Microbiological index of water pollution in Lake Kivu, Rwanda

Abstract

Investigation of the microbiological purity of Lake Kivu as index of water pollution was carried out in Gisenyi, Kibuye and Cyangugu over a period of 24 months. Microbial load did not differ significantly with season and locations but Fecal Coliform (FC) had positive significant correlation (r = 0.36; p<0.05) with season. Mean Total Coliform (TC) (cfu/100ml) was highest 7.7 x 105 in Gisenyi and lowest 1.7 x 105 at Cyangugu. These values exceeded the 5000 colony forming units/100ml recommended by WHO for public surface water supplies. Total heterotrophic bacterial (THB), FC, TC and Fecal streptococcus (FS) were widespread with abnormally high values in the sampling locations signifying poor water quality. Microbial isolates from the water samples were of wide range of groups and their occurrence and distribution varied from location to location. Bacillus sp, E. coli, Citrobacter freundii, Klebsiella pneumonia and Proteus sp were the cosmopolitan microbial species in the lake water. The microbial quality of the water was poor rendering it unsafe for domestic purposes without treatment and this was largely caused by direct contamination of the lake by animals and human domestic wastes.