Theses And Dissertations

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Browsing Theses And Dissertations by Author "Igbinosa, Etinosa Ogbomoede"

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    Surveillance of invasive vibrio species in discharged aqueous effluents of wastewater treatment plants in the Eastern Cape province of South Africa.
    (University of Fort Hare, 2010) Igbinosa, Etinosa Ogbomoede
    Vibrio infections remain a serious threat to public health. In the last decade, Vibrio disease outbreaks have created a painful awareness of the personal, economic, societal, and public health costs associated with the impact of contaminated water in the aquatic milieu. This study was therefore designed to assess the prevalence of Vibrio pathogens in the final effluents of wastewater treatment plants (WWTPs) in the Eastern Cape Province, as well as their abilities to survive the treatment processes of the activated sludge system either as free cells or as plankton-associated entities in relation to the physicochemical qualities of the effluents. Three wastewater treatment facilities were selected to represent typical urban, sub-urban and rural communities, and samples were collected monthly from August 2007 to July 2008 from the final effluent, discharge point, 500 meter upstream and downstream of the discharge points and analysed for physicochemical parameters, Vibrio pathogens prevalence and their antibiogram characteristics using both culture based and molecular techniques. Physicochemical parameters measured include pH, temperature, electrical conductivity, salinity, turbidity, total dissolved solid (TDS), dissolved oxygen (DO), chemical oxygen demand (COD), nitrate, nitrite and orthophosphate levels. Unacceptably high levels of the assayed parameters were observed in many cases for COD (<10 - 1180 mg/l), nitrate (0.08 - 13.14 mg NO3- as N/l), nitrite (0.06 - 6.78 mg NO2- as N/l), orthophosphate (0.07-4.81 mg PO43- as P/l), DO (1.24 - 11.22 mg/l) and turbidity (2.04 -159.06 NTU). Temperature, COD and nitrite varied significantly with season (P < 0.05), while pH, EC, salinity, TDS, COD, and nitrate all varied significantly with sampling site (P < 0.01; P < 0.05). In the rural wastewater treatment facility, free-living Vibrio densities varied from 0 to 3.45 × 101 cfu ml-1, while the plankton-associated Vibrio densities vary with plankton sizes as follows: 180 μm (0 – 4.50 × 103 cfu ml-1); 60 μm (0 – 4.86 × 103 cfu ml-1); 20 μm (0 – 1.9 × 105 cfu ml-1). The seasonal variations in the Vibrio densities in the 180 and 60 μm plankton size samples were significant (P < 0.05), while the 20 μm plankton size and free-living vibrios densities were not. Molecular confirmation of the presumptive vibrios isolates revealed V. fluvialis (36.5 %), as the predominant species, followed by V. vulnificus (34.6 %), and V. parahaemolyticus (23.1%), and V. metschnikovii (5.8 %) (detected using only API 20 NE), suggesting high incidence of pathogenic Vibrio species in the final effluent of the wastewater facility. Correlation analysis suggested that the concentration of Vibrio species correlated negatively with salinity and temperature (P < 0.001 and P < 0.002 respectively) as well as with pH and turbidity (P < 0.001), in the final effluent.