Environmental Engineering Reference
In-Depth Information
area, which includes residential development, commercial area and part of the home
industries plot.
The water quality at the control point reflects the background pollution for Harare area
(Hranova et.al. 2002), for all parameters except for nitrate, which at this point was about
10 times higher. The stream water quality at F shows a distinct increase in pollutant
concentrations with respect to all tested
Table 5.3. Water quality characteristics at points C,
F and control.
Parameter
Point
C
Point
F
Control
Mean Median
Std.
Dev.
Mean Median
Std.
Dev.
Mean Median
Std.
Dev.
pH
8.7
9.3
1.11
6.7
7.0
0.75
7.2
7.6
0.89
Conductivity
(µS/cm)
538
-
184
206
200
19
165
-
3
COD (mg/l)
64
45
54.5
39
40
11.4
7
5
2.9
TKN (mg/l)
2.31
1.12
2.713
1.23
0.56
0.964
0.26
0.37
0.191
Ammonia (mg/l)
2.00
0.62
2.693 0.53
0.65 0.332 0.12
0.08 0.138
Nitrate (mg/l)
3.20
2.40
1.931 2.30
1.82 1.633 1.22
1.54 0.642
TSS (mg/l)
51
38
53.7
39
40
89.1
17
4
24.3
TP (mg/l)
1.90
2.00
1.212
1.8
2.00
0.871
0.05
0.00
0.084
Ortho-P (mg/l)
1.10
1.20
0.963 0.74
0.53 0.751 0.04
- 0.075
Fe (mg/l)
5.70
4.71
8.012
5.73
3.22
7.244 0.041
-
0.053
Pb (mg/l)
0.060
-
0.0711 0.355
-
0.3353 0.050
-
0
Ni (mg/l)
0.215
-
0.1863 0.280
0.311
0.1674 0.013
-
0.0051
Zn (mg/l)
0.520
-
0.7252 0.201
0.179
0.1792 0.012
-
0.0023
Cu (mg/l)
0.043
-
0.0581 0.148
0.192
0.0981 0.005
-
0.0007
Number FC/100
ml
0-
100
-
-
0-80
-
-
0
-
-
parameters, except for pH. This reflects the impact of the informal agriculture area
together with the impact of solid waste dumped on the streambed and stream banks. It is
impossible to distinguish between the two possible causes of pollution, but it is more
likely that it is due to the solid waste depositions, because of the very low contribution of
runoff during this specific season, as discussed in the following section. The data set
regarding this point shows a good distribution with a relatively low difference between
mean and median values. The comparison with the acting regulations with respect to the
safe limit (WWEDR 2000) shows that the mean values measured during this study
