Water samples for physico-chemical, heavy metals and bacteriological analyses were collected from 4 selected points along Mitheu Stream flowing through Machakos Municipality once every month from June 2019 to September 2019. The samples were analyzed in Kenya Plant and Health Inspectorate Service and Water Resources Authority laboratories then data subjected to one-way analysis of variance to test significant differences (P≤0.05). The results were compared with World Health Organization guidelines to assess the suitability of the water for irrigation use. Results showed that the levels of the Biological Oxygen Demand and the Chemical Oxygen Demand in Mitheu Stream were higher than critical values permitted by the World Health Organization for irrigation water. Nitrates and Sulphates were within critical limits; however, Phosphates were higher than permissible limits at all the sampling points. Heavy metals concentrations for Cu, Pb, Zn and Cr were within allowable limits for irrigation water, but Cd was above the limit. Both total coliforms and Escherichia coli counts exceeded allowable limits for irrigation water. As such, Mitheu Stream can be considered polluted and the water unfit for irrigation farming. The Municipal authorities, working with other relevant stakeholders should take appropriate measures to mitigate stream pollution from untreated effluent discharged into the stream.
Key words: Physico-chemical, heavy metals, total coliforms, effluent.