Browsing by Author "Ombui, P."

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  • Publication
    Publication
    Composition and design of vegetative filter strips instrumental in improving water quality by mass reduction of suspended sediment, nutrients and Escherichia coli in overland flows in eastern escarpment of Mau Forest, Njoro River Watershed, Kenya
    (Springer Link, 2016-06-13) Olilo, Casianes; Onyando, Jack; Moturi, Wilkister; Muia, Wairimu; Roegner, Amber; Ogari, Zachary; Ombui, P.; Shivoga, William
    This study assessed the effect of vegetative filter strip (VFS) in removal of suspended sediment (SS), total nitrogen, total phosphorus and Escherichia coli (E. coli) in overland flow to improve receiving water quality standards. Four and half kilograms of cowpat manure was applied to the model pasture 14 m beyond the edge of vegetated filter strip (VFS) comprising 10-m Napier grass draining into 20-m Kikuyu grass (VFS II), 10-m Kikuyu grass draining into 20-m Napier grass (VFS III) and native grass mixture of Couch–Buffel (VFS I-control). Overland flow water samples were collected from the sites at positions 0, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25 and 30 m along the length of VFSs. E. coli removal by Napier grass VFS was on the order of log unit, which provided an important level of protection and reduced surface-flow concentrations of E. coli to below the 200 (CFU 100 mL−1) recommended water quality standards, but not for nutrients and SS. The Napier grass showed highest efficiency (99.6 %), thus outperforming both Kikuyu grass (85.8 %) and Couch–Buffel grasses VFS (67.9 ± 4.2 %) in removing E. coli from overland flow. The low-level efficiency of native Couch–Buffel grasses in reducing E. coli in overland flow was because of preferential flow. Composition and design of VFS was instrumental and could be applied with a high potential of contracting the uncertainty in improving water quality standards through mass reduction of SS, nutrients and E. coli load in watersheds.
  • Publication
    Publication
    Effect of vegetated filter strips on infiltration and survival rates of Escherichia coli in soil matrix at Mau, Njoro River Watershed, Kenya
    (Springer Link, 2017-04) Olilo, C. O.; Muia, A. W.; Onyando, J. O.; Moturi, W. N.; Ombui, P.; Shivoga, W. A.
    Overland flows contaminated with manure borne pathogens pose risks to public health, because fecal pathogens may infiltrate into soil matrix from overland flows and contaminate soil water aquifers. The objective of this study was to evaluate the effect of vegetative filter strip (VFS) on infiltration rates (CFU 100 ml−1 h−1) of Escherichia coli (E. coli) in overland flow and their survival rates in soil matrix. Thirty samples of the specimen were collected from VFSs each sampling time. The samples were each filtered, followed by a series of ten dilutions; then analyses for E. coli using membrane filtration technique. Wet oxidation method and potassium persulfate technique were used to analyze particulate organic carbon (POC) and dissolved organic carbon (DOC) at (p < 0.05) level of significance, respectively. A strong relationship was obtained between E. coli, POC and DOC in the overland flows (R2 = 0.89, p ≤ 0.05; df = 29). This study confirms the hypothesis that DOC released from Napier grass and Kikuyu grass exudates supported the initial survival, subsequent growth and adaptation of E. coli in its new secondary habitat outside its primary host. Thus, in the soil habitat, DOC and POC provided the initial energy for microbial cell multiplication from the VFS grasses. VFS influenced partitioning, infiltration and survival of E. coli in the overland flow into soil matrix. Thus, root zone retention data and information on E. coli in VFS systems are significant and could be used for scientific and management of soil erosion and the control of fecal pathogens entering surface water ecosystems both locally in Mau Ranges, Njoro River Watershed and internationally in other areas with similar environmental problems. VFS could be utilized under various designs of VFSs with different plants that have different setup of plants’ root zone cover and penetrations systems that could help in infiltrating overland flow manure borne pathogens, a process that could be useful in the management of these pathogens in agro-pastoral systems locally and internationally.
  • Publication
    Publication
    Effect of vegetated filter strips on transport and deposition rates of Escherichia coli in overland flow in the eastern escarpments of the Mau Forest, Njoro River Watershed, Kenya
    (Springer Link, 2016-06) Olilo, C. O.; Onyando, J. O.; Moturi, W. N.; Muia, A. W.; Ombui, P.; Shivoga, W. A.; Roegner, A. F.
    The fate and transport of Escherichia coli (E. coli) in lotic waters through vegetated filter strips (VFSs) was evaluated in a field model pasture, utilizing VFSMOD Windows along with direct pathogen testing. This study assessed effects of VFS on transport and deposition rates of E. coli in lotic overland flow waters. The VFS measured 44 m long by 40 m wide, covering an area of 1584 m2 and land slope of 15 %. Cowpat was applied onto the model pasture and washed by overland flow into the VFS. The 4-methylumbelliferyl β-D-glucuronide substrate confirmed the identity of E. coli prior to cowpat application and after isolating them from soil using centrifugation and membrane filtration techniques. Napier grass root system recorded the highest recovery rates of E. coli at 99.9 % along the length of VFS III. This efficiency reduced significantly (p < 0.05; df = 29) to 95 % in Kikuyu grass and 75 % in Couch grass-Buffer grass. The data demonstrated similarity in transport of manure-borne E. coli and organic carbon (OC) through all the simulated VFS. These results indicated that OC could be used as a true natural tracer of manure-borne E. coli, a pollution indicator organism of lentic and lotic surface waters provided the OC release kinetics from cowpat were similar to that of E. coli kinetics. Thus, efficient filtering to reduce E. coli concentrations and load in overland flows requires managing combined grass species, agro-pastoral systems models and dispersed or preferential flows to enhance surface water quality standards.