Bioremediation of Spent Engine Oil Contaminated Soil with Bacteria Isolated from Municipal Waste Dumpsite Amended with Water Hyacinth (Eichhornia Crassipes) Leaves as Biostimulant

The paper reports the investigation bioremediation of spent engine oil-contaminated soil augmented with bacteria isolated from municipal dumpsite leachate and amended with water hyacinth leaves (Eichhornia crassipes) as bio-stimulants using appropriate standard methods. Data obtained showed that morphological and biochemical analyses identified six gram-negative and two gram-positive isolates, including Klebsiella pneumoniae, Enterobacter cloacae, Pseudomonas aeruginosa, Staphylococcus aureus, Pseudomonas putida, Escherichia coli, Enterococcus faecalis, and Citrobacter koseri. Qualitative screening using the redox indicator dye 2,6-Dichlorophenol indophenol indicated that Pseudomonas aeruginosa and Staphylococcus aureus exhibited the highest hydrocarbon degradation capabilities. For the bioremediation study, sterilized spent engine oil was introduced into uncontaminated soil at a concentration of 25 g/kg. The contaminated soil was divided into several treatment sets: SET A (control), SET B (with Pseudomonas aeruginosa), SET C (with Staphylococcus aureus), and SET D (with both microorganisms). Additionally, water hyacinth leaves were added in parallel experiments, creating groups SET E (with water hyacinth), SET F (with Pseudomonas aeruginosa and water hyacinth), SET G (with Staphylococcus aureus and water hyacinth), and SET H (with both and water hyacinth). The remediation process, monitored for eight weeks, revealed total petroleum hydrocarbon (TPH) losses of 0.02%, 21.09%, 16.17%, 23.64%, 0.03%, 31.57%, 20.13%, and 39.04% for the respective treatments. This study establishes that indigenous bacterial isolates, particularly Pseudomonas aeruginosa and Staphylococcus aureus, possess significant hydrocarbon-degrading abilities and that the addition of water hyacinth enhances biodegradation, providing a dual benefit of removing this invasive plant species from waterways while remediating oil-contaminated soils.