Presentation on theme: "Surface and ground water pollution status in Addis Ababa, Ethiopia Tamiru Alemayehu ADDIS ABABA UNIVERSITY, Ethiopia Solomon Waltenigus & Yirga Tadesse."— Presentation transcript:
Surface and ground water pollution status in Addis Ababa, Ethiopia Tamiru Alemayehu ADDIS ABABA UNIVERSITY, Ethiopia Solomon Waltenigus & Yirga Tadesse ADDIS ABABA WATER SUPPLY & SEWARAGE AUTHORITY, Ethiopia
INTRODUCTION Addis Ababa is the capital of Ethiopia Since its foundation, the city has grown from sparse and scattered settlements to an expansive and highly populated city.
Addis Ababa lies in the center of the country on the western escarpment of the main Ethiopian rift. The altitude of the city varies from 2100 m a.s.l. to 2700 m a.s.l. The city covers an area of about 530 km 2 with a population of more than 3,000,000 inhabitants. The environment of the city is threatened by severe pollution due to anthropogenic activities for more than a century.
GEOLOGY The region is constituted by volcanic rocks ranging from acidic to basic in composition (27 to 3.2 Ma). The typical volcanic centers of the region are the Entoto Ridge (3200 m a.s.l), Mt. Wochacha (3385 m a.s.l), Mt. Yerer (3100 m a.s.l), Mt. Furi (2839 m a.s.l).
DRAINAGE Big and Little Akaki rivers, with their different tributaries, drain the city from north to south. Big Akaki (900 km 2 ) and Little Akaki basin has a catchment area of about 540 km 2.
The rocks are highly fractured and permit fast circulation of the pollutants over large distances and to a great depth. Taking into consideration the underlying fractured rocks and the widespread uncontrolled waste disposals, groundwater in Addis may be generally considered as highly vulnerable to any type of pollution. IT IS UNLIKELY TO CLEAN POLLUTED AQUIFERS. Hence groundwater must be protected above all where, rising up in the form of springs, are the only source of water supply for the community.
The streams serve as natural sewerage lines for domestic and industrial wastes, hence making them known for their offensive odor. Eutrophication process in the streams is a result of water pollution
WASTE DISPOSAL In the city are septic tanks, open dumps and surface impoundments. The majorities of private septic tanks are characterized by open bottoms or peculiar channels, which facilitate the seepage in depth or the direct connection with the nearby streams. Large and small-scale factories are clustered within the city having unregulated waste disposal systems.
The major solid waste disposal site of the city is located within the city premise that pollute the urban environment. It is open system, no impermeable layer with continuous low temperature burning.
The most known large-scale human activities producing dangerous refuses are: garages, car washing centers, petrol stations, chemical factories, paint factories, tanneries, slaughterhouses, market centers, breweries, textile factories, hospitals tyre factories, thread and garment factories, oil mills, flour mills, metal works, tobacco factories, pharmaceutical factories, Cemeteries
The most widespread diseases in the city are: flu, typhus, acute bronchitis, bronco pneumonia
Water supply: There are three dams that supply the city with treated water. At least there are about 271 boreholes distributed in the city with a maximum yield of a single well of 87l/s. Highly productive aquifers are located in the southern part of the city. Numerous cold and thermal springs
Volume Three dams= 173,000 m3/day Wells & springs=10,000 m3/day Akaki wells= 30,000 m3/day Supply cover=70% of the population
Surface water pollution problem: Turbidity and algae Increase in the use of AlSO4 for coagulation due to increase in turbidity leave Al in public water Use of CuSO4 for Algae eradication leaves Cu in public water There is a basin plan study but requires financial support
GROUNDWATER POLLUTION PROBLEM Case study: - Focused on streams, rivers, springs and boreholes Heavy metals, total coliform and nitrate
Streams (ppb) Heavy metals pH Mn Cr < <0.1< < Ni <0.1< <0.1 As <0.12.3< Pb <0.1<0.1<0.1<0.1<0.1<0.1<0.1 Zn <0.1<0.1<0.1<0.1<0.1<0.1<0.1
Springs (ppb) Heavy metals MCL pH Mn Cr Ni <0.1<0.1< As 1.0<0.1< Pb <0.1<0.1< Zn <0.1<0.1<
BOREHOLE (ppb) Heavy Metals pH Mn Cr Ni < As Pb Zn
Total coliform count Sample code. Streams /ml 02 Too Many to Count (TMC) /ml 04 Too Many to Count (TMC) /ml 06 Too Many to Count (TMC) Springs /ml /ml 09 Nil
CONCLUSION Heavy metal pollution Total coliform and pathogen pollution The major part of the city including some part of the Akaki well field, has bare rock outcrop–high risk for pollution The Akaki well field is crossed by railway and high way-potential danger The unconfined aquifer in the city center and along the rivers is vulnerable.
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