Environmental Engineering Reference
In-Depth Information
Table 3.3. Mean values and standard errors of the
physical and chemical parameters for six sets of
samples collected during the wet season of 1991.
Parameter
MUK1
MUK2
MUK3
WHO Limits
Temperature (ºC)
23.5 +/ -1.5
23.2 +/ -1.4
30.0 +/ -0.6
-
Conductivity (µS/m)
568 +/ -95
660 +/ -161
697 +/ -85
500
pH
7.1 +/ -0.2
7.6 +/ -0.5
7.5 +/ -0.3
6.5-8.5
Nitrate (mg/l)
3.4 +/ -1.3
2.4 +/ -1.9
1.5 +/ -0.8
10
Phosphate (mg/l)
0.5 +/ -0.5
1.0 +/ -0.9
0.9 +/ -0.8
0.3
D O (mg/l)
4.7 +/ -1.2
6.0 +/ -1.4
3.0 +/ -1.7
> 6
Table 3.4. Mean values of the various parameters at
Points 1 to 4.
PARAMETERS
POINT1
POINT2
POINT3
POINT 4
Temperature (ºC)
19.0 +/ -3.6
18.8 +/ -0.5
15.5 +/ -0.6
21.5 +/ -4.7
Conductivity (µS/m)
190 +/ -72
1550 +/ -135
325 +/ -110
2140 +/ -970
pH
6.9 +/ -0.3
3.9 +/ -0.4
7.2 +/ -0.2
3.7 +/ -0.2
Nitrate (mg/l)
4.0 +/ -1.3
42.0 +/ -23.1
13.5 +/ -1.7
17.5 +/ -12.7
Phosphate (mg/l)
4.3 +/ -2.1
11 +/ -3.9
9.3 +/ -1.4
11.7 +/ -12.1
from Point 1 to Point 2. A decrease in the level of pollutants at Point 3 indicates some
degree of natural recovery and self-purification, or dilution, in a distance of only 3 km
down-stream of Point 2. A seasonal examination of the results obtained, show that the
impact of Zimphos is more pronounced during the dry season, and most probably is due
to the pollution from ground water recharge. Increased volumes of the river flow during
the wet season lead to dilution of the contribution of the plant.
Jarawaza (1997) reported data about the water quality of Upper Manyame River and
tributaries, collecting the effluents from the satellite town of Chitungwiza, based on the
continuous monitoring program of the city of Harare during 1996. It has shown
considerable pollution of the River, as a result of the overloading of the existing waste
stabilization ponds system and urban runoff from the satellite town of Chitungwiza,
which has a land use pattern similar to high-density urban developments in Harare. The
data obtained by the monitoring program served as an alarm for the managing authorities
and the upgrading of the existing facilities was undertaken. The new BNR plant was
commissioned in 2002.
