Investigating the potential for microplastic removal in wastewater treatment: Ankara example

With the increasing use of plastics, it has become important to identify different sources of microplastics (MPs), which are considered as pollutants of concern in aquatic ecosystems. Studies on the removal efficiency of these pollutants of concern in wastewater treatment plants, which are considered as both the receiver and source of MPs, have gained importance in recent years. In this thesis, it was aimed to determine the MP load and removal efficiency of Ankara Province Central Wastewater Treatment Plant (Tatlar WWTP), the largest wastewater treatment plant in Turkey. Within the scope of the study, five different points, including three stations selected on the inlet, discharge and arrival line, were sampled representing the wet (April-2022) and dry (August-2022) periods. In addition, samples were taken from all stations to evaluate the physico-chemical parameters of the water. In order to determine the size diversity in MPs, the samples were passed through a sieve system with different mesh openings and transferred to sterile glass bottles and taken to the laboratory environment. The MP samples were subjected to organic removal process. Then they were classified according to their shape, size and colour under stereo microscope. The amount of MP was determined as 191.3 MP/L at the inlet point (MP4) and 38.7 MP/L in the discharge water (MP5) during the wet period and 175 MP/L at the inlet point and 24.1 MP/L in the discharge water during the dry period. While the detected MP types were fibre, fragment, film, microbead and foam, the dominant MP type was fibre (79.50%-69.80%) in all stations during the wet and dry periods. The dominant colours of microplastics in wet and dry periods were black and blue, and the dominant size range was 10-100 µm (77.42%-72.46%). Polymer structures were characterised by Fourier Transform Infrared (FTIR) spectroscopy and 13 different types were identified and it was determined that polyethylene (PE), polypropylene (PP) and polystyrene (PS) were the dominant types in both periods. MP removal efficiency of Tatlar WWTP was found to be 80% in the wet period and 86% in the dry period. As a result, the findings obtained within the scope of this thesis study show that different removal technologies and innovative solutions are needed to reduce MP pollution in Tatlar-WWTP.