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Enhanced nitrate reduction in water by a combined bio-electrochemical system of microbial fuel cells and submerged aquatic plant Ceratophyllum demersum
- Xu, Peng, Xiao, Enrong, Wu, Junmei, He, Feng, Zhang, Yi, Wu, Zhenbin
- Journal of environmental sciences (China) 2019 v.78 pp. 338-351
- Ceratophyllum demersum, Flavobacterium, Geobacter, Pseudomonas, Rhodobacter, algae, cathodes, denitrification, electrochemistry, eutrophication, lakes, microbial fuel cells, nitrate reduction, nitrates, oxygen, power generation, sediments, stable isotopes, submerged aquatic plants, surface water
- High nitrate (NO3−) loading in water bodies is a crucial factor inducing the eutrophication of lakes. We tried to enhance NO3− reduction in overlying water by coupling sediment microbial fuel cells (SMFCs) with submerged aquatic plant Ceratophyllum demersum. A comparative study was conducted by setting four treatments: open-circuit SMFC (Control), closed-circuit SMFC (SMFC-c), open-circuit SMFC with C. demersum (Plant), and closed-circuit SMFC with C. demersum (P-SMFC-c). The electrochemical parameters were documented to illustrate the bio-electrochemical characteristics of SMFC-c and P-SMFC-c. Removal pathways of NO3− in different treatments were studied by adding quantitative 15NO3− to water column. The results showed that the cathodic reaction in SMFC-c was mainly catalyzed by aerobic organisms attached on the cathode, including algae, Pseudomonas, Bacillus, and Albidiferax. The oxygen secreted by plants significantly improved the power generation of SMFC-c. Both electrogenesis and plants enhanced the complete removal of NO3− from the sediment–water system. The complete removal rates of added 15N increased by 17.6% and 10.2% for SMFC-c and plant, respectively, when compared with control at the end of experiment. The electrochemical/heterotrophic and aerobic denitrification on cathodes mainly drove the higher reduction of NO3− in SMFC-c and plant, respectively. The coexistence of electrogenesis and plants further increased the complete removal of NO3− with a rate of 23.1%. The heterotrophic and aerobic denitrifications were simultaneously promoted with a highest abundance of Flavobacterium, Bacillus, Geobacter, Pseudomonas, Rhodobacter, and Arenimonas on the cathode.