School of Engineering, University of Mount Union, Alliance, OH, USA.
Department of Civil, Environmental, and Construction Engineering, University of Central Florida, Orlando, FL, USA.
J Air Waste Manag Assoc. 2021 Jul;71(7):906-922. doi: 10.1080/10962247.2021.1911874. Epub 2021 May 28.
To achieve a more sustainable waste-to-energy (WTE) process, the recycling of solid waste incineration (MSWI) bottom ash (BA) has received large attention nowadays. This study investigated how WTE BA form is changed after the hydration and the impacts of WTE BA hydration on its leaching characteristics by using geometrical and leaching tests when incorporated in cement matrix for the recycling. The material composition and characteristics of anhydrous BA, hydrated BA, cement paste, Portland cement concrete (PCC), and BA-combined PCC were evaluated through scanning electron microscopy, X-ray spectroscopy and X-ray diffraction analyses. The results confirmed that the WTE BA newly formed a complex phase of hydration products in a cement matrix. Synthetic precipitation leaching procedure (SPLP) test was also conducted to investigate the leaching behaviors of alkaline components and metals of BA in the crushed BA-PCC samples. Through the leaching study, the leachability of crushed BA-combined concrete was rigorously evaluated when recycled as construction materials (e.g. base, subbase, subdrainage, etc.), which is the worst-case scenario. The results revealed that the release of highly alkaline elements increases with increasing BA content. However, the release of trace metals was reduced by 20-30% significantly when mixed properly with Portland cement concrete (PCC), which is due to both physical and chemical binding in cement hydration products. In addition, the thresholds of water regulations, set by the World Health Organization (WHO) and the Environmental Protection Agency (EPA) of the United States, were assessed as the basis for evaluating the extent of the risk of the leaching of toxic materials. This study investigated how waste to energy (WTE) bottom ash (BA) form is changed after the hydration and the impacts of WTE BA hydration on its environmental leaching characteristics by using geometrical and leaching tests when incorporated in cement matrix for the recycling. Incorporating of WTE BA in cement mixture can form new mineralogical phases of hydration products in cement matrices such as Copper Hydrogen Arsenate Hydrate and Jahnsite. A significant reduction of alkaline elements (Si, Al, and K) from crushed PCC mixed with WTE BA due to the hydration. The lowest concentrations of major alkaline elements leached from the crushed PCC containing either 10% or 20% of BA contents. The averaged leaching concentration of detected elements is substantially below the water quality guidelines (provided by U.S. EPA and WHO) except Al.
为了实现更可持续的废物能源化（WTE）过程，如今人们对回收利用固体废物焚烧（MSWI）底灰（BA）给予了极大关注。本研究通过几何和浸出测试，调查了 WTE BA 在水合作用后形态的变化以及 WTE BA 水合作用对其浸出特性的影响，这些测试是将 WTE BA 用于水泥基质中的再循环时进行的。通过扫描电子显微镜、X 射线光谱和 X 射线衍射分析，评估了无水 BA、水合 BA、水泥浆、波特兰水泥混凝土（PCC）和 BA 结合 PCC 的材料组成和特性。结果证实，WTE BA 在水泥基质中形成了一种复杂的水化产物相。还进行了合成沉淀浸出程序（SPLP）测试，以研究破碎的 BA-PCC 样品中碱性成分和金属的浸出行为。通过浸出研究，当作为建筑材料（例如基层、次基层、次排水等）回收利用时，对破碎的 BA 结合混凝土的浸出行为进行了严格评估，这是最坏的情况。结果表明，随着 BA 含量的增加，高碱性元素的释放增加。然而，当与波特兰水泥混凝土（PCC）适当混合时，痕量金属的释放减少了 20-30%，这是由于水泥水化产物中的物理和化学结合。此外，还评估了世界卫生组织（WHO）和美国环境保护署（EPA）设定的水质法规阈值，作为评估有毒材料浸出风险程度的依据。本研究通过几何和浸出测试，调查了废物能源化（WTE）底灰（BA）在水合作用后形态的变化以及 WTE BA 水合作用对其环境浸出特性的影响，这些测试是将 WTE BA 用于水泥基质中的再循环时进行的。将 WTE BA 掺入水泥混合物中，可以在水泥基质中形成新的水化产物矿物相，如铜氢砷酸盐水合物和 Jahnsite。由于水化作用，从与 WTE BA 混合的破碎 PCC 中大量减少了碱性元素（Si、Al 和 K）。从含有 10%或 20%BA 含量的破碎 PCC 中浸出的主要碱性元素的最低浓度。除 Al 外，检测到的元素的平均浸出浓度大大低于水质指南（由美国 EPA 和 WHO 提供）。
