The investigation of microplastics is an important task, which still has to be performed due to lack of long term data on composition and variability of pollution present. Currently, there is no standard operational protocol while several methods for sampling and microplastic extraction are available. The analysis of the effluent of two wastewater treatment plants on two different days showed exemplary, that the microplastic emissions at the effluent might be highly variable. The determined particle composition differs remarkably between the two days. Additionally our results showed that the post filtration unit in Oldenburg reduces the microplastic concentration by more than 70 % and removes particles > 300 µm with high efficiency. The overall determined particle sizes show a high emission of particles smaller 50 µm in size through the waste water treatment plant effluent, whereas particles > 100 µm were removed with good efficiency
