4. Anthropogenic Pollution Impact on Microbial Contamination of Lake Kivu, Rwanda

Abstract

Investigation of the anthropogenic pollution impact on microbial contamination of Lake Kivu, Rwanda was carried out in Gisenyi, Kibuye and Cyangugu over a period of 24 months. Total coliforms (TC), total heterotrophic bacteria (THB) and fecal coliforms (FC) counts were monitored. Indicator bacteria were enumerated by membrane filtration while pathogenic bacteria were recovered by broth enrichment of water samples. 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/100 ml) was highest 7.7 × 105 at Gisenyi and lowest 1.7 × 105 at Cyangugu. These values exceeded the zero faecal coliforms counts/100 ml recommended by WHO for water considered safe for human consumption. Total heterotrophic bacteria (THB), fecal coliforms (FC), total coliforms (TC) and Fecal streptococcus (FS) were widespread with abnormally high values at 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 dominant microbial species in the lake water. The microbial quality of the water was poor, suggesting contamination of the lake water by animals and human domestic wastes and other anthropogenic activities, such as laundry, swimming, farming, transportation, etc. The lake water is unfit for human domestic use without any form of treatment.