Application of cowdung and sawdust as biostimulants for enhanced bioremediation of diesel contaminated soil
The study was aimed at exploring the use of cow dung (CD) and sawdust (SD) as bio stimulants for enhanced ex-situ bioremediation of diesel fuel contaminated soil. Results of the microbial populations in a gram of soil showed that diesel polluted soil amended with CD had the highest total culturable heterotrophic bacterial (TCHB) population range (1.42 x 106 - 1.56 x 107Cfu/g), total fungal (TF) (1.0 x 106 – 1.60x107Cfu/g), hydrocarbon utilizing bacteria (HUB) (4.5 x 106 – 2.05 x 107Cfu/g) and hydrocarbon utilizing fungi (HUF) (3.5 x 106 – 1.3 x 107Cfu/g) respectively during the study. Diesel polluted soil amended with SD had lower TCHB populations (1.32 x 106 – 2.0 x 107Cfu/g), TF (6.0 x 106 – 3.6 x 107 Cfu/g), HUB (5.4 x 106 – 1.28 x 107Cfu/g) and HUF (1.2 x 106 – 2.0 x 106Cfu/g) respectively, while the microbial populations in option C (control) were TCHB (1.14 x 106 – 1.18 x 107Cfu/g), TF (1.7 x 106 – 7.0 x 106Cfu/g), HUB (4.2 x 106 – 7.8 x 106Cfu/g) and HUF (1.1 x 106 – 5.0 x 107Cfu/g) respectively. Changes in pH values showed reductions in CD (7.10 – 6.20) and SD (5.78 – 4.88) amended soils. Percentage losses in TPH from chromatography results showed diesel polluted soil amended with CD (61.30%), SD (41%) and control (4.11%) respectively. Characterization and identification tests of bacterial isolates revealed that a microbial consortium comprising of the following HUB genera; Bacillus, Pseudomonas, Proteus, Alcaligenes, Klebsiella, Enterobacter, Citrobacter, Corynebacterium and Escherichia coli was implicated in the biodegradation process. Similarly, the HUF encountered were Fusarium, Aspergillus, Microsporium, Penicilium and Mucor. The results suggest that the application of cow dung as biostimulant will enhance the bioremediation of diesel contaminated soil than the application of sawdust.
Keywords: Cowdung, Sawdust, Bioremediation, Biostimulation