Investigation of the fate of microplastics during the disintegration process of urban sewage sludge

Plastic particles smaller than 5 mm, that is, microplastics, are among the important pollutants that have attracted attention recently. Wastewater treatment facilities are generally the leading source of microplastic pollution. Studies on this subject have gained momentum in the academy. Within the scope of the thesis study, it was aimed to determine the optimum disintegration process conditions in the sewage sludge taken from Denizli Central Wastewater Treatment Plant, the effect of disintegration on microplastics and biochemical methane potential during anaerobic digestion, and the concentrations, shapes and sizes of microplastics. For this purpose, first characterization processes were carried out on sewage sludge. Fenton and ultrasonic processes, which are disintegration processes, were carried out on the treatment sludge whose characterization was determined. Optimum process conditions have been determined for disintegration processes. For this purpose, first characterization processes were carried out on sewage sludge. Fenton process, which is chemical disintegration, and ultrasonic process, which is physical disintegration, were applied to the treatment sludge whose characterization was determined. After the disintegration processes, optimum process conditions were determined. After disintegration with the Fenton process, the optimum H2O2 dose was determined as 60 g/kg and the optimum Fe (II) dose was determined as 3g/kg. After disintegration with the ultrasonic process, the optimum amplitude (amp) value was determined as 30% and the optimum time value was determined as 50 minutes. The effect of disintegration on the quenching process in sewage sludge was made with the help of Capillary Suction Time (CES, CST) experiment, and it was observed that the quenching time of sewage sludge disintegrated with the Fenton process was shortened, while the quenching time of sewage sludge disintegrated with the ultrasonic process was prolonged. BMP (Biochemical Methane Potential) experimental studies were carried out under optimum disintegration process conditions. The highest BMP value was observed in the sludge sample disinfected with ultrasonic treatment and then in the sludge sample disinfected with Fenton. At the end of the disinfection processes and isolation studies in wastewater treatment sludge samples under optimum conditions, all samples were stained with "Nile Red" dye and microplastics were analyzed. Fiber-shaped microplastics were observed extensively in the sewage sludge.