Determination of microbiological water quality in mid-reaches of River Njoro,Nakuru,Kenya

Abstract

Faecal and total coliforms counts were used to determine the microbiological water quality of Njoro River, which is fed by a watershed characterised by sanitation problems, thereby exposing people and animals using the river to high risks of contracting waterborne diseases. These sanitation problems are as a result of increase in population and concomitant change in land use in the watershed. Spatial and temporal variations of these parameters were studied in a period of six months covering both dry and wet seasons. Membrane filtration was used to enumerate faecal and total coliforms. In-situ measurements of water temperature, specific conductivity, pH, dissolved oxygen and turbidity were conducted in each sampling occasion. Temperature, specific conductivity, pH and dissolved oxygen were measured using a hydro lab multi-parameter while turbidity was measured using a long transparent tube with a circular mark at the bottom. Data were analysed using STATISTICA statistical package. A two way ANOVA showed significant variation among sampling sites and occasions (p<0.05). Egerton University sewage, Njoro canning upstream and Njoro canning downstream recorded the highest mean bacterial counts among all the sites sampled, while October, November and December, the wettest months during the study period, recorded the highest mean bacterial cotmts among all the months in which sampling took place. Upstream forest sites characterised by minimal human activity, recorded the lowest mean bacterial counts. Turbidity had the highest level of correlation (r = 0.44) with biological parameters, followed by temperature and conductivity. Mean bacterial counts exceeded the WHO water quality standards for drinking, recreation and irrigation. Strong recommendations are made in the light of the findings towards alleviation of microbiological water pollution of the river. Apart from producing new knowledge, the findings are part of information useful in successful river and waterborne diseases management.