ACKNOWLEDGMENT

We thank the Almighty God who has been the source of our strength during the whole period
of our study. We also convey our outstanding appreciations to Dr. Sweya Ngalya, Dr. Ruhinda
and all our lectures who have provided us with a lot knowledge by guiding us has made this
study successful. We also thank the officials at Sinza ward especially Sinza D and the all
interviewees for their valuable response during the whole period of accomplishing our study
on sewerage and drainage and storm water systems and faecal sludge management at the area.

i
 ABSTRACT

Sewerage and drainage systems as well as faecal sludge management imply the collections of
waste water from the point of generation and conveying them to the point of disposal and how
wastes are managed after they have been generated. Sewage, storm water and faecal sludge are
to be properly managed to create a better environment for the occupants. The main objective of
the study was to design sewerage, stormwater and faecal sludge management system at Sinza
D which involved studying of the existing sewage, storm water and faecal sludge management,
challenges and come up with the possible remedies. The data collection methods that were used
were site visitation and physical observation, checklist and questionnaire whereby 100
questionnaires were distributed to the interviewees to say on the existing situation of the area.
The proposed sewerage, stormwater and faecal sludge management systems will ensure proper
management of sewage, storm water and faecal sludge and thus a safe environment free from
pollution and exposure to diseases for the residents at Sinza D.

ii
 ABBREVIATIONS

DAWASA- Dar es salaam Water and Sanitation Authority

FSM- FAECAL SLUDGE MANAGEMENT
GWSP-Global Water Security and Sanitation Partnership
MAPET-Manual Pit Emptying Technology
MoW- Ministry of Water
NAT GEO- National Geographic
NGOs -Non-Governmental Organizations
PHF -Peak Hour Factor
PVC-Polyvinyl Chloride
SDGs- The Sustainable Development Goals
TMA- Tanzania Meteorological Authority
UTI- Urinary Tract Infections
VIP- Ventilated Improved Pit latrine
WB- World Bank
WHO-World Health Organization
WWTP- Waste Water Treatment Plant

iii
 LIST OF FIGURES

Figure 2.1 Global use of freshwater.

Figure 2.2 Variation of men and women in a water sector positions
Figure 2.3 components contributing to the quantity of waste water flowing in sewers
Figure 2.4 Graph for the determination of peak flows from the daily flow rate
Figure 2.5 Separated sewer system
Figure 2.6 Hydrogen sulphide gas causing corrosion in the pipes when combining with the
water
Figure 2.7 Installation pipes in the trench
Figure 2.8 Determination of head in a system
Figure 2.9 Sample of air test set up
Figure 2.10 Example of the smoke test
Figure 2.11 A diagram showing manhole structure
Figure 2.12 double manhole Medford mass
Figure 2.14 Types of lamp-holes
Figure 2.13 A picture of flush man-hole
Figure 2.15 Street inlet alongside the road
Figure 2.16 An example of catch basin
Figure 2.17 Ventilating column
Figure 2.18 discharging the desludged faecal sludge to the decentralized treatment plant
Figure 3.1 Group members conducting questionnaire to the dwellers
Figure 4.1 Amount of rainfall in different months of the year in Dar es salaam
Figure 4.2 Population Distribution in Sinza ‘D’
Figure 4.3 Water supply sources in the study area
Figure 4.4 Water treatment methods used by the households
Figure 4.5 Types of the toilet facilities present in the study area
Figure 4.6: wastewater from toilets discharged into the streams
Figure 4.7: Emptying system at Sinza D
Figure 4.8: septic tanks
Figure 4.9: pit latrine or drop and store
Figure 4.10: manual emptying technology
Figure 4.11: mechanical emptying technology

iv
Figure 4.1: Narrowed water stream due to over construction in water ways
Figure 4.12: Bank of the house raised to avoid entrance of storm water during rainy season.
Figure 4.13: Local drainage systems at Sinza D

v
 LIST OF TABLES

Table 2.1 below, describes various design periods for the design of wastewater facilities
Table 2.2: Values of roughness coefficient ‘n’ for use in Kutter’s and Manning’s formulae
Table 2.3: Values of Bazin’s for various surface material
Table 3.1 mathematical formulas used in this report
Table 4.1 Number of social and public services facilities at Sinza D.
Table 4.2 Economic status of residents in Sinza ‘D’
Table 4.3 water storage facility statistics
Table 5.1 total discharge flows in different institutions
Table 6.1 Area based and Coefficients of runoffs of urban areas
Table 6.2 Area distribution based on various runoff coefficients

vi
 TABLE OF CONTENTS
ACKNOWLEDGMENT........................................................................................................... i

ABSTRACT ............................................................................................................................... ii

ABBREVIATIONS................................................................................................................... iii

LIST OF FIGURES................................................................................................................... iv

LIST OF TABLES .................................................................................................................... vi

CHAPTER ONE ........................................................................................................................ 1

1.0 INTRODUCTION............................................................................................................ 1

1.1 Background ...................................................................................................................... 1

1.2 Problem statement ............................................................................................................ 2

1.3 Objectives ......................................................................................................................... 2

1.3.1 Main Objective .............................................................................................................. 2

1.3.2 Specific objectives .................................................................................................... 2

1.4 Scope ................................................................................................................................ 3

1.5 Significance of the project ............................................................................................... 3

CHAPTER TWO ....................................................................................................................... 4

2.0 LITERATURE REVIEW................................................................................................. 4

2.1 Introduction ...................................................................................................................... 4

2.2 Global water coverage, challenges and strategies ............................................................ 4

2.2.1 Water as a resource ................................................................................................... 4

Examples of surface water ..................................................................................................... 5

2.2.1.2 Ground water sources ............................................................................................. 5

2.2.2 Water accessibility across the global ........................................................................ 6

2.2.3 Water Quantity .......................................................................................................... 7

2.2.4 Water Quality ............................................................................................................ 7

• Suspended Impurities........................................................................................................... 8

• Total dissolved solids (TDS) ............................................................................................... 8

vii
• Temperature ......................................................................................................................... 8

• Turbidity .............................................................................................................................. 8

• Salinity ................................................................................................................................. 8

2.2.5 Water Treatment........................................................................................................ 9

2.3 Global challenges of water supply ................................................................................. 10

2.3.1 Climate change ........................................................................................................ 10

2.3.3 Rapid population growth and urbanization ............................................................. 11

2.3.4 Exclusion role of women in water supply sectors ................................................... 12

2.3.6 Water supply issues in Developing countries ......................................................... 13

2.3.7 Challenges facing water sector in developing countries ......................................... 13

• Poor infrastructure for water supply .................................................................................. 13

• Floods and droughts ........................................................................................................... 14

• Contamination of water sources ........................................................................................ 14

• Poverty ............................................................................................................................... 14

• Inadequate financing and low levels of investment ........................................................... 14

2.3.8 Strategies implemented to combat water challenges in developing countries ........ 15

2.4 Sanitation........................................................................................................................ 15

2.4.1 Types of sanitation system ...................................................................................... 15

2.4.2 On site sanitation system ......................................................................................... 16

Advantages of on-site sanitation .......................................................................................... 16

❖ Disadvantages of on-site sanitation ........................................................................... 16

2.4.3 Off-site sanitation system ........................................................................................ 17

Advantages of off-site sanitation ......................................................................................... 17

2.5 Sewerage system ............................................................................................................ 18

2.5.1 Types of sewerage system ....................................................................................... 18

2.5.2 Combined system .................................................................................................... 18

❖ Disadvantages ............................................................................................................ 19

viii
 2.5.3 Separate system ....................................................................................................... 19

❖ Advantages ................................................................................................................ 20

2.5.4 Partially separate system ......................................................................................... 20

❖ Disadvantages ............................................................................................................ 20

2.6 Design of the sewerage system ...................................................................................... 21

2.6.1 Predesign Activities ................................................................................................ 21

2.6.2 The Sewerage system Design Capacity .................................................................. 21

2.6.3 Design Criteria for the Conventional gravity sewers .............................................. 26

2.6.4 Profile of sewer system ........................................................................................... 29

2.6.5 Plans and Nomenclature .......................................................................................... 29

2.6.6 Sewer network layout .............................................................................................. 30

2.6.7 Hydraulic formulas for the design of sewers .......................................................... 30

V= C ............................................................................................................................ 30

Ganguillet-Kutter Formula ................................................................................................... 31

2.6.8 Construction of Sewer ............................................................................................. 33

2.6.9 Testing of sewer ...................................................................................................... 35

2.6.10 Water Test ............................................................................................................. 35

2.6.11 Test for Obstruction .............................................................................................. 38

3.8.6 Sewer appurtenances ............................................................................................... 38

• Drop man-hole ................................................................................................................... 39

• Flushing man-holes ............................................................................................................ 40

• Lamp-holes ........................................................................................................................ 40

• Street inlets ........................................................................................................................ 41

• Catch Basins ...................................................................................................................... 41

Inverted siphons ................................................................................................................... 42

2.6.13 Cleaning and ventilation of sewers ....................................................................... 42

2.7 Maintenance of sewerage system ................................................................................... 43

ix
 2.8 Transfer station for waste water treatment plant ............................................................ 44

2.8.1 Mobile transfer stations ........................................................................................... 44

2.8.2 Fixed transfer stations ............................................................................................. 45

Disadvantages ...................................................................................................................... 45

2.8.3 Health aspects/acceptance ....................................................................................... 46

2.8.4 Costs considerations ................................................................................................ 46

2.8.5 Operation & maintenance ....................................................................................... 46

2.8.6 Applicability ............................................................................................................ 47

CHAPTER THREE .................................................................................................................. 53

3.0 METHODOLOGY ......................................................................................................... 53

3.1 Introduction .................................................................................................................... 53

3.2. Data collection .............................................................................................................. 53

3.2.1 Site visiting and Physical observation..................................................................... 53

3.2.2 Questionnaire .......................................................................................................... 53

3.2.3 Interview ................................................................................................................. 54

3.3. Data analysis ................................................................................................................. 54

3.4. Data interpretation ......................................................................................................... 55

• Software’s .......................................................................................................................... 55

• Mathematical calculations ................................................................................................. 55

• Design considerations and criteria (Mackenzie L, 2010) .................................................. 57

3.5 Site description ............................................................................................................... 58

CHAPTER FOUR .................................................................................................................... 60

4.0 RESULTS AND DISCUSSION .................................................................................... 60

4.1 Introduction .................................................................................................................... 60

4.2 Climatic condition .......................................................................................................... 60

4.2.1 Temperature ............................................................................................................ 60

4.2.2 Rainfall .................................................................................................................... 60

x
 4.2.3 Topography and Soils ............................................................................................. 61

4.2.4 Water table .............................................................................................................. 61

4.3 Population ...................................................................................................................... 61

4.4 Socio-Economic status ................................................................................................... 62

4.4.1 Social and public services ....................................................................................... 62

4.4.2 Economic status ...................................................................................................... 62

Table 4.2 Economic status of residents in Sinza ‘D’ ........................................................... 62

4.5 Water amenities and service........................................................................................... 63

4.5.2 Cost of water available ............................................................................................ 64

4.5.3 Availability of water ............................................................................................... 65

4.5.4 Water quality ........................................................................................................... 65

4.5.5 Water treatment methods ........................................................................................ 65

4.5.5 Water storage facilities ............................................................................................ 66

Table 4.4 Water storage facility statistics ............................................................................ 66

4.5.6 Water demand and consumption estimation ........................................................... 67

4.6 Sanitation system ........................................................................................................... 67

4.6.1 Onsite sanitation facilities ....................................................................................... 68

4.6.2 Methods of emptying .............................................................................................. 69

4.7 Problems of sanitation in relation to water supply; ........................................................ 70

4.8 Measures to be taken to improve the sanitation system ................................................. 72

4.11 Storm water management and drainage systems ......................................................... 74

4.11.1 Storm water management ...................................................................................... 74

4.11.2 Drainage system .................................................................................................... 75

CHAPTER 5............................................................................................................................. 77

5.0 DESIGNING OF THE SEWERAGE SYSTEM AT SINZA D......................................... 77

5.1 Selection of the design period ........................................................................................ 77

5.2 Population forecasting .................................................................................................... 77

xi
 5.3 Water Demand Projection .............................................................................................. 77

5.4 Waste water generation .................................................................................................. 78

5.4.1 Domestic wastewater generation............................................................................. 78

5.4.2 Institutional wastewater generation......................................................................... 78

5.6 The Commercial waste water generation ....................................................................... 79

5.7 Peak waste waterflow ................................................................................................ 79

5.8 Inflow and Infiltration ............................................................................................... 79

5.9 The proposed Sewer Layout ...................................................................................... 80

CHAPTER 6............................................................................................................................. 81

6.0 DESIGN OF THE STORMWATER DRAINAGE SYSTEMS AT SINZA D ............. 81

6.1Design period .................................................................................................................. 81

6.2The Runoff coefficient for runoff estimations ................................................................ 81

6.3 Rainfall Intensity (mm/hr).............................................................................................. 82

6.4 Drainage systems Design ............................................................................................... 82

6.5. Surface Runoff Estimation ............................................................................................ 83

6.6. Hydraulic Longitudinal Profile for the Design ............................................................. 84

CHAPTER EIGHT................................................................................................................... 90

COST ESTIMATION .......................................................................................................... 90

8.1 Cost estimation for sewerage system designing............................................................. 90

8.1.1 Pipe cost estimation................................................................................................. 90

8.1.2 Excavation costs ...................................................................................................... 91

8.2 Cost estimation for stormwater management systems ................................................... 93

8.2.1 Stormwater lining costs ............................................................................................... 93

8.2.2 Stormwater earthworks costs .................................................................................. 94

8.3 Cost estimation for additional requirements and activities for both sewerage and
stormwater management systems ......................................................................................... 95

8.4 Cost estimation for faecal sludge management systems ................................................ 96

xii
 8.5 TOTAL DESIGNING COST ......................................................................................... 97

CHAPTER NINE ..................................................................................................................... 98

9.0 CONCLUSION AND RECOMMENDATIONS ........................................................... 98

9.1 Conclusion...................................................................................................................... 98

9.2 Recommendations .......................................................................................................... 99

REFERENCES ....................................................................................................................... 100

xiii
 CHAPTER ONE

1.0 INTRODUCTION

1.1 Background

Water is a finite and valuable resource, fundamental for human existence and well-being and
can only be sustainable if well managed. The access to clean water and sanitation are recognized
by the United Nations as human rights thus, the lack of access to safe, sufficient, affordable
water, sanitation and hygiene facilities has a devastating effect on the health, dignity and
prosperity of the people, and has significant consequences for the realization of other human
rights (WHO, 2010).

Currently, sanitation is deployed as a way to contain, transport and treat wastewater, so as to

protect human health and the environment. Inadequate sanitation is estimated to cause 432,000
diarrhea deaths annually and is a major factor in several neglected tropical diseases, including
intestinal worms, schistosomiasis, and trachoma (WHO, 2010). In assessing and dealing with
the issue tactical motives and efforts are required in ensuring that there is proper management
of the wastewater preferably in the engineering context specifically by proper designing of
sustainable and efficient sewerage systems the communities will be ensured that there is an
efficient convey of the domestic, industrial, commercial and storm water, hence ensuring that
the public health’s are at safe hands and maximum reduction in the pollution of water sources
and supply systems through intrusion of the wastewater in their pathways, inclusive of the storm
water management systems, and specific faecal sludge management facilities as the
fundamental key role in the onsite sanitation systems. All these efforts are not intended on only
managing the wastewater quantitatively, but comprehended also on the recycling of the
nutrients and resources obtained from the wastewater.

