Efficacy of bioremediation for soil contaminated with polycyclic aromatic hydrocarbons (PAHs) may be limited by the fractions of soil-bound PAHs that are less accessible to PAH-degrading microorganisms. In previous test-tube-scale work, submicellar doses of nonionic surfactants were screened for their ability to enhance the desorption and biodegradation of residual PAHs in soil after conventional bioremediation in a laboratory-scale, slurry-phase bioreactor. Polyoxyethylene sorbitol hexaoleate (POESH) was the optimum surfactant for enhancing PAH removal, especially the high-molecular weight PAHs. This work extends that concept by treating the effluent from the slurry-phase bioreactor in a second-stage batch reactor, to which POESH was added, for an additional 7 or 12 days. Surfactant amendment removed substantial amounts of the PAHs and oxy-PAHs remaining after conventional slurry-phase bioremediation, including more than 80% of residual 4-ring PAHs. Surfactant-amended treatment decreased soil cytotoxicity, but often increased the genotoxicity of the soil as measured using the DT-40 chicken lymphocyte DNA damage response assay. Potential ecotoxicity, measured using a seed germination assay, was reduced by bioreactor treatment and was reduced further after second-stage treatment with POESH. Of bacteria previously implicated as potential PAH degraders under POESH-amended conditions in a prior study, members of the Terrimonas genus were associated with differences in high-molecular weight PAH removal in the current study. Research using submicellar doses of surfactant as a second-stage treatment step is limited and these findings can inform the design of bioremediation systems at field sites treating soil contaminated with PAHs and other hydrophobic contaminants that have low bioaccessibility.

中文翻译：

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常规生物修复后添加低水平表面活性剂改善污染土壤中多环芳烃生物降解

对多环芳烃 (PAH) 污染的土壤进行生物修复的效果可能会受到土壤中 PAH 降解微生物难以接近的部分的限制。在之前的试管规模工作中，对亚胶束剂量的非离子表面活性剂进行了筛选，以确定它们在实验室规模的浆相生物反应器中进行常规生物修复后增强土壤中残留多环芳烃的解吸和生物降解的能力。聚氧乙烯山梨糖醇六油酸酯（POESH）是增强多环芳烃去除的最佳表面活性剂，尤其是高分子量多环芳烃。这项工作通过在添加了 POESH 的第二阶段间歇式反应器中将浆相生物反应器的流出物再处理 7 或 12 天，扩展了这一概念。表面活性剂改良剂去除了传统淤浆相生物修复后剩余的大量 PAH 和含氧 PAH，包括 80% 以上的残留 4 环 PAH。表面活性剂改良处理降低了土壤细胞毒性，但通常会增加土壤的遗传毒性，如使用 DT-40 鸡淋巴细胞 DNA 损伤反应测定所测量。使用种子萌发测定法测量的潜在生态毒性通过生物反应器处理降低，并在用 POESH 进行第二阶段处理后进一步降低。在先前的研究中，先前在 POESH 修正条件下被认为是潜在 PAH 降解剂的细菌中，Terrimonas 属的成员与当前研究中高分子量 PAH 去除的差异有关。