Water pollution status in Addis Ababa, Ethiopia

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					 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 km2
    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 km2) and Little Akaki basin has a
    catchment area of about 540 km2.
   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
     01       02     03     04     05     06     07

pH   7.59    7.68    7.90   8.00   8.03   7.31   7.51
Mn    34.1   1756    6531   1219   1190   2044   2538
Cr   <0.1    14.12   <0.1   <0.1   2.28   <0.1   13.31
Ni   44.45   4.8     <0.1   <0.1   5.05   8.9    <0.1
As   <0.1    2.3     <0.1   0.6    0.42   2.2    2.88
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
      08   09      10     11     12     13     MCL

pH  6.90   6.50    6.32   6.40   5.93   7.60
Mn   0.3   21.47   128    5.1    24     0.39   100
Cr 1.88    1.18      0    5.85   1.21   0.94   50
Ni <0.1    <0.1    <0.1   0.49   0.92   0.53   100
As  1.0    <0.1    <0.1   0.22   0.2    0.2    50
Pb <0.1    <0.1    <0.1   8.33   4.31   15.5   50
Zn <0.1    <0.1    <0.1   9.35   8.06   0.87   5000
BOREHOLE (ppb)
   Heavy Metals
      14     15     16     17     18     19     20

pH   7.62    7.44   6.98   7.53   6.42   8.03    7.68
Mn   0.86    0.64   5.25   3.48   1.97   16.9    1.75
Cr   0.69    0.86   3.29   0.22   0.72   0.24    1.8
Ni   0.57    0.31   0.33   0.69   0.63   <0.1    0.51
As   0.37    0.3    0.3    0.32   0.2    0.63    0.5
Pb   25.1    8.98   10     25.3   15.7   9.75    4.66
Zn    23.3   85.8   3.9    34.2   33.5   10.3    20.5
Total coliform count
       Sample code
. Streams 01           560/ml
            02         Too Many to Count (TMC)
            03        660/ml
            04        Too Many to Count (TMC)
            05       1010/ml
            06       Too Many to Count (TMC)
 Springs 07               290/ml
            08             350/ml
            09             Nil
Total coliform count
    Borehole
    10          10/ml
     11         160/ml
     12         24/ml
     13         16/ml
     14         340/ml
     15         24/ml
     16         8/ml
    Storm drain
     17     3000000/ml
     18       350000/ml
     19      6000000/ml
     20        20000/ml
     21       100000/ml
          Nitrate


Streams    8.9-531 mg/L

Springs   55-728 mg/L

Boreholes 0-35 mg/l
N


4
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.
   Klimas A.A. (1998) Impact of urbanization and protection of water
    resources in the Vilnius district, Lithuania. Hydrogeology Journal
    3(1):24-35.
   Lerner D.N and Barrett M.H (1996) Urban groundwater issues in the
    United Kingdom. Hydrogeology Journal. 4(1): 80-89.
   Tamiru Alemayehu (1999). Groundwater pollution in Addis Ababa.
    Ethiopian Herald. Wednesday May 19, 1999
   Tamiru Alemayehu (2000). Water pollution by natural inorganic
    chemicals in the central part of the Main Ethiopian Rift (SINET:
    Ethiopian Journal of Science 23(2):197-214.
   Tamiru Alemayehu (2000). Effects of uncontrolled waste disposal on
    surface and ground water system in Addis Ababa: a case study.
    Ethiopian Herald Tuesday Agust1-2000
   Tamiru Alemayehu (2001). The impact of uncontrolled waste
    disposal on surface water quality in Addis Ababa. (SINET: Ethiopian
    Journal of Science 24(1):93-104