FATE AND EFFECT OF POLYAMIDE MICROPLASTICS DURING ANAEROBIC DIGESTION PROCESS OF SLUDGE

Date

2023-6-02

Author

Şimşek, İrem

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Microplastics are plastics smaller than 5 millimeters in size; they enter wastewater treatment plants (WWTPs) in large quantities and accumulate in sludge. Researchers have demonstrated that the effect of polymers on anaerobic digestion (AD) varies depending on the polymer type. This thesis aims to determine the effects of polyamide-6 (PA6) microplastics on the AD process and their fate. PA6 is a prevalent polymer found in WWTPs. The dose-effect at various concentrations (0, 10, 30, 60, 100, and 200 PA6 particles/g TS) was evaluated using biochemical methane potential (BMP) test reactors. The reactors were run at mesophilic (35°C) and thermophilic (55°C) temperatures. It was found that the impact on methane production varied based on the dose or operational temperature of the reactors were operated. After 60 days of operation under both mesophilic and thermophilic conditions, the produced methane has increased for both the highest (200 PA6 particles/g TS) and lowest doses (10 PA6 particles /g TS) of PA6 when compared to the reactor with no PA6 added. However, thermophilic conditions have a more significant impact on gas production in the presence of PA6. Thermophilic AD conditions have also a greater impact on polymers than mesophilic AD conditions. Following the mesophilic and thermophilic BMP tests, PA6 particle crystallinity values decreased by 17.4% and 18.2%, respectively. The carbonyl index values were unaffected by thermophilic and mesophilic AD. However, the considerable increase in PA6 particle mass under mesophilic and thermophilic conditions observed possibly due to biofilm formation on their surfaces.

Subject Keywords

Anaerobic Digestion, Microplastic, Polyamide-6, crystallinity, carbonyl index

URI

https://hdl.handle.net/11511/104395

Collections

Graduate School of Natural and Applied Sciences, Thesis