Prieto-Espinoza Maria, Susset Bernd, Grathwohl Peter
Center for Applied Geosciences, University of Tübingen, Schnarrenbergstr. 94-96, 72076 Tübingen, Germany.
Institute Earth and Environment (ITES UMR 7063), University of Strasbourg, CNRS/EOST, 5 Rue Descartes, 67084 Strasbourg, France.
Materials (Basel). 2022 Jan 23;15(3):858. doi: 10.3390/ma15030858.
The recycling of mineral materials is a sustainable and economical approach for reducing solid waste and saving primary resources. However, their reuse may pose potential risks of groundwater contamination, which may result from the leaching of organic and inorganic substances into water that percolates the solid waste. In this study, column leaching tests were used to investigate the short- and long-term leaching behavior of "salts", "metals", and organic pollutants such as PAHs and herbicides from different grain size fractions of construction & demolition waste (CDW) and railway ballast (RB) after a novel treatment process. Specifically, silt, sand and gravel fractions obtained after a sequential crushing, sieving, and washing process ("wet-processing") of very heterogeneous input materials are compared with respect to residual contamination, potentially limiting their recycling. Concentrations in solid fractions and aqueous leachate were evaluated according to threshold values for groundwater protection to identify relevant substances and to classify materials obtained for recycling purposes according to limit values. For that, the upcoming German recycling degree was applied for the first time. Very good agreement was observed between short and extensive column tests, demonstrating that concentrations at L/S 2 ratios are suitable for quality control of recycling materials. Different solutes showed a characteristic leaching behavior such as the rapid decrease in "salts", e.g., SO and Cl, from all solid fractions, and a slower decrease in metals and PAHs in the sand and silt fractions. Only the gravel fraction, however, showed concentrations of potential pollutants low enough for an unlimited re-use as recycling material in open technical applications. Sand fractions may only be re-used as recycling material in isolated or semi-isolated scenarios. Leaching from heterogeneous input materials proved harder to predict for all compounds. Overall, column leaching tests proved useful for (i) initial characterization of the mineral recycling materials, and (ii) continuous internal (factory control) and external quality control within the upcoming German recycling decree. Results from such studies may be used to optimize the treatment of mixed solid waste since they provide rapid insight in residual pollution of material fractions and their leaching behavior.
矿物材料的回收利用是一种可持续且经济的方法，可减少固体废物并节约原生资源。然而，它们的再利用可能会带来地下水污染的潜在风险，这可能是由于有机和无机物质渗入渗透固体废物的水中而导致的。在本研究中，采用柱淋溶试验来研究经过新型处理工艺后，建筑与拆除废物（CDW）和铁路道砟（RB）不同粒度级分中“盐类”、“金属”以及多环芳烃（PAHs）和除草剂等有机污染物的短期和长期淋溶行为。具体而言，将经过对非常不均匀的输入材料进行连续破碎、筛分和洗涤过程（“湿法处理”）后获得的粉砂、砂和砾石级分在残留污染方面进行比较，这可能会限制它们的回收利用。根据地下水保护的阈值评估固体级分和淋滤液中的浓度，以识别相关物质，并根据限值对回收用材料进行分类。为此，首次应用即将出台的德国回收等级。短期和长期柱试验之间观察到非常好的一致性，表明液固比为2时的浓度适用于回收材料的质量控制。不同溶质表现出特征性的淋溶行为，例如所有固体级分中“盐类”（如硫酸根和氯离子）的迅速减少，以及砂和粉砂级分中金属和多环芳烃的缓慢减少。然而，只有砾石级分显示潜在污染物浓度低到足以在开放技术应用中作为回收材料无限制地再利用。砂级分只能在孤立或半孤立场景中作为回收材料再利用。对于所有化合物而言，来自不均匀输入材料的淋溶情况更难预测。总体而言，柱淋溶试验被证明对（i）矿物回收材料的初始表征，以及（ii）即将出台的德国回收法令中的内部（工厂控制）和外部质量控制很有用。此类研究的结果可用于优化混合固体废物的处理，因为它们能快速洞察材料级分的残留污染及其淋溶行为。
