Environmental Engineering Reference
In-Depth Information
River and during this period, a higher influence with respect to metals concentrations
could be expected. Additional investigation would be needed to evaluate in more details
the impact of the pasture on the aquifer, and the surface water - groundwater interactions.
With respect to the possible beneficial uses of the groundwater (Tables 9.4 and 9.5),
the high metal concentrations in respect to Cr, Ni and Pb makes it unsuitable for any of
the categories listed. The use for potable purposes should not be recommended even after
conventional treatment because it does not provide for the removal of dissolved metals
and a very complex and costly treatment should be applied in order to achieve the
recommended criteria.
5 CONCLUSIONS
Sewage sludge disposal on land could be considered as an extensive, low capital and
operational cost technology, suitable for application in the countries of the Southern
African region, because of the favorable climatic conditions and land availability.
However, if not applied adequately it could be viewed as a diffuse source of pollution to
groundwater and a possible reason for soils' degradation. In order to avoid such
undesirable effects and to improve the operational practice, some general
recommendations were made in Chapter 8. They are applicable for this case too. In
addition, the following could be stated:
Table 9.5. Ground water quality characteristics -
metals.
Parameter Sampling point
Maximum recommended levels for different
water uses
1
2
3
4
5
Average
wells
6
Control
Domestic* Domestic** Livestock Irrigation
Cd
mg/l
0.09
0.07
0.08
0.08
0.07
0.08
0.08
5
10
10
(0.082) (0.011) (0.033) (0.035) (0.023) (0.013)
(0.053)
0.003
Cr
mg/l
3.62
5.00
4.05
4.61
3.59
4.17
3.99
0.05
0.05
1
0.1
(3.072) (1.713) (1.142) (0.483) (1.421) (1.375)
(0.723)
Cu
mg/l
0.04
0.04
0.09
0.03
0.05
0.05
0.05
2
1
5
0.2
(0.042) (0.032) (0.031) (0.023) (0.034) (0.014)
(0.042)
Fe
mg/l
4.16
4.16
11.09
2.70
3.60
5.14
1.38
0.3
0.1
10
5
(2.773) (3.714) (7.721) (1.413) (1.711) (3.234)
(0.921)
Ni
mg/l
1.31
1.83
1.91
1.78
1.96
1.76
1.66
0.02
--
1
0.2
(0.902) (0.532) (0.522) (0.154) (0.453) (0.264)
(0.332)
