Isolation of Pathogenic Bacteria Associated with Effluent Sludge from ObafemiAwolowo University Oxidation Pond.

Abstract

This study was carried out to isolate and identify the pathogenic bacteria associated with effluent sludge and receiving stream of ObafemiAwolowo University sewage treatment pond according to standard microbiological methods. The effluent sludge and water samples were subjected to different treatment such as sunlight, temperature and sodium chloride and their physicochemical properties were determined using conventional methods.The bacterial count in the effluent sludge ranged from 2.87×107 cfu/ mL at day 0 to 1.18×107 cfu/ mL at day 20 after sunlight exposure while in receiving stream it ranged from 1.20×107 cfu/ mL at day 0 to 0.03×107 cfu/ mL at day 20. The species of pathogenic bacteria isolated in both the effluent sludge and the receiving stream include; Escherichiacoli, Salmonellatyphi, Enterococcusfeacalis, Enterobacteraerogenes, Clostridiumperfringens, Alcaligenesfeacalis and Bacilluscereus. Escherichiacoli, Bacilluscereus and Clostridiumperfringens appeared throughout the days of sunlight exposure while the occurrence ofAlcaligenesfeacalis was least in the effluent sludge. The least occurred bacterium in the receiving stream is the Enterobacteraerogenes. Physicochemical parameters (such as biochemical oxygen demand, dissolved oxygen, nitrate, etc.) of the effluent sludge and the receiving stream was determined before and after exposure to sunlight. The biochemical oxygen demand, nitrate, and magnesium of both the effluent sludge and receiving stream decreased while the dissolved oxygen increased from day 0 to 20. A similar decrease in the total bacterial count and total coliform count of both the effluent sludge and the receiving stream was also observed when exposed to salt (NaCl) and different temperature gradients. The highest bacterial count was observed at the temperature 300C for both the effluent sludge and receiving stream. No bacteriun was detected at temperature above 600C. It can therefore be concluded that there are significant reductions in the bacterial load of both the effluent sludge and the receiving stream when subjected to some parameters like sunlight, salt and increasing temperature.