Assessing the impact of alkali and thermal disintegration on methane production and BPA leaching from polycarbonate microplastics in wastewater sludge

Date

2026-8-3

Author

Ayça, İpek

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Microplastics (MPs) are persistent contaminants widely detected in environmental compartments. Wastewater treatment plants act as major sinks for MPs, with approximately 90% being retained in sewage sludge. Polycarbonate (PC), widely used plastic, contains bisphenol A (BPA), an endocrine-disrupting chemical that can be released during sludge treatment. Although sludge disintegration is commonly applied prior to anaerobic digestion (AD) to enhance hydrolysis and methane production, its potential to accelerate the degradation of PC MPs and BPA release has received limited attention. This study investigated the effects of alkaline, thermal, and combined disintegration on sludge solubilization, methane production, PC MP degradation, and BPA leaching. Batch biochemical methane potential tests were performed using sludge containing different PC MP and BPA concentrations. BPA was quantified using solid-phase extraction followed by GC-MS, while changes in the physicochemical properties of PC MPs were evaluated by fourier-transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), and gel permeation chromatography (GPC). The alkaline-thermal sequence achieved the highest degree of sludge disintegration (61.4%) and produced substantially greater BPA release than the other methods, reaching approximately 1500-fold higher concentrations than the untreated control. While alkaline-thermal disintegration enhanced methane yield in sludge without MPs by 40.4%, increasing PC MP doses progressively reduced this benefit because of elevated BPA release up to 84%. FTIR and GPC analyses confirmed that polymer degradation occurred predominantly during disintegration rather than during AD. In the BPA-spiked reactors, moderate BPA concentrations stimulated methane production, and BPA removal during AD occurred primarily through adsorption onto sludge solids rather than biodegradation.

Subject Keywords

Microplastics, Polycarbonate, Bisphenol A, Anaerobic Digestion, Disintegration

URI

https://hdl.handle.net/11511/120571

Collections

Graduate School of Natural and Applied Sciences, Thesis