Pivato A, Raga R
IMAGE Department, University of Padua - via Loredan 20, I 35131 Padova, Italy.
Waste Manag. 2006;26(2):123-32. doi: 10.1016/j.wasman.2005.03.009. Epub 2005 Jun 4.
Uncontrolled leachate emissions are one of the key factors in the environmental impact of municipal solid waste (MSW) landfills. The concentration of ammonium, given the anaerobic conditions in traditional landfills, can remain significantly high for a very long period of time, as degradation does not take place and volatilisation is not significant (the pH is not high enough to considerably shift the equilibrium towards un-ionised ammonia). Recent years have witnessed a continuous enhancement of landfill technology in order to minimize uncontrolled emissions into the environment; bottom lining systems have been improved and more attention has been devoted to the study of the attenuation of the different chemicals in leachate in case of migration through the mineral barrier. Different natural materials have been considered for use as components of landfill liners in the last years and tested in order to evaluate the performance of the different alternatives. Among those materials, bentonite is often used, coupled with other materials in two different ways: in addition to in situ soil or in geocomposite clay liner (GCL). A lab-scale test was carried out in order to further investigate the influence of bentonite on the attenuation of ammonium in leachate passing through a landfill liner. Two different tests were conducted: a standardized batch test with pulverized bentonite and a batch test with compacted bentonite. The latter was proposed in order to better simulate the real conditions in a landfill liner. The two tests produced values for the partition coefficient K(d) higher than the average measured for other natural materials usually utilized as components of landfill liners. Moreover, the two tests showed similar results, thus providing a further validation of the suitability of the standard batch test with pulverized bentonite. A thorough knowledge of attenuation processes of ammonium in landfill liners is the basis for the application of risk analysis models for the evaluation of the failure of bottom liners or their components.
未经控制的渗滤液排放是城市固体废弃物（MSW）填埋场对环境产生影响的关键因素之一。鉴于传统填埋场的厌氧条件，由于降解未发生且挥发不显著（pH值不够高，不足以使平衡显著向未电离氨方向移动），铵的浓度在很长一段时间内会一直保持在较高水平。近年来，填埋技术不断改进，以尽量减少向环境中的无控排放；底部衬里系统得到了改善，并且更加关注渗滤液中不同化学物质在通过矿物屏障迁移时的衰减研究。在过去几年中，人们考虑使用不同的天然材料作为填埋场衬垫的组成部分，并进行了测试，以评估不同替代方案的性能。在这些材料中，膨润土经常被使用，它与其他材料以两种不同方式结合：除了与原位土壤结合外，还用于土工合成粘土衬垫（GCL）。为了进一步研究膨润土对渗滤液中铵通过填埋场衬垫时衰减的影响，进行了一项实验室规模的试验。进行了两项不同的试验：一项使用粉碎膨润土的标准化批量试验和一项使用压实膨润土的批量试验。提出后者是为了更好地模拟填埋场衬垫中的实际情况。这两项试验得出的分配系数K(d)值高于通常用作填埋场衬垫组成部分的其他天然材料的平均测量值。此外，这两项试验结果相似，从而进一步验证了使用粉碎膨润土的标准批量试验的适用性。深入了解填埋场衬垫中铵的衰减过程是应用风险分析模型评估底部衬垫或其组件失效的基础。
