OPTIMIZATION OF BIOSTIMULANTS REQUIREMENTS FOR ENHANCED BIOREMEDIATION OF CRUDE OIL SLUDGE POLLUTED SOILS

Abstract

The study was aimed at investigating the optimal requirement of biostimulants in the bioremediation of crude oil sludge polluted soils. The contaminated environment was simulatedwith 1.0kg crude oil sludge on 2.0kg soil and uniformly homogenized. The polluted soils were then simulated with NPK, Cowdung and Moringaleaf powder based on total biostimulant to soil ratio of 0:1 to 0.75:1. These biostimulants were applied individually and in varying combinations to the polluted soils in three distinct segments (1, 2, 3) corresponding to the total biostimulant to soil ratios 0.25:1, 0.50:1 and 0.75:1 respectively while the control experiment which proceeded on natural attenuation was 0:1. Results of the experiments which lasted for 92 days showed marked reduction in Total Petroleum Hydrocarbon (TPH) content in the biostimulated experiments, E1 to E30. The control experiment, E31, which was non-biostimulated showed minimal reduction in TPH throughout the experiment due to the absence of added nutrients. In the single biostimulant application, moringa leaf powder (MLP) was found to give the best degradative performance at an optimal biostimulant to soil ratio of 2.04:1corresponding to 99.9957% bioremediation of the polluted soil being investigated. This result justifies the introduction of MLP as a suitable biostimulant for bioremediation studies and a possible substitute for NPK which is very expensive and not readily available for use. In the double biostimulant combination category, NPK + mlp mixing resulted in the best degradation efficiency. The optimum extent of degradation was 100% at optimum biostimulant to soil ratio of 2.04:1. The optimum extent of remediation for combination of all three biostimulants (NPK + CD + MLP) were found to be 99.15% at optimal biostimulant to soil ratio of 2.04:1.