Environmental Engineering Reference
In-Depth Information
Considering the high TC and EC values measured, it could be expected that they would
be supplemented by concentrations higher than the measured ones. This discrepancy
needs additional investigation. It might be due to a consistent error in the laboratory
analytical procedures. Such a possible scenario would require a thorough examination of
the existing laboratory procedures and the implementation of a reliable quality assurance
program in the corresponding laboratories. UN/ECE (1996) could provide useful
information in this direction.
2.6
Discussion
The land use patterns along the stretch of the river vary, where the conditions along the
upper reaches of the river, near the Dzalanyama Forest Reserve and the Kamuzu Dams,
could be evaluated as pristine. The agricultural areas downstream of the Dams do not
have an adverse impact on the river water quality and this could be expected, as informal
and small-scale agriculture usually does not apply large amounts of fertilizers and
pesticides, which could have an adverse effect on the river water quality. A high level of
pollution found during this specific study, was significant with respect to TC only, and
could be associated mainly with the pattern of informal and quasi-formal settlements
along the riverbanks. It was not possible to account for the contribution of each specific
area, but this rapidly spreading form of uncontrolled urban development could be a
serious threat and if not controlled, inevitably, would lead to larger pollution loads in
future. The industrial enterprises located just upstream the abstraction point of
LWBWTW, together with the denser informal settlements development in this area
contribute to the increase in the pollution constituents of the river water.
A point of serious concern is the recent trend of uncontrolled urban development along
the upper reaches of Lilongwe River. Such a development is a direct contradiction to the
recommendations for source control measures, aiming at the control of diffuse pollution
problems. Informal settlements with no basic sanitation facilities create conditions for
diseases' spreading and environmental pollution. Instead of creating new environmental
buffer zones between settlements and riverbanks, the existing ones have been destroyed
to create living space for the new-coming population.
The location of industrial enterprises in such proximity to the water supply source of
the city is highly unacceptable and is another point of concern, which needs to be
addressed with urgency. The recent study, due to its limitations, shows only a limited part
of the whole picture of the water quality status of the river. The parameters studied, do
not show a serious danger with respect to the water supplied to the city, as during the
treatment process and after disinfection, the produced water should correspond to the
requirements for potable use. However, a most thorough investigation and a continuous
monitoring program could show the presence of pollutants, such as higher BOD or COD
values, or some trace toxic elements released from the industrial enterprises, which could
not be eliminated by the conventional process of the treatment plant. High organic
pollution loads of natural water are of serious concern, when such water is used as a
source of potable water, even after conventional water treatment. Such loads could be the
bases for THMs formation after disinfection, which have carcinogenic and mutagenic
effects, when present in excessive concentrations in potable water.
