【作者】 万春黎；

【导师】 杜茂安；

【作者基本信息】 哈尔滨工业大学 ， 市政工程， 2010， 博士

【摘要】 落地油是石油污染土壤的重要来源之一,落地油产生后,若不及时处理,就会成为老化石油。由于老化石油不仅具有复杂的石油烃组分,还容易与土壤颗粒紧密结合,造成土壤的低渗透性,导致修复难度增大,因此针对老化石油污染土壤的有效修复研究具有重要意义,基于此,本研究以长期暴露于环境中的老化石油污染土壤为修复对象,将电渗析修复技术与微生物修复技术组合来处理土壤中的老化石油,并对修复效能及影响因素进行了探索研究。本研究首先通过常规的土壤分析技术,比较研究了不同污染程度的老化石油污染土壤的主要理化性质及微生物学性质,结果表明,与未污染土壤相比,老化石油污染土壤的pH及含水率变化与土壤中的总石油烃(TPH)含量直接相关,均表现为下降趋势,而呼吸强度和典型酶(脱氢酶及过氧化氢酶)含量略有升高,变性梯度凝胶电泳(DGGE)技术对微生物群落的分析结果表明这是石油作为有机底物刺激了土壤中部分细菌的生长繁殖所导致的。本研究首次提出采用β-环糊精作为增溶剂来促进老化石油从土壤颗粒表面的解吸,并通过静态试验证实了针对高污染强度(78.6mg/g soil)的老化石油污染土壤,β-环糊精促进TPH的解吸效率达到79.4%,虽然略低于于表面活性剂SDS(86.5%),但β-环糊精更具有环境安全性,可以作为老化石油增溶剂的理想选择,其增溶机理主要是依靠β-环糊精与石油烃发生的n:1(n>1)包合反应,根据本试验中老化石油的污染强度(78.6mg/g soil),β-环糊精的最佳使用浓度为1674mg/L,此时,TPH的解吸过程符合假二阶动力学模型,初始的pH及Ca2+浓度对解吸过程的影响较小,但β-环糊精在促进土壤中TPH解吸的过程中存在少量的吸附损失,约为18.7mg/g soil,吸附损失符合Freundlich等温吸附模型,求得吸附损失的方程表达式为:lnqea=ln0.0018+lnCs/0.664。然后将β-环糊精促进石油烃解吸的条件应用于电渗析修复过程强化土壤中石油烃类污染物的去除,结果表明,石墨电极的修复效果优于金属电极,选择石墨电极采用单阳极单阴极工艺进行修复过程中,在电场强度为2V/cm时,可以将土壤中石油烃含量从78.6mg/g soil降至50.2mg/g soil,获得36.1%的去除率,呼吸强度及典型酶含量均出现不同程度的降低,阳极土壤的pH降低幅度较小,从8.38降至7.22,DGGE图谱显示阳极土壤中微生物群落结构受到的影响较小,从细菌种属的多样性来看,通电修复技术后,阳极土壤中仍然包含了原始土样中可检测的11个细菌种属中的8个。采用多阳极单阴极电动工艺在2V/cm的电场强度下虽然可以获得38.3%的去除率,但是电能效率只有2.65g/kWh,远低于单阳极单阴极工艺(7.799g/kWh)。通过传统的平板分离法,从老化石油污染的土壤中筛选获得了三株具有高效降解石油烃能力的菌株,分别命名为S1、S11、D7,16SrRNA序列分析比对结果显示,其与Bacillus flexus、Pseudomonas seudoalcaligenes、Pseudomonas aurantiaca,相似性分别为100%、99%、97%,在石油培养基中对TPH均具有40%的去除率,其中S1和S11是通过自身产生脂肽类生物表面活性剂促进石油烃增溶来进行降解。试验中针对实际老化石油污染土壤,采用了生物泥浆法考察了复配菌液对TPH的去除效果,结果表明,当S1:S11:D7按体积比为0.5:2:2复配时可以获得的去除率最高,达到40.8%,调整初始pH为7.0时,可以将去除率进一步提高到43.7%。最后,本研究通过小试试验证实了电动修复与微生物修复技术联合进行土壤中老化石油去除的有效性,并考察了氮源、磷源、铁镁离子、β-环糊精、硝酸盐氮及生物载体投加等环境因素对修复过程的影响,结果表明,氨氮和硝酸盐氮是影响其原位微生物修复的关键因素,试验的初始条件为:在每300g阳极土壤中加入复配菌液180mL,完全混合后装入圆筒形工艺,形成的土柱高度约为15cm,试验过程中每2d翻土一次,每10d加入约60mL水,并翻土混匀,当投加2g氨氮时,土壤中石油烃的去除率可达61.3%,而投加2g硝酸盐氮时,石油烃的去除率可达74.9%,同时对土壤中的微生物群落结构进行DGGE分析,结果表明,氨氮及硝酸盐氮的投加均丰富了土壤中细菌种群的多样性,投加硝酸盐氮后还促进了Pseudomonas sp.、Rhodococcus sp.、Rhodobacter sp.、Mycobacterium monacense等具有反硝化能力菌株的出现并大量增殖,分析认为强化反硝化作用能够有效提高土壤中TPH的去除效率。更多还原

【Abstract】 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 properties of 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.更多还原