Microplastics in two German wastewater treatment plants: Year-long effluent analysis with FTIR and Py-GC/MS

Microplastics (MP) have been recorded in various environments around the globe. For a better understanding of dis-tribution patterns and for providing a basis for risk assessments, detailed data on MP concentrations and polymer com-positions are required. This study investigated the effluents of two German wastewater treatment plants (WWTP) monthly over one year, in order to better understand their temporal input of MP into the receiving river systems. MP item data down to 11 mu m were obtained by means of Fourier Transform Infrared (FTIR) spectroscopy under the application of an improved polymer database. Complementary mass data were obtained by pyrolysis gas chromatography-mass spectrometry (Py-GC/MS) (for one WWTP). Both FTIR and Py-GC/MS analysis revealed a ho-mogeneous polymer composition over the year, with a general dominance of polyolefins. Elevated MP item and mass concentrations (maximum: 3 x 10(4) items m(-3) and 3.8 x 10(3) mu g m(-3)) were observed during winter months and were accompanied by either heavy rainfall (increased discharge and total organic carbon) or elevated turbidity values. These observations emphasize the need for the assessment of background parameters in future MP monitoring studies. By providing monthly data over one year on MP items and masses in WWTP effluents, this study helps enhancing the understanding of temporal MP dynamics and can act as a valuable reference point for future assessments.

Automated summary

In this study, the effluents of two German wastewater treatment plants were investigated monthly over one year to understand the temporal input of microplastics (MP) into the receiving river systems. The study revealed elevated MP concentrations during winter months, possibly due to increased discharge and total organic carbon or elevated turbidity values caused by heavy rainfall. This study provides valuable data on the temporal dynamics of MP and highlights the importance of considering background parameters in future monitoring studies.