A case study on Addis Ababa city Rivers · Web viewA case study on Addis Ababa city Rivers...
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A case study on Addis Ababa city Rivers Monitoring of Little and Great Akaki Rivers Little and Great Akaki Rivers are Rivers passing through the city of Addis Ababa. They have many tributaries. To monitor the quality of water of the two Rivers 30 sampling points were selected on the two Rivers and samples were collected from these 30 sampling points in three seasons over a period of one year. The samples were analyzed in two laboratories to determine the concentration of the physical, chemical and bacteriological water quality indicators. The objective of this study is To identify and evaluate the source, types and trends of water pollution in the two rivers To provide base line data that helps in evaluating the future change of the river water quality. To device appropriate water management plan for the two rivers. Description of sampling sites For the purpose of sampling the study area was stratified in to three parts, i.e. source of
Transcript of A case study on Addis Ababa city Rivers · Web viewA case study on Addis Ababa city Rivers...
A case study on Addis Ababa city Rivers
Monitoring of Little and Great Akaki Rivers
Little and Great Akaki Rivers are Rivers passing through the city of Addis Ababa. They have many tributaries. To monitor the quality of water of the two Rivers 30 sampling points were selected on the two Rivers and samples were collected from these 30 sampling points in three seasons over a period of one year.The samples were analyzed in two laboratories to determine the concentration of the physical, chemical and bacteriological water quality indicators.The objective of this study is
To identify and evaluate the source, types and trends of water pollution in the two rivers
To provide base line data that helps in evaluating the future change of the river water quality.
To device appropriate water management plan for the two rivers.
Description of sampling sites
For the purpose of sampling the study area was stratified in to three parts, i.e. source of the streams (natural environment), residential, commercial and Industrial spots and down stream where human intervention is very limited.
The sample collection program was divided in to three phases from August to October (Summer or Kiremt). December to February (Dry season) and March to May (wet or belg season)
In each sampling site two separate samples were collected for physico chemical and bacteriological analysis. Temperature and PH were determined on the spot. The other important parameters were determined in our laboratory and AAWSA laboratory. Out of the 30 sampling sites examined 20 (1-20) were on the little Akaki River and the remaining 10 were located on Great Akaki River.
Laboratory Results and Discussion
Physical Observation
When we see the Great and Little Akaki Rivers, in most of the sampling
sites are turbid, black and grayish in color especially in the dry season.
During rainy season the river water the river water has reddish and dark
color, which is mainly coming from erosion of clay and black cotton soil
from open spaces in different parts of the city. It has also bad odor due
to the discharge of domestic as well as Industrial liquid wastes from
different factories located near to the Rivers.
The physical and chemical parameters, which are determined in the
laboratories, are SS, TDS, BOD, COD, and NO3-. These parameters are
compared with the River water standard.
1-Suspended Solids(SS)
The Suspended Solids test is a measure of the amount of undissolved
and colloidal suspended matter (organic and inorganic) in the water
bodies . Suspended Solids test measures the dry weight of solids retained
on a filter or a centrifugal cell. The method selection between filtration
and centrifugation is dependent upon the concentration of the suspended
solid in the water.
Water quality guideline for River water indicates the maximum limit for
suspended solids is 50mg/l.
2-Total Dissolved Solids(TDS)Total Dissolved Solids (TDS) consists of both organic and inorganic
molecules and ions that are present in solution. The main constituents
are cations of calcium, magnesium, sodium and potassium in addition
to carbonate, bicarbonate, chloride, sulphate and nitrate anions. TDS
is the other parameter used to identify the accumulation of soluble
substances in the two Rivers. The TDS values for the sample water
were compared to the maximum limit of 450mg/l.
S1 S3 S5 S7 S9S11 S13 S15 S17 S19
Standa
rd0
200
400
600
800
1000
1200
Total Dissolved Solid in Little Akaki River
Series1 Series2 Series3
Sampling Site
Valu
e in
mg/
l
xx
S1 S3 S5 S7 S9S11 S13 S15 S17 S19
Standa
rd0
200
400
600
800
1000
1200
Total Dissolved Solid in Little Akaki River
Series1 Series2 Series3
Sampling Site
Valu
e in
mg/
l
xx
S21 S22 S23 S24 S25 S26 S27 S28 S29 S30
stand
ard0
100
200
300
400
500
600
700
800
900
1000
Total Dissolved solids in Great Akaki River
1st collection season 2nd collection season3rd collection season
Sampling sites
TDS
valu
e in
mg/
l
3- Biological Oxygen Demand (BOD)The most widely used parameter of organic pollution applied to surface water is the 5-day BOD (BOD5). This determination involves the measurement of the dissolved oxygen used by microorganisms in the biochemical oxidation of organic matters present in the stream and as such measures the degree of wastes discharged and existing in the natural stream water coarse. The higher the level of BOD5 in the stream, the lower will be the oxygen content of the natural stream and the self purification capacity will be affected. BOD normally gives an indication of Biodegradable organic carbon and under certain condition, the oxidizable Nitrogen in the waste.
