Micro- and Nano-Plastics and Their Interaction with Other Pollutants in Wastewater Treatment Systems: Monitorization, Management, and Impact on Receiving Waters and Soils

Dear Colleagues,

Wastewater treatment plants (WWTPs) are an important source of microplastics (MPs; plastics < 5 mm in any dimension) and nanoplastics (NPs; < 1 µm in any dimension) in the aquatic environment. Even though these systems reach highly efficient removal rates from influent to effluent (up to 98.5%), WWTPs release between 0.3 and 3 tones of MP per year and about 0.05 t NP y⁻¹ (1,2) to receiving waters. Furthermore, during wastewater purification processes, micro- and nanoplastics (MNPs) accumulate in sewage sludge, with reported concentrations of MPs oscillating from 0 to 300 particles per gram of sludge (3). Although it has been shown that NPs yield larger negative effects on sludge stability than MPs, no current study has reported their occurrence in sewage sludge, pointing to the need to develop new techniques that are able to determine the presence of NPs in sewage sludge.

In some countries, following circular economy practices, sewage sludge is applied to agricultural soils after being subjected to processes such as lime stabilization or composting. Still, it is estimated that MP concentrations released to these soils reach up to 430,000 t y⁻¹ in European farmlands (4). These high concentrations are claimed to pose risks to the terrestrial environment and, ultimately, human health, since current legislation does not set any limit for MNP occurrence in sludge before land application.

In addition, during wastewater treatment processes, because of their physical and chemical properties such as high hydrophobicity and resistance to degradation, MNPs can interact with other toxic pollutants, including persistent organic pollutants, pharmaceutical, heavy metals, and pathogens.

This Special Issue aims to advance the current understanding of the cutting-edge methodologies developed to analyze MNPs and the other organic pollutants or pathogens that they may interact with during wastewater treatments, as well as on their potential impacts in receiving waters and soils.

Original research articles and review papers are welcome. Research topics of interest include, but are not limited to, the following:

• MNP monitorization across whole treatment schemes in WWTPs, focusing on the most effective processes to remove these pollutants.
• Improved mechanisms to remove MNPs from wastewater and sewage sludge.
• Interactions between MNPs with other pollutants in these systems.
• Integration of advanced spectroscopic approaches to assess the ecological and health risks associated with MNPs in WWTP systems.
• Release of MNPs through the effluent, and the impacts on receiving waters.
• Accumulation of MNPs in raw and treated sludge, and impacts on receiving soils.
• Sludge management and applications.

We look forward to receiving your contributions.

References

1. Simon, M., van Alst, N., Vollertsen, J. (2018). Quantification of microplastic mass and removal rates at wastewater treatment plants applying Focal Plane Array (FPA)-based Fourier Transform Infrared (FT-IR) imaging. Water Res. 142, 1−9.
2. Xu, Y., Ou, Q., Wang, X., Hou, F., Li, P., van der Hoek, J.P., Liu, G. (2023). Assessing the Mass Concentration of Microplastics and Nanoplastics in Wastewater Treatment Plants by Pyrolysis Gas Chromatography-Mass Spectrometry. Environ Sci Technol. 28, 57(8): 3114–3123. https://doi.org/10.1021/acs.est.2c07810
3. Cydzik-Kwiatkowska, A., Milojevic, N., & Jachimowicz, P. (2022). The fate of microplastic in sludge management systems. Sci Total Environ. 848, 157466. https://doi.org/10.1016/j.scitotenv.2022.157466
4. Luca, N., Martyn, F., Sindre, L. (2016). Are agricultural soils dumps for microplastics of urban origin? Environ Sci Technol. 50 (20): 10777–10779.

Dr. Isabel Marín Beltrán
Dr. Carlos Edo
Dr. Sara Raposo
Guest Editors

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• micro- and nanoplastic pollution
• plastic additives
• wastewater treament plants
• sewage sludge
• monitorization
• advanced analytical techniques
• ecological and human health risk assessment