Determination of key factors affecting biofilm formation on the aged Poly(ethylene terephthalate) during anaerobic digestion.

Biofilm formation on plastic surface is a growing concern because it can alter the plastic surface properties and exacerbate the ecological risk. Identifying key factors that affecting biofilm formation is critical for effective pollution control. In this study, the poly (ethylene terephthalate) (PET) was aged in water and air conditions with UV irradiation, then incubated in the digestate of food waste anaerobic digestion to allow biofilm formation. Surface analysis techniques, including scanning electron microscopy (SEM), atomic force microscopy (AFM), and Fourier-transform infrared spectroscopy with attenuated total reflection (FTIR-ATR), were utilized to investigated the changes in the topography, roughness, hydrophily, and functional groups change of the PET surface during the aging process. Confocal laser scanning microscopy (CLSM) was used to determine the distribution of microorganisms on the PET surface after incubation in the digestate. This study focused on understanding the interactions between the PET surface and biofilm to identify critical surface factors that affect biofilm formation. Results showed that the four months aging process decreased the contact angle of the PET surface from 96.92° to 76.08° and 68.97° in water and air conditions, respectively, corresponding to an increase of 44% and 70% in the surface energy. Additionally, aging in air conditions led to a rougher surface compared to water conditions. The arithmetic roughness average (Ra) of the PET-Water was 11.0 nm, comparable to that of the pristine PET, while the value of PET-Air was much higher (43.9 nm). The results further indicated that biofilm formation during anaerobic digestion was more sensitive to roughness than hydrophily. The PET surface aged in air conditions provided a more suitable environment for microbial reproduction, leading to the aggradation of living cells.