In situ investigation of acute exposure of graphene oxide on activated sludge: Biofilm characteristics, microbial activity and cytotoxicity

• Published in: Ecotoxicology and environmental safety 2020-08, Vol.199, p.110639-110639, Article 110639
• Main Authors: Zhu, Chao, Mahmood, Zarak, Zhang, Wenting, Akram, M. Waqar, Ainur, Dyussenova, Ma, Hongrui
• Format: Article
• Language: English
• Subjects: Activated sludge; Biofilm; Laser scanning confocal microscopy; Nano-graphene oxide; Raman spectroscopy
• ISSN: 0147-6513; 1090-2414
• DOI: 10.1016/j.ecoenv.2020.110639

Graphene Oxide (GO) has wide applications in many fields which has caused a large expected quantity of the graphene-based wastes. It is necessary to understand the toxic effects of the GO on the activated sludge (AS) considering its inevitable discharge to the wastewater treatment plants as the ultimate repositories for these wastes. In this study, the acute exposures of the multilayer Nano-graphene oxide (MNGO) at different dosages were conducted in order to investigate its integrated effects on the formation of the biofilm, mature biofilm and the microbial activity of the activated sludge. Raman spectroscopy and laser scanning confocal microscopy (LSCM) were adopted for the in-situ characterization of the biofilm with the exposure of the MNGO. The results showed that the activated sludge was tolerable to the acute exposure of the less than 100 mg/L of the MNGO, especially for the mature biofilm, and only a subtle decrease was found in the size and thickness during the formation of the biofilm, while the amount of 300 mg/L of the MNGO caused the sever deterioration on the activated sludge system. The microbial metabolic activity, viability, and the biological removal of the nutrients were significantly affected with the more than 100 mg/L of the MNGO. It was also demonstrated by the microbial cytotoxicity tests that the increase in the exposure of the MNGO was related to the increase in the reactive oxygen species (ROS) and the damaging degree of the cell membrane. •Exposure of MNGO (>100 mg/L) on AS affected the forming and mature stages of biofilm.•MNGO (>100 mg/L) exposure increased the ROS and LDH level, caused in cell lysis.•Acute exposure of MNGO (>100 mg/L) caused significant drop in microbial metabolic activity.•AS can tolerate much higher exposure level of graphene oxide than pure microbial culture or simple communities.