negatively on the environment and human health. More so, with the current separate
human excreta and solid waste management, the co-composting of organic solid waste with
human excreta is impossible even in the near future. Although co-composting of organic solid
waste is not practice, the low compost production in the city is attributed to the low urban
agriculture and high transport cost to take compost to rural areas. Based on this scenario, the
level of BOD, TN and TP in the environment will be excessively high. These high organic
loads negatively impact on the receiving surface water, wetlands and groundwater sources as
discussed earlier. More so, the disposal approach in practiced call in for more landfill space
and lost of precious nutrients.
The “more enforcement” scenario portrayed that by 2052 the accumulated global quantity of
wet urban waste in the environment is reduced by about 40% compared to the “business as
usual” scenario. The loads into the environment for the different parameters are in Table 9.
The BOD surface load in the parishes ranges from about 0.5 Tons Ha-1 to 68 Tons Ha-1 (Fig.
15). The decreased BOD loading to the environment is explained by the increased number of
enforcement officers and active participation by LC1s in enforcing the solid waste ordinance
and sewage regulations at households. For example, by making defaulters to serve in
community works in waste management instead of paying will makes them to change their
negative altitudes toward waste management. This is because if someone can afford to pay
fine he/she may not change, but by doing physical work the defaulter will be punished, and as
well as trained to manage the waste. To effectively enforce sanitation regulations and solid
waste ordinance, appropriate technological options that are affordable, efficient and effective
are needed. The lack of capacity such as lack of planners to effect development control, lack
of equipment to facilitate enforcement of development control and effective policy and legal
framework such as absolute laws, which do not facilitate enforcement of development. These
enabled the growth of illegal settlements in low-lying areas particularly wetlands.
22
The policy on packaging of fresh food stuff partly explains on the reduction of the organic
load to the environment. Introducing policy on packaging waste control regulation such as
production of reusable packages also reduce on the quantity of solid waste generated and
subsequently, the quantity disposed.
The “more enforcement” scenario also shows that the solid waste disposed in landfill
increased as shown in Table 9 when compared to the “business as usual” scenario. The
compost increased due to the enforcing of the communities to sort and burry the organic
fraction on-site where land is available. The increased in solid waste disposed to landfill
improved the environmental quality. But the landfill filled up within three to four years, and
thus, more land is required to expand the landfill. The fact that land value appreciates yearly,
managing solid waste by dumping to landfill may not be sustainable due to the high cost of
land. More so, the transport cost increases in terms of fuel usage as result of increase number
of routes. If transport is not improved to match the increased solid waste volume then the
skips will fills up very fast and overflows into the environment.
The “more collection” scenario estimated the accumulated organic load in the environment
by 2052 reduced by 26% when compared with to the “business as usual” scenario. The
values of the BOD, TN and TP in the environment are shown in Table 9. The spatial
distribution of the BOD at parish level ranges from 0.7 Mtons to 210 Mtons (Fig. 16). The
spatial distribution of BOD surface loads ranges from 0.7 tons Ha-1 to 86 tons Ha-1 (Fig. 15).
This reduction is attributed to a number of factors such as increased number of skips,
improved transport (wheelbarrows and carts), and active involvement of CBOs and NGOs in
the solid waste collection. The emptying of faecal sludge using MAPET and vacutug and
construction of three additional faecal sludge treatments reduced organic load via illegal
discharge and leakage. The increased coverage by PSPs increased the quantity of solid waste
disposed at the landfill. By tasking PSPs to serve the medium- and high-income groups, the
KCC can work closely with CBOs to serve the low-income residents. The provision of
23
sanitation such as deep pit latrine is almost impossible in areas of high water table. Therefore
alternative would be to regularly construct shallow toilet facilities which eventually are very
expensive due to land constraints. As a consequence, the residents resorted to indiscriminate
disposal of human excreta leading to cholera out break in these areas. Where toilet facilities
existed, due to high demand would fill up, fast and were emptied into the nearby drainage
channels.
