Circulation of microplastics in a municipal wastewater treatment plant with multiphase activated sludge

Microplastic particles are a growing environmental concern due to their increasing presence in the natural environment. There is an urgent need to identify their sources and fate in wastewater treatment processes. It is important to understand the extent to which municipal wastewater treatment plants contribute to environmental pollution with microplastics. The aim of this study is to examine the distribution of microplastics (45 µm to 5 mm in size) in a municipal wastewater treatment plant. This includes raw wastewater, treated wastewater, sewage sludge, and leachate from sludge treatment. To gain a better understanding of the behavior of microplastics in wastewater treatment plants, their physical properties, such as shape, size, and colour, as well as their chemical composition (type of plastic polymer), were thoroughly analysed. The study determined that the raw wastewater contained 4.13±0.056 pcs MP/L. The analysis confirmed that microplastics present in raw wastewater are recycled along with leachates from sewage sludge processing. Furthermore, the majority of microplastics accumulate in sewage sludge (13.64×103±10.00 pcs MP/kg DS). The concentration of microplastics in different stages of wastewater treatment plants is influenced by their physical and chemical characteristics.