When polyethylene terephthalate microplastics meet Perfluorooctane sulfonate in thermophilic biogas upgrading system: Their effect on methanogenesis.

Microplastics (MPs) and Perfluorooctane sulfonate (PFOS) are two hard-biodegradable pollutants widely existing in the waste streams treated by anaerobic digestion. However, their synergistic effect on methanogenic metabolism is still unknown. This study investigated the impact of polyethylene terephthalate (PET) MPs alone and co-existing with PFOS on CO ₂ conversion to CH ₄ in a thermophilic biogas upgrading system. The results showed that either PET MPs addition alone or coexisting with PFOS improved the ultimate CH ₄ percentage and increased CO ₂ utilization rate. When Fe ⁰ was added into the reactors with PET to enhance the interspecies electron transfer, a potential defluorination was observed with a defluorination rate of 15.88 ± 1.53%. Exposure of the reactor to PFOS of 300 μg/L could change the methanogenic pathway, resulting in a newly emerged Methanomassiliicoccus with dominance of 16%. Furthermore, under the exposure of PFOS, the number of predicted genes regulating enzymes in methanogenic steps from CO ₂ increased. These results suggest that the co-existence of PET MPs and PFOS will not inhibit the activity of hydrotrophic methanogenes, and a portion of PFOS may be biodegraded during the methanogenesis under Fe ⁰ regulation.
Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests XIN KONG reports financial support was provided by National Natural Science Foundation of China. XIN KONG reports financial support was provided by Shanxi Province Department of Education.
(Copyright © 2024 Elsevier B.V. All rights reserved.)