THREE EMERGENT AQUATIC PLANTS ON NITROGEN REMOVAL AND ELECTRICITY GENERATION PERFORMANCE OF CW-MFC COUPLING SYSTEM

To explore the effects and mechanisms of different wetland plants on nitrogen removal and electricity generation performance of CW-MFC coupling system, three groups of CW-MFC pilot systems were constructed with reed, Lythrum salicaria, and Canna indica, which were recorded as CM-R, CM-L, and CM-C, respectively. The results revealed that: 1) the output voltage and power density of CW-MFC coupling system were CM-L>CM-C>CM-R; 2) the NH₄⁺-N and TN removal rates of CM-R coupling system (76.8±9.9)%; (54.2±8.2)% were higher than that of CM-L system (61.2±8.0)%; (43.1±6.5)%, which were higher than that of CM-C system (58.9±9.5)%; (42.0±9.8)%, P<0.01; 3) the overall growth rate of plants was CM-R> CM-C>CM-L, and the MDA content was the highest in the leaves of Lythrum salicaria (CM-L), indicating that the degree of its damage may be higher; 4) Geobacter, as a typical electrogenesis genus, had a high abundance (4.45% to 7.64%) in all three coupling systems, and its abundance was consistent with the change trend of output voltage and power density, whereas the relative abundance of Acinetobacter and Flavobacterium in CM-R was 21.10% and 14.37%, significantly higher than that of the other two systems (CM-L: 0.33% and 0.10%; CM-C: 0.75% and 0.07%), which was the most dominant genus of denitrification bacteria in CM-R; 5) combined with the FACOPTAX predictions, a total of 47 functional groups including chemoheterotrophy, aerobic chemoheterotrophy, iron respiration, nitrate reduction and nitrogen respiration were detected, and the results also showed that the functional groups of the CM-R were quite different from the other two systems, among which the functional groups of chemoheterotrophy and aerobic chemoheterotrophy accounted for a relatively high proportion in CM-R. The results will help to strengthen plant understanding of the effects of electrogenesis and denitrification performance on the CW-MFC coupling system.