Effectiveness Of Microbial Load On The Removal Of Total Petroleum Hydrocarbon From Drill Cuttings

ABSTRACT

Petroleum hydrocarbons (PHCs) are common site contaminants, but they are not generally regulated as hazardous wastes. TPH refers not only to analytical results, but also to environmental and health properties of PHCs. Biodegradation by natural populations of microorganisms represents one of the primary mechanisms by which petroleum and other hydrocarbon pollutants can be removed from the environment and is cheaper than other remediation technologies. The environmental implication associated with Drill cuttings and its unfriendly environmental treatment operation posed high threat to the human and the ecosystem. In quest to seek for more friendly treatment of drill cuttings biotic removal were opted for. The microbiological analyses of samples, which involved determination of Total heterotrophic Bacteria and Fungi number, the number of bacteria-degrading petroleum hydrocarbons and fungi in comparison to the resident TPH. Four substrate inhibition models (Haldane, Yano, Aiba and Edwards) were compared by fitting them to the experimental data using Matlab 8 version software. Curve fitting from the Matlabs was used to determine the model constant. The concentration of TPH and Microbial Load were determined every three weeks and validated using kinetic model. At 42 days of active removal of the TPH by THB (Yano Model), the HDF & HDB sparked up an effective increase in growth as displayed by Edwards Model. This can be as a result of more activities of Microbial load striving at lower concentration of contaminate & good succession habitat. The time duration for effective removal of Drill cuttings was 105 days with an optimum day at 42days (Removal efficiency of approximately 50%). The results indicated that the specific growth rate displayed a monotonic & linear relationship with TPH from Yano Model analysis. It was observed that Edward model; secondly Yano model fitted growth kinetic data better than Haldane and Aiba. The removal efficiency of 95.10 % was obtained on the 15 week indicating the efficiency and effectiveness of the process. Edwards Model displayed well defined typical growth phase for HDB and HDF best fitted than the other models. It can be concluded that HDB & HDF could be utilized to remove TPH from Drill Cutting. Correlation coefficiency of the degradation of TPH to Removal efficiency is -0.9936. Accounting for effectiveness of the biotic removal of TPH from the sample by microbial load. The biodegradation kinetics process in a plot of In TPHø against time was linear. The biodegradation kinetics process followed first order with a rate constant was observed to be 0.0657day-1. The correlation analysis of R2 for the TPH biodegradation kinetics process was also observed to be 0.8647, signifying linearity & positive correlations for the decrease in concentration as a function of time. Biodegradation isotherm was found to be minus unity expressing the opposite linear relationship between the concentration of the contaminant in the soil TPHø and the concentration degraded by the microbes TPHBcumulative at different time intervals for the removal period. Recommend further research on the removal of TPH from drill cutting using two bioreactors namely Batch Stirred Tank Reactor (BSTR) & Internal Loop Airlift Reactor (ILALR) and evaluate their performance. To identify the most active Heterotrophic microorganism and the hydrocarbon degradable organism responsible for removal of TPH.  

Keywords: Microbial load, specific growth rate, substrate inhibition constant, biodegradation isotherm, best  fit knetic model, total petroleum, hydrocarbon, drill cuttings