In Tanzania, despite of all efforts redirected to evaluate and solve the sanitation issue still the
efforts lag behind, as currently, the percentage of population covered by sewerage system in
these towns is as follows; Arusha is only 9%, Tanga 15%, Mwanza 13%, Moshi 7%, Dar es
Salaam 13%, Mbeya 4%, Tabora 3% and Iringa 3% (MoWL, 2005). Denoting that, our country
still is in need for proper planning and design of the sanitation facilities as noted that the
dependency on the on-site sanitation system is somehow not much efficient, in the rapid

1
increase in the population and urbanization context hence even more technical knowhows are
required so as to protect the public health and facilitating our nation’s development.

1.2 Problem statement

Dar es salaam is the high growing city in the Tanzania with high rate of unplanned settlement
and unorganized facilities. As a result, it accelerates the production of waste water, faecal
sludge and storm water which when not well managed results to environmental pollution. In
which improper management of waste water, faecal sludge and storm water leads to the rise of
eruption of diseases, flood, and also water pollution. Shockingly some of wastewater generated
is discharged into water stream which interferes the natural water bodies which enhance
environmental pollution.

Sinza D street is highly affected by poor waste water management, improper faecal sludge
management and poor drainage system which encounter the effect of storm water due to poor
management. The existing technology of domestic and commercial wastewater, faecal sludge
management and storm water is very limited and hence innovative technology is needed to
improve the situation facing Sinza residents.

1.3 Objectives

1.3.1 Main Objective

• The main objective of the project is to design sewerage, drainage and faecal sludge
management systems at Sinza D street.

1.3.2 Specific objectives

• Identifying and analyzing the existing demographical data, water supply, sanitation
facilities, faecal sludge and storm water management situations at Sinza D street.

• Assessing the prevailing problems and their adverse impacts, including provisioning of
solutions on the existing sanitation facilities, faecal sludge and storm water
management systems at Sinza D.

2
 • Designing of the Sewerage, stormwater and faecal sludge management systems at Sinza
D street.

• Estimating costs of various construction materials, labour works, transportation and

earthworks for the designed project.

1.4 Scope

This project covers on the assessment of sewerage and faecal sludge management in relation of
determining on the sanitation facilities used, problem and challenges that are facing residents
of Sinza D and providing solutions on the problems and challenges examined. Finally,
designing of sewerage and faecal sludge management.

1.5 Significance of the project

The project significantly is important to the community as it provides proper means of

managing both sanitary wastewater and stormwater, integrated with engineering knowledge on
proper designing and cost saving techniques as a mitigative measure in ensuring that the
environment is well conserved and free from the exposure of faecal matter, chemical and
biological pollutants conveyed by the wastewater generated from the domestic households,
industries, institutions and various commercial vicinities aiming on public health protection and
promoting a waterborne diseases-free community at Sinza D.

3
 CHAPTER TWO

2.0 LITERATURE REVIEW

2.1 Introduction

Referring from the Urbanization context and population growth, urgent needs are required to
provide the sufficient and constant quantity of water through the designed network of pipes in
the water supply system. Taking into consideration that almost 60 – 90% of the water supplied
to the communities are turned into wastewater thus infrastructure for the collection,
transmission, treatment, storage, distribution of water for homes, commercial establishments,
industry, and irrigation are relative highly required (Haile et al., 2014).

2.2 Global water coverage, challenges and strategies

2.2.1 Water as a resource

Water is the most abundant compound in nature. It covers almost about 75% of the earth
surface. About 97.3% of water is contained in the great oceans that are saline and 2.14% is held
in icecaps glaciers in the poles, which are also not useful. Were as the remaining 0.56% found
on earth is in useful form for general livelihood (Franzini et al, 1991). Water sources on the
earth are categorized into three types;
• Surface water sources

• Ground water sources

2.2.1.1 Surface water sources

These are water found on the earth surface such as in a stream, river, lake, wetland or ocean. It
can be formed due to outflow and rainfall (Fetter, 2008). Surface are easily available and
accessible and this makes it easier to be polluted. Pollution can be from diffuse sources, arising
from land-use activities in both urban and rural areas that are dispersed across the water surface.
Diffuse sources include surface runoff, as well as subsurface drainage, from activities on land.

Types of surface water

4
There are three types of surface water; perennial, ephemeral, and man-made. Perennial, or
permanent, surface water persists throughout the year and is replenished with groundwater
when there is little precipitation. Ephemeral, or semi-permanent, surface water exists for only
part of the year. Ephemeral surface water includes small creeks, lagoons, and water holes.
Manmade surface water is found in artificial structures, such as dams and constructed wetlands
(NAT GEO, 2015).
Examples of surface water

• Rivers and streams

Water flowing in rivers and streams consists of direct precipitation runoff and other tributaries
on the ground surface, or overflow from lakes and swamps and also the water seeping from
the ground.
• Lakes and ponds

Water from lakes, ponds and artificial or impounding reservoirs have the standard quality than
water flowing in the river due to less turbidity.
• Wetland

Wetland are areas of marsh, fen, peat land or water, whether natural or artificial, permanent or
temporary, with water that is static or flowing, fresh, brackish or salty, including areas of marine
water, the depth of which does not exceed six meters. These are largely found in coastal regions
and rift valleys areas.
2.2.1.2 Ground water sources

Groundwater water varies its properties from place to place, some places have high salinity and
color, also smell while in other places are suitable for human consumption. Ground water are
formed due to infiltration and from the rocks in the crust, its availability is detected after
exploration in the ground, excessive underground water causes springs.

Types of ground water

• Shallow wells

5
Are those developed in the surface deposits of materials overlaying and impervious stratum,
shallow wells are constructed in the uppermost layer of the earth’s surface. They are ranging at
depth of 5m to 15m.
• Infiltration Galleries

Infiltration galleries like shallow wells are developed in shallow water bearing strata adjacent
to springs or ponds a horizontal nearly horizontal tunnel which is constructed through water
bearing strata for tapping underground water near rivers, lakes or streams.
• Deep Wells

The deep wells that extend 35m or more below on the ground and obtain their quota of water
from an aquifer below the impervious layer. The theory of deep well is based on the travel of
water from the outcrop to the site of deep well. The outcrop is the place where aquifer is exposed
to the atmosphere.

2.2.2 Water accessibility across the global

Water is at the center of economic and social development; it is vital to maintain health, grow
food, management of the environment, and create jobs opportunity either. Despite all water
importance and necessity, over 663 million people in the world still lack access to improved
drinking water sources (WB, 2017).
Yet over 40% of the global population does not have access to sufficient clean water. By 2025,
1.8 billion people will be living in countries or regions with absolute water scarcity, (UNWater,
2018). The lack of water poses a major threat to several sectors, this including food security.
Agricultural activities use about 70% of the world accessible freshwater.
However, The Sustainable Development Goals (SDGs) on Water and Sanitation proposes a
broader agenda: By 2030, universal and equitable access to safe and affordable drinking water
for all, and access to adequate and equitable sanitation and hygiene for all, and ending open
defecation, paying special attention to the needs of women and girls and those in vulnerable
situations such as disabled people. This new goal imitates the growing position of water and
sanitation as a human right. Additional targets that go beyond access are also being considered,
such as improving water quality by reducing pollution, contamination and considerably
increasing water-use efficiency (WBG, 2017).

6
2.2.3 Water Quantity

Water quantity is the amount of water supplied to a given community. While designing the
water supply scheme for a town or city, it is necessary to determine the total quantity of a water
required for various purposes by the city. As a matter of fact the first duty of the engineer is to
determine the water demand of the town and then to find suitable water sources from where the
demand can be met. Water Demand is the amount of water that a water user actually applies to
a beneficial use, within the terms of his or her water right and applicable law.
Types of water demand of a town or city are: -
• Domestic water demand

• Industrial water demand

• Institution and commercial water demand

• Demand for public use

• Firefighting water demand

• Water losses

Also, there are factors which affect water demand of any given community, those factors are;

• Size of the community to be served

• Climatic condition

• Living standard of the people

• Industrial and commercial activities

• Quality of water

2.2.4 Water Quality

Pure water is never found in nature and contains number of impurities in varying amounts. The
rainwater which is originally pure, also absorbs various gases, dust and other impurities while
falling. This water when moves on the ground further carries salt, organic and inorganic
impurities. So, this water before supplying to the public should be treated and purified for the
safety of public health, economy and protection of various industrial process. Water quality is

7
referred to characteristic of water with no impurities and any kind of contaminant. For the aim
of classification, the impurities present in water may be divided into the following three
categories;
• Physical Characteristics

• Chemical Characteristics

• Biological Characteristics

The above impurities occur in three progressive finer states, suspended impurities, colloidal
and dissolved substances. Below are the characteristics of water quality based on number of
impurities: -
• Suspended Impurities

Solid suspended in water may consist of organic such as plant fibers and biological solids (algal
cells, and bacteria) or inorganic such as clay, silt or of immiscible liquids are common in surface
water. (Hofkes et al, 1986).
• Total dissolved solids (TDS)

The material remains in water after filtration for the suspended solid analysis is considered to
be dissolved. The materials are left as a solid residue upon evaporation of water constituents.
• Temperature

Temperature is one of the most important parameters in natural surface water systems. The
temperature of surface waters governs largely the biological species present and their rates of
activity. Temperature also has pronounced solubility of gases in water (Chatterjee, 1998).
• Turbidity

Turbidity is a measure of the extent to which light is either absorbed or scattered by the
suspended material. Turbid water is aesthetically displeasing. The total colloidal associated
with turbidity provides adsorption sites for chemicals that may be harmful.

• Salinity

Drinking water is ought to be tasteless and odorless, the consumer associates tastes and odor
with contamination and may prefer to use tasteless, odorless water that might actually pose

8
more of a health threat. The salt content of given water may be measured indirectly by the
electrical conductivity method. (Hofkes et al, 1986).
2.2.5 Water Treatment

Water treatment describes those processes used to make water more acceptable for a desired
endues. These can include use as drinking water industrial processes, medical and many other
uses. The goal of all water treatment process is to remove existing contaminants in the water,
of reduce the concentration of such contaminants so it becomes fit for its desired end-use. Water
available in various sources contains various types of impurities and cannot be directly used by
the public for various purposes, before removing those impurities. For portability water should
be free from unpleasant tastes, odor and must have sparkling appearance and must be free from
disease-spreading germs. In order for the water to be clean, fit and safe for drinking, the
treatment methods should be adopted.
The amount and type of treatment procedures that should be adopted will depend on;

• The quality of raw water

• The standards of quality of raw water

• The standards of quality to be required after treatment.

Treatment of water consists of many methods that may either be chemically, biologically or
physically. These methods can further be categorized into two main groups of units, Unit
operation that include all physical methods of treatment of water such as screening,
sedimentation, filtration and boiling. Other unit is Unit processes that include all chemically
and biologically methods of water treatments such as disinfection. The general treatment
methods are such as discussed below;
2.2.5.1 Sedimentation

This is the unit operation that involves the removal of suspended solids from raw water.
Sedimentation is necessary for permitting settle able solids to be deposited and thus reduce the
concentration of suspended solids that must be removed by filters. Factors that influence
sedimentation are particle size, shape and weight of the floc, viscosity and temperature of water,
effective average period available for sedimentation, effective depth of the basins, surface
overflow rate, velocity of flow and inlet and outlet designs of basins.

9
2.2.5.2 Filtration

This is the removal of suspended solids and bacteria from water. The degree of removal of
bacteria by filtration should at least be 90%-98% (McGhee, 1990). Turbidity of filtered water
should be less than 1 unit. Types of filters widely used within a large-scale treatment plant are
slow sand filters, rapid sand filters, pressure filters and diatomaceous-earth filters.
2.2.5.3 Boiling

This method is mostly used within household levels where by water is boiled up to 100°C in
order to kill pathogens then it filtered to remove suspended particles remained.
2.2.5.4 Disinfection

This is the process of killing the diseases causing organisms (Pathogens) from the water and
making it safe to the user. The water which comes out from the filter may contain some disease
– causing bacteria in addition to the useful bacteria. Before the water is supplied to the public
it is outmost necessary to kill all the disease-causing bacteria. The chemicals or substances
which are used for killing the bacteria are known as disinfectants. The popular disinfectant used
is chlorine. It is the most choice because its dosage can be controlled precisely.
2.3 Global challenges of water supply

The scale of the challenge is large and becoming more composite. Population and economic
growth are pushing the limits of the world to finite water resources. And in some areas, water
scarcity is constraining economic growth.
2.3.1 Climate change

Climate change is already affecting water access for people around the world, mostly
developing countries and causing more severe droughts and floods. Increasing global
temperatures is the core and main contributors to this problem. Climate change impacts the
water cycle by influencing when, where, and how much precipitation falls. It also leads to more
severe weather events varying over time. Increasing global temperatures causes water to
evaporate in larger amounts, which will lead to higher levels of atmospheric water vapor and
more frequent, heavy, and intense rains in the coming years.
2.3.2 Expansion of Industries and Agricultural activities
Scarcity as a result of consumption is caused primarily by the extensive use of water in
agriculture or livestock breeding and industry. People in developed countries generally use

10
about 10 times more water daily than those in developing countries. A large part of this is
indirect use in water-intensive agricultural and industrial production processes of consumer
goods, such as fruit, oilseed crops and cotton (Charlie, 2012). Other activities ranging from
industrialization to services such as tourism continues to expand rapidly, this expansion
requires increased water services counting both supply and sanitation, which can lead to more
pressure on water resources and natural ecosystem.

Figure 2.1: Global use of freshwater. Source;( FAO, 2016)

2.3.3 Rapid population growth and urbanization

The competition for water resources has becomes more intense, consumption of water is
increasing and competition of water arising from industries and urbanization process, thus
water demand will increase gradually unless measure of water conservation and recycling are
increases (World Bank, 2019).
The trend towards urbanization is accelerating, small private wells and septic tanks that work
well in low-density communities are not feasible within high-density urban areas. Urbanization
requires significant investment in water infrastructure in order to deliver water to individuals
and to process the concentrations of wastewater, (Foster, 2006). These polluted and
contaminated waters must be treated or they pose unacceptable public health risks.

11
2.3.4 Exclusion role of women in water supply sectors

Less than one in five water workers are women, according to new research by the World Bank’s
Water Global Practice. Women are also underrepresented in participation in water supply
issues, agenda and water related activities.
Around the world, women are largely responsible for fetching and using water for household
purposes. But the water sector is yet to fully recognize important position and benefit from
women contributions as water managers and providers. The gender gap in water-related
employment needs to be closed if the world is to reach its commitments on water and sanitation
for all (GWSP, 2019).

Figure 2.2 Variation of men and women in a water sector positions (Source: WB, 2017)

2.3.5 Strategies implemented to overcome challenges of water supply

The Strategy aims to reduce disease and save lives, eradicate poverty, and promote sustainable
economic growth, increase food and energy security, build peace and security, and open up
international markets and advanced technologies and approaches as international engagement
will, also inform best practices and cultivate opportunities to strengthen water security across
the globe. To advance the vision of the Strategy, the WHO and U.S. government will work with
partner countries, the private sector, and other stakeholders to advance water resources
conservation and protection. Some of the strategies implemented are;

12
 • Promote sustainable access to safe drinking water and sanitation services,
and the adoption of key hygiene behaviors.
• Encourage the sound management and protection of freshwater resources.

• Strengthen water sector governance, financing, and institutions.

• Strengthen partnerships, intergovernmental organizations, and the

international community
• Promote science, technology, innovation, and information.

