Treating highly CPs- and PAHs-contaminated soil using an on site two-stage process

[[abstract]]氯酚(CPs)及多環芳香烴(PAHs)，為環保署優先處理之化合物，兩者亦皆具有毒性、化學穩定性和致癌性，亦常見於污染土壤中。當上述污染土壤濃度過高不適合直接以生物方式進行降解處理時，如可先以化學氧化方法處理並將污染濃度降至生物可分解程度，再以生物方式接續處理，應是一合理之降解程序。故本研究結合化學氧化法及生物技術兩種方法針對上述高污染土壤進行復育處理。第一階段之化學氧化法分別以EDTA-Fe+Heme處理CPs及用EDTA-Fe處理PAHs，兩者之氧化劑皆為過氧化氫。第二階段之生物處理則是添加微生物及基質於土壤中，利用微生物自然降解污染物。本研究目的為：(1) 探討CPs及PAHs在兩階段處理程序中之降解效率，(2) 分析不同階段處理程序之菌相變化及(3) 決定兩階段處理之最適化操作程序。上述菌相變化量測乃是運用分子生物技術T-RFLP(Terminal restriction fragment length polymorphism)針對兩階段處理之反應槽中微生物的菌相變化進行分析。本研究係以600 g污染土壤置於反應槽並設有控制組(不添加催化劑與氧化劑)與氧化組(添加催化劑與氧化劑)，兩階段反應時間共為92天，定期採樣並以GC-FID分析土壤中有機污染物其含量，同時間採得土樣亦進行土壤中微生物之DNA萃取、PCR擴增及T-RFLP分析等。 本研究結果顯示，氧化組於第一階段化學處理中，3-MCP和3 5-DCP平均降解效率達98%，PCP 為93%；另二環及三環之PAHs平均降解效率分別為98%和68%。惟於第二階段生物處理令CPs及PAHs平均降解效率並不顯著，以分子生物技術T-RFLP分析CPs及PAHs反應槽中細菌與古細菌在兩階段處理程序間之差異，其結果顯示反應槽中之菌相經氧化後明顯變少且古細菌族群較細菌族群多樣。[[abstract]]Chlorophenols (CPs) and Polycyclic aromatic hydrocarbons (PAHs) the priority list chemicals by the Environmental Protection Administration in Taiwan are both toxic stable and carcinogenic substances and also commonly seen in polluted soils When the soil CPs and/or PAHs content is high the direct bioremediation of such soil is not applicabe Using a chemical mean to detoxicify the soil first followed by a biological treatement seems doable This study combines chemical oxidation and natural bioattenuation to deal with such a highly CPs- or PAHs-contaminated soil We called this a two-stage treatment process At the first stage EDTA-Fe plus Heme were employed as catalysts and peroxide was used as oxidant to oxidize the CPs or PAHs and at the second stage the bioattenuation mean was employed to degrade the target compounds further The main objectives of this study included: (1) to explore the degradation efficiencies of CPs and PAHs in both treatmnet stages (2) to analyze the soil microbial shift over time and (3) to determine an appropriate strategy in coping with the two stage process Pan with 600 grams of either CPs- or PAHs-contaminated soil was treated first by chemical oxidation followed by bioattenuation so did the control and blank runs A total of 92 days spent in order to complete the two stage process Samples were collected and analyzed for target compounds microbial DNA 16S rDNA and t-RFLP The results showed that during the oxidation stage the average oxidation of 3-MCP and 3 5-DCP was close to 98% and PCP close to 93% Also the average degradation of two- and three-ring PAHs were 98 and 68% respectively Degradation efficiency of the bioattenuation in the second stage showed limited degradation The t-RFLP analysis indicated that minimal microbial species existed The bioaugmentation of pure microbes and the addition of substrate failed to activate the bioactivity good enough to show satisfactory target compound removal Oxidation step did eliminate more microbes out of the system and over the treatment process the archeal species was rather diverse than the bacterial grou