The CBO involvement generally arises because the authorities are unable to cope up with the
increasing demand on the formal system. This works well if the communities are motivated
and are willing to manage. However, communication should be enhanced between the
communities and the city authority so that the communities feel that they are part of the
system. If there is lack of communication, a close working relationship between the
communities and city authority should be formed in planning primary waste collection
schemes. This can be achieved via community workshops facilitated by NGOs and awareness
campaign. Awareness raising and education are important in changing attitudes towards
health and environmental benefits. For instance, providing vaccination against the spread of
Hepatitis B to create awareness of waste management is helpful in gaining the confidence of
the residents.
In contrast to the “more enforcement” scenario, the “more collection” scenario indicated a
low reduction of organic load in the environment. This is because the “more enforcement”
scenario focused on improve performance of on-site sanitation facilities, increased access to
sanitary facilities and discouraging illegal disposal of waste. On the other hand, the low
reduction of organic load in the “more collection” scenario is explained by the low sewerage
coverage and vehicular inaccessibility in densely built-up areas to empty the toilets, and lack
of PSPs involvement. However, for effective and sustainable collection of waste, the waste
generators should pay the cost for collection, transportation and disposal of the waste. This
can be attained through public awareness campaign accompanied by enforcing compliance.
24
The “Proper management” scenario showed that the organic waste matter accumulated in the
environmental compartment reduced by about 38% compared to the “business as usual”.
The organic loads into the environment for the selected wastewater parameters after 50 years
are shown in Table 9. The accumulated BOD surface loads across the parishes ranging from
0.5 tons Ha-1 to 50 tons Ha-1 (see Fig. 15). The reduction of the organic load into the
environmental subsystem is explained by the co-composting of the human excreta with the
organic solid waste. Since organic solid waste is the highest component it implies that
composting would reduces about 80% of solid waste dumped into landfill. The improved
access to on-site sanitation by using small and medium size trucks, vacutugs and MAPET in
densely built-up areas reduced the organic waste load to the environment. By ensuring all
households have access to toilets eliminates the flow of human excreta into the environment
via open defecation.
The increased compost production matches well with the promotion of urban agriculture, but
this may be problematic since urban agriculture is low. Nonetheless, the compost produced
from the city can be taken to rural areas to substitute the expensive chemical fertilizers saving
the country’s foreign exchange. Compost is a soil conditioner, and source of nitrogen,
phosphorus, potassium, calcium and magnesium required for plant growth (Daskalopoulos et
al., 1998; Hasan et al., 2004; Sufian and Bala, 2006). More so, food stuff produced using
organic fertilizer has higher cost than those grown using chemical fertilizer. Composting also
has a significant advantage regarding the potential nutrient enrichment of the receipts and
groundwater as the release and seepage of nutrient is considerably low when using compost
instead of chemical fertilizer (Ramboll Danmark AIS, 2008). More so, composting have a
lower release of climate gases compared to landfill as there is a small release of nitrous oxide
and methane. But compost produced from municipal solid waste will never be of the same
quality as compost produced from clean organic due to presence of toxic substances
(Massoud et al., 2003).
25
At community level backyard composting is commonly applied solid waste disposal methods
in rural areas. The rural settings of the peri-urban areas of the city could continue relying on
this method since access to such areas is normally not adequately developed. However,
training would be required for effective composting especially with increasing settlement
densities in such areas. Small composting enterprises could also be involved. In this case, the
city council could pay small composting operations for each ton of waste material diverted
from the landfill. This payment should be based on the disposal costs that the council could
have incurred if the solid waste was dumped in the landfill.
The “proper management” scenario is sustainable and realistic as the efforts required to
manage the waste combine technology and behaviour change. But the “more enforcement”
and “more collection” scenarios concentrates only on behaviour change and technology
respectively. For instance, if illegal dumping and open defecation are eliminated without any
major improvement in the collection means, the faecal material in these facilities will
overflow into the environment when filled. Like wise, if the transport and collection points
are not increased for solid waste increased due to discouraging indiscriminately dumping,
then the solid waste will still pollutes the environment.