2.3.6 Water supply issues in Developing countries

Developing countries are most affected by water deficiencies, flooding and poor water quality.
Up to 80% of illnesses in the developing world are linked to inadequate water and sanitation.
In many developing countries, pollution and contamination of water sources is the major
problem. Also, water stress and lack of sanitation disproportionately affect women and girls in
the community. These factors are threatening public health, safety and opportunity to engage
in economic activities. Women and girls are often the primary managers of natural water
resources, particularly for both household uses and small-scale farming. They are the key and
play an important role in sustaining water management practices, (Government of Canada,
2017).

2.3.7 Challenges facing water sector in developing countries

Most of developing countries especially in Africa have sufficient lakes, runoff, dams, springs
and reservoirs. However, challenges to water sources and water supply systems has become
inevitable and this is a commencing of scarcity of drinking-water, several challenges and effects
that encounter this sector have been addressed, these are;
• Poor infrastructure for water supply

Water supply infrastructure are of low quality and unreliable, this undermine the development
of accessing clean and safe water since constructed infrastructure are being destroyed by natural
phenomenon or human activities, also poor design, operation, maintenance and management is
a common barrier of improvement in accessing supply of clean water

13
 • Floods and droughts

Droughts and floods are problems that almost are uncontrollable in poor countries and their
coexistence poses a potent threat to environmental health, these situations cannot eradicate
rather than to be managed. Heavy rains and floods cause high turbidity and affecting the quality
of water, also they usually having high pressure hence destruct largely water infrastructures and
drainages as long as they are poor and cannot withstand critical situations. Transfer of the
surplus rains water to areas of water deficit is a potential possibility for controlling floods, and
s would also help create additional irrigational potential, the generation of hydropower, as well
as overcoming regional imbalances (WMO, 2007).
Drought is a natural feature which results from the lack of precipitation over an extended period
of time, it affects more than 40% in water supply system and also causing plants and animal
suffocation as well as social disruption (Rangachari, 2007). Absence of active alternative
sources of water that are annually functionality and absence of enough storage water devices
and reservoirs that can supply enough water during droughts is undermining the development
of water sectors in developing countries.
• Contamination of water sources

Populations is rapid growing in developing countries and those attempts to obtain potable water
from a variety of sources, such as aquifers, groundwater, and surface waters, which can be
easily contaminated. Freshwater access is also inhibited by insufficient wastewater and sewage
storage and treatment. Improvement have been made over recent decades to improve water
access, but huge populations are still live-in conditions with very limited access to reliable and
clean drinking water.
• Poverty

Developing countries are poor, this is the main cause of poor water supply. It causing lack of
proper design, construction and maintenance of water supply schemes. Approximately 50% of
clean water produced are lost as non-revenue water due to leakage and poor protection of water
infrastructure, a lot of water schemes are abandoned and failing because of running out of funds
to manage schemes.
• Inadequate financing and low levels of investment

Very few amounts of water or wastewater utilities in the developing world recover adequate
operation and maintenance costs from customers and only a handful recovers debt service and

14
depreciation. Despite the importance of water for development, in a recent sample of 37
countries from Africa, 82% of governments indicated that financing was insufficient to reach
national targets for drinking water. The uncertainties brought about by political economy and
climate change are also considerable challenges (Duke University, 2018).
2.3.8 Strategies implemented to combat water challenges in developing countries

• Population growth control

• Climate change mitigation

• Improve distribution of infrastructure

• Develop and enact better policies and regulations

• Improve water catchment and harvesting technologies

• Increasing efficiency of recycling wastewater

2.4 Sanitation

Sanitation mostly refers to the promotion of hygiene and prevention of diseases by maintaining
sanitary conditions (clean drinking water and adequate treatment and disposal of human excreta
and sewage). The prevention of excreta with human contact is part of sanitation. It aims to
protect human health by preventing transmission of communicable water diseases and to
promote aesthetic environment (Gates foundation, 2010).
A sanitation system includes the capture, storage, transport, treatment and disposal or reuse of
human excreta and wastewater. (WHO, 2017) Reuse activities within the sanitation system may
focus on the nutrients, water, energy or organic matter contained in excreta and wastewater.
2.4.1 Types of sanitation system

There are two types of sanitation system

• On site sanitation system

• Off-site sanitation system

15
2.4.2 On site sanitation system

Is the sanitation system in which excreta and wastewater are collected and stored or treated on
the plot where they are generated (Tilley, 2014) Example: Pit latrines and septic tanks. This
system is often connected to faecal sludge management systems in which the faecal generated
onsite is treated at an off-site location. Wastewater (sewage) is only generated when piped
hence water supply is available within the buildings or close to them.
The groundwater pollution may cause by On-site sanitation as a major concern in many urban
and peri-urban areas when organized sewerage is lacked and where the drinking water
requirements are met from groundwater sources. The contamination is likely to take place in
the event of a pathway existing between a ground water source and an on-site sanitation facility.
The growing population has led to adopt the On-site sanitation system as compared to
conventional sewerage. The On-site sanitation system poses a significant adverse impact on the
groundwater quality in the long run. It assumes more importance when the geological settings
favor the migration of contaminants. The problem becomes alarming when the groundwater
table is shallow. The groundwater quality studies were reported by (NEERI, 2005) pertaining
to the impact of septic tanks. (Pujari my et al, 2007) found that the increased concentration of
nitrate and bacteria in groundwater near On-site sanitation system and showing the impact on
groundwater quality.
Advantages of on-site sanitation

• Low cost

• Small water demand

• No sewer networks

• Reliable techniques

• No energy necessary

❖ Disadvantages of on-site sanitation

• No control of performance

• Needs maintenance by users

16
• Large space required

• It is not well adapted to densely populated areas as the large space is required to build
onsite sanitation facilities.
•
2.4.3 Off-site sanitation system

Is a sanitation system in which excreta and wastewater are collected and conveyed away from
the plot where they are generated. An off-site sanitation system relies on a sewer technology
for conveyance.
Advantages of off-site sanitation

• High removal of organic matter, nutrients and pathogenic bacteria.

• Good adapted to urban areas.

• Good controllability.

• Space required for WWTP (0.5 - 2 sq.m/person).

Disadvantages of off-site sanitation

• High cost in investment and

operation.
• Requires highly skilled personnel.

• High water demand - for the operation of a sewer network high water
consumption is required to prevent sewer clogging.

17
 Energy and large machinery necessary.

• Materials are often not locally available.

2.5 Sewerage system

Sewerage system main part is made up of large pipes (sanitary sewers) that conveys the sewage from
the point source to the treatment or discharge point. It includes components such as receiving drains,
manholes, pumping stations, storm overflows, and screening chambers of the combined sewer or
sanitary sewer. Sewerage ends at the entry to a sewage treatment plant or at the point of discharge
into the environment. There is sanitary sewer that include gravity sewers (combined sewer, simplified
sewerage and storm drain) other sanitary sewer are not relying solely on gravity including vacuum
sewers.
2.5.1 Types of sewerage system

There are three main types of sewerage systems including: -

• Combined system

• Separate system

• Partially separate system

2.5.2 Combined system

Is the system of conveying sewage in which a single sewer is intended to carry both the domestic
sewage, industrial as well as surface and the stormwater flow. This type of system is mostly applied
or adopted to places where;
• Rainfall is even throughout the year.

• Both the sanitary sewage and the stormwater have to be pumped.

• The area to be severed is heavily built-up and space for laying pipes is not enough.

• Effective or quicker flows have to be provided.

• Sewers are laid along with the overall development of the area.

18
 ❖ Advantages
• Rainwater keeps sewage fresh, that make it easier and more economical for treatment
purpose.
• It helps in dilution, as the one of the methods of treatment

• Automatic flushing is provided by water.

• It is a simplest method of collection and house plumbing economies.

❖ Disadvantages

• The bigger size of the sewer would involve larger excavation.

• Overflowing under worst conditions may endanger public health.

• Cost of pumping and treatment would increase due to the large quantity of sewage to be
handled.
• The dry weather flow is a small amount of the total flow, the large size of the sewer would
often result in causing silting up due to low velocity of flow during the dry period of the
year.

2.5.3 Separate system

Is the type of sewer system that, the domestic sewage and industrial wastes are carried by one sewer
system whereas the storm and surface water are carried in another sewer system. This type of sewer
is adopted to places where;
• Rainfall is uneven.

• Sanitary sewage is to be pumped.

• The ground has steep slopes.

• Sanitary sewage is to have one outlet and other outlets for store or surface water is
available.
• If the system is laid before the area is developed.

19
 ❖ Advantages

• Being smaller in size, the sewers are economical.

• There is no risk of stream pollution as no storm overflows are to be provided.

• The quantity of sewage to be treated is small, the disposal or the treatment works can be
economically designed.
• If the pumping of sewage is necessary, the pumping cost would be much less compared to
the combined system.
❖ Disadvantages
• Risk of encroachment by unauthorized rainwater collection and consequent overflows of
sewage may be there.
• Maintenance costs of two systems are greater than that for one.
Self-cleaning velocity in the sewer cannot be assured unless it laid at a steep gradient thus
flushing shall have to be done. This may prove unsatisfactory and expensive.

2.5.4 Partially separate system

Is a modification of the separate system in which in this type of sewer the discharging of sewage
involves domestic sewage and industrial wastes also contain a portion of the surface drained from
back-paved yards and roofs of the house.

❖ Advantages

• It simplifies the drainage of the houses.

• It provides reasonable sizes of sewer and is economical.

• The rainwater provides some safeguard against silting in the sewer.

❖ Disadvantages

• Low velocity during the dry period.

• Storm overflows may be found necessary.

20
2.6 Design of the sewerage system

2.6.1 Predesign Activities

2.6.1.1 Preliminary Investigations

The preliminary investigations include gathering of data such as demographics, wastewater

production estimates and maps. This also includes an underground survey to locate obstacles such as
existing sewers, water mains, gas lines, electrical and telephone lines, and similar features. An
environmental review will be conducted to identify potential soil contamination from abandoned
waste disposal sites and service stations, to avoid any interventions in the sewerage system (Moser,
2001).
2.6.1.2 Surveying and Mapping

In order to prepare construction drawings, the following survey work must be conducted to identify
the location of streets, rights-of-way, basements and their, location of natural features such as streams
and ditches, and construction of elevation profiles. In addition, benchmarks must be established for
use during construction, that for sewer system layout, the map scale used is on the order of 1:1,000 to
1:3,000. For construction drawings, the map scale is on the order of 1:480 to 1:600. When there is
significant relief, contours are shown at intervals ranging from 250 mm to 3 m. Elevations of street
intersections, abrupt changes in grade, building foundations, and existing structures that new
construction must connect with are included on the map (Mackenzie L, 2010).
2.6.2 The Sewerage system Design Capacity

The fundamental prerequisite to begin the design of wastewater facilities (Sewerage system) is
the determination of its design capacity. This, in turn, is a function of the wastewater flow rates,
pipe sizes, choice of pipe materials and time (design period). The determination of wastewater
flow rates consists of five namely: - • Selection of a design period,
• Estimation of the population and commercial and industrial growth

• Estimation of wastewater flows

• Estimation of infiltration and inflow

• Estimation of the variability of the wastewater flow rates.

21
2.6.2.1 Selection of the Design Period

Design periods that are commonly employed in practice and commonly experienced life
expectancies. Normally, the design periods provide much explanations on how the certain
project or a designed facility would sustain the sizes of its functionality in terms of time and
the required capacity.
The table 2.1 below, describes various design periods for the design of wastewater facilities
(Metcalf & Eddy, 2003).
Type of facility Characteristics Design period Life expectancy

Treatment plants

• Fixed facilities  Difficult and 20 – 25 50+

expensive to
enlarge/replace

 Easy to

• Equipment refurbish/replace 10 – 15 10 – 20
Collection systems

 Trunk lines and  Replacement is 20 -25 60+

interceptors > 60 expensive and
cm difficult

 Laterals and  Easy to

mains > 30cm
refurbish/replace To 40 - 50

Development

(Build Out) full

22
2.6.2.2 Estimation of the population and commercial and industrial growth

The design should first consider the satisfaction of the future needs, since the designed project
is to fit the future requirements, hence time dependent. The project to be designed should
anticipate the population, industrial and commercial growths. Various population forecasting
methods could be of crucial use, as derived from the water supply variety of data can be
obtained to fit the project (Moser, 2001).
2.6.2.3 Estimation of wastewater flows

Normally, the design of the sewers in a conventional gravity sewerage consists of a series of
discharges from various sources, that are either indirectly or directly incorporated in the
sewerage system. The wastewater may be classified into the following components:
 Domestic or sanitary wastewater: This involves wastewater discharged from
residences, commercial (e.g., banks, restaurants, retail stores), and institutional facilities
(e.g., schools and hospitals).
 Industrial wastewater: The wastewater discharged from industries (e.g.,
manufacturing and chemical processes).
 Infiltration and inflow: This involves water that enters the sewerage system from
groundwater infiltration and storm water that enters the system from roof drains,
foundation drains, and submerged manholes.
 Storm water: Runoff from rainfall and snow melts in cold regions.

23
 Figure 2.3 components contributing to the quantity of waste water flowing in sewers

The determination of the key components of the sources provides an anticipated knowledge
regarding the estimations of the expected flow that may be incorporated in the sewerage system
as described below:

2.6.2.3.1 Domestic Wastewater Flows Residential Districts

Considering the proposed project is in a community with an existing wastewater collection

system, the community’s historic records may provide the best estimate of wastewater
production. Conversion of total wastewater flow to a per capita basis allows for the separation
of population growth from the growth in unit production of wastewater, thus installation of
temporary flow meters or nearby communities with similar demographics are good alternative
sources of data (ASCE, 1982).
When the demographics differ in some particular aspect such as a higher or lower density of
commercial facilities or a major industrial component, adjustment in the total wastewater
production will be appropriate. All the water withdrawn for use does not end up in the sewer
respectively. A rough estimate of 60 to 90 percent of the domestic water-withdrawal rate may
be used to estimate the production of residential wastewater (Metcalf & Eddy, 2003).

24
2.6.2.3.2 Commercial Districts and Institutional Facilities

Normally, estimates for commercial wastewater flows range from 7.5 to 14 m 3 /ha·d (Metcalf
& Eddy, 2003). The ranges are measured as the function of the area to which the sewerage
system has to offer as to obtain the flows.
2.6.2.3.3 Industrial Wastewater Flows

If the water requirements of the respective industry are known, estimates on wastewater flow
may be made by assuming about 85 to 95 percent of the water consumed becomes wastewater
assuming no internal water recycled is to be practiced.
Normally, typical design value for estimating the flows from industrial districts that have few
wet processes is in the range 7.5 to 14 m 3 /ha·d for light industrial development and 14 to 28
m 3 /ha·d for medium industrial development (Metcalf & Eddy, 2003).
2.6.2.3.4 Infiltration and Inflow

Infiltration: Refers to the water entering a sewerage system, including sewer connections and
from the ground through the pipe joints, connections, or defective pipes manhole walls (Federal
Register, 1974).
Inflow: The water discharged into a sewer system, including service connections from such
causes as leaders, basement, yard, and area drains, springs, swampy areas, storm water; surface
runoff; street wash water; or drainage, the inflow of the water alters much the flowrates in the
sewers especially during the wet seasons, hence altering the flows in the sewers and increasing
chances of overflowing.
2.6.2.4 Variations of flow rates in sewers

Surprisingly, the flows in the open channel sewer hydraulics is not constant. Since the system
is not completely confined hence, much factors can pose an appreciable variation in the
flowrates in sewer as follows: -
2.6.2.4.1 Domestic Wastewater Flows

The water consumptions and wastewater production normally change appreciably with the
seasons, days of the week, and the hours of the day. Fluctuations are greater in small
communities than in large communities, and during short rather than long periods of time.
Variations in wastewater flow rates is normally reported as a factor of the average day.

