Bioaugmentation Efficiency of Different LIBEM Strains in ASP Treatment of Oil Sludge-Contaminated Soil

This study investigates the bioaugmentation potential of five locally isolated beneficial microorganisms (LIBeM), namely Candida tropicalis-RETL-Cr1, Chromobacterium violaceum-MAB-Cr1, Pseudomonas aeruginosa-BAS-Cr1, Sphingomonas paucimobilis-RETOS-Cr1, and Stenotrophomonas maltophilia-RAS-Cr, for remediating oil sludge. Contaminated soil using an aerated static pile (ASP) system. The experiments were conducted using ASP bioreactor systems that provided continuous aeration to 10 kg soil samples amended with 5%, 10%, 15%, and 20% (v/v) oil sludge, while natural attenuation served as the control treatment. The TPH (total petroleum hydrocarbon) degradation was monitored for three months at 7-day intervals. Rapid TPH reduction occurred within the first 14–28 days, followed by a gradual decline. LIBEM strains P. aeruginosa-BAS-Cr1 achieved the highest reductions with 40.0, 85.2, 128.9, and 178.5 g/kg for the respective sludge concentrations, which are 1.0–1.25 fold higher than C. violaceum-MAB-Cr1. Other strains demonstrated strong performance, with reductions of 32.5–173.0 g/kg (C. tropicalis-RETL-Cr1), 37.2–177.2 g/kg (S. paucimobilis-RETOS-Cr1), and 33.4–174.0 g/kg (S. maltophilia-RAS-Cr1). All treatments achieved significantly higher TPH removal compared to natural attenuation, which recorded only 27.4% removal. The results indicate that the ASP system’s continuous oxygen supply enhances microbial activity, promoting the degradation of long-chain alkanes and overall remediation efficiency. These findings demonstrate that combining LIBeM bioaugmentation with ASP technology offers a scalable, eco-friendly solution for treating hydrocarbon-contaminated soils. The results also provide a basis for optimizing strain combinations and operational parameters in future large-scale applications.