With the rapidly growing rate of waste generation, depletion of landfill space, and problems
in obtaining new disposal sites enhancing solid waste recycling is important than simply
enhancing the efficiency of solid waste management relating to waste disposal (Suttibak and
Nitivattananon, 2008). Recycling is attractive because of its potential to reduce disposal costs
and waste transport costs, and to prolong the life spans of sanitary landfill sites. Therefore
waste should be recovered at source, during transportation or at the disposal site. Integrating
waste sorting and resource recovery, reduces the quantity of solid disposed (Fruredy and
Chowdhury, 1996), and as well as improve the household income (Carina, 2003). Waste
sorting at source ensures the compost produced and recyclables are of high quality, prevents
pollution (Massoud et al., 2003), minimises the exploitation of natural resources, and
subsequently reduces the negative impact of urban ecological footprint (Kim, 1998). The
26
waste sorting at household can be enforced by adopting the polluter pays principle so that the
waste generator takes the responsibility. This will results in community participation leading
to a decentralized approach of waste management and makes the residents less dependent on
the collection by KCC and PSPs. The earlier the waste is sorted the higher quality and value
to the end users. Therefore incentives that integrate and foster involvement of the informal
sectors is vital to improved waste minimisation. Additionally, organising the informal waste
pickers to a form CBO to collect high value recyclable materials at households can improve
the waste minimisation. Publicizing the prices of the recyclables can help stimulate the
market and mitigate possible exploitation of the scavengers by intermediaries. The secondary
markets need to be foster since the extent to which a material is recovered is dependent on the
existence of local industries that can use the recovered material. More so, secondary markets
to serve these industries do not always develop independently.
Understanding community composition and structure is important in designing waste
management system. The poor and weaker sections of the society, particularly the women
who manages waste at household are important. Waste management cannot be successfully
operated without full involvement and commitment of users. Therefore where individuals find
separation of waste time consuming and unpleasant, there is need to educate on the
importance of waste collection and recycling with respect to health, environmental and social
benefits. Introducing incentives to the community, for example, by providing scholastic
materials for children in exchange for sorted waste can encourage the community to
participate in waste sorting. Where waste is not considered to be a potential income
generating resource, the facilities for waste recovery should be put close to the generated
waste. Use of low cost technologies to integrate resource recovery and recycling allows
communities to profit in addition to environmental benefit of avoiding landfill, reducing
manufacture of new product (Curran et al., 2007). The marketing of compost can eventually
lead to some profit-running schemes for the low-income communities. Unlike collection and
27
disposal services, recycling and composting results in social benefits to the low-income
household some income through sales of compost and recyclables.
4.
Conclusion
Current urban waste management, particularly the solid waste in Kampala is inadequate and
lags behind due to inadequate enforcement officers, low composting and recycling. The
“proper management” scenario showed the best waste management options in improving the
environmental quality as well as resource recovery. Other scenarios reduce the negative
impact but not sustainable in terms of implementation. The co-composting of organic solids
with human excreta at household or community levels will lead to a decentralized approach of
urban waste management. Thus, solid waste segregation and co-composting organic solid
waste with human excreta, awareness and enforcement enhancement improves the urban
environmental quality, and enhances resource recovery with public participation in regulating
and monitoring waste generation.
