Microplastics in sewage sludges.

Microplastics enter the sewage sludge via waste water. Recycling as fertiliser leads to the entry of microplastics in soils. This study provides an overview of the microplastic load of sewage sludge and their temporal variability. The starting point is an initial survey in 2020 at 35 wastewater treatment plants in Austria. For this purpose, 20 plants were repeatedly sampled and analysed in 2021/22 sewage sludge. The origin of polyurethane, the dominant plastic of the first survey, was also investigated. The composition of the plastics was consistent. Temporal deviations of the microplastic concentrations coincided with the type of canal system, an urban or rural character of the catchment area and the inhabitants:inside values of the installations. High polyurethane loads are presumably due to industrial inductors, but also entries from households are significant.