Sarti Chiara, Cincinelli Alessandra, Bresciani Riccardo, Rizzo Anacleto, Chelazzi David, Masi Fabio
Department of Chemistry "Ugo Schiff", University of Florence, Via della Lastruccia 3, 50019 Sesto Fiorentino, Italy; Iridra Srl, Via La Marmora 51, 50121 Florence, Italy.
Department of Chemistry "Ugo Schiff", University of Florence, Via della Lastruccia 3, 50019 Sesto Fiorentino, Italy; Department of Chemistry "Ugo Schiff" and CSGI, University of Florence, Via della Lastruccia 3, 50019 Sesto Fiorentino, Italy.
Sci Total Environ. 2024 Nov 20;952:175864. doi: 10.1016/j.scitotenv.2024.175864. Epub 2024 Aug 29.
Combined sewer overflows (CSOs) release a significant amount of pollutants, including microplastics (MPs), due to the discharge of untreated water into receiving water bodies. Constructed Wetlands (CWs) offer a promising strategy for CSO treatment and have recently attracted attention as a potential solution for MP mitigation. Nevertheless, limited research on MP dynamics within CSO events and MP removal performance in full-scale CW systems poses a barrier to this frontier of application. This research aims to address both these knowledge gaps, representing the first investigation of a multi-stage CSO-CW for MP removal. The study presents one year of seasonal data from the CSO-CW upstream of the WWTP in Carimate (Italy), evaluating the correlation of MP abundance with different water quality/quantity parameters and associated ecological risks. The results show a clear trend in MP abundance, which increases with rainfall intensity. The strong correlation between MP concentration, flow rate, and total suspended solids (TSS) validates the first flush phenomenon hypothesis and its impact on MP release during CSOs. Chemical characterization identifies acrylonitrile-butadiene-styrene (ABS), polyethylene (PE), and polypropylene (PP) as predominant polymers. The first vertical subsurface flow (VF) stage showed removal rates ranging from 40 % to 77 %. However, the unexpected increase in MP concentrations after the second free water surface (FWS) stage suggests the stochasticity of CSO events and the different hydraulic characteristics of the CW units have diverse effects on MP retention. These data confirm filtration as the main retention mechanism for MP within CW systems. The MP ecological risk assessment indicates a high-risk category for most of the water samples, mainly related to the frequent presence of ABS fragments. The results contribute to the current understanding of MPs released by CSOs and provide insights into the performance of different treatment units within a large-scale CSO-CW system, suggesting the requirement for further attention.
合流制下水道溢流（CSOs）会排放大量污染物，包括微塑料（MPs），因为未经处理的污水会排入受纳水体。人工湿地（CWs）为CSO处理提供了一种有前景的策略，并且最近作为减轻微塑料的潜在解决方案受到关注。然而，关于CSO事件中微塑料动态以及全尺寸人工湿地系统中微塑料去除性能的研究有限，这对这一应用前沿构成了障碍。本研究旨在填补这两个知识空白，是对用于去除微塑料的多级CSO-CW的首次调查。该研究展示了来自意大利卡里马泰污水处理厂上游CSO-CW的一年季节性数据，评估了微塑料丰度与不同水质/水量参数的相关性以及相关的生态风险。结果显示微塑料丰度有明显趋势，随降雨强度增加。微塑料浓度、流速和总悬浮固体（TSS）之间的强相关性验证了首次冲刷现象假说及其对CSO期间微塑料释放的影响。化学表征确定丙烯腈-丁二烯-苯乙烯（ABS）、聚乙烯（PE）和聚丙烯（PP）为主要聚合物。第一个垂直潜流（VF）阶段的去除率在40%至77%之间。然而，第二个自由水面（FWS）阶段后微塑料浓度意外增加，这表明CSO事件的随机性以及人工湿地单元不同的水力特性对微塑料截留具有不同影响。这些数据证实过滤是人工湿地系统中微塑料的主要截留机制。微塑料生态风险评估表明大多数水样处于高风险类别，主要与ABS碎片的频繁存在有关。研究结果有助于当前对CSO释放的微塑料的理解，并深入了解大型CSO-CW系统中不同处理单元的性能，表明需要进一步关注。
