| At present,environmental pollution especially water pollution and energy scarcity are two major challenges that the world is facing nowadays.As an important part of the water environment ecosystem,submerged plants have important application value in the field of water restoration.Microbial fuel cell?MFC?is a sustainable technology that has received extensive attention in recent years and has the capability of wastewater treatment and energy recovery,while the sediment microbial fuel cell is a special type of MFC,which provides a potential method for contaminated sediment restoration.In this study,the sediment from contaminated water was used as the substrate,the domestic wastewater was used as the overlying water,meanwhile,Vallisneria natans and sediment microbial fuel cell were introduced.All of these constructed the submerged plant-sediment microbial fuel cell?P-SMFC?system.The power generation performance and the effect on the recovery of sediment and overlying water of the system were investigated.The main conclusions are as follows.?1?Three experimental systems including experimental group without plant?group B?,experimental group only with plant?group V?and experimental group with plant?group P?were constructed,and each group was three parallel.Among them,group B was the SMFC system,group P was the P-SMFC system,and the power generation performance of the two MFC systems was examined.After operation of 65 days,both group B and group P were successfully started.During the third power generation period of start-up phase,the maximum voltage of group P reached 423 mV and the daily maximum voltage appeared at more than 300 mV for 22 days,compared with 398mV and 16 days of group B.During the stable operation phase,the output voltage of group P and B fluctuated because group P was affected by the photosynthesis of Vallisneria natans,and group B might appear biological disturbance and bubble interference.Polarization curve and power density curve of the cell were measured by the variable resistance method.The maximum power density and the internal resistance was 7.10 mW·m-2 and 644?in group P,and 4.12 mW·m-2 and 1718?in group B,respectively.Thus,the maximum power density of group P was close to twice larger than that of group B and the internal resistance was about 1/3 of the latter.?2?Four indexes of COD,total nitrogen?TN?,total phosphorus?TP?and ammonia nitrogen in overlying domestic wastewater from group B,V and P were determined.Among them,the removal rates of COD,TN,TP,and ammonia nitrogen in overlying water of group P were?48±3.3?%,?86.5±2.6?%,?100±0.0?%,and?94±1.0?%,respectively.In group B,they were?33±4.1?%,?35±3.8?%,?73±4.3?%,and?61±2.4?%,respectively,and in group V,they were?34±3.4?%,?86.1±0.4?%,?100±0.0?%,and?97±0.0?%,respectively.Compared with group B and V,the removal rate of COD was increased by about 50%in group P.The removal rate of nitrogen and phosphorus in overlying water of group P was significantly higher than that of group B,but it was similar to that of group V.The reason is that Vallisneria natans played a key role and SMFC played a supporting one in the reduction of these pollutants,and the two are superimposed on each other,making the group P have the best comprehensive removal effect on overlying water pollutants.?3?Four indexes of organic matter,total nitrogen,total phosphorus and ammonia nitrogen in sediment of group B,V and P were measured.Among them,the removal rates of organic matter,total nitrogen,total phosphorus,and ammonia nitrogen in the sediment of group P were?8.3±1.0?%,?16.45±1.08?%,?5.9±0.2?%,and?14.9±1.6?)%.In group B,they were?6.8±0.9?%,?15.3±1.6?%,?6.0±0.8?%and?18.0±2.2?%,respectively,and in group V,they were?3.7±1.3?%,?9.9±0.4?%,?10.34±0.55?%,and?42.7±4.9?%,respectively.Through significant analysis,it was found that the organic matter content in the sediment of group P was significantly different from that of the original samples after the end of power generation?P<0.05?,but there was no significant difference between original samples and group B and V?P>0.05?.The contents of total nitrogen,total phosphorus and ammonia nitrogen in the sediment of group B,V and P were significantly different from those of the original samples.These results showed that group P was able to repair the sediment.However,it was not too obvious that the ability of group P to repair the sediment was affected by Vallisneria natans in a short period of time. |
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