Effects of Land Use Types on the Levels of Microbial Contamination Based on Total Coliform and <i>Escherischia coli</i> counts on the Mara River, East Africa

Abstract

The effects of land use types on levels of microbial contamination based on total coliforms and E. coli (faecal coliform) levels was investigated in the Mara River system, Kenya and Tanzania. Water samples were taken from five sampling sites with different land uses and the Most Probable Number (MPN) method used to determine the total coliforms. A biochemical test was done and the proportions of E. coli bacteria given per study site. The mean concentration of total coliforms was lowest at Silibwet Bridge and highest at Kirumi Bridge. However, counts of E. coli were highest at an urban site (Bomet Bridge) and lowest at a swamp site (Kirumi Bridge). Overall, the proportion (40.9%) of Eosin Methylene Blue (EMB) broth plates that produced E. coli in the study sites was higher than the WHO recommended standards of 0% per 100 ml in potable water. The results show that sections of the river with most human activity and inappropriate types of land-use contributed to high levels of coliform bacteria, particularly E. coli. This may indicate the existence of point sources of faecal contamination along the Mara River and corrective measures should be taken to control them.

Keywords: E. coli, faecal coliform bacteria, land use type, most probable number, Mara River.