0

20

40

60

80

100

120

140

160

180

B1 B2 B3 B4 B5 C2 C1

Co

nce

ntr

atio

n (

mg

/l)

Drinking Water Sources

Nitrate Content in Drinking Water

U.S EPA & WHO

Standard

10mg/L

Well Water Collected Rainwater

55% (Pit Latrines)

12% (Ventilated Pit Latrines)

24% (Septic Tanks)

1% (Open defecation)

8% (Connected to sewerage

System)

Figure 3: Distribution of Sanitary Technologies in Dar-es-Salaam

Only 8% of the households from this community have access to

sewerage system, the rest are contributing to improper disposal of

wastewater. The highest percentage use pit latrines and septic tanks

which are not designed and constructed to meet the minimum

requirement to function properly.

In urban areas of Dar-es-Salaam, Tanzania, water scarcity and wastewater

management are two of the greatest challenges communities face as a

result of because very high population, close proximity of houses to each

other, and failure of the sanitation facilities to comply with proper design

specifications to minimize contamination.

Water Quality Improvement Through Proper Design and Construction of

Wastewater Collection Systems in Dar-es-Salaam, Tanzania

By Tula Ngasala

INTRODUCTION

NEXT STEP…

REFERENCES

ACKNOWLEDGEMENTS

• In Summer 2015, extensive sampling of water for

domestic use from all three sources in Study Area.

• Additional surveys with the goal of determining the

extent of contamination, potential sources of

contamination, and associated health risks.

• Estimation of the wastewater loading coming from

upstream, which contributes to the contamination of

the river in the Study Area.

STUDY AREA

LONG TERM OBJECTIVES

CHALLENGES

WATER QUALITY TEST

Three main sources of water for domestic use in this area are from

private wells (70-80 m deep), rain water collected and stored in

surface or underground tanks, and from vendors (See Figures 8, 9

and 10).Community get City Water only once or twice a month.

Figure 9: Rain Water

Collection System

Figure 4: Pour flush toilet with 2-chamber

septic Tank and soak pit

Figure 5: Offset single pit toilet

with pour flush

The insufficient treatment and improper disposal of wastewater is very

common, which results in contamination of nearby waterbodies

including rivers, lakes, and beaches.

• The study area is the small part of urban area in Dar-es-Salaam, with a

population of approximately 5000 people.

• The community members have a very low income and spend nearly 70% of

their income paying for domestic water and wastewater management.

• Untreated sewerage is commonly discharged into the river or released onto

the ground surface, especially during rainy seasons, when the wastewater

is intentionally mixed with runoff.

• Other major contributions to the surface water contamination are

wastewater coming from university dormitories and industrial wastes from

Industrial Processing Zone (see Figure 2). The contaminated water from the

river is used to irrigate food crops, which are sold to the local community.

EXISTING CONDITION

Figures 4 and 5 below show two types of wastewater

collection systems commonly used. These latrines function

as both a toilet and shower/bathroom. The combined

collection of wastewater (wash water and feces) results in the

rapid filling of the storage pits that are often allowed to

overflow on streets, especially during rainy season.

0

200

400

600

800

1000

1200

1400

1600

B1 B2 B3 B4 B5 C2 C1 C3

Co

nce

ntr

atio

n (

mg

/l)

Drinking Water Sources

Total Dissolved Solids Content in Drinking Water

U.S EPA &WHO

Standard 500mg/L

Well Water Collected Rainwater

Study Area

Surface and Groundwater Contamination

Common Sanitation Practices

Water Scarcity

Distribution of Monthly Expenditures

Drinking Water Contamination

Wastewater Management

3%

Domestic Water Use

65%

Other Expenses

32%

Figure 11: Monthly income expenditure

Figure 10: Vendor selling water obtained from unknown sources

Figure 8: Pumping

well

Figure 6: Sewage overflow from an outfall

structure

Figure 7: River contaminated by

sewage

Figure 2: Mabibo Area in Dar-es-Salaam: (1) Red circles show drinking water sampling locations,

(2) Locations A, B and C are University Dormitories, Industrial Processing Zone and Vegetable

Farm Land respectively.

Figure 1: Study area location located on the eastern part of Tanzania

Due to the scarcity of water in the area, the local community has few

options but to drink poor quality surface and ground water. Most of the

drinking water is likely contaminated with sewage due to poor design

and construction of sanitation facilities and wells.

Figure 12: Groundwater Pollution from Pit Latrines

(Dahi, 1996)

A

B

C

• Modeling of low-cost decentralized wastewater

treatment system to predict the resulting

improvements in surface water and drinking water

quality.

• Sources, Fate, and Transport of Nitrate and other

contaminants in the study area

• Special thanks to my advisors: Drs. Susan Masten and

Phanikumar Mantha for their guidance

• The Department Chair, Dr. Neeraj Buch for his financial

support

B5

C3 B1

B2

B4

B3

C1

Community members from this area spend approximately 68% of

their income to purchase water and pay for emptying their pit latrines

and septic tanks.

The figures below show the results of the analysis of

drinking water samples. As noted, most samples contain

these analytes at concentrations greater than the

minimum standards for drinking water. The presence of

nitrate indicates the possibility of fecal contamination.

1. Introduction to Environmental Sanitation. 2015. Available at:

http://www.slideshare.net/ZakiUddinAhmad/introduction-to-

environmental-sanitation. Accessed March 1, 2015.

2. WHO. Guidelines for drinking-water quality, volume 3: Drinking-water

quality control in small-community supplies, WHO, Geneva, 1985.

Legend:

- Sampling sites

University

Dormitories

Industrial

Processing

Zone

Vegetable

Farm Land

C2