School of Sustainable Engineering and the Built Environment, Arizona State University, Tempe, Arizona 85281, United States.
Biodesign Swette Center for Environmental Biotechnology, Arizona State University, Tempe, Arizona 85287, United States.
Environ Sci Technol. 2023 Mar 14;57(10):4167-4179. doi: 10.1021/acs.est.2c06433. Epub 2023 Mar 3.
Fe is a powerful chemical reductant with applications for remediation of chlorinated solvents, including tetrachloroethene and trichloroethene. Its utilization efficiency at contaminated sites is limited because most of the electrons from Fe are channeled to the reduction of water to H rather than to the reduction of the contaminants. Coupling Fe with H-utilizing organohalide-respiring bacteria (i.e., ) could enhance trichloroethene conversion to ethene while maximizing Fe utilization efficiency. Columns packed with aquifer materials have been used to assess the efficacy of a treatment combining in space and time Fe and a-containing culture (bioaugmentation). To date, most column studies documented only partial conversion of the solvents to chlorinated byproducts, calling into question the feasibility of Fe to promote complete microbial reductive dechlorination. In this study, we decoupled the application of Fe in space and time from the addition of organic substrates and-containing cultures. We used a column containing soil and Fe (at 15 g L in porewater) and fed it with groundwater as a proxy for an upstream Fe injection zone dominated by abiotic reactions and biostimulated/bioaugmented soil columns (Bio-columns) as proxies for downstream microbiological zones. Results showed that Bio-columns receiving reduced groundwater from the Fe-column supported microbial reductive dechlorination, yielding up to 98% trichloroethene conversion to ethene. The microbial community in the Bio-columns established with Fe-reduced groundwater also sustained trichloroethene reduction to ethene (up to 100%) when challenged with aerobic groundwater. This study supports a conceptual model where decoupling the application of Fe and biostimulation/bioaugmentation in space and/or time could augment microbial trichloroethene reductive dechlorination, particularly under oxic conditions.
铁是一种强大的化学还原剂，可用于修复包括四氯乙烯和三氯乙烯在内的氯化溶剂。但由于铁释放的电子大部分被用于还原水生成 H，而不是还原污染物，因此其在污染场地的利用效率有限。将铁与利用氢的有机卤代物呼吸细菌（即）耦合，可以增强三氯乙烯向乙烯的转化，同时最大限度地提高铁的利用效率。填充含水层材料的柱状物已被用于评估将铁和含碳培养物（生物增强）在空间和时间上结合的处理效果。迄今为止，大多数柱研究仅记录了溶剂部分转化为氯化副产物，这使得铁促进完全微生物还原脱氯的可行性受到质疑。在这项研究中，我们将铁的空间和时间应用与有机底物和含碳培养物的添加解耦。我们使用了一个含有土壤和铁（在孔隙水中为 15 g L）的柱状物，并以地下水作为生物刺激/生物增强土壤柱状物（Bio 柱状物）的替代物，模拟上游由非生物反应和生物刺激/生物增强土壤主导的铁注入区。结果表明，从铁柱接收还原地下水的 Bio 柱支持微生物还原脱氯，三氯乙烯转化率高达 98%。当用有氧地下水挑战时，用铁还原地下水建立的 Bio 柱中的微生物群落也能维持三氯乙烯还原为乙烯（高达 100%）。这项研究支持了一个概念模型，即通过空间和/或时间上解耦铁的应用和生物刺激/生物增强，可能会增强微生物三氯乙烯还原脱氯，特别是在有氧条件下。