25
2.6.4.2.2 Commercial, Institutional, and Industrial Wastewater Flows

If the commercial, institutional, and industrial wastewater flows make up a significant portion
of the average flows at least 25%, Peak factors for each category sector should be processed
unconnectedly (Mackenzie L, 2010).
2.6.4.2.3 Infiltration Flows

The amount of groundwater flowing from a given area varies from a negligible amount for a
highly impervious area to 25 to 30 percent of the total rainfall for a pervious area with a sandy
penetrable subsoil. The infiltration of groundwater into the sewer may range from 0.01 to more
than 1.0 m 3/d·mm.km (Metcalf & Eddy, 2003)
Alternatively, some curves may serve as a means of estimating peak infiltration flows, basing
on empirical researches. These curves may be considered conventional for most new sewer
designs.

Figure 2.4 Graph for the determination of peak flows from the daily flow rate

2.6.3 Design Criteria for the Conventional gravity sewers

The designing of the conventional gravity sewers, normally involves the following parameters
including: -
• Location

• Pipe Size

• Slope

26
 • Alignment
2.6.3.1 Location

In the construction for new residential areas, the sewer is commonly placed on one side of the
roadway in the right-of-way. Connections to the sewer from buildings on the opposite side of
the street may be made by boring under the street.

Figure 2.5 Separated sewer system

In vertical planes the sewers should be at such a depth that they can receive the contributed
flow by gravity. Where houses have basements, the invert of the sewer is placed a minimum of
3.0 to 3.5 m below grade. Where there is no basement, it is placed to provide sufficient cover
to protect the pipe from live load and dead load damage the sewer invert depth of 1.8 to 2.4 m
below grade when basements are not present (GLUMRB, 2004).
2.6.3.2 Pipe Size

The sewers normally are designed for a half flow operation, so as to provide a space for
allowing the emitted gases from the bacterial decomposition reactions. Also, the pipes are
designed on basis of the allowable factored flows as follows: -
 All main sewers should start with pipes not less than 200mm (MoW, 2020).

 Any new sewer connection should use plastic pipes of diameter not less than 150mm
for further extensions and only 5 users are compatible.
 Lateral sewers, incorporating more than 5 sewer connections and that may need further
extensions in future should involve plastic pipes of diameter not less than 200mm.

27
  Commercial and public sewer connections at lodges, hotels, business centers,
institutions, industries, apartments and others should use plastic pipes of not less than
200mm.
2.6.3.3 Slope

Slopes in sewers should be designed to maintain self-cleansing velocities at all rates of flow,
for construction, or to control sewer gases, that may lead to the crown corrosion. To prevent
deposition of mineral matter, a mean velocity of 0.75 m/s is required (Metcalf & Eddy, 2003).
Normally, sewers 1.2 m and larger should be designed and constructed to give mean velocities,
when flowing full of not less than 0.9 m/s. Oversizing sewers to justify flatter slopes is
prohibited, since the use of larger pipes at flatter slopes will reduce the velocity well below the
self-cleaning velocity.

Figure 2.6 Hydrogen sulphide gas causing corrosion in the pipes when combining with the
water
The flow velocity below the self-cleansing one normally facilitates the erosive action of the
material suspended in the wastewater depends on the nature of the material and the velocity at
which it is carried along, such that the erosive action determines the maximum safe velocity of
the wastewater to a maximum mean velocity of 2.5 to 3.0 m/s at the design depth of flow will
not damage the sewer (Metcalf & Eddy, 2003). In case, velocities are greater than 4.6 m/s
special monitoring must be made to protect against displacement by erosion and impact.

28
2.6.3.4 Alignment

Generally, sewers less than or equal to 600 mm in diameter must be laid in straight alignment
between manholes. Curvilinear alignment of sewers large than 600 mm may be permitted if
compression joints are specified. Slopes must be increased with curvilinear alignment to
maintain a minimum velocity above 0.6 m/s for sanitary sewers, 0.7m/s for partially combined
sewers and 1m/s for the storm sewers. The recommended practice is to use extra manholes and
straight alignment between manholes (Mackenzie L, 2010).
In case, of the change in pipe size a smaller pipe joins a larger one, the invert of the larger sewer
should be lowered sufficiently to maintain the same energy gradient. In no instance should a
larger pipe discharge into a smaller pipe. Even though a smaller pipe at a steeper slope may be
able to carry the larger flow, there is at high potential for objects that will travel freely in the
larger pipe to obstruct the smaller pipe, hence blockage of the sewers and overflow.

2.6.4 Profile of sewer system

The vertical profile is drawn from the survey notes for each sewer line. All longitudinal sections
are indicated with reference to the same datum line. The vertical scale of the longitudinal
sections are usually magnified ten times the horizontal scale. The profile shows ground surface,
tentative manhole locations, grade, size and material of pipe, ground and invert levels and extent
of concrete protection, etc. At each manhole the surface elevation, the elevation of sewer invert
entering and leaving the manhole are generally listed.
2.6.5 Plans and Nomenclature

The following procedure is recommended for the nomenclature of sewers: -

First distinct number such as 1, 2, 3, etc., is allotted to the manholes of the trunk sewers
commencing from the lower end (outfall end) of the line and finishing at the top end.
Manholes on the mains or sub mains are again designated numbers 1, 2, 3, etc., prefixing the
number of the manhole on trunk/main sewer where they join. Similar procedure is adopted for
the branches to branch main; the similar procedure is also done on the manholes from further
branches to the main branch when all the sewer lines have been connected to the main line If
two branches, one on each side meeting the main sewer or the branch sewer, letter ‘L’ (to

29
represent left) or letter ‘R’ (to represent right) is prefixed to the numbering system, depending
on the direction of flow.
If there is more than one sewer either from the left or right, they are suitably designate as L1,
L2, L3, or R1, R2, R3, the subscript refers to the line near to the sewer taking away the discharge
from the manhole
The first numeral (from the left) is the number of the manhole on the trunk sewer. The numerals
on the right of this numeral, in order, represent the manhole numbers in the main, sub main,
etc., respectively.
The first letter immediately preceding the numeral denotes the main and that it is to the right of
the trunk sewer. Letters to the left in their order represent sub main, branch respectively.
2.6.6 Sewer network layout

The sewers should be shown as thick lines and the manholes as small circles in the plan. In the
section, the sewer may be indicated by a line or two lines depending upon the diameters and
scales adopted. Grade, size and material of pipe, ground and invert levels and extent of concrete
protection should be indicated.
In case of design of sewer network using computer programme, there is no restriction in the
nomenclature of the sewers and manholes as required for the manual design. It is sufficient to
give node numbers as well as pipe (link) numbers in any manner in the sewer network for design
of the network for using computer software.
2.6.7 Hydraulic formulas for the design of sewers

The sewers are generally designed as open channels except when it is specially required to
design them as conduits carrying sewage under pressure as in the case of inverted siphons.
Thus, various empirical formulae which are used for the design of open channels are used for
the design of sewers.
The following empirical hydraulic formulae are commonly used for the design of sewers:

Chezy’s Formula

Chezy (1775) gave the following formula for velocity of flow:

V= C

Where:

30
 • V = velocity of flow (m/s)

• R = hydraulic mean depth or hydraulic radius (m)

• S = slope of the sewer or hydraulic gradient

• C = Chezy’s coefficient

The hydraulic mean depth or hydraulic radius R is given by the following expression:

𝑊𝑒𝑡𝑡𝑒𝑑 𝑐𝑟𝑜𝑠𝑠 𝑠𝑒𝑐𝑡𝑖𝑜𝑛 𝑎𝑟𝑒𝑎 (𝑚2 )

R= 𝑤𝑒𝑡𝑡𝑒𝑑 𝑝𝑒𝑟𝑖𝑚𝑒𝑡𝑒𝑟 (𝑚)

The Chezy’s coefficient C depends on various factors such as: -

• Roughness of inner surface of sewer

• Hydraulic mean depth

• Size and shape of sewer

The value of Chezy’s coefficient C can be obtained by using: -

• Ganguillet-Kutter formula

• Bazin formula

Ganguillet-Kutter Formula

Two Swiss engineers Ganguillet and Kutter (1869) gave the following expression for Chezy’s
coefficient C;

0.00155 1
23+ +
𝑆 𝑛
C= 0.00155 𝑛
1 +(23+ )
𝑆 √𝑅

Where:

• R = hydraulic mean radius

• S = slope of the sewer or hydraulic gradient

31
 • n = roughness coefficient or rugosity coefficient (Kutter’s n)

The value of n varies widely depending upon the nature of inside surface of the sewer and its
condition. Values of n for different types of surfaces commonly encountered in practice are
given in table below;
Table 2.2: Values of roughness coefficient ‘n’ for use in Kutter’s and Manning’s formulae

Source: (Vemuri, 2012)

Bazin’s Formula:

Bazin (1897) gave the following expression for Chezy’s coefficient C:

157.6
C= 𝑚
1.81+
√𝑅

32
Where:

• R = hydraulic mean radius

• m =Bazin’s roughness coefficient

Some of the values of m proposed by Bazin are given in table 2.3 below: -

Table 2.3: Values of Bazin’s for various surface material Source: (Vemuri, 2012)

Manning’s Formula:

Manning (1889) gave the following formula for velocity of flow-

Where:

• V = velocity of flow (m/s)

• R = hydraulic mean radius

• S = slope of the sewer

2.6.8 Construction of Sewer

The basics of sewer construction is lateral in the ground, initial elevation is determined and an
ending elevation is suggested accordingly to the minimum slope required to enhance the self-
cleansing velocity in a sewerage system. After the trench is excavated, when entering an open

33
trench, the pipe layer prepares the trench on its bottom by removing loose dirt and grading the
trench bottom smoothly to allow for proper flow of sewage contents within the pipe.
It is required to ensure that the material beneath the pipe is solid enough such that the pipe does
not “sag” after it is backfilled. Normally, if the actual ground beneath the new pipe is not
disturbed and graded properly, the pipe will be adequately supported by the ground that it is
posed. But if the original ground is over excavated, however, it will need to install compacted
sand (soil) or gravel bedding beneath the pipe in order to provide support to the pipe. Once the
ground is well prepared, pipes are laid on the stabilized soil. In most cases, pipes are starting to
be laid on the low end of the trench and a work goes a way up to the connecting points. If “hub”
pipe is used, that is, pipe with an integral pipe built into the pipe, you should lay your first pipe
beginning on the low end of the run with the hub on the uphill side of the pipe.
If connection is using PVC pipe, both ends of the pipe should be primed with purple primer
prior to laying it. To connect the two ends of the pipe, you apply glue to the male and to the
female ends of the pipe, being careful to not allow dirt to stick to the glued ends of the pipe,
insert the male end into the female end and spin the pipe. Hold the two pipes in place for ten
seconds to ensure that they do not come apart.
Once the pipes are fully connected, then it is ready to “bed” the pipe. Then it should be placed
on sand or gravel around and over the pipe enough to just to cover the top of the pipe entirely.
Once this is complete, material around the pipe are compacted. It is important to pay attention
to this compaction process so that the pipe does not lift or compressed while you are compacting
because it may lead damage to the system. Once the bedding process is complete, all remained
pipes are laid on the same pattern. It is important to note that as you install more pipe, the level
or slope should be recognized more carefully such that no errors can be induced in the
construction and the chance of obstruction of the system is totally minimized.

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 Figure 2.7: Installation pipes in the trench

2.6.9 Testing of sewer

The testing of sewers constructed is necessary as it relieve any leakage, straightness, improper
joints or obstruction of sewers that may occur during laying of sewers. These defects may be
removed or repaired after detection during the testing. Thus, there are various tests through
which these defects in a system may be detected. These tests are: -

• Water test

• Air test

• Smoke test

• Test for Obstruction

2.6.10 Water Test

This test is carried out for sewer lines between two manholes. Plugging is done by rubber plug
at its lower end then rubber plug is connected with air blown and the upper end of sewer is
plugged with a connection to the funnel. Then sewer is filled with water and to maintain the
required head, water level in the funnel is kept 2 m above the upper end. This head varies with
the material used for construction of sewer.

35
In case of cast iron sewer, the head should be at 9m. The acceptable loss or head loss should
not exceed 2 litres/cm of length of the sewer. To perform this test sufficient amount of water
should be available.

Figure 2.8: Determination of head in a system

2.6.10.1 Air Test

When sufficient amount of water is not available, then air test is to be carried out to detect
abnormality in the functioning of the system.
Air is pumped into the pipeline, usually via a handpump with a control valve, until the reading
on the manometer is around 125 – 150mm. The set-up is then left for 5 -10 minutes to allow
for temperature recognized on within the pipe before the pressure is reduced to exactly 100mm
on the manometer scale.
The manometer is then monitored for a period of 5 minutes; the level of water in the manometer
should not fall below the 75mm mark during this period. This is termed to be a ‘pass’ and the
pipeline is declared satisfactory and can be backfilled. However, if the level in the manometer
does fall below the 75mm mark, then the equipment should be checked and cleaned and the
pipeline examined either for leaks or defects.
If there are any problems are identified, they should be repaired properly before re-testing the
system.

36
 Figure 2.9: Sample of air test set up

2.6.10.2 Smoke Test

The main purpose of the smoke testing is to find potential points of inflow and infiltration in
the sanitary sewer system that could lead to high flows during a storm.
Smoke testing forces smoke-filled air through a sanitary sewer line. The smoke under pressure
will fill the main line plus all connected sections and then follow the path of any leak to the
ground surface, quickly revealing the source of the problem. Only enough force to overcome
atmospheric pressure is required.

Figure 2.10: Example of the smoke test

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2.6.11 Test for Obstruction

For straightness or obstruction of pipe, this test can be used. There are many methods for
obstruction or straightness test, these are;
1. To check the obstruction of sewer pipe, a ball of suitable diameter is rolled down
from upstream side. The diameter of ball should be less then the diameter sewer. If
there is no obstruction, the ball can be taken out at downstream side.
2. The straightness can also be checked by placing a lamp at one end and a mirror at
the other end. If the full circle of light is visible at other end, then the sewer is
straight and there is no obstruction. If there is any obstruction within the sewer line,
it can also be traced out.
3.8.6 Sewer appurtenances

Sewer appurtenances are the various accessories on the sewerage system and they are necessary
for the efficient operation of the system. These includes man holes, lamp holes, street inlets,
catch basins, inverted siphons, and so on.
2.6.12.1 Man-holes

• Man-holes are the openings of either circular or rectangular in shape constructed on the
alignment of a sewer line to enable a person to enter the sewer for inspection, cleaning
and flushing.
• They serve as ventilators for sewers, by the provisions of perforated man-hole covers.
Also, they facilitate the laying of sewer lines in convenient length.

Man-holes are provided at:

• All junctions of two or more sewers,

• Whenever diameter of sewer changes,

• Whenever direction of sewer line changes

• When sewers of different elevations join together.

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 Figure 2.11: A diagram showing manhole structure

3.8.6.2 Special Man-holes

• Junction chambers

Man-hole constructed at the intersection of two large sewers.

• Drop man-hole

When the difference in elevation of the invert levels of the incoming and outgoing sewers of
the man-hole is more than 60 cm, the interception is made by dropping the incoming sewer
vertically outside and then it is jointed to the man-hole chamber.

39
 Figure 2.12: double manhole Medford mass

• Flushing man-holes

They are located at the head of a sewer to flush out the deposits in the sewer with water.

