Simultaneous effect of municipal solid waste compost and some fertilizers on biodegradation of oil-contaminated soils

Soil contamination with crude oil and its derivatives is one of the most dangerous type of environmental pollution. The objective of this study was to evaluate and optimize the indigenous soil microorganisms using nitrogen, phosphorus and potassium fertilizers and municipal compost contaminated with fuel oil (130g/kg), and their reclamation influence as well as optimum mixing ratio with soil. For this purpose, different levels of municipal composts with two ratios of NPK (5, 10. 15 percent) fertilizers (10:2:1 and 10:1:1 ratios) were applied into experimental soil samples. After initial equilibrium period (10 days), the amount of hydrocarbon contaminants in soil under aerobic conditions were determined. The results showed an increased percentage in the compost and declined soil emissions of oil such that treatment of 15% had the highest reduction rate between 59 to 62 percent. The results of two applied fertilizers, confirmed the usefulness of 10:2:1 ratio. The applied amendments to all treatments lead to effective oil degrading bacteria, especially during first week after equilibrium. This can be related to faster breakdown of short-chain compounds such as alkanes. The results further indicated an effective correlation between rate of TPH decomposition and CO2 of microbial activity. There was a direct correlation between crude oil degradation and microorganisms activity. Simultaneous treatment of municipal solid waste compost (15%) and NPK fertilizers (10:2:1 ratio) with six weeks was an effective treatment to clean up oil-contaminated soils by decomposition rate of 62 percent.