Abstract

Water sampling and testing was done on nine points along the Lilongwe River course and on all the confluences of the main tributaries of Lilongwe River that lie between Dzalanyama Forest reserves up to where the Lilongwe City Assembly Sewage Treatment Works discharges its treated wastewaters into Lilongwe River at Kauma. The sampling covered a distance of approximately 50 km downstream. The water samples were analysed for pH, total dissolved solids, electrical conductivity, hardness, suspended solids, biochemical oxygen demand, chemical oxygen demand, nitrates, phosphates, potassium, sodium, lead, cadmium and faecal coliforms as biochemical parameters that were used to determine the quality of the water. The sampling was done at three different times of the year. First sampling was done at the beginning of the rainy season in November, 2006 (two days after the main rains had just started). The second sampling was done in the middle of the rainy season in February, 2007, when the main rains were at the peak. The third sampling was done in September, 2007, long after the main rains were gone. This was done in order to determine any trends in water quality at different times of the year. A socio-economic study was done in the study area, especially around the sampled sites in order to identify any human activities that may be taking place and in the process contribute wastes into the river system which had impacts on the quality of water in Lilongwe River. The effluent disposal system of a number of industries and institutions that are found in the catchmemt study area were investigated. Wastewater effluent samples that were trickling from these identified industries and institutions into the Lilongwe River water system were collected and analysed for biochemical constituents. These were correlated with the chemical constituents that were identified in the river water samples that were collected from the sites where the industrial wastewaters were discharging into the Lilongwe River. vii The socio-economic survey identified 29 industrial/institutional activities in the upper catchment segment, 66 in the middle catchment segment and 106 in the lower catchment segment. The biochemical constituents analysis showed significant difference amongst the three periods of sampling (seasons). At the first flash of the main rains the water samples showed the highest range of pH (6.23 – 7.77), and highest concentration of nitrates (0.01- 0.13mg/l), potassium (0.50 – 3.23mg/l), Hardness (24 - 280mg/l), lead (0.452–1.033mg/l), faecal coliforms (315–40,500 counts/100ml), BOD (6.30–79.33mg/l), DO ( 2.48 – 9.45mg/l) and COD (7.43–133.53 mg/l) of all the sampled periods. Phosphate (0.02 – 0.29mg/l) and SS (5.0 – 811 mg/l) were found to be highest in the rainy season only while cadmium (0.002 – 0.006 mg/l), EC. (72–919 µs/cm), sodium (10.8–37.8mg/l) and total dissolved solids (54–660mg/l) were found to have highest concentration range in the dry season. The results indicated that waste from the industries and institutions, mainly in the built-up area of the City also contribute heavy metals such as lead (0.295-1.033 mg/l) and cadmium (0.01-0.06 mg/l) in Lilongwe River. The findings have shown that the anthropogenic activities in and around the City of Lilongwe are contributing to the pollution and deterioration of the quality of water in Lilongwe River. It is recommended that more studies be done for all biochemical parameters of water quality importance so that information for rehabilitation programs can be made based on comprehensive data.

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School	: School of Natural and Applied Sciences
Issued Date	: 2009

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