28
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Table 1: IUWFM and UBOS aggregated population projections for Kampala City
Model
Estimated population
Year
2010
2015
IUWFDM
1,605,900
1,921,900
UBOS (Uganda Bureau of Statistic, 2007) 1597,900
1,923,900
32
Table 2: Parameters and variables use in the solid waste sub model
Parameter
Unit
Value
Sources
Population growth rate
%
3.8
(Uganda Bureau of Statistic, 2006)
Initial population (2002)
Persons
1,208,196
(Uganda Bureau of Statistic, 2006)
Landfill threshold
Kg
2x109
(Antonio de Pina et al., 2005)
Compost threshold
Kg
2.2 x 1010
Computed
33
Table 3: Parameters and variables use in the calibration of the model
Parameter
BOD
TN
TP
Faecal Coliforms
Unit
capita-1
Value
d-1
Reference
40
10
3
2.6 x 109
(Mara, 1976)
(Mara, 1976)
(Mara, 1976)
(Mara, 1976)
On-site sanitation system
g
g capita-1 d-1
g capita-1 d-1
CFU capita-1
d-1
%
86
Centralised sanitation system
%
5
Sewage pond system
%
2
No sanitation
%
7
Fraction leaking from on-site
Vacuum truck collection
Centralised Sewage treatment
efficiency
Centralised Sewage Plant BOD
threshold
Sewage Pond BOD threshold
On-site BOD threshold
%
%
%
18
25
60
(National
Water
Corporation, 2004)
(National
Water
Corporation, 2004)
(National
Water
Corporation, 2004)
(National
Water
Corporation, 2004)
Estimated
Computed
Measured
Kg
7.3 x107
Computed
Kg
Kg
6 x 106
1.5 x 1011
Computed
Computed
34
and
Sewerage
and
Sewerage
and
Sewerage
and
Sewerage
Table 4: Composition of solid waste in Kampala city
Solid waste type
Paper and board
Glass
Metal
Plastic
Organic
Textiles
Construction
Street sweepings
Total
Percentage (April 2009)
5.3
1.1
0.9
7.7
83.2
0.4
1.5
100.0
Table 5: Sanitation coverage for 1991 and 2002 (National Water and Sewerage Corporation, 2004;
Uganda Bureau of Statistic, 2006)
SANITATION CATEGORY
1991 CENSUS DATA
2002 CENSUS DATA
Sewer (NWSC and others)
9%
7%
Septic tanks
5%
19%
35
Pit latrines
84 %
69%
No sanitation facility
2%
5%
100 %
100 %
Total
Table 6: Solid waste and sanitation data for Dar es salaam
Parameter
Unit
Value
Source
Solid waste generation rate
Kg capita-1 day-1
0.815
(Environmental
Resources
Management, 2004)
Total solid waste generation rate
Kg day-1
3,092
(Environmental
Resources
Management, 2004)
Solid waste collected
%
44
Solid waste recycled
%
9
36
Health Officer
Solid waste flow to the environment
%
31.2
(Environmental
Resources
Management, 2004)
Solid waste composted
%
9
Health Officer
Solid waste buried or burnt at source
%
25
Proportion of population on-site
%
90
(Dar es Salaam Water and
Sewerage Corporation, 2007)
Proportion of population connected
to sewer
%
7
(Dar es Salaam Water and
Sewerage Corporation, 2007)
No access to sanitation
%
4
(Dar es Salaam Water and
Sewerage Corporation, 2007)
Table 7: Solid waste composition for Dar es Salaam, Tanzania
Category
Composition 2006 (%)
1.
Papers and paperboards
8
2.
Textile
1
3.
Plastics
5
4.
Metals
2
5.
Glass
3
6.
Leather/rubber
1
37
7.
Ceramic/stone/soil
1
8.
Organic (Kitchen, Grass/wood)
64
9.
