Surface waters, including lakes, rivers and dams are essential water sources. However, these sources are vulnerable to pollution. This presents serious economic, ecological and public health, problems that are of global concern. Therefore, frequent monitoring of physicochemical and microbiological properties of water resources is necessary. This is instrumental in identifying impairments for protection of public health and environment.
Thika River, whose source is Aberdare ranges, is a major surface water resource in Yatta sub-county. Its water is used for domestic, agricultural and raw water abstraction purposes. Being such an important resource in a semi-arid area, its water quality should be monitored frequently. Therefore, this research undertook to investigate water quality in the river through analysis of physical, chemical and bacteriological parameters of water samples from the river.
The analysis was carried out in two phases, that is, in October 2018 during the dry season and in January 2019 during the rainy season. Standard Methods for Examination of Water and Wastewater were used in sampling and testing of water samples from different sampling stations that were 23 km apart. Five samples were collected during each phase for testing and analysis.
Laboratory and in situ results of the examination showed that the water met most of the physical and chemical requirements set by WHO and Kenyan Standards. During phase two analysis, Iron and Total suspended solids were however found to be above the acceptable limits of 0.3 mg/l and 0 mg/l respectively, as required by WHO and KS.
Bacteriological analyses of the samples also showed that Total Coliforms and Fecal Coliforms were present in all the samples. TC counts for the first phase ranged from 28 to 460 MPN/100ml. For phase two, TC concentrations ranged between 21 and 240 MPN/100ml. FC counts were only investigated during phase two and they were between 15 and 93 MPN/100ml. From the above results, it was concluded that the water was a threat to public health. The contamination was found to be more severe during the dry season when water in the river was minimal.