Denitrification of overlying water by microbial electrochemical snorkel

Qinzheng Yang, Huazhang Zhao, HuiHui Liang

Abstract

A novel microbial electrochemical snorkel (MES) bioreactor was constructed by inserting an iron rod into the sediment of a simulated natural water body for the first time. Its nitrate removal performance and mechanism were investigated. The DNA high-throughput sequencing analysis indicates that denitrifying bacteria were grown on the iron rod in the overlying solution. The XRD analysis on the oxides formed on the surface of the iron rod indicates that they are goethite and green rust. In the MES system, the green rust on the iron rod can concentrate nitrate and denitrifying bacteria, forming an anaerobic biocathode. The denitrifying bacteria can reduce the nitrate into nitrogen with the electrons moved from the sediment. The nitrate removal efficiency reached 98% in 16 days. This novel MES system showed excellent in-situ nitrate removal performance by moving and concentrating the electrons in sediment and the nitrate in overlying solution in an anaerobic microenvironment.

Keywords: Iron rod; Microbial electrochemical snorkel; Nitrate.