Environmental Engineering Reference
In-Depth Information
urbanizing and is faced with the effects of urbanization such as population growth,
pollution, and demand for land for settlement. The rapid population growth and demand
for land has lead to non-ideal residential development, where residential stands are
developed in close proximity to pollution sources. This is especially problematic where
shallow groundwater is used as a water source.
Among the more significant municipal facilities to impact on groundwater quality are
landfills and cemeteries. In this study, the pollution of shallow groundwater around
Harare's largest landfill and its largest cemetery is characterized and recommendations
made for mitigating the facilities' impact and for medium-term urban planning.
1.2
Solid waste disposal and its impact
Due to rapid urbanization groundwater is becoming increasingly vulnerable to pollution
from human activities (Aldrick et al
.
1999). Some of the most problematic sources of
groundwater pollution in the urban environments are municipal landfills (Dutova et al.
1999). Formal municipal landfills are often major sources of contamination - especially
where they are unlined, as is common in the developing world. A whole suite of
contaminants such as sodium, potassium, ammonia, nitrate, nitrite, chloride and heavy
metals such as iron, manganese, lead, mercury and chrome, can leach out of landfills
(Fetter 1994, Stone 1996, Zhu et al
.
1997), although leachate composition and pollution
loadings are also affected by climate (Tatsi & Zouboulis 2002). The strategic impact of a
landfill can be considered as a result of three factors: pollution load, permeability and
reactivity of the unsaturated zone and the value of the groundwater resource under threat
(Parsons & Jolly 1994).
The location of a landfill, like any other potential contaminator of groundwater, is
critical. Proximity to faulted or unstable areas and wetlands can be highly problematic
(USEPA 1993), as such proximity increases the risk of contamination, or the speed of
movement of the contaminant plume, or both. Faulted areas allow easier contamination of
groundwater by leachate, unstable areas (such as seismically active zones or sinkhole
areas) risk collapse of the landfill and wetlands are ecologically highly sensitive to many
forms of contamination.
1.3
Cemeteries and groundwater quality
Large-scale human decomposition processes associated with cemeteries could be
interpreted as special kind of landfills (Dent & Knight 1998, Dent et al
.
2004). In
cemeteries, human corpses may cause groundwater pollution not by virtue of any specific
toxicity they possess, but by increasing the concentrations of naturally occurring organic
and inorganic substances to a level sufficient to render groundwater unusable or unfit for
potable purpose (Usisik & Rushbrook 1998).
The nature of pollution emanating from a cemetery site differs from that produced by
conventional solid waste-disposal sites, primarily because cemetery leachate pose a
greater health hazard. Studies in a graveyard in Wolverhampton found out that the
groundwater was contaminated by bacteria from decaying bodies (Trick et al. 2002).
Microbiological tests indicated thermo-tolerant coliforms and fecal streptococci at
concentration above World Health Organisation standards (Trick & Klinck, 2001). This
