Bioremediation of Illegally Refined Crude Oil Residue Using Soybean Waste and Cow Dung

Aims: This study was carried out to compare the effectiveness of soybean wastes and cow dung as an organic treatment for stimulating the hydrocarbon utilising Bacteria.

Study Design: In the laboratory, about 1000g of soil samples were weighed and transferred in to sterile pots labelled EP1, EP2, and EP3. The biostimulants were respectively transferred into the pots accordingly. The setup was watered and tilled once a week to provide moisture and oxygen for the organisms

Place and Duration of Study: Kpo fire contaminated soil samples were collected in plastic bag from four different points in marine base, Port Harcourt, Rivers State, Nigeria. The GPS of the location is given as N4°46’11.1252” E7°1’38.1324. The study was from March to April, 2018.

Methodology: The standard plate count method was used for the enumeration of the total heterotrophic and hydrocarbon utilising bacteria. One gram (1 g) of soil sample was weighed and aseptically transferred into test tube containing 9ml sterile normal saline. This was serially diluted to 10-6. 10-2 and 10-4 dilutions were inoculated onto the mineral salt medium and nutrient agar medium respectively. Inoculated plates were spread using sterile bent glass rod and incubation at 37 0C followed. The duration of incubation were 24 hours and 5-8 days for the total heterotrophic bacteria and total hydrocarbon utilising bacteria respectively. This was done for all the soil samples.

Results: The total heterotrophic bacterial loads revealed that the EP1 (control) ranged from 3.15 to 4.613 Log10Cfu/g. The EP2 ranged from 4.9 to 7.4 Log10Cfu/g while the EP3 ranged from 5.2 to 7.6 Log10Cfu/g. The hydrocarbon utilising bacterial loads revealed that EP1 (control) ranged from 1.0 to 4.2 Log10Cfu/g. The EP2 ranged from 4.7 to 6.9 Log10Cfu/g while the EP3 ranged from 4.9 to 7.4 Log10Cfu/g. The HUB identified in this study were Citrobacter species, Bacillus species, Serratia species, Clostridium species, Micrococcus species Pseudomonas species, Proteus species and Enterobacter species.

Conclusion: From the investigation of the bioremediation potential of contaminated soil supplemented with soybean wastes and those supplemented cow dungs, it was observed that both stimulants yielded good results and can be used as organic stimulants. Furthermore, this study has shown that the cow dung stimulants yielded better results than soybean waste simulants.