Comparative bioremediation of petroleum hydrocarbon-contaminated soil by biostimulation, bioaugmentation and surfactant addition

A bench-scale biopiling experiment was conducted to compare the ability of different techniques to enhance petroleum hydrocarbon bioremediation in a chronically contaminated soil. After 195 days, 10%-32% removal of TPHs (total petroleum hydrocarbons) occurred in unamended soil (control). Biostimulation by inorganic nutrient addition enhanced TPH removal (49%) confirming that bioremediation was nutrient limited and the soil contained a well-adapted hydrocarbonoclastic microbial community. The addition of organic amendments including green waste at 25% and 50% (w/w) and a commercial product called DaramendTM had a further biostimulatory effect (50%-66%, 34%-59% and 69%-80% TPH removal respectively). Bioaugmentation using two commercially available petroleum hydrocarbon degrading microbial cultures with nutrients enhanced TPH removal in the case of RemActivTM (60%-69%), but had a marginal effect using Recycler 102 (49%-55%). The effect of a non-ionic surfactant in green waste amended soil was variable (52%-72% TPH reduction), but its potential to enhance biodegradation presumably by promoting contaminant bioavailability was demonstrated. High degradation of artificially added polycyclic aromatic hydrocarbons (PAHs) occurred after 106 days (75%-84%), but significant differences between the control and treatments were unapparent, suggesting that spiked soils do not reflect the behavior of contaminants in genuinely polluted and weathered soil.