Abstract
The recovery of oil based drilling muds was monitored for a period of 12 weeks upon inoculation with kitchen effluent. Oil based drilling muds inoculated with varying volumes (200ml, 250ml and 300ml) of kitchen effluent constituted the experimental set-ups, while the control set-ups were made up of oil based drilling muds inoculated with varying volumes (200ml, 250ml and 300ml respectively) of sterile distilled water. In the experimental 4 + 0.12 cfu/ml) as well as phosphate (3.63 mg/l), sulphate (3.0 mg/l) and nitrate (15.60 mg/l) present in the kitchen effluent, both dissolved oxygen (DO) and residual oil concentration (ROC) decrease rapidly while the increasing trends in biochemical oxygen demand (BOD) were much more pronounced over the period when compared with the control set-ups. However, analysis of data obtained from this study revealed that the differences between the mean residual oil concentration of the experimental set-ups and that of the control set-ups for A and B are insignificant while that of C differed significantly at 5% probability level indicating that the magnitude of loss in residual oil concentration increases as the volume of kitchen effluent inoculated increases. Therefore, it may be necessary to use kitchen effluent as alternative inoculum in bioremediation of oil contaminated drilling muds. @ JASEM. J. Appl. Sci. Environ. Manage, December, 2010, Vol. 14 (4) 5 - 11
Highlights
An important aspect of the environmental impact of offshore drilling operations is the discharge of oil based drilling muds
The initial drop in total heterotrophic microorganisms (THM) of the experimental set-ups (Tables 1, 3 and 5) confirms the toxic impacts of the hydrocarbon products present in the drilling muds which is in accordance with the previous reports by Atlas (1981), Nwachukwu and Ugoji (1995), and Nwachukwu (2000b), and probably prove that some of the microorganisms introduced into the experimental setups from the kitchen effluent can not survive in an oil polluted environment (Nwachukwu, 2000b), compared to the control set-ups (Tables 1, 3 and 5) which do not show any initial decrease in THM
The percentage total hydrocarbon utilizers (% THCU) calculated for both experimental set-ups and control set-ups relative to the total heterotrophic microorganisms, THM (Tables 1, 3 and 5) differed significantly at 5% probability level (t = 3.833; 3.844 and 3.840 for A, B and C respectively; t from statistical table = 2.179)
Summary
An important aspect of the environmental impact of offshore drilling operations is the discharge of oil based drilling muds. Investigations of biodegradation of cutting piles and the microbial population associated with drilling muds have been conducted (Nnubia and Okpokwasili, 1993; Benka-Coker and Olumagin, 1995; Nweke and Okpokwasili, 2003). Both bacteria and fungi have been developed and used to enhance rehabilitation of environments polluted with crude petroleum and its products (Nwachukwu et al, 1999; Eriksson et al, 2000; Nwachukwu, 2000a; Sayler and Ripp, 2000, Mishra et al 2001). The impacts of addition of kitchen effluent to enhance rehabilitation of oil based drilling muds were investigated
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