Figure 2.13: A picture of flush man-hole

• Lamp-holes

Lamp holes are the openings constructed on the straight sewer lines between two man-holes
which are far apart and permit the insertion of a lamp into the sewer to find out obstructions if
any inside the sewers from the next man-hole.

Figure 2.14: Types of lamp-holes

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 • Street inlets

Street inlets are the openings through which storm water is admitted and conveyed to the storm
sewer or combined sewer. The inlets are located by the sides of pavement with maximum
spacing of30m.

Figure 2.15: Street inlet alongside the road

• Catch Basins

Catch basins are small settling chambers of diameter 60 – 90 cm and 60 – 75 cm deep, which
are constructed below the street inlets. They interrupt the velocity of storm water entering
through the inlets and allow grit, sand, debris and so on to settle in the basin, instead of allowing
them into sewer:

Figure 2.16: An example of catch basin

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Inverted siphons

These are depressed portions of sewers, which flow full under pressure more than the
atmospheric pressure due to flow line being below the hydraulic grade line.
• They are constructed when a sewer crosses a stream or deep cut or road or railway line.
• To clean the siphon pipe sluice valve is opened, thus increasing the head causing flow.
• Due to increased velocity deposits of siphon pipe are washed into the sump, from where
they are removed.
2.6.13 Cleaning and ventilation of sewers

Generally. It involves their cleaning to keep them free from any clogging and to carry the repairs
to the damaged portions, it is necessary in order to make the sewerage system function
efficiently. Frequent inspection, supervision, measuring the rate of flow, cleaning and flushing
repairing the leaking joints

Ventilation of sewers

Sewerage system can be ventilated by the following means;

• Use of ventilating columns

• Use of ventilating manhole covers

• Proper design of sewers

• Use of mechanical device

Artificial ventilation

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 Figure 2.17: Ventilating column

2.7 Maintenance of sewerage system

The proper maintenance and operation of the sewerage system is essential if the systems are to
achieve their designed objectives. There are some good practice and guidance to assist when
maintenance of sewerage system is taking place.

Maintenance Objectives

The objectives for proper maintenance and operation include:

a) To offer a quality of service that is acceptable, having regard to costs and to effects on
the environment, and to remedy recognized deficiencies.
b) To monitor the capacity of the system and to restore the flow capacity by removal of
excessive accumulation of silt and grease
c) To monitor and maintain the structural integrity of the system;

d) To prevent excessive infiltration and inflow;

e) To attend to complaints of blockage, flooding and damage to sewerage systems; and

f) To provide feedback on the need for planning and implementation of improvement and
upgrading works.

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2.8 Transfer station for waste water treatment plant

Transfer stations or underground holding tanks act as intermediate dumping points for faecal
sludge and septage when it cannot be easily transported to a Semi-Centralized Treatment
facility. A vacuum truck is required to empty transfer stations when they are full.
Sewer discharge stations are similar to transfer stations, but instead of simply being a holding
tank, the stations are directly connected to the sewer transporting the sludge to a semicentralised
treatment facility.

Figure 2.18: discharging the desludged faecal sludge to the decentralized treatment plant

2.8.1 Mobile transfer stations

Mobile transfer stations are nothing more than larger tanker trucks or trailers that are
deployed along with small vacuum trucks and motorcycle or hand carts. The smaller vehicles
discharge to the larger tanker, which then carries the collected sludge to the treatment plant.
These work well in scheduled desludging business models.

44
2.8.2 Fixed transfer stations

Fixed transfer stations are dedicated facilities installed strategically throughout the municipality
that serve as drop off locations for collected faecal sludge. They may include a receiving station
with screens, a tank for holding the collected waste, trash storage containers, and wash down
facilities
Transfer stations reduce transport distance, may encourage more community-level emptying
solutions and prevent illegal dumping. The moderate capital costs may be offset with access
permits and the construction and maintenance can create local income. However, expert design
and construction supervision are necessary. A transfer station consists of a parking place for
vacuum trucks or sludge carts, a connection point for discharge hoses, and a storage tank. The
dumping point should be built low enough to minimize spills when labourers manually empty
their sludge carts.
Additionally, the transfer station should include a vent, a trash screen to remove large debris
(garbage) and a washing facility for vehicles. The holding tank must be well constructed to
prevent leaching and/or surface water infiltration. Furthermore, transfer stations can be
equipped with digital data recording devices to track quantity, input type and origin, as well as
collect data about the individuals who dump there. In this way, the operator can collect detailed
information and more accurately plan and adapt to differing loads
Transfer stations have both advantages and disadvantages as a component of wastewater
collection system:
Advantages
• Makes sludge transport to the treatment plant more efficient, especially where
small-scale service providers with slow vehicles are involved.
• May encourage more community-level emptying solutions.

• May reduce the illegal dumping of faecal sludge.

• Costs can be offset with access permits.

• Potential for local job creation and income generation.

Disadvantages

• Requires expert design and construction.

• May cause blockages and disrupt sewer flow.

45
 • Sludge requires secondary treatment and/or appropriate discharge.

• Requires an institutional framework taking care of access fees, connection to

sewers or regular emptying and maintenance.
• Can lead to odors if not properly maintained.
2.8.3 Health aspects/acceptance

Transfer stations have the potential to significantly increase the health of a community by
providing an inexpensive, local solution for faecal sludge and septage disposal. By providing a
transfer station, independent or small-scale service providers are no longer forced to illegally
dump sludge, and homeowners are more motivated to empty their pits. When pits are regularly
emptied and illegal dumping is minimized, the overall health of a community can be
significantly improved. The location must be carefully chosen to maximize efficiency and
minimize odors and problems to nearby residents
2.8.4 Costs considerations

The moderate capital costs may be offset with access permits and the construction and
maintenance can create local income. The system for issuing permits or charging access fees
must be carefully designed so that those who most need the service are not excluded because
of high costs, while still generating enough income to be sustainable and well-maintained. Also,
the costs for maintenance, observation and operation of the facility must be considered.
2.8.5 Operation & maintenance

Screens must be frequently cleaned to ensure a constant flow and prevent back-ups. Sand, grit
and consolidated sludge must also be periodically removed from the holding tank. There should
be a well-organized system to empty the transfer station; if the holding tank fills up and
overflows, it is no better than an overflowing pit. It is important, that there is a person or
organization responsible who organizes the logistic of the facility.
The pad and loading area should be regularly cleaned to minimize odors, flies and other vectors
from becoming nuisances. It should be ensured that the sludge from transfer or sewer discharge
stations is treated in an appropriate secondary treatment facility (e.g. planted or unplanted
drying beds, anaerobic digestion or composting large scale) and not be illegally dumped. Also,
the sewers need to be inspected periodically to avoid blockages.

46
2.8.6 Applicability

Transfer stations are more useful in areas with dense population where there are discharge
points for faecal sludge, whereas establishing multiple transfer stations may help to reduce the
incidence of illegal sludge dumping and promote emptying market.
Transfer stations are especially adequate where small-scale sludge emptying takes place (i.e.,
Where sludge is manually removed from pits and septic tanks). In big cities, they can reduce the
costs incurred by truck operators by decreasing transport distances and waiting times in traffic
jams. Local service providers can discharge sludge at transfer stations during the day, while large
trucks can empty the tanks and go to the treatment plant at night when traffic is light.
Fecal sludge management
Fecal sludge (also called sludge) is excreta from a non-sewered sanitation technology (also called
on-site sanitation technology, like a pit latrine or septic tank) that may also contain used water,
anal cleansing materials, and solid waste. Fecal sludge should not to be confused with wastewater
that has been transported through a sewered system.
Also, Fecal sludge is a mixture of human excreta, water and solid substances such as toilet papers
or other cleansing materials as well as menstrual hygiene materials that are disposed of in pits,
tanks or vaults of onsite sanitation systems. (Nikiema et al 2018) Fecal sludge comprises all
liquid and semi-liquid contents of pits and vaults accumulating in onsite sanitations installations,
namely unsewered public and private latrines or toilets, and septic tanks. Fecal sludge production
increases with the increase of population(urbanization). Fecal sludge accumulation depends on
the filling capacity of onsite facilities and the rate of addition or degradation. (foxon et al, 2011).
Faecal sludge management is the collection, transportation and treatment of faecal sludge, that is
a mixture of human excreta, water and solid wastes which are disposed from onsite sanitation
system that include, pit latrine, septic tank and others. Faecal sludge management services are
usually provided by formal and informal private sector services providers, local governments,
water authorities and utilities.
The collected faecal sludge may be transported to treatment plants using a vacuum truck, a tank
and pump mounted on a flatbed truck, a small tank pulled by a motorcycle or in containers on a
hand cart (Reymond, Ph. and Zurbrügg, C,2014). This service is provided to the areas with high
population that are not connected to the sewerage system and the covering and rebuilding of pit
latrines is not possible.

47
Generally, the purpose of faecal sludge management is the same as for any sanitation system, as it
is to contribute to public health, and in particular environmental health.
Faecal sludge management can have the following benefits;
• Reduce the potential for human contact with faecal borne pathogens by improving the
functioning of onsite sanitation systems.
• Minimize odors and nuisances, and the uncontrolled discharge of organic matter from
overflowing tanks or pits.
• Reduce indiscriminate disposal of collected faecal sludge.
• Stimulate economic development, and job creation and livelihood opportunities.
• Production and sale of the end-products of the sludge treatment process. These products
may include recycled water for agriculture and industry, soil conditioners from composting or co-
composting materials, and energy products such as biogas, biodiesel, charcoal pellets, industrial
powdered fuel, or electricity.

2.9 Faecal Sludge Management Chain

Faecal sludge management have a complete chain which include, the storage, collection,
transport, treatment and safe end use or disposal of faecal sludge.

Figure. Show faecal sludge management chain.

This chain can be weakened by various factors include;
• Narrow lanes and paths leading to houses cannot be able to accessed by trucks for
collecting and transport of faecal sludge.
• Lack of legitimate faecal sludge discharge locations or treatment facilities.

48
• Operators not able to afford the transport of faecal sludge over long distances to treatment
facilities.
Typical duties and responsibilities of fecal sludge management.
Typical duties and responsibilities of FS collection and transport service providers include those that
occur prior to the FS removal, the FS collection itself, and the subsequent transportation to the
treatment facility. Some activities that would ideally be performed prior to sludge removal tasks
include the following
A. Interfacing with clients
❖ The operator who collects the FS is the only person interacting with residents regarding their
onsite systems, thus, needs to be knowledgeable of the systems, and be able to communicate
the benefits of sludge removal to the clients
❖ Since the operators see the systems when they are full and empty, they should use the
opportunity to assess the functionality and needs for repair in relation to proper operation
that might increase the lifespan.
❖ Operators can troubleshoot the system and be a valuable source of information about FSM in
the community
❖ Services providers can work with the LGA to disseminate information, such as pamphlets on
the proper care of septic tanks, or information on how unimproved latrines might be
updated/improved
❖ Service providers work with residents to determine the locations of the onsite systems
requiring emptying, identify access manholes, and identify where to place their emptying
equipment
❖ Therefore, cooperation and communication with residents at the household level is critical,
and makes the emptying process more efficient.

An example, where an emptying operation is in process, with the service provider entering a courtyard
to access the onsite system.
B. Locating the system to be emptied

Normally, the location of the onsite sanitation system that needs emptying is not obvious; for example,
septic tank is typically buried and their location may not be known, and if latrines are grouped it is
not always apparent for which one the service is hired
Methods to locate sanitation systems tanks include the following
❖ Asking the client, the location of the tank

49
 ❖ If not known, looking for obvious indicators like manholes, tank lids or exposed concrete
slabs
❖ Identifying sewer cleanouts outside or under the building (the direction of the cleanout might
indicate the location of the septic tank)
❖ Hammer a metal probe (e.g., 1 cm diameter metal rod) gently into the ground and determine
by feel if rocks or tanks are encountered.
❖ Looking for depressions in the yard around the house, which may signify the location of an
underground tank
❖ If the house is on piers, looking underneath to inspect the plumbing and determining if sewer
lines or vent stacks are buried, they might indicate the location of the tank
❖ If the house is constructed on top of a concrete slab, gently taping with an iron bar on the
floor to reveal hallow sound.
C. Determining accessibility

Determining the accessibility of septic tanks or pit latrines involves first determining if the site itself
is accessible, and then assessing if each compartment of the system can be accessed to accommodate
the FS emptying service.
The following are typical factors that determine accessibility of a site:
• Width of the road

If using a truck, roads need to be wide enough to accommodate the truck or sludge emptying
equipment.
• Access to the site

Does neighboring property need to be accessed to reach the system; Are there any weather-related
concerns regarding site access, such as stream, crossings, or roads which are impassable during heavy
rain event.
• Location of the site

If a truck or cart is being used, is the onsite system located close enough to the parking area to facilitate
the emptying operation; Is the client’s location close enough to a FS treatment plant (FSTP) to
accommodate transport.

50
 D. Tools of the trade

The sludge emptying process requires that the service provider has access to a number of tools and
that the equipment is properly used and maintained. The specific tools used by service providers vary
based on the technology used and the availability on the local market. Some tools common to all
service providers include:
❖ Shovels, pry bars and probes to locate tanks and manholes;
❖ Screwdrivers and other hand tools to open manholes and access port lids;
❖ Long handle shovels and buckets which may be necessary to remove solids that cannot
otherwise be removed;
❖ Hooks to remove non-biodegradable solids;
❖ Hoses for FS pumping as well as for adding water to tanks if available;
❖ Safety equipment including:
• wheel chocks to prevent the vehicle from moving when parked;
• personal protective equipment such as hardhat, face protection, eye protection, boots
and gloves;
• disinfectants, barriers, sorbents and bags for cleaning up and collecting spilled
material.

2.10 Properties of Faecal Sludge In Relation To Collection And Transportation.

FS can be removed from septic tanks or latrines through the use of manual and mechanized
technologies that may rely upon hand tools, vacuum trucks, pumping systems or mechanical augers.
The specific method utilized will be based on the type of onsite system, accessibility of the site, type
of equipment owned by the service provider, and level of expertise. Awareness of the properties of
faecal sludge is necessary in order to understand the challenges faced in the collection and transport.
These properties are primarily influenced by the
• water content
• sludge age
• presence of non-biodegradable material
• organic material

For example, within a pit latrine containment system, recently deposited FS found in the top portion
typically has higher water and organic content than that found in deeper layers and consequently a
lower density. The top layer is therefore less viscous and relatively easy to collect. The absence of

51
water and organic content in the deeper, older and more digested layers make collection much more
difficult, this condition is frequently referred to as thick. Depending on the collection method, thick
FS needs to have water added to facilitate pumping. This suggests that the deposition period could be
used as a strong indicator of the ease with which FS could be collected.

52
 CHAPTER THREE

3.0 METHODOLOGY

3.1 Introduction

In this study a qualitative method was used to obtain information on current sewerage, drainage
system and fecal sludge management at Sinza D street. In this project different methods were
used to collect information related Sewerage and fecal sludge management at Sinza D street.
These methods include data collection, data analysis and data interpretation.

