Pilot-scale in situ bioremediation of uranium in a highly contaminated aquifer. 1. Conditioning of a treatment zone
Pilot-scale in situ bioremediation of uranium in a highly contaminated aquifer. 1. Conditioning of a treatment zone
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DOI：
10.1021/es051954y
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发表时间：
2006-06-15
影响因子：
11.4
通讯作者：
Criddle, Craig S.
中科院分区：
文献类型：
--
作者：
Wu, Wei-Min;Carley, Jack;Criddle, Craig S.
为了评价原位生物修复U（VI）转化为难溶U（IV）的潜力，我们在美国加州大学3号区建造了一个中试试验设施。S.位于田纳西州橡树岭的能源部自然和加速生物修复研究（NABIR）现场研究中心（FRC）。该设施毗邻前S-3池塘，该池塘接收了数万亿升的酸性电镀废物。铀的含量很高，土壤中高达800 mg kg（-1），地下水中为84-210 mu M。环境地下水具有类似于3.4的高度缓冲的pH值和高水平的铝（12-13 mM）、钙（22-25 mM）和硝酸盐（80-160 mM）。将含水层内地下水的pH值调节至接近5将使大量氢氧化铝沉淀存款。地下水中的钙含量会抑制U（VI）的还原，但注入高pH值溶液去除钙会产生堵塞沉淀。硝酸盐也抑制U（VI）还原，并且以如此高的浓度存在，以至于通过原位反硝化将其去除将产生大量的N-2气体和生物质。为了建立和维持水力控制，我们安装了一个平行于地质走向的四口井再循环系统，内部循环嵌套在外部循环中。为了进行监测，我们在内环线上垂直于走向钻了三个钻孔，并在其中安装了多级采样管。一个示踪剂脉冲与清洁水建立旅行时间和威尔斯之间的连通性，使污染物从土壤基质中释放的评估。随后，通过去除堵塞剂和抑制剂并增加pH值，为生物刺激准备了地下的高导电区域。2个月后，从水力传导区抽取地下水;处理以去除铝、钙和硝酸盐，并补充自来水;调节至pH 4.3-4.5;然后返回水力传导区。该方案除去了大部分铝和钙的水溶液。然后将注入的经处理的水的pH增加至6.0-6.3。随着额外的冲洗，提取的水的pH值逐渐增加到5.5-6.0，硝酸盐浓度下降到0.5-1.0 mM。这些条件被认为适合生物刺激。在一篇配套论文（Wu et al.，Environ. Sci. 2006，40，3978-3987），我们描述了乙醇添加对原位反硝化和U（VI）还原和固定的影响。
To evaluate the potential for in situ bioremediation of U( VI) to sparingly soluble U(IV), we constructed a pilot test facility at Area 3 of the U. S. Department of Energy Natural and Accelerated Bioremediation Research (NABIR) Field Research Center (FRC) in Oak Ridge, TN. The facility is adjacent to the former S-3 Ponds which received trillions of liters of acidic plating wastes. High levels of uranium are present, with up to 800 mg kg(-1) in the soil and 84-210 mu M in the groundwater. Ambient groundwater has a highly buffered pH of similar to 3.4 and high levels of aluminum (12-13 mM), calcium (22-25 mM), and nitrate (80-160 mM). Adjusting the pH of groundwater to similar to 5 within the aquifer would deposit extensive aluminum hydroxide precipitate. Calcium is present in the groundwater at levels that inhibit U( VI) reduction, but its removal by injection of a high pH solution would generate clogging precipitate. Nitrate also inhibits U( VI) reduction and is present at such high concentrations that its removal by in situ denitrification would generate large amounts of N-2 gas and biomass. To establish and maintain hydraulic control, we installed a four well recirculation system parallel to geologic strike, with an inner loop nested within an outer loop. For monitoring, we drilled three boreholes perpendicular to strike across the inner loop and installed multilevel sampling tubes within them. A tracer pulse with clean water established travel times and connectivity between wells and enabled the assessment of contaminant release from the soil matrix. Subsequently, a highly conductive region of the subsurface was prepared for biostimulation by removing clogging agents and inhibitors and increasing pH. For 2 months, groundwater was pumped from the hydraulically conductive zone; treated to remove aluminum, calcium, and nitrate, and supplemented with tap water; adjusted to pH 4.3-4.5; then returned to the hydraulically conductive zone. This protocol removed most of the aqueous aluminum and calcium. The pH of the injected treated water was then increased to 6.0-6.3. With additional flushing, the pH of the extracted water gradually increased to 5.5-6.0, and nitrate concentrations fell to 0.5-1.0 mM. These conditions were judged suitable for biostimulation. In a companion paper (Wu et al., Environ. Sci. Technol. 2006, 40, 3978-3987), we describe the effects of ethanol addition on in situ denitrification and U(VI) reduction and immobilization.