Research On Enhanced Removal Of Carbon Nitrogen And Phosphorus From Water Body By Bioelectrochemical System With Submerged Plants Reaeration

This research focused on constructing and optimizing a bioelectrochemical system with submerged-plant rearation to restore an inland river,Harbin,the operational efficiency of the system under the continuous flow was studied.The study aimed at removing the pollutants in surface water and sediment simultaneously while recovering energy,and proving a novel technology for in situ repairation of polluted surface water.The construction of the coupled system was studied first.Hydrilla verticillata with 20 g/L biomass was optimized in terms of pollutant removal and oxygen production,which were further added into the bioelectrochemical system.After the coupled system starting-up,the removal of TOC and TN reached to 56.4% and 55%.The maximum power density and current density were 1.42 W/m3 and 4.50 A/m3,indicating the possible operation of the system.The pollutant removal under batch and continuous flow was studied.In the batch mode,the TOC,TN and TP removal were 34.5%,57.2% and 48.1% at day 2,which was 1.73,3.64 and 4.00 times higher of that in control system.All these demonstrated the better performance of the coupled system.After running for 15 days in the continuous mode,the coupled system also showed an excellent performance than other two systems with simultaneous pollutants removal in water and sediment.The removal of TOC,TN and TP in water body eventually stabilized around 20.1%,46.0% and 38.5%,the maximum removal of TC and TN in the sediment was 23.1% and 7%.In case of energy recovery,the maximum power density of the coupled system was 1.78 W/m3,which was 34.8% higher than the system without plants.The effect of submerged plants on the microbial community structure of biocathode in bioelectrochemical system was also explored,The electrochemical performance of biocathode of two systems was studied in a three-electrodes system.The result showed the biocathode from coupled system could generate current density of 125 A/m3 at potential 190 mV at the oxygen-saturated condition,which was 2.5 times higher than that in system without any plants.By comparing the microbial community structure of biocathode and bioanode from two systems,it was concluded that the submerged plant mainly affected biocathode microbial community because the relative abundance of aerobic bacteria in the coupled systemic biocathode was significantly higher than that without plants.The dominant genus of microbial communities in bioanode was Citrobacter and Macellibacteroides,which could degrade organics contained in the sediment.In addition,the coupled system was rich in higher relative abundance of electrochemically active microorganisms,like bacillus and Paenibacillus.