3.2. Data collection

Data collection method includes the following techniques

3.2.1 Site visiting and Physical observation

On the site visiting, different areas at Sinza D were visited to observe, study and collect useful
information concerning the existing situation on sewerage and fecal sludge management, the
intention was to see the followings;
• The lay out/network of the sewers used for the collection of sewage and fecal sludge at
Sinza D.
• Sanitation practices, a factor which can be used to determine water consumption and
waste water generated at Sinza D.
• Topography of the area, which is one of the factors to be considered in sewerage and
fecal sludge management design.
• Social, economic and institutional activities which relies on water. These activities also
are helpful in determining water demand and waste water generated.
3.2.2 Questionnaire

A questionnaire is a set of printed or written questions with a choice of answers, devise for the
purpose of a survey or statistical study. Questionnaire was conducted by asking series of well-
prepared technical questions to the respondents for the purpose of gathering information. The
aim of administering questionnaires was to obtain data basing on personal experience on water
supply and sanitation in relation to sewerage, drainage systems and fecal sludge management
at Sinza D. In this method random sampling was the way of gathering information, where a

53
selected sample represented the whole community at Sinza D. 100 questionnaire were chosen
as respondent’s sample, where by the number of representative questionnaires was selected
depending on 10% of number of households, of which most stay in clusters of households

Figure 3.1 Group members conducting questionnaire to the dwellers

3.2.3 Interview

Interview was conducted by asking different interview questions to the local government
officials especially chairperson on water supply such as water sources, water demand, water
consumption, existing sewer systems and how they practice fecal sludge management which
are the main concerns of our case study at Sinza D.
3.2.4 Checklist
This is the set of tools, questions, and details that ensures the questionnaires correlates with
existing situation at the study area, it is normally prepared on the basis of the questionnaires
prepared for collection of data.
3.3. Data analysis

This technique generally includes the analysis of information that were obtain at the site. This
information is such as number of households, population, the existing sewerage and drainage
system. The analysis of these information involved charts, graphs and bars that represented the
data collected at the site.

54
3.4. Data interpretation

Data that were collected direct from the site were analyzed and later interpretated in a more
useful form. These data were processed by using excel tables and formulas. Moreover, data
were presented in pie-charts, graphs and mathematical calculations in order to obtain in details
different findings that is water usage, sanitary and sewer and drainage systems available at the
site and how management of fecal sludge is practiced at Sinza D. Ultimately these data were
useful in designing of sewerage system and fecal sludge management for the whole community,
To obtain the design of our case study, the analyzed data were fed into several design
software’s, mathematical calculations, and design considerations, such as:

• Software’s
ArcGIS 10.7.1
Sewer cad V8i
Storm cad V8i
Google earth pro 2020
Microsoft excel 2019
AutoCAD civil 3D 2018

• Mathematical calculations
Table 3.1 mathematical formulas used in this report
POPULATION FORECASTING
𝑛
𝑟 The Geometric Progression Method
Population growth, 𝑃𝑛 = 𝑃 (1 + ( 100 ))

WATER DEMAND ESTIMATION

The water demand = Population x Per capita The Population estimation method is
water demand chosen, as an estimate equivalent to
the Design manual, 2020 for water
supply.
WATER DEFICIT ESTIMATION

The total water demand – Standard Demand from the design period = Water Deficit

55
PEAK DAILY FLOW RATE
Average daily flow x PHF = Peak daily flow

COEFFICIENT OF RUNOFF ESTIMATION

Whereby;
𝐶1𝑎1+ 𝐶2𝑎2+ 𝐶3𝑎3 C = Total Coefficient of runoff
Coefficient of runoff, C = ( )
𝑎1 + 𝑎2 + 𝑎3
Cn = Coefficient of runoff at
Catchment n
A1 = Area of Catchment
SURFACE RUNOFF ESTIMATION BY RATIONAL METHOD
Whereby;
Surface Runoff Flow, 𝑄 = (𝐾𝐶𝐼𝐴) Q = Surface runoff
K = Conversional Factor
C = Coefficient of Runoff
I = Intensity of Rainfall
A = Area of Catchment
TRAPEZOIDAL SECTION DESIGN FORMULAE
Whereby;
𝐴 = 𝑏𝑦 + 𝑚𝑦 2 A = Trapezoidal Sectional Area
m = Side Slope
b = Breadth of the Section
y = Normal depth
Whereby;
𝑇 = 𝑏 + 2𝑚𝑦 T = Top width of the section
b = Breadth of the section
y = Normal Depth
m = Side Slope
POPULATION RATIO METHOD
The method is used to find an estimate of the Whereby;
population that is to be served by a certain lateral Po = Population at Area in Zone
in the Sewerage system design. Pn = Projected Population
Ao = Area in Zone

56
 𝑃𝑜 𝐴𝑜 An = Total Area in Zone
=
𝑃𝑛 𝐴𝑛

• Design considerations and criteria (Mackenzie L, 2010)

This table shows typical design criteria for gravity sewers

57
 This chart was used for determining the values of V/Vfull as well as the Q/Qfull values.

3.5 Site description

Sinza D is an administrative street of the Sinza ward in Kinondoni Municipal of Dar es Salaam
region. It is located at North Eastern Part of the Dar es salaam region with coordinates
6ᵒ47’14.73” S, 39ᵒ13’33.71” E and 39.32m from the sea level. It borders with the other streets
Kilimani, Sinza B, Sinza C and Sinza E.

The street consists of various human activities such as business and trading, transportation
activities, carpentry and other activities assisting earning of income for day to day lives of
people.

58
Figure 3.2 Topographical map of Sinza D area

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 CHAPTER FOUR

4.0 RESULTS AND DISCUSSION

4.1 Introduction

This chapter presents the current general situation of Sinza ‘D’ street in relation to water supply,
waste water and faecal sludge management. Information of geographical location, climatic
condition, population and social demographic data are well addressed, analyzed and
represented into charts and tables
4.2 Climatic condition

The climatic condition of Sinza ‘D’ is as follows;

4.2.1 Temperature

The area and generally the city experience a modified type of equatorial climate. It is generally
hot and humid throughout the year with an average temperature of 29ºC. The hottest season is
from October to March during which temperatures can raise up to 34ºC. It is relatively cool
between May and August, with temperature around 25ºC. (TMA, 2020)
4.2.2 Rainfall

Sinza ‘D’ experiences two rainfall seasons, December to January with an average rainfall of
111.07mm and March to May with an average rainfall of 195.08mm (Dar-es-salaam Master
Plan, 2010). The driest weather is in August when an average of 36mm (1.41in) of rainfall
occurs.

Figure 4.1 Amount of rainfall in different months of the year in Dar es salaam

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4.2.3 Topography and Soils

4.2.3.1 Topography

Topographical condition of Sinza ‘D’ consists of contours ranging from 32m- 49m with a slope
gradient ranging from 0 - 0.5% that is nearly level. Generally, land in Dar es Salaam consists
of geological fluvial marine deposits of sands and silt.

4.2.3.2 Soils

The type of soil found in the project area is sand soil which have high permeability rate due to
the nature of its grain size and arrangement.
4.2.4 Water table

The water table of Sinza ‘D’ area is high, it varies from 1.5m – 2m from the ground surface.
This is due to sand soil type. This makes the toilets to be full in small amount of time than the
desired designed time and hence increases the desludging costs.
4.3 Population

According to the street census held in 2020, Sinza ‘D’ has a total population of 13079 people
and 2180 households. The total number of men are 5650 equals to 43.2% and total number of
women are 7429 equals to 56.8%. The street consists of 975 houses with the total of 2180
households.

POPULATION
Men Women

43%

57%

Figure 4.2 Population Distribution in Sinza ‘D’

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4.4 Socio-Economic status

4.4.1 Social and public services

Sinza ‘D’ street as other streets in Ubungo municipal consists of number of social and public
services. The services and the number of social services present in Sinza ‘D’ are presented in
the table below.
Table 4.1 Number of social and public services facilities at Sinza D.
Services Number

Schools 6

Dispensary 3

Church 3

Mosque 1

Guest house 5

Bars & Hotels 9

4.4.2 Economic status

Quantitative analysis of the administered questionnaire shows that the residents at Sinza ‘D’
are engaged in several activities to support their daily lives. Most of the respondents are either
employed in government or non-governmental organizations (NGOs) other are self-employed
in either business or other commercial activities while the rest are unemployed at all.
Table 4.2 Economic status of residents in Sinza ‘D’
Economic status Number of respondents Percentage (%)

Employed by Government 32 32

Self Employed 57 57

Unemployed 11 11

Total 100 100

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However, the economic status based on an individual’s salary income can be categorized as

High income, medium income and low income.

4.4.3 Individuals income distribution
The income distribution of the study area according to the questionnaire conducted was greatly
the middle income ranging from 300,000 Tsh to 500,000 Tsh per month which was 54% of the
respondent answers. 32% of the respondents claimed that their monthly income ranges from
50,000 Tsh to 200,000 Tsh, 5% of the respondents had monthly income of more than 500,000
Tsh, whereas 9% of the respondents were not ready to mention their monthly income.

Income distribution (Tsh.)

5%
9%
50,000-20,000
300,000-500,000
32% 54%
Above 500,000
Unvieled

Figure 4.3: Individual’s income distribution

4.5 Water amenities and service

4.5.1 The major source of water and the supply.

The major source of water in Sinza ‘D’ is the surface water, that is the water from DAWASA
which originates from the lower Ruvu chini reservoir. The source takes 92% of the water used
in the study area according to the respondents.
Other alternative source of water in Sinza ‘D’ is the Underground water source, that is the water
from the shallow wells which were private or public owned. This source takes up to 8% water
used in the study area according to the respondents.

63
 Sources of water

8%
Surface water from
DAWASA
Shallow wells

92%

Figure 4.4: Water supply sources in the study area

In many cases, majority of the households (74%) were possessing the water supply taps
conveying water from DAWASA who supply water to others neighboring residents lacking
taps for water supply in their houses (26%). The water charges applied is Tsh 100 for a one
20Litres bucket.
Other source of water used in Sinza ‘D’ is Rainwater which is limited and only used in rainy
seasons for all the uses except for drinking and cooking due to the poor condition of the roofs
which are the primary rainwater catchment in the households.
4.5.2 Cost of water available

The cost for one unit of water for those having tap water from DAWASA is Tsh. 1650/= bill
paid per units in every month of use. The water payment within the households is Tsh.100/=
per bucket of 10L and 200/= per bucket of 20L for those lacking the water supply taps and buy
water in the neighbor houses.
From the respondents owning the water supply taps, 81% often pay around 15,000-20,000 Tsh
per monthly; implying that the taps give service to many users whereas only 8% pay around
5,000-10,000 Tsh per monthly implying that the consumption is very low which is due to a
smaller number of people to be served by the taps in the given area; and 11% pay around
20,000-50,000 implying that the area has high water consumption and were mainly commercial
and institutional areas.

64
Table 4.3 Water consumption per monthly
Price paid per Respondents Total units Implications on the
monthly (Tsh) (%) used water usage
15,000-20,000 81% 9-12 Taps provide service
to many users
5,000-10,000 8% 3-6 Private taps serving a
single household
20,000-50,000 11% 12-30 Commercial and
Institution
consumption

4.5.3 Availability of water

At Sinza ‘D’ many people do get water for a full time, but also some respondents complain of
shortage of water that is, they just get water periodically, from our result we observed that 91%
of the respondents get water full time and 9% of the residents get water periodically, that is they
either get water once in a day, or once in two up to three days. This may be caused due to the
maintenance in the water supply pipelines especially in the southern part of the study area near
Kilimani street.
4.5.4 Water quality

The quality of the water supplied to the case study area according to the respondent answers is
of satisfactory condition. 99% of the respondents claimed that the water supplied is of the good
and acceptable quality whereby only 1% claimed that there is the fluctuation of turbidity in the
supplied water.
4.5.5 Water treatment methods

Most of the households (89%) treats water by using the disinfectant, that is by using water
guards, only few households treat water by the means of boiling (7%), filtration method (2%)
or sedimentation (2%). Most of the people prefer the use of water guards due to the high costs
of charcoal for boiling the water and the wastage of time during boiling and cooling.

65
 Water Treatment methods
100%
89%
90%
80%
70%
60%
50%
40%
30%
20%
7%
10% 2% 2%
0%
DISINFECTANT BOILING FILTRATION SEDIMENTATION

Figure 4.5: Water treatment methods used by the households

4.5.5 Water storage facilities

For ensuring water is available all the time in the families together with the business areas,
different ways are used for storing the water which are the use of buckets, tanks, and plastic
containers. From the result 59% of the respondents use buckets as the storage facility, 6% use
tanks and 35% use plastic containers. The tank systems used were mainly the elevated and
ground plastic tanks of several capacities. The figures below showing the storage facilities used
at the households and the business areas.
Table 4.4 Water storage facility statistics
Storage facility Litres stored (L) Number of respondents Percentage
(%)

Bucket 20 59 59%

Drums 20 35 35%

Tanks 250-10000 6 6%

Total 100 100%

66
4.5.6 Water demand and consumption estimation

Water demand is the amount of water that a water user actually applies to a beneficial use,
within the terms of his or her water right and applicable law. Water supply at Manzese SINZA
D is aimed to meet daily requirements such as cooking, washing, bathing, commercial
operations such as bars, guest houses, shops.

Domestic daily water consumption

According to the questionnaire conducted, 85% of the respondents in households consumes

60L per day while 15% consumes more than 60L per day.
Water consumption at the case study area hence ranges from 3 to 4 buckets of water of 20 liters
each per person per day, leading to an average of 70 litres per person per day. Therefore, total
water consumption is

Total quantity of water used= Per capita demand × population

=70L/c.p. d d x 1307

= 915,530litres/day

Water Deficit

Taking the standard average water consumption of a person per day, that is 110L/c.day
(MoW,2020), The water demand for the area would hence be equals to

110L/c.d x 13079 = 1,438,690litres/day

Water deficit = 1,438,690 – 915,530

= 523,160 litres/day

Hence there is the shortage of 523,160 litres so as to meet the standard average water
requirements of the people at the area in every day.

4.6 Sanitation system

Sinza D is still improving in the development, proportional to the number of residents those
who are using pour flush latrines is larger comparing to the residents who are using pit latrines
and other residents who do not have a toilet facility at all. Also, no sewer network (off-site

67
facility) constructed for disposing waste across the whole Sinza D street. Pour flush latrines are
favorable in Sinza D street because water is easily accessible.
In Sinza D street, has onsite sanitation system as the produced faecal matter is treated at the
vicinity point. This type of sanitation used in Sinza D is varying in accordance with water
supply availability, areas with high ratio of water supply have advanced in sanitation system
comparing to the areas with water scarcity.
4.6.1 Onsite sanitation facilities

Sinza D street have a better sanitation situation due to availability of reliable water supply
system which is almost covered the whole zone, as a result 78% of people are using pour flush
with septic tank, 12% of people are using VIP latrines mixed with 9% who are using local pit
latrines without vent a pipe and 1% have no toilet facility at all.

Toilet Facility

1%

9%
Pour flush
12%
VIP latrine
Pit latrine
No toilet facility
78%

Figure 4.5 Types of the toilet facilities present in the study area

Therefore, Sinza D street is largely using pour flush latrines, which mainly are designed for the
daily uses. During rainy seasons the people of Sinza D face a huge problem of overflow of
toilets due to the place having a water table that is high, thus it forces them to do emptying of
the septic tanks and pits for a weekly duration as result it induces contamination to the street
runoffs and available wells.

