Phosphorus And Nitrogen Recovery By Coupling Circulated Electrode-chamber Electrochemical System With Microbial Fuel Cell

The recovery of nitrogen and phosphorus from wastewater is an important subject in the field of wastewater treament.Currently,traditional electrochemical technology was still unable to selectively separate and retrieve low concentrations of nitrogen and phosphorus from wastewater.Microbial fuel cells(MFCs)are innovative devices that can perform wastewater treatment and electricity generation simultaneously.However,the power generation of MFCs at present was still insufficient and difficult to directly run a practical electric equipment.In this dissertation,the possibility of using traditional capacitive deionization(CDI)technology to selectively concentrate nitrogen and phosphorus was explored.Then,a novel circulated electrode-chamber electrochemical reactor(CEER)was designed to selectively concentrate and recover low concentrations of phosphate and ammonium from wastewater.Furtherly,an MFC-CEER coupling system was invented and fabricated for nitrigen and phosphorus recovering driven by electricity generated from purification of organics in wastewater.An electrical energy harvesting system based on the capacitors in alternate charging and discharging(ACD)mode was designed and used to enhance the performance of the MFC-CEER coupling system.Based on the study of CDI,a novel CEER was invented which could keep concentrating nitrogen and phosphorus continuously due to its circulated electrode chambers.It could also recover nitrogen and phosphorus selectively by increasing the concentration of NaCl in electrode chambers.During experiment period,the concentration of ammonia nitrogen and total phosphorus could be concentrated to 5 and 4 times respectively of those in the initial wastewater.In the long-term operation,total phosphorus removal efficienies could approach 100% when integrating the struvite formation method with CEER.By optimizing the electrode materials and the configuration of CEER,the concentrating and recovering efficiencies of total phosphorus could be increased by 80% and 99% respectively,while those of ammonia nitrogen could be increased by 13.8% and 24.5% respectively.In the harvesting system based on the capacitors in ACD mode,performance on wastewater treatment and nutrients recovery of MFC were both improved by adjusting the charging and discharging frequency.The average current output was increased from 0.67 mA to 1.59 mA by 439%.The COD removal efficiency was increased from 37% to 63% by 70%.The MFC-CEER coupling system was constructed,which could achieve selfdriven ‘organics removing-nutrients recovering' two purposes from the wastewater simultaneously.The recovery efficiencies of ammonia nitrogen and total phosphorus could reach 17.5% and 38.6% respectively.Furtherly,by introducing the ACD mode to the coupling system,the COD removal rate was increased by 50%,and overall recovery of ammonia nitrogen and total phosphorus was increased by 26% and 20% respectively.