Assessment of the quality of SOBO industrial wastewater and its impact on water quality in Nankhaka River

摘要

An assessment of the quality of industrial (effluent) from soft drink manufacturer Southern Bottlers (SOBO) factory in Lilongwe was carried out to determine the impact of pollution in Nankhaka River. Both the effluents and the water samples at selected points in the river were analysed for pH, suspended solids (SS), total dissolved solids (TDS), phosphate, nitrates, dissolved oxygen (DO), biochemical oxygen demand (BOD), chemical oxygen demand (COD) and faecal coliform (FC) using standard methods. The levels of SS, TDS, phosphate, BOD and COD with mean values of 111, 803, 4.61, 186 and 570 mg/l respectively, in the SOBO industrial wastewater were outside the Malawi Standard recommended limits for effluents discharged into inland waters. However, the levels of pH (8.29) and nitrates (0.031 mg/l) were within the recommended limits whereas the levels of faecal coliform (42,900 counts/100ml) and DO (2.50 mg/l) were not specified in the standard. The variation in water quality between upstream and downstream parameters was statistically significant (p 0.05) at 95% confidence level. The results suggest that SOBO effluent pollutes the water in the river rendering it unfit for human consumption. It is therefore recommended that the discharge of poor quality effluents should be discouraged. Authorities should enforce the laws governing the disposal of wastes to protect the lives of the people who use the water in Nankhaka River.