Microplastics in sewage sludge.

Microplastics enter the sewage sludge via wastewater. Recycling as fertilizer leads to the entry of microplastics into soils. This study provides an overview of the microplastic contamination of sewage sludge and its temporal variability. The starting point is an initial survey in 2020 of 35 wastewater treatment plants in Austria. For this purpose, sewage sludge from 20 plants was repeatedly sampled and analysed in 2021/22. The origin of polyurethane, the dominant plastic of the initial survey, was also investigated. The composition of the plastics was consistent. Temporal deviations in microplastic concentrations were related to the nature of the sewer system, an urban or rural character of the catchment area, and the population values of the facilities. High polyurethane loads are probably due to industrial dischargers, but entries from households are also significant.