Other
15
Total
100
Table 8: Parameters and variables used in scenarios
Parameter
Technology
Enforcement
Awareness
Unit
Scale
scale
scale
Business as
usual
1
1
1
Scenarios
More
More
Enforcement
Collection
1.75
4.50
4.50
1.75
1.75
1.75
38
Proper
Management
3.0
2.5
2.5
Table 9: Simulation output for the four scenarios
Unit
Business
Parameters
as usual
BOD
Mtons
310
TN
Mtons
7.6
TP
Mtons
3
Compost
Mtons
2,200
Landfill
Mtons
130
Global warming potential
Mtons
241
KgCO2 eq/ton waste landfill
39
More
enforcement
192
4.3
1.8
7700
2200
4070
More
collection
230
2
2
5100
300
555
Proper
management
150
5.6
2
22,000
44
81
40
Fig. 1: The map of Kampala showing the divisions, streams, wetlands and sewer coverage
41
Fig. 2: Structure of the IUWFM
42
Fig. 3: IUWFM representation in SMILE
43
Fig. 4: Representation of the population sub model in SMILE
44
Fig. 5: The solid waste sub model represented in SMILE
45
Fig. 6: The human excreta sub model represented in SIMILE
46
2,000
Waste at landfill
(Tons x 1000)
1,500
1,000
500
2002
2003
2004
2005
2006
2007
Year
Simulated
Measure
Fig. 7: Calibration plot for measured and simulated solid waste disposed in landfill at Kitenzi
47
2008
Measure Landfill waste (Tons x
1000)
3000
y = 0.7204x + 254.6
2500
R2 = 0.9991
2000
1500
1000
500
0
0
500
1000
1500
2000
2500
3000
Simulated Landfill waste(Tons x 1000)
Fig. 8: Calibration plot for measured against simulated solid waste disposed in landfill at Kitenzi
48
3500
3,000,000
Waste (Tons)
2,500,000
2,000,000
1,500,000
1,000,000
500,000
2001
2002
2003
2004
2005
2006
Years
Landfill (Tons)
Measured (Tons)
Fig. 9: Plots for simulated and measured solid waste dumped at the dump site over time
49
2007
3,000,000
Simulated (Tons)
2,500,000
2,000,000
y = 0.8207x + 518656
R2 = 0.991
1,500,000
1,000,000
500,000
1,000,000
1,500,000
2,000,000
2,500,000
3,000,000
Observed (Tons)
Fig. 10: Plots for measured cumulative solid waste mass against simulated value at the dump site
50
Fig. 11: Waste flows in the “Business as usual” scenario
51
Fig. 12: Waste flow in the “more enforcement” scenario
52
Fig. 13: Waste flows in the “More collection” scenario
53
Fig. 14: Waste flow diagram for proper management scenario
54
“business as usual” 0.5 tons ha-1 to 110 tons ha-1
More enforcement BOD 0.5 tons ha-1 to 68 tons
ha-1
More collection BOD 0.7 Tons ha-1 to 86 Tons ha-1
Proper management BOD 0.5
Tons Ha-1
tons Ha -1 to 50
Fig. 15: BOD spatial distribution maps for the four scenarios (Top-left: “business as usual”; Top-right:
“more enforcement”; bottom-left: “more collection”; bottom-right: “proper management”).
55
Business as usual
Proper management
More collection
More enforcement
Business as usual
350
BOD (Tons X 10 3)
300
TN (Tons x 103)
250
200
150
100
50
0
2014 2020
2026 2032
2008
2014
2020
2038 2044 2050
Proper management
More collection
More enforcement
More enforcement
2026
2032
2038
2044
2050
Years
Years
Business as usual
More collection
8
7
6
5
4
3
2
1
0
2002
2002 2008
Proper management
Business as usual
Proper management
More enforcement
TP (Tons x103)
3
Compost (Tons x10 )
4
More collection
3
2
1
0
2002 2008 2014 2020 2026 2032 2038 2044 2050
Years
Business as usual
More enforcement
proper management
20000
16000
12000
8000
4000
0
2002 2008 2014 2020 2026 2032 2038 2044 2050
Years
More collection
3
Landfill (Tons x 10 )
400
300
200
100
0
2002
2008
2014
2020
2026
2032
2038
2044
2050
Years
Fig. 16: Simulation plots for the four scenarios (Top-left: biological oxygen demand, BOD; top-right:
Total Nitrogen, TN; middle-left: Total Phosphorous, TP; middle-right: compost; bottom-left: Landfill)
56