EFFECTS AND FATE OF POLYCARBONATE MICROPLASTICS DURING MESOPHILIC AND THERMOPHILIC SLUDGE DIGESTION WITH DIFFERENT SLUDGE DISINTEGRATION METHODS

Date

2025-8-20

Author

Sakınmaz, Kıymet Eda

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Microplastics (MPs), defined as plastic particles smaller than 5 mm, are effectively removed in wastewater treatment plants (WWTP) but accumulate in sludge, posing potential risks to anaerobic digestion (AD) processes. Although various polymers were studied for their impact on AD, polycarbonate (PC) was investigated in a single study. Due to the presence of ester bonds in its structure, PC is susceptible to alkali-catalyzed hydrolysis, leading to bisphenol A (BPA) release. Its degradability increases under alkaline, thermal, and enzymatic conditions, which overlap with disintegration methods aimed at enhancing methane production by disrupting sludge flocs. This study investigated the effects of PC MPs and two combined disintegration methods on AD performance under mesophilic and thermophilic conditions, as well as PC transformations throughout the process. For this purpose, sludge was spiked with PC doses of 0, 1, 3, 6, and 10 mg/g TS (250–500 μm), and subjected to 0.5 M alkali (48 hours) and 127 °C (120 minutes) thermal combined disintegration, and thermal at 127 °C (120 minutes) and 150 mg/g TS enzyme (24 hours) combined disintegration. Both methods were applied before 60-day biochemical methane potential tests. Alkali-thermal method achieved 62.6% sludge solubilization and 48% PC mass loss, while thermal-enzymatic disintegration provided 37.1% solubilization and 25% mass loss. Despite temporary inhibition due to BPA release, methane yield increased by 26.6% in alkali-thermal reactors, and by 19.5% in thermal-enzymatic reactors. Moderate physical and chemical changes in PC MPs observed imply degradation and increase of methane yields show applicability in in WWTP.

Subject Keywords

Polycarbonate Microplastics, Anaerobic Digestion, Sludge, Disintegration, Morphology, Molecular Weight

URI

https://hdl.handle.net/11511/115539

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Graduate School of Natural and Applied Sciences, Thesis