S21 S22 S23 S24 S25 S26 S27 S28 S29 S30
stand
ard0
100
200
300
400
500
600
700
800
900
1000
Total Dissolved solids in Great Akaki River
1st collection season 2nd collection season3rd collection season
Sampling sites
TDS
valu
e in
mg/
l
s1
s2
s3
s4
s5
s6
s7
s8
s9
s10
s11
s12
s13
s14
s15
s16
s17
s18
s19
s20
Standard
0
100
200
300
400
500
600
700
800
900
1000
BOD in Little Akaki River
1st Collection Seasons 2nd Collection Seasons 3rd Collection Seasons
sampling Site
valu
e in
mg/
l
BOD standard of River water =0.1mg/L
s21
s23
s25
s27
s29
Standa
rd0
10
20
30
40
50
60
70
80
90
100
BOD in Great Akaki River
1st Collection Seasons 2nd Collection Seasons 3rd Collection Seasons
Sampling site
Valu
e in
mg/
l
4- Chemical Oxygen Demand (COD) COD is used as a measure to indicate the equivalent amount of oxygen required to totally oxidizing both biologically degradable and non-degradable organic and inorganic matter present in sewage, Industrial waste and polluted waters. Due to this, the COD test results are usually higher than those of BOD tests carried out on the sample. COD test is valuable for such wastes where BOD test is not applicable due to the presence of toxic substances, low rate of oxidation etc.The COD results can be determined in 3 hours that is shorter time than BOD results, which is determined by 5 days.
s21
s23
s25
s27
s29
Standa
rd0
10
20
30
40
50
60
70
80
90
100
BOD in Great Akaki River
1st Collection Seasons 2nd Collection Seasons 3rd Collection Seasons
Sampling site
Valu
e in
mg/
l
s1 s3 s5 s7 s9 s11
s13
s15
s17
s19
Standard
0
200
400
600
800
1000
1200
1400
1600
1800
COD in Little Akaki River
1st collection Seasons 2nd Collection seasons 3rd Collection Seasons
Sampling site
valu
e in
mg/
l
5-
Nitrogen The Nitrogen present in waste water systems can exist in four forms ammonia, organic nitrogen, nitrate and nitrite. The nitrogenous organic matter consists of urea, proteins and hydrocarbons undergoes decomposition resulting in the formation of ammonia. Ammonia is first converted into nitrite (NO2-) by partial oxidation and then finally to nitrate (NO3-) when nitrogenous materials are present in the receiving stream the nitrifying bacteria exert an additional oxygen demand. NO3- and NO2- ions are monitored regularly in water supplies as they are deemed to be potentially hazardous to health if their maximum admissible concentration are exceeded.
s21
s23
s25
s27
s29
Standa
rd0
50100150200250300
COD in Great Akaki River
1st Collection Seasons 2nd Collection Seasons3rd Collection Seasons
Sampling site
Valu
e in
mg/
l
ConclusionThe mentioning of quality parameters and levels of pollutants in Little and Great Akaki Rivers waters are polluted indiscriminately by Domestic, industrial, institutional, agricultural, fuel stations and garage wastes.
S1 S3 S5 S7 S9S11 S13 S15 S17 S19
Standa
rd0
5
10
15
20
25
30
NO3- in Little Akaki River
1st Collection Season 2nd collection Season
3rd Collection season
Sampling Site
valu
e in
mg/
l
S21 S22 S23 S24 S25 S26 S27 S28 S29 S30
Standa
rd0
1
2
3
4
5
6
7
8
9
NO3- in Great Akaki River
1st Collection Season 2nd Collection Season
3rd Collection Season
Sampling site
valu
e in
mg/
l
Recommendations1- For controlling untreated industrial effluents discharge to the River
system implement pollution control regulations.2- Immediate actions are required to be taken by the concerned
government bodies and different NGOs to find remedial measures for improving the stream sanitation and try to find a solution for the down stream people for access to clean water. (FEPA, AAEPA and OEPB have started the management plan of the two rivers)
3- Improve solid waste management system. By improving Collection capacity and introducing recycling, reuse.
4- Institutions like hotels and hospitals should handle their waste properly.
Picture showing that domestic liquid and solid waste around kera
