微米铁-氢自养微生物耦合修复地下水氯代烃污染的自驱动机制与效能

Zero valent iron based in-situ chemical reductive technologies are widely used for chlorinated hydrocarbon contaminated groundwater remediation. However, the produced hydrogen from hydrogen-evolutional corrosion could not be efficiently used as secondary electron donor, which accelerated ZVI surface passivation, activity loss and porous media clogging, and further negatively affected the remediation efficiency. In this study, in order to enhance the hydrogen utilization efficiency and raise the remediation efficiency, microscale zero valent iron (mZVI) particles, which display low microbial toxicity, high long-term reactive stability and great gas-liquid mass transfer enhancement performance, will be injected into aquifers to form reactive zones and simultaneously stimulate in-situ functional autotrophic hydrogen-bacteria, so as to establish a self-propelled coupling abiotic-biotic remediation system. Through a combination of advanced technologies (such as X-ray absorption near edge structure, stable isotope, metagenomics, etc.) and batch/column experiments, the mZVI-groundwater-microorganism three-phase interface mass transfer and reaction mechanism will be explored. And the response model of remediation efficiencies to mZVI injection parameter variations will be established, to further guide the self-propelled stimulation of the coupling abiotic-biotic remediation system. Then the long-term remediation performance of mZVI-autotrophic hydrogen bacteria coupling remediation system will be comprehensively evaluated and optimized, which would provide theoretical and technological support for efficient remediation of chlorinated hydrocarbon contaminated groundwater.

零价铁被广泛用于氯代烃污染地下水的修复，但析氢腐蚀等反应会加速材料钝化、失活和含水介质堵塞，成为影响其应用的关键瓶颈。本课题以提高伴生氢气利用率和氯代烃修复效率为目标，评估并选用微米级零价铁（microscale zero valent iron, mZVI）注入地下含水层，依托其生物毒性低、反应持久性强、可促进气液传质等性能优势，对土著氢自养微生物进行加速激活，构建mZVI-氢自养微生物自驱动耦合修复系统；通过X射线吸收近边结构谱、稳定同位素、宏基因组学等手段和批量/柱槽模拟试验，分析并阐明系统中mZVI-地下水-微生物三相界面的传质和反应机制，建立mZVI注入参数和修复效率之间的响应关系模型，从而指导实现以氢气的自产生和利用过程为纽带驱动原位地层中化学-微生物同步脱氯与交互强化；并进一步评估和优化该系统对地下水氯代烃污染的长期修复效能，为我国氯代烃污染地下水高效修复提供理论和技术支撑。

目前，国内外针对地下水氯代烃污染的原位修复技术主要包括基于零价铁（Zero valent iron，ZVI）的化学还原技术和基于厌氧微生物的生物还原技术两大类。但是，这两类技术单独应用都存在各自的瓶颈问题。因此，以H2作为化学与生物技术修复氯代烃污染的桥梁，构建ZVI和氢自养微生物（autotrophic hydrogen-bacteria, AHB）耦合修复体系，有望极大提高氯代烃污染地下水的修复效率。本课题瞄准微米铁（microscale zero valent iron, mZVI）-AHB耦合修复系统，考察其对代表性氯代烃三氯乙烯（trichloroethylene，TCE）的去除效能，探究mZVI与氢自养微生物之间的交互作用机制。此外，由于实际地下水成分复杂，其中的常量组分（如NO3－和SO42－）可能与目标污染物竞争电子供体或对ZVI和微生物的反应活性产生影响改变电子传输，进而降低修复速率、目标有效性和诱发负面环境效应。因此，本研究重点关注mZVI-AHB耦合体系中的电子竞争作用和电子传递规律，在综合考虑技术指标、环境指标和经济指标的前提下，明确mZVI参数变化对体系氯代烃综合去除效能的影响，从而指导原位地下水中化学-微生物同步脱氯与定向调控。研究发现，mZVI-AHB耦合体系对TCE的去除效果明显优于单一mZVI体系，在30 d内，耦合体系对TCE的去除率是单一mZVI体系的1.24倍。虽然耦合体系倾向于呈现化学还原的反应特征，但mZVI和微生物之间被证实存在交互作用且有利于脱氯过程。AHB利用了mZVI腐蚀产生的氢气用于自身生长与氯代烃去除，同时，AHB的存在抑制表面钝化产物的积累并改变了其组分构成，从而增加了mZVI反应活性，延长了mZVI的使用寿命。共存电子受体对耦合体系TCE降解的影响规律与共存电子受体类型和浓度有关。考虑到氯代产物、NH4+等有毒有害物质产生的潜在负面环境效应，构建了包含TCE去除率、TCE去除速率、完全脱氯率、N2选择性、电子选择性、成本指标的多目标评价体系，通过调控mZVI的粒径和投加量，对耦合体系进行优化以实现绿色可持续的修复目标。.