68
4.6.2 Methods of emptying

In this area there are a various emptying technique used such as

4.6.2.1 By using vacuum tankers

This method is used by majority of people and it is affordable. The amount charged for
emptying depends on the size of the vehicle whereby for a small vacuum tanker the amount is
Tsh 80,000/= and for the large vacuum tanker the amount is Tsh 150,000/=. This amount
becomes favorable as for those who live in rented houses contribute an equal amount so that
they can pay thus leading to about 65% of the Sinza D residents to use this technology.
4.6.2.2 Manual pit emptying technology (MAPET)

This technology involves manually handled equipment such buckets, shovels, and portable
hand pumps during emptying of toilet facilities. This makes up about 26% of the residents at
the study area.
4.6.2.3 Releasing to water streams

This is the illegal act and it normally occurs during rainy seasons, where residents with latrines
close to the Ng’ombe river stream tend to release their waste water generated to the streams
and rivers hence this leads to the contamination of the water sources. 9% of these residents of
Sinza D use this method.

Figure 4.6: wastewater from toilets discharged into the streams

69
 EMPTYING METHODS
9%

26% vacuum tanker

MAPET
release to streams
65%

Figure 4.7: Emptying system at Sinza D

4.7 Problems of sanitation in relation to water supply;

• Pollution of water sources:

Some of the wastewater and sludge from the septic tanks are taken into the river and drainages, mostly
during the rain this affects quality of the water on the runoff and thus destroying the sources of water
that could be used to supply clean water to the residents

Fig 4.8: Household waste water pipe discharging waste water into a water stream

70
 • Reducing available sources of water:

Presence of many polluted water resources in the area causes shortage of available sources of
water which forces residents rely mainly on water supplied from DAWASA for all activities,
this situation is difficult for the non-customers of DAWASA.

Fig 4.9: A polluted water source

• Pollution of underground water:

Some latrine design exceeds the water table level, and also wastewater flowing through the
unauthorized drainages, this exhibit quality of the underground water that can be useful as
alternative source of water for sanitary uses.
• Presence of bad smell and insect breeding,
This brought about by poor design of the latrines and release of water in the streams and drains

Fig 5.0: A poorly constructed pit latrine

71
• Occurrence of waterborne diseases such as typhoid, cholera

4.8 Measures to be taken to improve the sanitation system

• Enforcement of policies and laws that discourage illegal dumping of waste water from
households and industries into natural water streams
• Improvement in the water supply such that water should be readily available so as to
avoid diseases like UTI caused by dehydration.
• Connection to sewer system to overcome the problems of smell and insect breeding,
pollution of water sources (surface and underground) and the possibility of exposure
to diseases.
• Maintenance of poorly designed pit latrines as a short-term solution
4.9. Fecal sludge management containments technologies.
In this area there are a various containments technique used such as:
4.9.1. Septic tank
A buried, watertight tank designated and constructed to receive and partially treat raw
domestic sanitary wastewater. Heavy solids settle to the bottom of the tank while greases and
lighter solids float to the top. The solids stay in the tank while the wastewater is discharged to
the drain field for further treatment and dispersal. Sinza D as a result, majority of the people
79% uses septic tank as the main technology for the containment of the fecal sludge which the
septic tanks separate the sludge and allows water to percolate to the ground.

Figure 4.8: septic tanks

72
 4.9.2. Pit latrine or drop and store.
A pit latrine, also known as pit toilet, is a type of toilet that collects human feces in a hole in
the ground. Urine and feces enter the pit through a drop hole in the floor, which might be
connected to a toilet seat or squatting pan for user comfort. This type of containment is used
to store the sludge till when is full and left for some time for decomposition or transported to
take place. From the site 19% uses pit latrine as the containment technology for storing the
fecal sludge before transporting to the treatment.

Figure 4.9: pit latrine or drop and store

4.10. Emptying technologies for the fecal sludge

Removal of fecal sludge from on-site systems and transportation to a treatment or disposal
facility are the second and third steps in the service chain for fecal sludge management. In
Sinza street, Sludge can be removed by mechanical means or manually. The specific method
depends on the type of containment system, the local climate, access to the site, the type of
equipment used by the service provider, and their level of expertise.
4.10.1. Manual emptying technology.
From the results 68% of the respondents uses manual method (direct lift method) during
emptying of the fecal sludge which are called frogmen. The direct lift method involves the
collection of FS from latrines or tanks by using long handled buckets and long handled
shovels. Filled buckets are hoisted to the ground surface, where they are emptied into tanks
fitted onto carts which are then transported to transfer stations or treatment sites. Though some
use to descend into pits to collect FS and is not safe. Dumping of FS directly into the

73
 environment rather than discharging at a transfer or treatment site is common and must be
avoided.

Figure 4.10: manual emptying technology

4.10.2. Mechanical emptying technology.
This technology involves the use of vacuum tankers in the transportation and emptying of the
fecal sludge from the area. The results show that 22% practice mechanical technology by the
use of vacuum tankers during emptying. The technology is done in every month at the site
with a certain amount paid for facilitating the emptying process to be done perfectly and with
high efficiency.

Figure 4.11: mechanical emptying technology

4.11 Storm water management and drainage systems

4.11.1 Storm water management

Storm water management is the huge problems during the rainy seasons and this is due to the
increase in the development activities including construction of houses and pavement especially
in the water ways and streams. Most of the houses in the case study area are so close to each
other, leaving only small portion as the water streams which become insufficient to hold the

74
quantity of water flowing in the rainy seasons. As the result of this problem, flooding in the
dwellers’ houses usually occur in the rainy seasons.

Figure 4.12: Narrowed water stream due to over construction in water ways

Some of the households as seen in the figure 4.8 Decided to raise the banks of their house so as
to avoid the entrance of overflowing water from the narrowed streams into their houses.

Figure 4.13: Bank of the house raised to avoid entrance of storm water during rainy season.

4.11.2 Drainage system

The drainage channel available in the case study area is open channels, among these channels
few are lined especially those found in the road sides. large percent of street drainages are not
lined. Other features of these drainages are;
• Most are artificial open channels.

• Irregular in shape and facilitate erosion.

75
• Associated with fecal sludge discharge activities.
• They are found with the problem of over flooding during rainy season.

Figure 4.14: Local drainage systems at Sinza D

76
 CHAPTER 5

5.0 DESIGNING OF THE SEWERAGE SYSTEM AT SINZA D

Design of sewerage system conducted through different parameters and analysis of the results
was confirmed from the sewerage design-related spreadsheets. As a fundamental pre requisite,
the following design criteria should be followed: -

5.1 Selection of the design period

The selection of the design period is opted to be 25 years, to sustain the design capacity at Sinza
D Street (Metcaff & Eddy, 2003).
5.2 Population forecasting

Onto satisfying the design capacity under the design period, the population forecasting is a
fundamental prerequisite in attaining so. On the basis that the population growth is under
geometric progression method the growth rate of 5.6% (NBS, 2016) for the Dar es salaam city.

Where:

P2046 = Population at 25 years

r= rate of population growth
P = Current population

5.3 Water Demand Projection

The water demand estimation is as follows: -

Consider the per capita water demand is 110L/ca/day (MoW, 2020)

The water demand = Population x Per capita water demand

77
The water demand = 51,070 x 110L/day

= 5,617,700 L/day

5.4 Waste water generation

5.4.1 Domestic wastewater generation

Considering that 60 – 90% of the water supply is turned into wastewater (Metcaff & Eddy,

2003). Thus; Taking 80% of the water consumed is generated as waste water;

(0.8) x 5,617,700 = 4,494,160 L/day as waste water.

Therefore, the total domestic wastewater discharge is 4,494.160 m3 to be discharged into the
sewerage system.

5.4.2 Institutional wastewater generation

The Institutional wastewater flow is estimated as area based from which the facilities do
occupy. Estimations cover that 7.5 – 10m3/ha/day rates of waste water are to be generated
(Metcaff & Eddy, 2003).
Table 5.1 total discharge flows in different institutions
Institution Population Area Projected Projected Per capita Discharge
(ha) Population Area (ha) Area flow flow
(m3/ha/day) (m3/day)
Schools 3279 0.792 12,804 3.093 10 7.92
Mosques 754 0.067 2,944 0.26 10 0.67
Hotels 487 0.247 1,902 0.965 10 2.47
Churches 1855 0.673 7,243 2.628 10 6.73
Bars 877 0.177 3,425 0.691 10 1.77
Dispensaries 67 0.058 262 0.227 10 0.58
TOTAL 20.14

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5.6 The Commercial waste water generation

From, the commercial wastewater generation estimations of 7.5 – 14m3/ha/day. The total
area covered withing the zones with commercial areas potential is 21ha, hence;
=14m3/ha/day x 21 ha

= 294.88m3/day.

The total area for the waste water generated in the zones is 21ha, located for the commercial
areas, marking the total flow of 294.88m3/day.

5.7 Peak waste waterflow

The total wastewater flow is the summation of the flow from the domestic, commercial and
institutional generated flows that is;

Average daily flow = (294.4 + 20.14 + 4494.16) m3/day = 4,808.7m3/day Thus,

(MoW, 2020) suggests that the flows ranging (2500 – 5000) m3/day.
The PHF to be used is 3.4.

Average daily flow x PHF

= 4,808.7m3/day x 3.4

= 16,349.58m3/day.

Hence the Peak hour flow is 16,349.58m3/day.

5.8 Inflow and Infiltration

The estimations of the infiltration and inflow is attempted as an area-based method since the
design is based on the newly established one is the known area. Hence from Figure 2…. The
total infiltration based on the whole area is 0.1819m3/day.

79
5.9 The proposed Sewer Layout

80
 CHAPTER 6

6.0 DESIGN OF THE STORMWATER DRAINAGE SYSTEMS AT SINZA D

The stormwater drainage design criteria were ultimately based on the estimation of the runoff from
the site using the rational method, since the area is less than 80ha and similarly in the terrain
characters in the area. There is several software used in designing this system such as Storm CAD,
Google Earth Pro, ArcGIS and Microsoft Excel. As, a prerequisite in the design the following
considerations were taken into account.
6.1Design period

The project is designed for satisfying the capacity for the waste water collection for 10 years, under
the design return period for the storm from the Intensity Duration Frequency curve of 5 years
(CPHEEO, 2019).
6.2The Runoff coefficient for runoff estimations

The coefficient of runoff (C), is a function of the nature of surface and assumed to be the same for
all storms of all recurrence probabilities. Basing on the area occupation the following data was
deducted: -
Table 6.1 Area based and Coefficients of runoffs of urban areas (CPHEEO, 2013)
Area Runoff Coefficient
Commercial and Industrial Area 70 – 90
Residential Area

- High Density 61 – 75

-Low Density 35 – 60
Parks and undeveloped areas 10 - 20

Depending on our site the following data was extracted, on the coefficient of runoff basis.
Table 6.2 Area distribution based on various runoff coefficients
Area Runoff Coefficients
Low density areas paved (22ha) 0.6
Paved commercial and roadways areas (21ha) 0.75

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Therefore, from;

Coefficient of runoff, C = (𝐶1𝑎1+ 𝐶2𝑎2+ 𝐶3𝑎3)

𝑎1 + 𝑎2 + 𝑎3
0.6×14+0.75 ×21+0.7×8
Coefficient of runoff, C = 14+21+8

The Ruoff coefficient, C = 0.7 for the site area.

6.3 Rainfall Intensity (mm/hr)

The rainfall intensity of the design was based on the rainfall data from the intensity duration
frequency curve (TMA, 2015) extract. The peak rainfall depth under the 5years return period is
36mm/hr, for the Sinza D area.

6.4 Drainage systems Design

The drainage systems to be designed at the site is proposed to be trapezoidal in shape, depending
on the side slopes for imposition of stability as the retaining structure along the road sides of
imposed traffic loads along the roadway.
Consider;

Figure 6.1 Trapezoidal channel for stormwater collection

82
In a trapezoidal channel, the area, A, and the top width, T, are presented by the following equations:

𝐴 = 𝑏𝑦 + 𝑚𝑦2

𝑇 = 𝑏 + 2𝑚𝑦

Whereby: b, y, and m are the bottom width, depth, and side slope (horizontal to vertical ratio) of the
channel, respectively.
6.5. Surface Runoff Estimation

The design is based on the Rational Method, in the runoff estimation that is given by:

Flow, 𝑄 = (𝐾𝐶𝐼𝐴)

Whereby;

K = Conversion Factor 0.002778

C = Coefficient of surface runoff i
= Rainfall depth (mm/hr)
A = Area (ha)

The area was further distributed into smaller zones that were served by a portion of the drainage
system. Furthermore, the flows were cumulating with the combination of various drainages
increasing the flow and the size of the channels as expressed in the spreadsheets.

83
6.6. Hydraulic Longitudinal Profile for the Design

84
 CHAPTER SEVEN

7.0. DESIGNING OF FECAL SLUDGE MANAGEMENT

The design of the faecal sludge management system is ultimately in concern to the onsite sanitation
facility users. The design of the faecal sludge management system currently focuses on ensuring a
complete linkage in the faecal sludge management chain hence providing safe containment, emptying
and transporting of the faecal sludge from the community.

7.1. Design of a suitable containment facility at Sinza D

The containment system suitably to be designed at the site is the Septic tank system, due to the
following reasons: -

• Septic tanks are highly efficient in odor reduction from the household vicinities hence
provide suitable satisfaction of sanitation means.
• Septic tanks provide best means of reducing the groundwater pollution since the released
effluent from the soak pit are less prone in affecting the groundwater table.
• They are quite more durable and enriches well the design period capacities. Furthermore,
they are offset from the superstructure thus the imposed loading is quite reduced, hence
offering a more life span.
• The initial costs and maintenance cost is well affordable to the Sinza D dwellers.
7.2. Design Considerations

Volume of liquid entering the tank each day

Vv = P x q

Where by;

Vv = volume of liquid to be stored in the septic tank

P = number of people using the tank

q = sewage flow = 80% of the daily water consumption per person

q = 0.8 x Q

q = 0.9 x 110 = 99 litres per person per day.

85
Therefore,

Vv = 6 x 99 = 594 litres.

The volume of sludge and scum is given by:-

Vs = P x N x F x S

where

B = volume of sludge and scum

P = number of people using the tank

N = period between desludging

F = sizing factor

S = sludge and scum accumulation rate

N is 3 years (Design Period)

F= 1.0; assuming that as all wastes go to septic tank

S = 40L per person per year.

Vs = 6 x 3 x 1.0 x 40

Vs = 720 litres

Total tank volume = Vv + Vs

= 720 + 594

= 1314 litres

Total tank volume= 1.314m3

7.3. Internal Dimension Design

Assume two compartments, are to be designed;

Length of first = 2W

Length of second = W

Volume of tank (V) = 1.5 x (2W + W) x W = 4.5 W²

86
Thus,

4.5 W² = 1.314 m³

W = 0.54m

Therefore:

Width of tank = 0.7m (MoW, 2020)

Length of first compartment = 1.08 m

Length of second compartment = 0.54 m

Depth of tank from floor to soffit of cover slab = liquid depth + freeboard

= 1.5 + 0.3

Depth of tank from floor to soffit of cover slab = 1.8 m

The Septic Tank designed is proposed to be sealed so as to prevent the ground water pollution from
the site.

7.4. Desludging and transportation of sludge from the Sanitation facilities

Criteria for use Emptying methods

Vacuum Manual
Emptying cost depending on income Vacutag tank Gulper emptying

50,000 - 200,000 ✔ ✔ ✔ ✔

300,000 - 500,000 ❌ ✔ ✔ ✔

Above 500,000 ❌ ✔ ✔ ✔
Sanitation facilities

Pit latrine ✔ ✔ ✔ ✔

Septic tank ✔ ✔ ❌ ✔

Buckets ❌ ❌ ❌ ❌
Accessibility
Width of road that gives access to the
emptying facility ✔ ✔ ✔ ❌

87
 Distance from WWTP
Depth of the pit

2-3m ✔ ✔ ❌ ✔

3-4m ❌ ✔ ❌ ❌

From the table above, the emptying method that is favorable for emptying the fecal sludge is by the
use of vacuum tank as follows: -

• The accessibility of the site well allows the use of the vacuum tankers in most of the areas.
• The vacuum tanker is well efficient in emptying basing on the rich various depths of pits from
the site and promoting the transportation of the sludge even in bulk volumes to the treatment
plants.

