Samples from the secondary clarifier effluent of a waste water treatment plant (serving 98500 inhabitants) were analyzed to determine the microplastics (MP) emission. The samples were collected using a stainless steel centrifugal pump and filtered through a 10 μm stainless steel cartridge filter. Microplastics particles (MPPs) and microplastics fibers (MPFs) were recovered by chemical and physical sample purification. To remove natural organic matter, the samples were first subjected to oxidative treatment with H 2 O 2 and NaClO. Inorganic materials were subsequently removed by density separation in ZnCl 2 (ρ = 1.9 g/cm 3 ) using a centrifuge. Special centrifuge tubes were developed for this purpose. Sample analysis was performed on a Si filter by Raman micro-spectroscopy. Particles with a diameter (d p ) ≥ 10 μm were analyzed. The results were differentiated by dry and wet weather samples. On average, 5900 MPPs m −3 were identified in the effluent on wet weather days compared to 3000 MPPs m −3 on dry weather days. Most of the MPPs detected were in the 30 μm < d p < 100 μm size range. The MPFs ranged between 100 μm and 1000 μm in length. While most of the MPFs were of PET origin, the MPPs consisted mainly of PET, PP, PE and PS.

The packaging material of bottled water is suspected to be a source of microplastics (MP). In this preliminary study, the screw cap system was examined for its MP release potential. Therefore, the concentration of MP (≥10 μm) was determined in reusable polyethylene terephthalate (PET) bottles with polypropylene (PP) caps and polyethylene (PE) seals after opening and closing once and 11 times. The entire contents of the bottles were filtered onto a silicon filter after opening. The inside of the bottles and caps was rinsed with filtered water. The total Si filter area was analyzed by Raman microspectroscopy. After one opening, 131 ± 25 microplastic particles (MPP) per liter were detected. After 11 openings and closings, 242 ± 64 MPP/L were detected. The increase is caused by a significant increase in the number of PP particles from 100 ± 27 to 185 ± 52 MPP/L. The concentration of PE and PET particles did not change significantly. Regardless of polymer type and the number of openings and closings, 80% of the MPP were identified in the smallest size class investigated (10−50 μm). Using a specially developed method, the concentration of MPP was determined before the screw cap system was opened and did not differ from the procedural blank.