Long-term exposure to nano-TiO2 interferes with microbial metabolism and electron behavior to influence wastewater nitrogen removal and associated N2O emission. (15th October 2022)

• Record Type: Journal Article
• Authors: Ye, Jinyu; Gao, Huan; Wu, Junkang; Yang, Guangping; Duan, Lijie; Yu, Ran
• Is Part Of: Environmental pollution. Volume 311(2022)
• Publication Date: 2022-10-15
• Subjects: Nano-TiO2 -- Nitrogen removal -- N2O -- Metabolic activity -- Recoverability; Pollution -- Periodicals; Pollution -- Environmental aspects -- Periodicals; Environmental Pollution -- Periodicals; Pollution -- Périodiques; Pollution -- Aspect de l'environnement -- Périodiques; Pollution -- Effets physiologiques -- Périodiques; Pollution; Pollution -- Environmental aspects; Periodicals; Electronic journals; 363.73
• DOI: 10.1016/j.envpol.2022.119930
• Languages: English
• ISSNs: 0269-7491

Abstract

Abstract: The extensive use of nano-TiO2 has caused concerns regarding their potential environmental risks. However, the stress responses and self-recovery potential of nitrogen removal and greenhouse gas N2 O emissions after long-term nano-TiO2 exposure have seldom been addressed yet. This study explored the long-term effects of nano-TiO2 on biological nitrogen transformations in a sequencing batch reactor at four levels (1, 10, 25, and 50 mg/L), and the reactor's self-recovery potential was assessed. The results showed that nano-TiO2 exhibited a dose-dependent inhibitory effect on the removal efficiencies of ammonia nitrogen and total nitrogen, whereas N2 O emissions unexpectedly increased. The promoted N2 O emissions were probably due to the inhibition of denitrification processes, including the reduction of the denitrifying-related N2 O reductase activity and the abundance of the denitrifying bacteria Flavobacterium . The inhibition of carbon source metabolism, the inefficient electron transfer efficiency, and the electronic competition between the denitrifying enzymes would be in charge of the deterioration of denitrification performance. After the withdrawal of nano-TiO2 from the influent, the nitrogen transformation efficiencies and the N2 O emissions of activated sludge recovered entirely within 30 days, possibly attributed to the insensitive bacteria survival and the microbial community diversity. Overall, this study will promote the current understanding of the stress responses and the self-recovery potential of BNR systems to nanoparticle exposure. Graphical abstract: Image 1 Highlights: Nano-TiO2 inhibited nitrogen transformation efficiency but increased N2 O emission. Nano-TiO2 decreased N2 O reductase activity and genus Flavobacterium abundance. Nano-TiO2 suppressed both microbial carbon source and nitrogen metabolism. Nano-TiO2 interfered with electron production, transport, and competition. The BNR performance could recover completely after withdrawing nano-TiO2 .