Department of Environmental Engineering, Technical University of Denmark (DTU), Bygningstorvet, Building 115, 2800 Kgs. Lyngby, Denmark.
Department of Environmental Engineering, Technical University of Denmark (DTU), Bygningstorvet, Building 115, 2800 Kgs. Lyngby, Denmark.
J Contam Hydrol. 2021 Jun;240:103794. doi: 10.1016/j.jconhyd.2021.103794. Epub 2021 Mar 5.
Over the last decade, activated carbon amendments have successfully been applied to retain chlorinated ethene subsurface contamination. The concept of this remediation technology is that activated carbon and bioamendments are injected into aquifer systems to enhance biodegradation. While the scientific basis of the technology is established, there is a need for methods to characterise and quantify the biodegradation at field scale. In this study, an integrated approach was applied to assess in situ biodegradation after the establishment of a cross sectional treatment zone in a TCE plume. The amendments were liquid activated carbon, hydrogen release donors and a Dehalococcoides containing culture. The integrated approach included spatial and temporal evaluations on flow and transport, redox conditions, contaminant concentrations, biomarker abundance and compound-specific stable isotopes. This is the first study applying isotopic and microbial techniques to assess field scale biodegradation enhanced by liquid activated carbon and bioamendments. The injection enhanced biodegradation from TCE to primarily cis-DCE. The Dehalococcoides abundances facilitated characterisation of critical zones with insufficient degradation and possible explanations. A conceptual model of isotopic data together with distribution and transport information improved process understanding; the degradation of TCE was insufficient to counteract the contaminant input by inflow into the treatment zone and desorption from the sediment. The integrated approach could be used to document and characterise the in situ degradation, and the isotopic and microbial data provided process understanding that could not have been gathered from conventional monitoring tools. However, quantification of degradation through isotope data was restricted for TCE due to isotope masking effects. The combination of various monitoring tools, applied frequently at high-resolution, with system understanding, was essential for the assessment of biodegradation in the complex, non-stationary system. Furthermore, the investigations revealed prospects for future research, which should focus on monitoring contaminant fate and microbial distribution on the sediment and the activated carbon.
在过去的十年中，活性炭改良剂已成功应用于保留地下水中的氯代乙烯污染物。该修复技术的概念是将活性炭和生物改良剂注入含水层系统以增强生物降解。虽然该技术的科学依据已经确立，但需要开发方法来对现场尺度的生物降解进行特征描述和定量。在这项研究中，在 TCE 羽流中建立了一个横截面处理区后，采用了一种综合方法来评估原位生物降解。该改良剂包括液体活性炭、氢供体和含有 Dehalococcoides 的培养物。该综合方法包括对流动和传输、氧化还原条件、污染物浓度、生物标志物丰度和化合物特异性稳定同位素进行时空评估。这是首次应用同位素和微生物技术评估液体活性炭和生物改良剂增强的现场生物降解。注入增强了从 TCE 到顺式-DCE 的生物降解。Dehalococcoides 的丰度有助于确定降解不足的关键区域，并提供可能的解释。同位素数据与分布和传输信息的概念模型提高了对过程的理解；TCE 的降解不足以抵消处理区流入和从沉积物中解吸带来的污染物输入。该综合方法可用于记录和描述原位降解，以及同位素和微生物数据提供了常规监测工具无法获得的过程理解。然而，由于同位素掩蔽效应，通过同位素数据定量降解受到限制。各种监测工具的组合，以及对系统的理解，对于评估复杂、非稳态系统中的生物降解至关重要。此外，研究结果揭示了未来研究的前景，未来的研究应侧重于监测污染物在沉积物和活性炭中的归宿以及微生物的分布。
