Ishii Kazuei, Furuichi Toru, Tanikawa Noboru
Laboratory of Sound Material-Cycle Systems Planning, Graduate School of Engineering, Hokkaido University, N13, W8, Kita-ku, Sapporo, 060-8628 Hokkaido, Japan.
Waste Manag. 2009 Feb;29(2):513-21. doi: 10.1016/j.wasman.2008.06.006. Epub 2008 Aug 8.
Bottom ash from municipal solid waste incineration (MSWI) is a main type of waste that is landfilled in Japan. The long-term elution of organic matter from the MSWI bottom ash layers is a concern because maintenance and operational costs of leachate treatment facilities are high. In closed system disposal facilities (CSDFs), which have a roof to prevent rainfall from infiltrating into the waste layers, water must be supplied artificially and its quantity can be controlled. However, the quantity of water needed and how to apply it (the intensity, period and frequency) have not been clearly defined. In order to discuss an effective watering plan, this study proposes a new washout model to clarify a fundamental mechanism of total organic carbon (TOC) elution behavior from MSWI bottom ash layers. The washout model considers three phases: solid, immobile water and mobile water. The parameters, including two mass transfer coefficients of the solid-immobile water phases and immobile-mobile water phases, were determined by one-dimensional column experiments for about 2 years. The intensity, period and frequency of watering and other factors were discussed based on a numerical analysis using the above parameters. As a result, our washout model explained adequately the elution behavior of TOC from the MSWI bottom ash layer before carbonation occurred (pH approximately 8.3). The determined parameters and numerical analysis suggested that there is a possibility that the minimum amount of water needed for washing out TOC per unit weight of MSWI bottom ash layer could be determined, which depends on the two mass transfer coefficients and the depth of the MSWI bottom ash layer. Knowledge about the fundamental mechanism of the elution behavior of TOC from the MSWI bottom ash layer before carbonation occurs, clarified by this study, will help an effective watering plan in CSDFs.
城市固体废弃物焚烧（MSWI）产生的底灰是日本填埋的主要废弃物类型。由于渗滤液处理设施的维护和运营成本高昂，人们担心MSWI底灰层中有机物的长期溶出问题。在具有防止降雨渗入废弃物层的屋顶的封闭系统处置设施（CSDF）中，必须人工供水且水量可以控制。然而，所需水量以及如何供水（强度、周期和频率）尚未明确界定。为了探讨有效的浇水计划，本研究提出了一种新的冲洗模型，以阐明MSWI底灰层中总有机碳（TOC）溶出行为的基本机制。该冲洗模型考虑三个阶段：固体、非流动水和流动水。通过约两年的一维柱实验确定了包括固体 - 非流动水相和非流动 - 流动水相的两个传质系数在内的参数。基于使用上述参数的数值分析，讨论了浇水强度、周期、频率及其他因素。结果，我们的冲洗模型充分解释了碳酸化发生前（pH约为8.3）MSWI底灰层中TOC的溶出行为。所确定的参数和数值分析表明，有可能确定每单位重量MSWI底灰层冲洗TOC所需的最小水量，这取决于两个传质系数和MSWI底灰层的深度。本研究阐明的关于碳酸化发生前MSWI底灰层中TOC溶出行为基本机制的知识，将有助于CSDF中的有效浇水计划。
