Emerging investigator series: inhibition and recovery of anaerobic granular sludge performance in response to short-term polystyrene nanoparticle exposure

Abstract

Anaerobic treatment systems play an important role in treating nanoplastic-containing wastewater, such as textile dyeing wastewater. However, the influence of nanoplastics on anaerobic granular sludge (AGS), a key parameter determining the performance of anaerobic bioreactors, has not received sufficient attention. In this study, inhibition and recovery of AGS performances in response to short-term polystyrene (PS) nanoparticle exposure were investigated. Results showed that cationic PS nanoparticles (PS-NH₂) had higher inhibition capacity on methane production than anionic PS nanoparticles (PS-SO₃H). At the end of the first cycle, cumulative methane production was reduced by 22.98% and 17.47% by exposure to 20 μg mL⁻¹ PS-NH₂ and 100 μg mL⁻¹ PS-SO₃H, respectively. However, the system recovered in the second cycle of experiments. Volatile fatty acid (VFA) concentration had no obvious relationship to PS nanoparticle addition. Both functionalized PS nanoparticles could change the protein secondary structures of extracellular polymeric substances (EPS) and penetrate EPS matrix into AGS at specific concentration. The response of AGS was explored through bacterial and archaeal communities as well as the relative abundance of methanogenic functional genes. These results elucidated the complex interactions of AGS, EPS and PS-NPs, which will expand the knowledge on the stability of AGS under short-term exposure to nanoplastics.