Verhalten von Mikrokunststoffen in Abwasserbehandlungsanlagen

Spelthahn, Vanessa; Pinnekamp, Johannes (Thesis advisor); Barjenbruch, Matthias (Thesis advisor); Wintgens, Thomas Josef (Thesis advisor)

Aachen : RWTH Aachen University (2023)
Dissertation / PhD Thesis

Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2023

Abstract

In addition to diffuse land and sea entry paths, wastewater treatment plants (WWTP) came into focus, representing potential entry paths for microplastics into water bodies. WWTPs built according to the state of the art are not designed to remove the smallest solid particles from the wastewater. There are no specifications or regulations defined as standards for sampling, sample preparation and analysis for the detection of microplastics in a wide variety of environmental matrices. Therefore, the level of knowledge about microplastics discharged into water bodies is low and not very comparable.The dissertation aims for proving the occurrence of microplastics in wastewater and their behavior in WWTPs. Various mechanical-biological WWTPs followed by filtration were examined, which differ in their population equivalent and process technology. In addition, a comparison was made with a combined sewer overflow (CSO) basin and the water pollution of a water body before and after the discharge point was identified. No dependence of the microplastic concentrations on the catchment areas of the WWTPs could be determined. Large microplastics can be removed more easily in the wastewater treatment process than small microplastics. Cleaning performance > 99% by weight could be determined for all three WWTPs. Therefore, it was irrelevant whether the wastewater treatment process was rather simple or more complex. Comparably high cleaning performance was also determined in rainy weather. However, the inflow concentration to the WWTP tends to decrease (dilution effect) and the discharge concentration increases. That was due to the higher hydraulic loading on the WWTP and the shorter retention times. The cleaning capacity of the CSO basin was significantly lower compared to the WWTPs. A convincing load assessment (extrapolation) for microplastic discharges via WWTPs and CSO basins in NRW and Germany couldn´t be concluded due to the very large ranges be-tween minimum and maximum concentrations in the discharged wastewater. The deviations in the load estimates for the best-case and worst-case scenarios are within the three to four-digit range (t/a). The heterogeneity of the values determined in this as well as in other scientific work must be considered when classifying and expressing the results. In addition, standards for the methods have to be defined for the comparability of future results.

Institutions

• Institute of Environmental Engineering [314110]