Assessment of the microbial load of Nyanchwa-Riana and Nyakomisaro-Riana Rivers, Kisii, Kenya

 

Author(s): Ogendi G. M, A. M. Getabu, J. M. Onchieku, J. M Babu

Abstract: Water is an elixir of life, a precious gift of nature to mankind and other animal and plant species living on the planet earth. Water quality was assessed in two parallel rivers flowing through Kisii town. Parameters assessed were; Electrical Conductivity, TDS, TSS, pH, temperature, total and fecal coliform counts monthly for 18 months along five sampling sites in the rivers’ transects. Mean TDS in Nyanchwa and Nyakomisaro rivers were 142.59±22.68 mgL-1 and 96.62±11.76 mgL-1 respectively. Nyanchwa had an overall EC of 110.35±2.09 µScm-1 while Nyakomisaro had 107.55±4.15 µScm-1. EC was also correlated with TDS, temperature, TSS, T-coli and F-Coli at all sites. TSS in Nyanchwa River and Nyakomisaro ranged from 2.00 – 396 mgL-1 with an overall mean of 53.86±5.67 mgL-1 and 56.38±6.45mgL-1 respectively. TSS had significant differences in sampling sites and was above the recommended NEMA levels of 30 mgL-1. F-Coli was strongly correlated with the T-Coli in the two rivers. Nyanchwa had an overall mean of fecal and total coliforms of 740± 94 cells100ml-1 and 627 ±112 cells100ml-1 respectively while Nyakomisaro had an overall mean of fecal coliform counts of 786±104 cells100ml-1 and mean total coliform counts were 842±105 cells100ml-1. Chlorophyll-a in both rivers was not significantly different across the sampling sites. Both rivers had chlorophyll-a concentrations beyond 10μgL-1. The results suggested that environmental loading of pollutants from car washing sites, leaked sewage, defecation in the bushes, organic wastes and dumping soils from construction sites adversely altered natural stream water quality dynamics, underlining the need for improved management practices, including controlling leachate from dumpsites into the rivers to minimize the large-scale escape of pollutants into the rivers.

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