7.5 Design of the Transfer Stations

The design of the transfer station is mainly based on the feacal sludge that is to be deposited from the
generation vicinities. The faecal sludge transfer station to be designed is the mobile transfer station,
since the Fixed transfer station would induce much cost on the demolition of premises from the site,
since the areas are quite condensed and fixed. Mobile transfer stations consist of easily transportable
containers providing temporary storage capacity at any point near the structure being emptied -
essentially a tank fitted on a wheeled chassis. The mobile transfer station well supported by the
motorized tankers, for disposing the contents directly to the wastewater treatment plants that are quite
far from the site, the stations will be located in specialized and optimized places to cover the whole
area.
7.5.1 Determination of the Faecal Sludge Transfer station volume
The determination of the Faecal Sludge Transfer station volume is much dependent on the quantity of
the faecal sludge produced from the area.
Thus;
From the current population; 13079 people
𝑛
𝑟
Population growth, 𝑃𝑛 = 𝑃 (1 + ( 100 ))

5.6
𝑃𝑛 = 13079 (1 + ( ))𝑛 = 17,175 people in 5 years
100

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The proposed feacal sludge production rate for the low-income countries in urban area is
250g/person/day (Jonsson et al. 2005). Thus, the generation of the sludge in the whole community is
given as;
Population, Pn x Feacal sludge generation rate = Total Faecal sludge Volume
= 17175 x 0.25kg/per/day = 4,294kg/day; The produced sludge is equivalent to 4.294tonnes.

Considering the sludge density of 1120kg/m3 (Metcaff & Eddy, 2003), thus the volume is given as;
Volume, V = Mass/ Density = 4294/1120 = 3.833m3 in a day.
Hence, to sustain the spatial distribution of the households, commercial and institution areas thus the
small sized (0.2m3 metal drums) are used for the design (McBride, 2012).
Thus, 20, small sized motorized metal drums are well to be spread to serve different areas at Sinza D.

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 CHAPTER EIGHT
COST ESTIMATION

8.1 Cost estimation for sewerage system designing

8.1.1 Pipe cost estimation

SEWERAGE
PIPES COST
ESTIMATION
S
Item Description Unit Diameter Total Quantity Unit Amount
Lengt lentgh (m) Rate
h
(m) (mm) (m) (Tsh) (Tsh)
1 Pipe uPVC 6 300 2630 439 9,000 3951000
2 Pipe uPVC 6 350 530 89 11,000 979000
3 Pipe uPVC 6 375 60 10 15,000 150000
4 Pipe uPVC 6 400 90 15 17,500 262500
5 Pipe uPVC 6 450 180 30 19,500 585000
6 Pipe uPVC 6 600 145 25 22,000 550000
7 Pipe uPVC 6 700 80 14 25,000 350000
Total 6,827,500

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8.1.2 Excavation costs

Line length Trench Excavation Excavation Cost Cost of

Width depth (m) volume per 1 excavation
(m) (m3) cubic (Tsh)
meter
(Tsh)
CO-1 90 0.5 2.090 94.050 1800 169290
CO-2 50 0.6 2.050 61.500 1800 110700
CO-3 90 0.6 2.090 112.860 1800 203148
CO-4 50 0.6 2.050 61.500 1800 110700
CO-5 50 0.65 2.000 65.000 1800 117000
CO-6 45 0.65 2.000 58.500 1800 105300
CO-7 45 0.7 1.910 60.165 1800 108297
CO-8 90 0.7 1.910 120.330 1800 216594
CO-9 90 0.8 1.950 140.400 1800 252720
CO-10 50 0.8 1.950 78.000 1800 140400
CO-11 60 0.8 1.940 93.120 1800 167616
CO-12 90 0.8 2.600 187.200 1800 336960
CO-13 90 0.8 1.940 139.680 1800 251424
CO-14 45 0.8 1.940 69.840 1800 125712
CO-15 90 0.8 2.510 180.720 1800 325296
CO-16 90 0.9 2.650 214.650 1800 386370
CO-17 110 0.9 2.000 198.000 1800 356400
CO-18 110 0.9 2.000 198.000 1800 356400
CO-19 60 0.9 2.000 108.000 1800 194400
CO-20 120 0.9 2.000 216.000 1800 388800
CO-21 90 0.9 2.150 174.150 1800 313470
CO-22 90 0.9 2.150 174.150 1800 313470
CO-23 90 0.9 2.400 194.400 1800 349920
CO-24 40 0.9 2.400 86.400 1800 155520

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CO-25 45 0.9 2.400 97.200 1800 174960
CO-26 90 0.9 2.400 194.400 1800 349920
CO-27 45 0.9 2.400 97.200 1800 174960
CO-28 45 0.65 2.700 78.975 1800 142155
CO-29 60 0.65 2.700 105.300 1800 189540
CO-30 60 0.65 2.700 105.300 1800 189540
CO-31 50 0.65 2.700 87.750 1800 157950
CO-32 80 0.7 2.700 151.200 1800 272160
CO-34 90 0.7 2.700 170.100 1800 306180
CO-35 50 0.7 2.700 94.500 1800 170100
CO-36 50 0.8 2.700 108.000 1800 194400
CO-37 100 0.8 2.700 216.000 1800 388800
CO-38 50 0.8 2.700 108.000 1800 194400
CO-39 120 0.8 2.700 259.200 1800 466560
CO-40 100 0.8 2.900 232.000 1800 417600
CO-41 90 0.8 2.900 208.800 1800 375840
CO-42 90 0.8 2.900 208.800 1800 375840
CO-43 50 0.9 3.400 153.000 1800 275400
CO-44 50 0.5 3.400 85.000 1800 153000
CO-45 50 0.5 3.400 85.000 1800 153000
CO-46 50 0.5 3.400 85.000 1800 153000
CO-47 45 0.55 3.400 84.150 1800 151470
CO-48 90 0.5 2.000 90.000 1800 162000
CO-49 90 0.55 2.000 99.000 1800 178200
CO-50 90 0.55 2.000 99.000 1800 178200
CO-51 45 0.5 2.000 45.000 1800 81000
CO-52 60 0.6 2.000 72.000 1800 129600
CO-53 90 0.65 2.000 117.000 1800 210600
CO-54 100 0.65 2.000 130.000 1800 234000
CO-55 60 0.55 2.000 66.000 1800 118800
CO-56 90 0.6 2.000 108.000 1800 194400

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CO-57 90 0.65 2.000 117.000 1800 210600
CO-59 90 0.65 4.310 252.135 1800 453843
CO-60 80 0.65 4.248 220.896 1800 397612.8
TOTAL 13,531,538

Total cost = Pipe costs + excavation costs

=6,827,500 + 13,531,538
= 20,359,038/= Tsh.
8.2 Cost estimation for stormwater management systems

8.2.1 Stormwater lining costs

STORMWATER
LINING COST
ESTIMATION
Channel Length Rate Cost (Tsh)
(m) (Tsh)
CH-1 80 16500 1320000
CH-2 70 9500 665000
CH-3 80 9500 760000
CH-4 40 9500 380000
CH-5 40 9500 380000
CH-7 80 9500 760000
CH-8 40 9500 380000
CH-9 45 9500 427500
CH-10 50 9500 475000
CH-11 60 9500 570000
CH-12 40 9500 380000
CH-13 99 9500 940500
CH-14 60 9500 570000
CH-15 80 9500 760000
CH-16 40 9500 380000
CH-17 90 9500 855000

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 CH-18 80 9500 760000
CH-21 60 9500 570000
CH-22 40 9500 380000
CH-24 90 9500 855000
CH-20 80 9500 760000
TOTAL 13,328,000

8.2.2 Stormwater earthworks costs

STORMWATER EARTHWORK COST ESTIMATION

Channel Length Depth Width Excavation Unit Total cost
(m) (m) (m) Volume cost (Tsh)
(m3) (Tsh)
CH-1 80 0.5 0.8 32 12000 384000
CH-2 70 0.5 0.8 28 12000 336000
CH-3 80 0.8 0.8 51.2 12000 614400
CH-4 40 0.8 0.8 25.6 12000 307200
CH-5 40 1.5 0.8 48 12000 576000
CH-7 80 1.5 0.8 96 12000 1152000
CH-8 40 1.5 0.8 48 12000 576000
CH-9 45 1.5 0.8 54 12000 648000
CH-10 50 1.5 0.8 60 12000 720000
CH-11 60 1.5 0.8 72 12000 864000
CH-12 40 2 0.8 64 12000 768000
CH-13 99 0.5 0.8 39.6 12000 475200
CH-14 60 0.5 0.8 24 12000 288000
CH-15 80 0.8 0.8 51.2 12000 614400
CH-16 40 0.8 0.8 25.6 12000 307200
CH-17 90 1 0.8 72 12000 864000
CH-18 80 1.5 0.8 96 12000 1152000
CH-21 60 0.5 0.8 24 12000 288000
CH-22 40 0.5 0.8 16 12000 192000

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 CH-23 90 0.5 0.8 36 12000 432000
CH-24 80 1 0.8 64 12000 768000
CH-20 80 1 0.8 64 12000 768000
TOTAL 13,094,400

Total cost = 13,328,000 + 13,094,400

= 26,422,400/= Tsh.
8.3 Cost estimation for additional requirements and activities for both sewerage and
stormwater management systems

Cost estimation for other requirement and activities

S/N Item Description Quantity Unit price Amount (Tsh)

Site clearance, installation 0f manholes,

1 1 16,000,000
bedding, and backfilling.

Provision for surveying equipment, establish

2 all necessary bench marks and setting out of 1 12,500,000
the works.

Rreports and preparation of as built drawings

3 1 4,070,000
as specified by the Engineer

Insurance Costs (third party liabilities,

accident or injury to workman, contractor’s
4 1 24,000,000
equipment, materials in transit to site and
vehicles)

5 Manholes quarrying 59 60000 4,000,000

Bedding materials 15,300,000

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 Establish, operate and maintain the
contractor’s office, stores, canteens including
7 mobilization of all required equipment, plants, 44,000,000
tools, machinery, manpower and their
accommodation.

8 Provisional sum for materials testing. 6,800,000

9 Excavation of sewer trench 52,420,000

Compensations cost 23,680,000
TOTAL; 199,000,000 Tsh.
8.4 Cost estimation for faecal sludge management systems

FAECAL SLUDGE MANAGEMENT SYSTEM COST ESTIMATION

CONTAINMENT FACILITY
TOTAL COST
S/N PARTICULAR QUANTITY UNIT COST (Tshs) (Tshs)

1 6" PVC Pipe Class B 3 13,000.00 39,000.00

2 T-Baffle PVC Pipe 2 6,000.00 12,000.00

3 1/2"mm steel Bars 3 17,000.00 51,000.00

4 1/4"mm steel Bars 4 14,000.00 56,000.00

5 Cement 9 13,500.00 121,500.00

6 Excavation Cost 1.5 15,000.00 22,500.00

7 Coarse aggregate 5 45,000.00 225,000.00

8 Sand 4 12,000.00 48,000.00

9 Labour Costs 250,000.00 250,000.00

10 4" Stainless steel nails 2 1,500.00 1,500.00

11 2x2" Cyprus Timber 3 5,500.00 5,500.00

12 Miscallenous Costs 70,000.00 70,000.00

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 12 Transportation Costs 4 50,000.00 200,000.00

TOTAL 1,102,000.00

DESLUDGING AND TRANSPORTATION FACILITY

UNIT COST
S/N PARTICULAR QUANTITY (Tshs) TOTAL COST

1 Vacuum Tanker Desludging Cost 150,000.00 150,000.00

2 8 Cumm Vacuum Tankers 2 75,000,000.00 150,000,000.00

3 MAPET (Gulper) 400,000.00 400,000.00

4 Miscallenous Costs 50,000.00 50,000.00

TOTAL 150,600,000.00

MOBILE TRANSFER STATION ESTABLISHMENT COST ESTIMATIONS

UNIT COST
S/N PARTICULAR QUANTITY (Tshs) TOTAL COST
Motorized 0.2m^3 Metallic 2"
1 thick drum minivan 21 21,000,000.00 441,000,000.00

2 4" Flexible Horse pipes 22 35,000 770,000.00

3 420 watts Vacuum pumps 22 520,000 11,440,000.00

TOTAL 453,210,000.00
Total cost = 1,102,000.00 + 150,600,000.00 + 453,210,000.00
= 604,912,000/= Tsh

8.5 TOTAL DESIGNING COST

Total designing cost is equal to the sum of total cost in each category
= 20,359,038 + 26,422,400 + 199,000,000 + 604,912,000
= 850,693,438 Tsh
Making 15% allowance (contigence)
= 850,693,438 + (0.15x850,693,438)
= 978,297,454 Tsh
Hence the overall total cost of the project is 978,297,454 Tsh.

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 CHAPTER NINE
9.0 CONCLUSION AND RECOMMENDATIONS

9.1 Conclusion

Sinza D area is amongst of the areas in Dar es salaam region which consists of number of human
activities used as the residents as their sources of income in day to day lives. The presence of these
human activities including settlements, commercial, institutional and probably industrial development
needs proper and well-designed systems for the collection of both solid wastes and liquid wastes
generated from them.
From the study area, the practice for management of these wastes were not of satisfactory conditions
since 9% of the residents were discharging their waste water from the kitchen and from the toilets to
the nearby stream of Ng’ombe river located which passes at most of the areas in the Sinza D street.
This poses great effects to the human health and the environment including the aquatic animals which
may be affected by the unsafe discharging of wastewater to the stream.
Also, the study area is associated with activities such as transportation and the construction of roads,
buildings and pavements which requires clearing of the bushes, compacting the soil mass and reduces
the natural vegetation cover of the area. These factors lead to the increase in the runoff during the
rainy seasons since the areas for infiltration and interceptions of the storm water have been greatly
reduced. This was seen by the residents who decided to raise the banks of their houses so as to avoid
the large quantity of water overflowing to their houses from the streams. (Refer to figure 4.8)
The project therefore was necessary to invent the solution to the existing problems related to
sanitation, wastewater and stormwater management including the frequent fulling of the faecal sludge
containments, flooding of the toilets during the rainy seasons and improper spreading of the faecal
sludge from the improper emptying methods; by the detail designing of the sewerage systems,
stormwater quantity management systems and the faecal sludge management systems at Sinza D area
which was subdivided to the three zones of service according to the morphology of the area. The
designed systems are suitable and affordable according to the reconnaissance of the average
individual’s income distribution of the area.

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9.2 Recommendations

From the existing situation pertaining the wastewater and faecal sludge management, the following
recommendations should be adopted for the proper environmental conditions and safe handling of
wastewater and faecal sludge;
• The authorities for the management of water and wastewater (DAWASA) should encourage
the connection of the residents to the conventional gravity sewer by lowering the connection
and monthly prices.
• The planning of new houses and the existing ones to have Rainwater harvesting systems so
as to reduce the quantity of the rainwater falling to the ground and hence reducing the
overland flow.
• Enforcement of the strong laws and policies to the residents, institutions and industries
discharging wastewater to the environment.
• Adopting of the reliable onsite sanitation facilities to those who cannot afford the connection
to the conventional gravity sewer.
• Regular maintenance and cleaning of the designed systems so as to maintain the designed
period of the systems and proper functioning.

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