Dissolved oxygen has no inhibition on methane oxidation coupled to selenate reduction in a membrane biofilm reactor. (November 2019)

• Record Type: Journal Article
• Authors: Shi, Ling-Dong; Wang, Min; Li, Zi-Yan; Lai, Chun-Yu; Zhao, He-Ping
• Is Part Of: Chemosphere. Volume 234(2019)
• Page Start: 855
• Page End: 863
• Publication Date: 2019-11
• Subjects: Selenate removal -- Aerobic methane oxidation -- Dissolved oxygen -- Selenate reducer -- Membrane biofilm reactor; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2019.06.138
• Languages: English
• ISSNs: 0045-6535

Abstract

Abstract: Methane oxidation coupled to selenate reduction has been suggested as a promising technology to bio-remediate selenium contaminated environments. However, the effect of dissolved oxygen (DO) on this process remained unclear. Here, we investigate the feasibility of selenate removal at two distinct DO concentrations. A membrane biofilm reactor (MBfR) was initially fed with ∼5 mg Se/L and then lowered to ∼1 mg Se/L of selenate, under anoxic condition containing ∼0.2 mg/L of influent DO. Selenate removal reached approximately 90% without selenite accumulation after one-month operation. Then 6–7 mg/L of DO was introduced and showed no apparent effect on selenate reduction in the subsequent operation. Electron microscopy suggested elevated oxygen exposure did not affect microbial shapes. 16S rDNA sequencing showed the aerobic methanotroph Methylocystis increased, while possible selenate reducers, Ignavibacterium and Bradyrhizobium, maintained stable after oxygen boost. Gene analysis indicated that nitrate/nitrite reductases positively correlated with selenate removal flux and were not remarkably affected by oxygen addition. Reversely, enzymes related with aerobic methane oxidation were obviously improved. This study provides a potential technology for selenate removal from oxygenated environments in a methane-based MBfR. Graphical abstract: Image 1 Highlights: Influent 6–7 mg/L DO had no inhibition on selenate reduction in a CH4 -based MBfR. Aerobic methanotroph Methylocystis remarkably increased after DO elevating. Likely selenate reducers Ignavibacterium and Bradyrhizobium weren't affected by DO.