Bio-denitrification performance enhanced by graphene-facilitated iron acquisition. (1st August 2020)

• Record Type: Journal Article
• Authors: Jiang, Meng; Feng, Leiyu; Zheng, Xiong; Chen, Yinguang
• Is Part Of: Water research. Volume 180(2020)
• Publication Date: 2020-08-01
• Subjects: Denitrification -- Graphene -- Nitrite -- Nitrous -- Iron transport; Water -- Pollution -- Research -- Periodicals; 363.7394
• DOI: 10.1016/j.watres.2020.115916
• Languages: English
• ISSNs: 0043-1354

Abstract

Abstract: Bio-denitrification is widely used for remediation of nitrate contaminated site or removal of nitrate from wastewater, but its efficiency is not always satisfied and high nitrite accumulation and nitrous oxide emission occur frequently. Iron plays an important role in achieving efficient biological denitrification. Nevertheless, its concentration in cells is usually inadequate, and additional supply of iron to denitrification system has been adopted in the literature. In this study, a novel approach to increase the intracellular iron concentration of denitrifying microbes by using graphene to accelerate iron transport, which significantly enhanced bio-denitrification and decreased intermediates accumulations, was reported, and the underlying mechanisms were explored. The presence of 50 mg/L of graphene was observed to not only significantly promote nitrate removal efficiency by 67.3%, but also decrease nitrite and nitrous oxide generation by 49.0% and 63.9%, respectively. It was found that graphene promoted the generation, transfer and consumption of electrons, increased the activities or gene expressions of Fe-containing enzymes (such as complex I, complex III, various cytochromes, and most denitrification reductases), and enhanced the growth of denitrifiers due to iron acquisition by denitrifying bacteria being remarkably facilitated, leading to a significant increment of intracellular iron concentration. Meanwhile, the intracellular proton-motive force and ATP levels were promoted as well. This study provided a new approach to enhancing bio-denitrification and revealed a novel insight into biological iron acquisition. Graphical abstract: Image 1 Highlights: Nitrate removal was significantly enhanced by graphene. Nitrite accumulation and N2 O generation were remarkably reduced. Cell growth was improved by graphene. The generation, transfer and consumption of electrons were all promoted. The concentration of intracellular iron was increased.