Electricity Generation And Sediment Remediation Based On Wetland Plant—Sediment Microbial Fuel Cell Systems

In this study, two Wetland Plant- sediment microbial fuel cells(P-SMFCs) and one sediment microbial fuel cell(SMFC) and two plants sediments simulated wetland system(PS1, PS2) were constructed to investigate electricity generation, the degradation of organic matter, the simultaneous migration and transformation of nitrogen and phosphorus in the sediment and overlying water, the influence of the system to simultaneous migration and transformation of the As, Zn, Cd and morphological changes of As in the sediment, the microbial community diversity of anode biofilm. The main research conclusions are as follows:(1) During the 200 days of operation stage, the treatment group of three electrodes can maintain a stable voltage output and the maximum voltage reached 0.69 V, 0.63 V, 0.66 V respectively, and the average output voltage were 0.32 V, 0.24 V, 0.28 V respectively. Three treatment groups of PSM1, SM, PSM2 the internal resistance were 602 Ω, 498Ω and 498Ω respectively, the maximum power density were 10.74 mW/m2, 7.90 mW/m2 and 10.05 mW/m2 respectively. Results show that plants in electric systems will slightly increase the maximum output voltage and significant increase the average output voltage, the maximum output power density were significantly increased, plant will increase the internal resistance of the system.(2) The anode electrode and the plants has a significant role in promoting to the degradation of the sediment organic matter. During the 200 days of operation stage, the organic matter degradation rate were PSM1(19.25%), SM(13.57%), PSM2(15.38%), PS1(8.70%), PS2(4.78%) respectively. During the 64 days of system operation stage, ammonia nitrogen content in the plant electrode treatment groups is significantly lower than in other three treatment groups, and there has no significant changes of each treatment groups along the running time; the ammonia nitrogen removal rates of five treatment groups are all above 80%,showing PSM1 83.67%, SM 81.28%, PSM1 83.79%, PS1 85.94%, PS2 84.62% respectively. During the whole operation stage, there is no special reinforcement effect of nitrate nitrogen removal by the introduction of the electrode and the electricity production process. The presence of anode electrode may inhibit the transfermation of phosphorus, and promote the stability of phosphorus in the sediment.(3) The electricity production process and the plants can promote the stability of Zn, Cd, As in the sediment, and can retard the release speed of the As, Zn, Cd in sediment. And the farther from the anode, the weaker of the anode electrode influence. Anode electricity process affects the plants absorption of As,Zn,Cd in the sediment. Anode electricity process can change the configuration of arsenic in the sediment which affect its overlying water release speed up, and contribute to the stability of arsenic, but it has a weak influence to acid extraction arsenic and Reducible arsenic. with the anode electrode distance increase, the anode electrode influence to morphological arsenic were more weak. In the system, the introduction of the plant increased the absorption of weak acid extracted state arsenic, and can reduce the activity of weak acid extraction state arsenic content.(4) The existence of the plant were contribute to the increase of the growth of microbes and bacteria community diversity of anode biofilm bacteria. In gate level of bacterial classification analysis, the primary microorganism of all treatment group were proteobacteria. Windmill grass significantly increased the quantity of Nitrospirae and GOUTA19. In genus level of bacterial classification analysis, the primary microorganism of all treatment group were Geobacter. Different plants will influence microbial community structure. PSM1, SM, PSM2 treatment groups microbial community structure were significantly different, and different plant species have different influence on the anode biofilm microbial community structure.(5) The introduction of windmill grass and Short leaf cyperus malaccensis had a significant effect to anode archaea community structure. The archaea community abundance order of each treatment group as follows: PSM1 > SM > PSM2, the existence of the windmill grass can help the archaea growth, while short leaf cyperus malaccensis can inhibit the growth of archaea. The introduction of plant can increase the archaea community diversity, and compared to the windmill grass, the short leaf cyperus malaccensis will more can increase the diversity of archaea community diversity. In gate level of archaea community classification, the primary microorganism of all treatment group were Euryarchaeota. In genus level of archaea community classification, the primary microorganism of all treatment group were Methanosaeta, the relative abundance were PSM1 21.43%, SM 25.00%, PSM2 23.16% respectively. And in gene sequences have been detected, only a minority of archaea sequence were ammonia oxidation, the rest of the all archaea sequence were methane sequence, the tota relative abundance of all above 30%. Three treatment groups have a different community structure, microbial community structure varied.