Environmental Engineering Reference
In-Depth Information
et al
.
2004a), Beatrice (Ravengai et al
.
, 2004b), Madziwa and Trojan (Lupankwa et al
.
2004a, 2004b) and Iron Duke (Ravengai et al. 2004c).
Grouting at the margins of the landfill with lime would raise the pH material. This
would change the chemistry of water seeping out of the landfill by raising the pH and
adding dissolved carbonate, thus precipitating dissolved metals. Future metal
contamination would thus be confined to the immediate environs of the landfill.
3.2
Granville Cemetery
The results of the study showed the presence of microbiological indicators (total coliform
and fecal col-iform) in the sampled groundwater. Total coliform (TC) and fecal coliform
(FC) bacteria had averages of 1 × 10
7
coliform forming units (cfu) and 5.2 × 10
4
cfu
respectively. TC were concentrated around the graves, with highest numbers in boreholes
in more recent graves (2002) (Fig. 7.14). FC were concentrated around the older graves
(1999-2000) and the pauper graves (Fig. 7.15). The results (GH3 and GBH8) indicate that
FC have not been carried far in groundwater;
All the boreholes had pH below the control, giving an average of pH 5.9 (Table 7.3).
This decrease in pH can be an influence of microbial activity within the graves. Calcium
had high levels, greater than 100 mg/l in boreholes GBH7 and GBH9 and the rest were
less than 50 mg/l. Iron is relatively high in the control since the borehole was cased using
metal, therefore the control borehole cannot be used for comparison of iron values.
Boreholes GBH4 and GBH5 had relatively high iron, most probably coming from the
graves. Fe, K and Ca were concentrated around the graves. Variation in the concentration
of Ca, K and Fe across the study area increases with the groundwater flow. There are two
possible explanations for this rise in metal levels with groundwater flow. One possibility
is that Ca, K and Fe could be released from decomposing corpses. Alternatively, the
increases could be due to water-rock interactions-especially the hydrolysis of feldspars,
which are abundant in the local granites (Baldock et al. 1991) and break down to release
Ca and K, especially where there is appreciable groundwater flow (Faure 1991).
Table 7.3. Groundwater quality data, 2003-2004,
Granville Cemetery, Harare.
pH
(pH
units)
K
(mg/l)
Na
(mg/l)
Fe
(mg/l)
Mg
(mg/l)
Ca
(mg/l)
NO
3
(mg/l)
Cl
(mg/l)
P
(mg/l)
SO
4
2
-
(mg/l)
Total
coliforms
/100 ml
Faecal
coliforms
/100 ml)
GBH1
5.67
3.4 21.26
13.61
0.54
4.94
0.04
0.13
0.42
22.24
0
0
GBH2
5.47
9.83 24.29
13.75
0.69
5.2
0.18
0.09
0.6
38.72
105000
350000
GBH3
5.98
8.1
29.4
7.5
2.92 179.94
0.07
0.22
0.4
<1.65
43000
0
GBH5
5.36
4.17 16.48
12.08
0.57
5.1
0.11
0.09
0.8
1.65
20000
9000
GBH7
5.39 10.67 24.77
0.81
1.94
9.35
0.09
0.09
1.17
118.63
700000
0
GBH8
6.67
6.57 18.87
5.66
2.87
0.57
0.07
0.18
0.02
<1.65
32000
0
GBH9
5.71
1.43 17.66
13.55
13.19 152.24
0.08
0.22
0.08
<1.65
0
0
Control
6.98
3.12 21.93
15.72
16.85
7.24
0.02
0.18
0.01
<1.65
0
0
