Browsing by Author "Ogendi, G. M."

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  • Publication
    Publication
    An Assessment of Some Physical, Chemical and Biological Characteristics of Nyanchwa - Riana River Flowing through Kisii Town in South West Kenya Ogendi G. M. A. M., Getabu
    (International Journal of Applied Science and Technology, 2015-04) Onchieku, J.; Ogendi, G. M.
    A study was conducted to assess the water quality of Nyanchwa-Riana River flowing through Kisii town during the period May 2013 to June 2014. Sampling stations were selected on a transect covering the upper and middle reaches of Nyanchwa stream. A further two sampling stations were added after the confluence on the Riana River downstream. The water quality parameters assessed were dissolved oxygen concentration, pH, conductivity, turbidity, chlorophyll-a, total and soluble phosphate and nitrate concentrations and coliform counts. Nutrient concentrations generally increased from the source of the Nyanchwa -Riana River towards the lower reaches of the river. Soluble nutrient concentrations exhibited the same trend. The total phosphorous to total nitrogen ratio of 1:3 varied from the Redfield ratio of 1:16 commonly found in natural habitats. Total coliform counts exceeded those recommended in the international water quality standards of less than 10 coliform cells/100ml of water and those of NEMA of nil100ml -1 . Observations on the physical and chemical parameters showed levels stressful to aquatic life, with dissolved oxygen concentrations less than 5 mgL -1 in some sampling points. These findings are useful in the management of the water quality in the two streams and on the River Riana flowing through Kisii town.
  • Publication
    Publication
    Effects of point source pollution on water quality, phytoplankton diversity and abundance in lake Victoria, Kenya
    (Semantic Scholar, 2015-05-01) Babu, J. M.; SitokiL, M.; Ogendi, G. M.; Getabu, A.; Akunga, P. N. G. N. B.; Nyaundi, J.; Njiru, J.; Mwayuli, G.; Olilo, C.
    Water quality deterioration remains a major problem in most fresh water lakes. This study was conducted to establish the extent of water quality deterioration in Kisumu Bay of Winam Gulf, Lake Victoria. The overall objective was to assess the effects of point source pollution on water quality and phytoplankton community structure. Sampling stations were selected randomly all over the bay and marked with a global positioning system (G.P.S). Triplicate samples of dissolved oxygen concentration, conductivity, ammonia, nutrients, chlorophyll-a and phytoplankton were taken for laboratory analysis. Mean overall dissolved oxygen concentration was 7.41±1.39 mg l-1. Mean conductivity level was 142.39±63.786 µScm-1 whereas mean soluble reactive phosphorus level was 330.02±311.9 mg l-1. The mean overall chlorophyll a level was 592.9± 604.4 mg l-1 indicating that the bay is eutrophic. The Duncan multiplernrange test showed significant variability of the means of this parameters at different sampling sites at p=0.005. At 46%, the diatoms were the most dominant phytoplankton family in the bay. There were significant differences in distribution of different phytoplankton taxa at different sampling sites (p=0.0001). The results of this study can be used to formulate management options for the improvement of water quality in the Kisumu Bay of Lake Victoria.
  • Publication
    Publication
    Nutrient removal efficiency by floating macrophytes; Lemna minor and Azolla pinnata in a constructed wetland
    (GJESM Publisher, 2019-07-13) Muvea, F. M.; Ogendi, G. M.; Omondi, S. O.
    The use of constructed wetlands for purifying pre-treated wastewater is a cost effective technology that has been found to be more appropriate for many developing countries. The technology is also environmentally friendly with the wetlands being habitats for many water birds and other aquatic organisms. This study assessed nutrient removal efficiency of two floating macrophytes (Lemna minor and Azolla pinnata). The data generated was analyzed using both descriptive and inferential statistics. The significance level was maintained at 0.05. The results showed that the wastewater physicochemical parameters did not vary during the study period. The concentrations of nitrites and nitrates increased over the experimental period in all the treatments (Azolla pinnata, Lemna minor and control), and the increase between the sampling occasions was statistically significant for the two nutrients (Nitrates: F=24.78, P= 0.00; Nitrates: F=198.26, P= 0.00). To the contrary, in all the treatments the concentrations of ammonia, total phosphorous, soluble reactive phosphorous and total nitrogen, decreased over the experimental period. The decrease in concentration for these nutrients between the sampling occasions was statistically significant (ammonia: F=195.57, p= 0.00; total phosphorous: F= 56.50, p= 0.00; soluble reactive phosphorous: F= 37.11, p= 0.00; total phosphorous: F= 104.025, p= 0.00). Azolla pinnata proved to be better than Lemna minor in the uptake of the nutrients particularly for the soluble reactive phosphorous (F= 35.18, P= 0.044). We conclude that the two macrophytes are good for wastewater treatment. It is recommended introduction and/or multiplication of Azolla pinnata in the constructed wetlands meant for wastewater treatment especially within the tropics.