Effect Of Heavy Metals On Microbial Fuel Cells For Landfill Leachate Treatment

The heavy metals in different leachate depending on the type and composition of waste,treatment and disposal technology,etc.,while the type and concentration of heavy metals in the substrate affects the microbial fuel cell（MFC）performance and anode microorganisms.This study investigated the effects of single heavy metal ion species and concentration in the substrate and the mixture of two heavy metal ions on the MFC performance,pollutant treatment performance and anode microbial community,and provided reference materials for the harmless treatment of leachate with complex composition.The results of the effect of adding single heavy metal to the leachate on the MFC showed that the MFC could maintain good power production performance and pollutant treatment performance under the conditions of low concentration of heavy metals,while high concentrations produced different degrees of inhibition:compared with the normal operation of the MFC,the maximum MFC at Cu²⁺,Pb²⁺,Cd²⁺and Zn²⁺concentrations of 200μmol/L in the leachate output power increased by 43.89,35.40,15.95 and 23.55%,respectively,and the removal rates of COD,ammonia nitrogen and heavy metals remained similar to those in normal operation.In contrast,the decreases in maximum power density were 40.94,71.94,42.96 and 5.42%for the maximum added concentrations of Cu²⁺,Pb²⁺,Cd²⁺and Zn²⁺at 1000,900,1100 and1200μmol/L,respectively,and the removal rates of COD,ammonia nitrogen and heavy metals were reduced by 18.78,37.88,20.26 and 6.56%for each group.The FTIR results showed that the intensity of the absorption peaks of the functional groups in the treated leachate decreased to different degrees,and the lower the concentration of the added heavy metals,the greater the decrease in the intensity of the absorption peaks.The fluorescence peaks representing soluble microbial degradation by-products disappeared,and the intensity of the peaks followed the pattern of Zn²⁺>>Pb²⁺>Cu²⁺>Cd²⁺.The addition of low concentrations of heavy metals promoted the secretion of extracellular polymers by anode microorganisms,but the secretion of extracellular polymers by heavy metals except Zn²⁺was significantly reduced at the maximum added concentration.The results of anode microbial sequencing showed that Bacteroidota,Proteobacteria and Firmicutes were the major electroproducing bacteria at the level of each group of phylum,Acinetobacter was the major electroproducing bacteria at the level of each group of genus,and Thioclava was the electroproducing bacteria at the level of low concentration of Pb²⁺and Zn²⁺genus.High concentrations of heavy metals decreased the abundance of each group of electroproducing bacteria and enhanced the diversity and relative abundance of the anode microbial community.The results of the effects of mixed heavy metals to the leachate on the MFC showed that the maximum output voltage of the MFC usually decreased with the increase of cycles and the running time usually increased with the increase of cycles.The maximum power density of the MFC containing Zn²⁺group tends to increase in the2nd or 3rd cycle compared to the previous cycle,while the other groups show a gradual decrease.The COD removal rate of Cu²⁺-Zn²⁺and Pb²⁺-Zn²⁺groups did not change much during the three cycles,while the COD removal rate of other groups decreased gradually with the increase of operating cycles.The ammonia removal rate of each group was similar within three cycles,but the difference between groups was significant.The FTIR results showed that the intensity of absorption peaks of functional groups in the original leachate decreased,except for the Zn²⁺group,which still had a strong absorption peak at 1420 cm^-1,but there was no significant difference between the groups.The EEM results showed that the original fluorescence peaks disappeared after MFC treatment,but only the fluorescence peaks representing soluble microbial degradation by-products appeared in the Cu²⁺-Zn²⁺,Pb²⁺-Cd²⁺and Pb²⁺-Zn²⁺groups,among which the fluorescence peaks in the Cu²⁺-Zn²⁺group were much higher than those in the other groups.The anodic microbial sequencing results showed that Bacteroidota,Proteobacteria and Firmicutes were the major electroproducing bacteria of MFC at the phylum level,and Geobacter was the major electroproducing bacteria of MFC at the experimental genus level in each group.The Cu²⁺-Cd²⁺combination had the highest biotoxicity and the Cu²⁺-Zn²⁺combination had the lowest biotoxicity.Figure 25 Table 7 Reference 145...