Experimental Study on Bioremediation of Heavy Oil Contaminated Soil

The loose and hard soil was named No.1 which formed by ground crude oil from Liaohe oilfield gathering station,with 7.4% oil and 17.8% water content,2.64 g/cm3density and 7.8 pH value.Heavy oil contaminated soft and bonding soil was named No.2,with 21.5% oil and 35.6% water content,2.23 g/cm3density and 7.8 pH value.Heavy oil contaminated No.1 soil contained 29.11% saturated hydrocarbon,22.54% aromatic hydrocarbon,30.26% colloid and 18.08% asphaltene.Heavy oil contaminated No.2 soil contained 25.19% saturated hydrocarbon,26.23% aromatic hydrocarbon,32.49% colloid and 16.09% asphaltene.1—5 strains was selected by enrichment and separation from heavy oil contaminated soil.Taking heavy oil as sole carbon source,the degradation rate of 1—5 strains to crude oil was 20.0%,6.1%,22.5%,12.7% and 34.7%,respectively.No.5 strain with higher degradation rate and No.1 strain with good adaptability to environment were isolated as predominant bacteria.The optimum N and P source of No.1 bacteria was(NH4)2SO4and K2HPO4,the corresponding degradation rate was 28.13% and 15.16%.And that of No.5 bacteria was KNO3and KH2PO4,the corresponding degradation rate was 49.12% and 50.04%.0.15% H2O2had a good effect of oxidative degradation and promoted a role,however,the degradation rate used H2O2alone was 25%(60 d).Within 60 days after adding surfactants,oily soil degradation rate greatly increased.The highest degradation rate of TW-80,TW-40 and rhamnolipid was 73%,70% and 84% respectively.So 0.1% TW-80 and 0.1% rhamolipid composite surfactant was selected as penetrating agent for oil soil microbial degradation.Through the small scale test,the degradation rate of No.1 and No.2 heavy oil contaminated soil achieved 66.7% and 73.5% respectively 80 days later which indicated the degradation effect was good.