The effects of electrical heating and additives on the microbial remediation of petroleum-contaminated soils

Abstract

Although petroleum is an important source of energy and an economic driver of growth, it is also a major soil pollutant that has destroyed large swathes of vegetation and forest cover. Therefore, it is vital to develop affordable and efficient methods for the bioremediation of petroleum-contaminated forest soils to restore vegetation and improve tree survival rates. In this study, bioremediation experiments were performed in an electrically heated thermostatic reactor to test the effects of organic matter additives, surfactants, and oxygen providers of nine hydrocarbon-degrading fungal strains on crude oil removal rates. In the three soil temperatures tested (20 °C, 25 °C, and 30 °C), the highest average crude oil removal rate was at 25 °C (74.8%) and the lowest at 30 °C (49.4%). At each temperature, variations in the addition of organic matter and oxygen providers had significant effects on crude oil removal rate. Variations in surfactant addition was significant at 20 °C and 25 °C but insignificant at 30 °C. Given the same surfactant treatment, variations in temperature, organic additives, and oxygen providers was significant for crude oil removal rate. Treatments without surfactants and treatments with Tween80 exhibited their highest crude oil removal rates at 25 °C. However, treatments that included the SDS surfactant exhibited their highest crude oil removal rates at 30 °C. Amongst the treatments without surfactants, treatments with corn cob addition had the highest crude oil removal rates, and with surfactants, treatments that included the organic fertilizer exhibited the highest crude oil removal rates. Given the same organic fertilizer treatment, the highest crude oil removal rate was at 25 °C. At each level of oxygen availability, the maximum crude oil removal rate always occurred at 25 °C, and the treatments that included organic fertilizer exhibited the highest crude oil removal rates. Amongst the treatments without oxygen providers, treatments without surfactants had the highest crude oil removal rates, and with an oxygen provider, treatments with SDS addition exhibited the highest crude oil removal rates. Based on the crude oil removal rates of the treatments, we determined that S1W1O1 (addition of Tween80, organic fertilizers, and H2O2) was optimum for remediating petroleum-contaminated forest soils in cold, high-altitude regions. This study is helpful to vegetation restoration and reforestation on petroleum contaminated forestlands.