| Crude oil is one of dominant sources of oil pollution. If it has not obtained immediate and appropriate treat, it would become aging petroleum which tends to combine with soil particles and affects permeability of soil, then it would be hard to remove. Thus, the remediation of aging oil polluted soil is of great importance present environmental science. This study took long-term aging oil polluted soil as the object, and combined electrokinetic (EK) and biological remediation technologies to remove the contaminant, and investigated removal efficiency and influencing factors. This study initially investigated the physicochemical and biological propertiesof aging petroleum polluted soil. The results revealed that pH and moisture content of polluted soil were lower than the healthy soil, while respiratory intensity and typical enzymes content were higher. The denaturing gradient gel electrophoresis profiles indicated that oil can stimulated the growth of partial bacteria as metabolic substrate.This is the first study usingβ-cyclodextrin (β-CD) as solubilizer to enhance desorption of aging petroleum from soil particles. It was demonstrated thatβ-CD can well improved the adsorption of TPH (the desorption efficiency reached 79.4%) in strongly polluted soil (oil content reached 78.6mg/g soil) by batch experiments. Though this was not as good as SDS did,β-CD was still the better choice of solubilizer because it is safer than SDS. According to the content of contaminant (78.6mg/g soil), the best dosage ofβ-CD was 1674mg/L. Meanwhile, the TPH desorption agreed with pseudo-second-order model. The desorption was slightly influenced by initial pH and Ca2+ concentration, but there are few adsorption lost in this process (about 18.7mg/g soil). And adsorption ofβ-CD fitted with Freundlich isothermal equation, and the adsorption equation was as followed: lnqea=ln0.0018+lnCs/0.664. Then,β-CD enhanced desorption conditions of oil were applied in EK remediation. The results presented that graphite electrodes were better than metallic ones. When 2V/cm of direct current using graphite as mono-anode and mono-cathode was applied, TPH content decreased from 78.6mg/g soil to 50.2mg/g soil. Respiratory intensity and typical enzyme content were all decreased. And pH at anode changed form 8.38 to 7.22. DGGE profiles indicated that bacterial community structure at anode was minor influenced, whose number of species changed from 11 to 8. Removal efficiency reached 38.3% when multi-anode and mono-anode was adopted, but the efficiency of electric energy was only 2.65g/kWh which was much lower than mono-anode and mono-cathode technique (7.799g/kWh).Three efficient oil degradation bacteria were screened from polluted soil by plated separation method and were named as S1, S11, and D7, respectively. The Blast results of 16S rRNA sequencing revealed that they were similar with Bacillus flexus, Pseudomonas seudoalcaligenes, and Pseudomonas aurantiaca, and the similarity was 100%, 99%, and 97%, respectively. About 40% TPH was removed. Meanwhile, S1 and S11 removed the THP by lipopetide bio-surfactant which was generated by themselves. The effect of mixed bacteria was studied and took natural aging petroleum polluted soil as objective. The results presented that best removal efficiency reached 40.8% when volume ratio of S1:S11:D7 was 0.5:2:2.Finally, laboratory test was taken to investigate EK technology and biological technology combined for removal of aging petroleum. And, effect of some crucial conditions such as: nitrogen, phosphorus, iron and magnesian ion,β-CD, nitrate, and bio-carrier was studied. The results presented that ammonia and nitrate had more effect on the remediation. The initial conditions were followed: 300g soil and 180mL mixed inoculums were loaded into a cylindrical reactor; height of the soil column was 15cm; the soil samples were cultivated every two days; 60mL water was added every ten days. When 2g ammonia was added, removal of petroleum reached 61.3%. While the removal efficiency reached 74.9% when 2g nitrate was added. Meanwhile, DGGE profiles revealed that addition of ammonia and nitrate enriched bacterial diversity. The denitrifiers (Pseudomonas sp., Rhodococcus sp., Rhodobacter sp., Mycobacterium monacense) were propagated because of addition of nitrate. Thus, enhanced denitrification can improve removal of aging petroleum efficiency.
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