Christenson Mark, Kambhu Ann, Reece James, Comfort Steve, Brunner Laurie
AirLift Environmental, LLC, 5900 N. 58th, Suite 5, Lincoln, NE 68507, USA; School of Natural Resources, University of Nebraska, Lincoln, NE 68583-0915, USA.
Department of Civil Engineering, University of Nebraska, Lincoln, NE 68583-0531, USA.
Chemosphere. 2016 May;150:239-247. doi: 10.1016/j.chemosphere.2016.01.125. Epub 2016 Feb 21.
In 2009, we identified a TCE plume at an abandoned landfill that was located in a low permeable silty-clay aquifer. To treat the TCE, we manufactured slow-release potassium permanganate cylinders (oxidant candles) that had diameters of either 5.1 or 7.6 cm and were 91.4 cm long. In 2010, we compared two methods of candle installation by inserting equal masses of the oxidant candles (7.6-cm vs 5.1-cm dia). The 5.1-cm dia candles were inserted with direct-push rods while the 7.6-cm candles were housed in screens and lowered into 10 permanent wells. Since installation, the 7.6-cm oxidant candles have been refurbished approximately once per year by gently scraping off surface oxides. In 2012, we reported initial results; in this paper, we provide a 5-yr performance review since installation. Temporal sampling shows oxidant candles placed in wells have steadily reduced migrating TCE concentrations. Moreover, these candles still maintain an inner core of oxidant that has yet to contribute to the dissolution front and should provide several more years of service. Oxidant candles inserted by direct-push have stopped reducing TCE concentrations because a MnO2 scale developed on the outside of the candles. To counteract oxide scaling, we fabricated a second generation of oxidant candles that contain sodium hexametaphosphate. Laboratory experiments (batch and flow-through) show that these second-generation permanganate candles have better release characteristics and are less prone to oxide scaling. This improvement should reduce the need to perform maintenance on candles placed in wells and provide greater longevity for candles inserted by direct-push.
2009年，我们在一个废弃垃圾填埋场发现了一处三氯乙烯羽流，该垃圾填埋场位于低渗透性粉质粘土层含水层中。为了处理三氯乙烯，我们制造了直径为5.1厘米或7.6厘米、长91.4厘米的缓释高锰酸钾柱（氧化剂柱）。2010年，我们通过插入等质量的氧化剂柱（直径7.6厘米与5.1厘米）比较了两种柱体安装方法。直径5.1厘米的柱体用直接压入杆插入，而直径7.6厘米的柱体放置在筛管中并放入10口永久井中。自安装以来，直径7.6厘米的氧化剂柱大约每年通过轻轻刮去表面氧化物进行一次翻新。2012年，我们报告了初步结果；在本文中，我们提供了自安装以来的5年性能评估。时间采样显示，放置在井中的氧化剂柱稳步降低了迁移的三氯乙烯浓度。此外，这些柱体仍保留着尚未对溶解前沿起作用的氧化剂内核，应能再提供数年的服务。通过直接压入插入的氧化剂柱已停止降低三氯乙烯浓度，因为柱体外部形成了二氧化锰垢。为了应对氧化物结垢，我们制造了第二代含有六偏磷酸钠的氧化剂柱。实验室实验（批量和流通实验）表明，这些第二代高锰酸盐柱具有更好的释放特性，且不易结垢。这一改进应能减少对放置在井中的柱体进行维护的需求，并延长通过直接压入插入的柱体的使用寿命。
