Optimization of Nutrients Concentration Required for the Bioremediation of Petroleum Contaminated Soil

Abstract

There is a growing public concern as petroleum hydrocarbons are being introduced inadvertently or deliberately in large volumes into the environment thus causing a long term threat to all forms of life. Thus remediation of these is of utmost importance. The bioremediation technology is being employed for the degradation of crude oil in soil matrix through microorganisms which can transform petroleum hydrocarbons into less toxic compounds. In this study, optimum nutrients (C: N: P) concentration required for the microbial growth was investigated. The petroleum oily sludge, contaminated soil, soil rich in native microorganisms was collected and the same was used to prepare simulated contaminated soil which was filled up to 3/4th of the reactors volume. All the parameters except the C: N: P ratio in the reactors were maintained constant throughout the study period. The C: N: P ratios varies from 100:2.5:0.25 to 100:20:2 in the twenty reactors, N and P were amended to make up the required ratios. N and P were not added into the control reactor. Treatability studies on TPH contaminated soil was conducted in all the reactors for a period of six weeks. The results of the study reveals that among the different C:N:P ratios, C:N:P ratio of 100:10:1 gave the maximum TPH removal of 59.57 % with biodegradation rate of 0.022 day/1, R² obtained was 0.968 which suggest that there exists a strong relationship between biodegradation and time. The results thereby imply that nutrients concentration is the most important factor that affects the biodegradation of petroleum-hydrocarbons in tropical soils.