Environmental Engineering Reference
In-Depth Information
permanganate in sulfuric acid titration method” was used to determine COD. EC and pH
were measured in the field using GIL International (model 33) meters.
The land use patterns and new developments were established through field
reconnaissance surveys in the area and the information obtained was compared with
existing maps. In addition, interviews were conducted with officials that are responsible
for such developments and practices. They were requested to cite problems they are
facing in managing their respective departments. These include the Lilongwe City
Council, the Ministry of Lands and Housing, the Department of Forestry, the Ministry of
Agriculture and Natural resources. The information with respect to existing land patterns
was obtained in the form of maps or any other documentation that was in existence.
These were obtained from the Department of Surveys and Ministry of Lands and
Housing.
Statistical data analysis was performed by the use of standard EXCEL statistical tools.
2.5 Results
Results obtained during the period of study show significant pollution in terms of EC and
TC only (Fig. 11.4 and 11.5). The values obtained with respect to pH are within the
normal range of 7 to 7.7 (variation of SD from 0.1 to 0.7) showing no signs of pollution
and no spatial variation.
The results with respect to dissolved nutrients (both phosphate and nitrate) vary within
the range of 0.01 mg/l to 0.04 mg/l. No significant spatial variation was found. The
magnitude of the dissolved nutrients concentrations observed is very low; showing no
impact of the different land use patterns on the river water quality in the study area. It
could be accepted that the measured concentrations are close to the background pollution
values. This suggests that the informal agriculture in the region does not have a
considerable impact on the river water quality in respect to nutrients.
The spatial variation of EC and TC concentrations along Lilongwe River is presented
on Figures 11.4 and 11.5 respectively. It shows a considerable increase in both
parameters after the confluence of the Lisungwi River and the Likuni River.
The EC values increase from about 100 mg/l at the control point, which could be
considered to be the background pollution value, to about 500 mg/l at point G. Although
this value of EC does not pose any imminent hazard to public health in terms of drinking
water quality requirements, it indicates a considerable pollution and the possible presence
of other pollutant constituents. At point E the measured concentration was lower due to
the dilution of the constituent. The same trend of spatial variation was shown with respect
to TDS values, confirming the indication of pollution with respect to dissolved ions.
The TC variation shows a very high level of pollution in terms of bacteriological
contamination and a high risk of diseases' spreading, if the water is consumed without
treatment. The trend of the spatial variation is similar to the EC variation, with the
highest mean concentration of 5812 mg/l at site E. In this case, it is possible that the
additional influx of coliforms from the informal settlements, the industrial site and the
livestock farm is considerable and could not be attenuated by the increased flow rates.
Similar results of high bacteriological contamination have been reported for other rural
areas in Malawi (Ndolo et al. 2002).
Search WWH ::




Custom Search