Environmental Engineering Reference
In-Depth Information
is despite the fact that some peri-urban communities near cemeteries depend upon
shallow groundwater as a water source. There is good evidence that bacteria, which
decompose corpses can reach the water table, especially where groundwater flows
through fractures, which provide faster and rapid movement (Trick et al
.
2002). Studies
in Germany reported high concentrations of bacteria, ammonium and nitrate in a
contamination plume, which rapidly diminished with distance from graves and a study in
the Netherlands reported a very saline (2300 µS/cm) plume of chloride, sulphate and
bicarbonate ions beneath graves (Usisik & Ruchbrook 1998).
The body of a 70 kg adult human male contains approximately: 16 kg carbon, 1.8 kg
nitrogen, 1.1 kg calcium, 500 g phosphorous, 140 g sulfur, 140 g potassium, 100 g
sodium, 95 g chlorine, 19 g magnesium, 4.2 g iron, and water 70-74% by weight (Usisik
& Rushbrook 1998). Human corpse undergoes autolysis and putrefaction in the early
stages of decomposition, then liquefaction and disintegration and final skele-tonization
(Dent et al. 2004). The leachate (liquids generated during decay) generally contain
contaminants such as ammonia, Ca, Mg, Na, Fe, K, P, Cl and SO
4,
as well as a variety of
pathogenic organisms, such as protozoa, many algae, fungi, bacteria and viruses
(Engelbrecht 1998, Environmental Agency 2002). The role of microbial contaminants in
groundwater is in the transmission of waterborne disease. Waterborne diseases of concern
such as cholera, typhoid fever, cryptosporidiosis and viral gastroenteritis can originate
from protozoa such as
Cryptosporidium parvum
,
Giardia lamblia
and bacteria such as
Legionella
or
Vibrio
species of enteric and other viruses (Centre of Disease Control and
Prevention 2000, Environmental Agency 1999). It is difficult or even impossible to detect
some pathogens of concern with the current technology; hence indicator bacteria
(coliforms) are used as indicators of possible contamination and as an index of water
quality deterioration.
1.4
Landfill study area
The recently developed suburb of Westlea, Harare is located very close to the municipal
Golden Quarry landfill, downwind and down-flow of the waste disposal site. Harare has
two active landfills: Golden Quarry in the Warren Hills area and Teviotdale in the
Pomona area. Both are former quarries. Solid waste also used to be dumped close to the
Mukuvisi River, immediately south of the main railway station (Zaranyika 1997). The
Golden Quarry is the largest municipal landfill in Harare, and is located some 7 km from
central Harare, on the edge of Westlea suburb, along the main road to Bulawayo,
westwards from the city center (Fig. 7.1.). The Golden Quarry landfill was selected for
study because of the availability of sixteen boreholes drilled in the late 1990s under a
project sponsored by SIDA-SAREC, and since it took the vast majority of the city's
waste (Rakodi 1995).
The landfill has been used for disposal of both domestic waste and industrial waste.
Figure 7.2 presents a location map of the study area, and Figures 7.3 and 7.4 illustrate the
physical appearance of the disposal site. At the same time, some of the residents depend
upon shallow groundwater as a water source.
There are trenches dug on the western side of the dump to capture runoff from the
western side of the landfill, and prevent it flowing to the Westlea residential area. Gum
trees are planted along the western and southern sides of the landfill. Shallow
