Microplastics in real wastewater treatment schemes: Comparative assessment and relevant inhibition effects on anaerobic processes

• Published in: Chemosphere (Oxford) 2021-01, Vol.262, p.128415-128415, Article 128415
• Main Authors: Pittura, Lucia, Foglia, Alessia, Akyol, Çağrı, Cipolletta, Giulia, Benedetti, Maura, Regoli, Francesco, Eusebi, Anna Laura, Sabbatini, Simona, Tseng, Linda Y., Katsou, Evina, Gorbi, Stefania, Fatone, Francesco
• Format: Article
• Language: English
• Subjects: Microplastics; Municipal wastewater; Polypropylene; Sewage sludge; UASB
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2020.128415

The occurrence, fate and removal of microplastics (MPs) in a wastewater treatment plant (WWTP) in Central Italy were investigated together with their potential adverse effects on anaerobic processes. In the influent of the WWTP, 3.6 MPs.L−1 were detected that mostly comprised polyester fibers and particles in the shape of films, ranging 0.1–0.5 mm and made of polyethylene and polypropylene (PP). The full-scale conventional activated sludge scheme removed 86% of MPs, with the main reduction in the primary and secondary settling. MPs particles bigger than 1 mm were not detected in the final effluent and some loss of polymers types were observed. In comparison, the pilot-scale upflow granular anaerobic sludge blanket (UASB) + anaerobic membrane bioreactor (AnMBR) configuration achieved 94% MPs removal with the abatement of 87% of fibers and 100% of particles. The results highlighted an accumulation phenomenon of MPs in the sludge and suggested the need to further investigate the effects of MPs on anaerobic processes. Accordingly, PP-MPs at concentrations from 5 PP-MPs.gTS−1 to 50 PP-MPs.gTS−1 were spiked in the pilot-scale UASB reactor that was fed with real municipal wastewater, where up to 58% decrease in methanogenic activity was observed at the exposure of 50 PP-MPs.gTS−1. To the best of our knowledge, the presented results are the first to report of PP-MPs inhibition on anaerobic processes. •Characterization of MPs in full-scale CAS and pilot-scale UASB + AnMBR configurations.•Overall greater removal of MPs by UASB + AnMBR (94%) compared to CAS (86%).•MPs retain and accumulate in the sludge line, mainly PE and PP.•PP-MPs inhibition on anaerobic processes is reported for the first time.•UASB tolerated up to 18 PP-MPs.gTS−1 but was inhibited by 58% at 50 PP-MPs.gTS−1.