Study On The Ol Degradation Abiity Of Imobilized Microor Gansman Oil -contaminatd Soil

Aiming at the remediation of oil-contaminated soil, high-efficiency oil-degrading strainswhich had screened in the laboratory including single strain SM-1 and SM-3, compoundstrain and mixed strains MM-7 were elected as experimental strains. The natural organicmaterials YJ-07 and YJ-05 were designed as carriers to obtain immobilized microorganism byadsorption method. The effect of different environmental factors on the oil degradation abilityof free and immobilized microorganisms was studied. The oil degradation abilities of differentstrains and immobilized microorganisms with different carriers under optimum conditionwere compared. Free and immobilized microorganisms were applied in the simulationremediation oil-contaminated soil in the indoor pot. The orthogonal experiment of five factors,four levels was designed on C/N/P, inoculated quantity, oil concent, oxidant and surfactant.The importance sequence of each influencing factor in different repair period, the repair effectof each strain under optimum condition and the changes of soil properties and biodiversitywere discussed.The results of the study on influence factors of immobilized microorganismsbiodegradating oil showed that the suitable pH value of free and immobilized strainsincluding SM-1, SM-3, MM-7 and compound strain was 7.0 ~ 8.0, the suitable salinity was5g/L ~ 7g/L, the suitable oil concentration was 3g/L ~ 10g/L, the suitable inoculated quantitywas 10%~30% and immobilized strain can more quickly adapt to the environment than freestrain. The oil degradation rates of immobilized strains were higher than free strains by 7% ~30%. The degradation rate of immobilized strains with YJ-07 as a carrier was higher than thatwith YJ-05 as a carrier by 4% ~ 42%. Compared with single strain, the degradation effect ofmixed strains was the best, that of compound strain was next. The degradation rate ofimmobilized strain SM-3 was the highest 73.5% under optimum condition that was pH valuewas 8, salinity was 5g/L, oil concentration was 3g/L, and inoculated quantity was 20%. The experiment of immobilized microorganism simulated repairing oil-contaminatedsoil showed that for different microorganisms, the importance of each factor changes indifferent periods. The effect of immobilized mixed strain MM-7 was the best after repairingoil-contaminated soil 21 days, the oil degradation rate of it was 27.12%. During thebiodegradation, inoculated quantity was always the most important factor. Surfactant in theearly period had a great effect on degradation rate, while in the middle and later period the oilconcentration became more important. The oil degradation rate of immobilized mixed strainMM-7 was the highest, which reached 22.3% under the condition that inoculated quantitywas 20%, surfactant was 0.05%, C/N/P was 100:5:1, oil concent of soil was 3% and oxidantwas 0.5%. In Bioremediation processes, organic carbon of soil, total nitrogen of soil, pHvalue and bacteria amount should been adjusted and the adjustment soil environment cycle ofimmobilized microorganisms was longer than free microorganisms (except total nitrogen ofsoil), immobilized microorganisms has obvious advantages. The analysis results ofShannon-Weiner index of soils and DGGE bands showed that the diversity of soil repaired byimmobilized microorganism increased and then decreased, while the diversity of soil repairedby free microorganism first decreased, then increased, last decreased. And the diversity ofsoil repaired by immobilized microorganism was in a higher level.